- Spray Polyurethane Foam Insulation South Africa

Transcription

Final Report:
Wind Uplift Behavior of Wood Roof Sheathing Panels
Retrofitted with Spray-applied Polyurethane Foam
______________________________________________
Submitted to:
Richard S. Duncan, Ph.D., P.E.
Senior Marketing Manager, Spray Foam Insulation
Honeywell Specialty Materials Fluorine Products
101 Columbia Road
Morristown, New Jersey 07962
Jinhuang Wu, Ph.D.
Technical Associate
Huntsman
2190 Executive Hills Blvd.
Auburn Hills, Michigan 48326
Prepared by:
David O. Prevatt, Ph.D.
Report No. 03-07
31 August 2007
Principal Investigator
Assistant Professor (Structures Group)
______________________________________________________________________
Department of Civil and Coastal Engineering
University of Florida
365 Weil Hall
P.O. Box 116580
Gainesville, FL 32611-6580
______________________________________________________________________
FOREWORD
The material presented in this research report has been prepared in accordance with
recognized engineering principles. This report should not be used without first securing
competent advice with respect to its suitability for any given application. The publication
of the material contained herein does not represent or warrant on the part of the
University of Florida or any other person named herein, that this information is suitable
for any general or particular use or promises freedom from infringement of any patent or
patents. Anyone making use of this information assumes all liability for such use.
ii
SUMMARY
This report presents the findings of a research program sponsored jointly by Honeywell
Specialty Materials (Honeywell) and Huntsman to identify structural benefits of sprayapplied polyurethane foam (SPF) in the mitigation of hurricane damage to residential
structures. The work was conducted at the University of Florida (UF) under the direction
of Principal Investigator, Dr. David O. Prevatt, assisted by civil engineering graduate and
undergraduate students and technicians. The project had three main goals:
1. To investigate the wind uplift behavior of wood roof sheathing connections
retrofitted with Spray-applied polyurethane foam;
2. To demonstrate by structural calculations the potential structural benefit (if any)
of SPF retrofit in roof truss-to-wall connections, and;
3. To review existing literature on the performance of unvented (sealed) attics and
racking strength of SPF-retrofitted panels.
UF conducted static wind uplift tests on ½ in. thick by 4 ft by 8 ft oriented strand board
(OSB) sheathing that were nailed to 2 in. by 4 in. southern yellow pine (SYP) wood
members spaced 2 ft apart. Approximately one third of the panels were retrofitted by an
SPF installer who applied 3 in. thick layers of closed cell spray-applied polyurethane
foam (ccSPF) and another third had ccSPF fillets installed along the joints between the
wood members and the ccSPF sheathing. The final final (control) set of panels were
conventionally constructed using either 6d common or 8d ring shank nails. Tests were
conducted at UF’s East Campus laboratory using a steel pressure chamber and vacuum
pump following a modified ASTM E330 test procedure. The suction pressure on the
exterior surface of the OSB sheathing was increased in stages until failure occurred. The
ultimate failure capacities of the retrofitted panels were recorded and compared with the
failure capacities of the non-retrofitted (control) panels.
A total of 49 panels were tested. The mean failure pressure of the control panels was 77
psf, and the full layer ccSPF retrofit increased the mean panel failure pressures by
almost 3.1 times, and the panels retrofitted with ccSPF fillets increased by 2.1 times.
These controlled experimental results indicate that ccSPF retrofit has potential to
improve the wind uplift performance of roof sheathing in wood-framed construction.
Additional considerations such as, effect of trapped water between OSB and ccSPF,
aged performance of the ccSPF, observed cupping of OSB sheathing, the effect of
increased roof shingle temperatures and performance of field retrofitted ccSPF panels
still need to be addressed in order to answer several concerns about the suitability of
using ccSPF as a retrofit approach in hurricane-damage mitigation.
The literature review revealed several recommendations of using ccSPF in the
construction of unvented attics. Researchers suggest that unvented attics may be
suitable for construction in the hot, humid climate zones (e.g. the south-east United
States). While vented attics were recommended as having improved resistance to wind
uplift during hurricanes, no scientific test data was found to support these conclusions.
KEYWORDS: SPF; Polyurethane; Foam; Wind uplift; Sheathing; Roof; Retrofit, ASTM,
Experimental Testing.
iii
TABLE OF CONTENTS
FOREWORD.....................................................................................................................II
SUMMARY.......................................................................................................................III
1.
INTRODUCTION.......................................................................................................1
1.1
2.
LITERATURE REVIEW ............................................................................................2
2.1
2.2
3.
RESEARCH OBJECTIVES ................................................................................................ 12
MATERIALS AND METHODS................................................................................12
4.1
4.2
4.3
4.4
5.
USING SPF TO IMPROVE IN-PLANE RACKING STRENGTH OF WOOD-FRAMED WALLS .......... 3
2.1.1 Discussion of NAHB Results ........................................................................... 6
USING ADHESIVES AS A RETROFIT MEASURE FOR ROOFS IN HIGH WIND AREAS ................ 7
2.2.1 Retrofit Structural Adhesive of Sheathing-to-Wood Member Connection....... 8
2.2.2 Retrofitting Roof Truss-to-Wall Plate Connections.......................................... 9
2.2.3 Discussion of Roof Truss-to-Wall Plate Retrofits .......................................... 11
EXPERIMENTAL INVESTIGATION OF CCSPF RETROFITTED PANELS ..........12
3.1
4.
BACKGROUND................................................................................................................. 1
TEST CHAMBER ............................................................................................................ 13
ROOF SHEATHING PANEL CONSTRUCTION ..................................................................... 14
CCSPF APPLICATION .................................................................................................... 16
TEST PROCEDURE ........................................................................................................ 18
RESULTS AND OBSERVATIONS .........................................................................20
5.1
5.2
5.3
FAILURE MODES FOR CCSPF RETROFITTED ROOF PANELS ............................................ 20
PHASE 1 TESTING ......................................................................................................... 22
PHASE 2 TESTING ......................................................................................................... 25
6.
DATA ANALYSIS ...................................................................................................32
7.
DISCUSSION OF RESULTS ..................................................................................36
7.1
7.2
7.3
8.
DESIGN WIND UPLIFT LOADS ACCORDING TO ASCE 7-05.............................42
8.1
8.2
9.
NAIL PULLOUT .............................................................................................................. 36
CCSPF FOAM RETROFIT ............................................................................................... 38
7.2.1 Configuration B – Foam Fillet ........................................................................ 38
7.2.2 Configuration C – Full Foam ......................................................................... 39
PANEL STIFFNESS......................................................................................................... 41
ROOF SHEATHING WIND UPLIFT DESIGN LOADS ............................................................. 42
ROOF-TO-WALL CONNECTION WIND DESIGN UPLIFT LOADS ........................................... 44
CONCLUSIONS......................................................................................................45
10. FUTURE WORK .....................................................................................................46
REFERENCES................................................................................................................48
LITERATURE REVIEW OF SEALED AND VENTED ATTICS ......................................50
APPENDIX A – DAILY TESTING REPORTS FROM SPF ROOF PANEL TESTING....57
APPENDIX B – INSULSTAR® BROCHURE .................................................................66
iv
LIST OF FIGURES
Figure 2.1 – Roof-to-Wall Connection Retrofit Methods Using Adhesives (from Jones
1998) ...............................................................................................................................10
Figure 4.1 – Suction Chamber Pump and Controls (Pump #2).......................................14
Figure 4.2 – Test Specimen Layout and Nail Schedule ..................................................15
Figure 4.3 – Application of Second Lift of ccSPF for the Full Foam Specimens .............16
Figure 4.4 – ccSPF Application: (a) Configuration B – Foam Fillet, (b) Configuration C –
Full Foam ........................................................................................................................17
Figure 4.5 – ccSPF Foam Fillets: (a) Phase 1 Fillet and (b) Phase 2 Fillet.....................18
Figure 4.6 – Suction Chamber with Roof Panel and Plastic ...........................................20
Figure 5.1 – Adhesive Failure Modes (from http://wikipedia.org) ....................................21
Figure 5.2 – Typical Failure Mode of No Foam Specimens using 8d Ringshank Nails...24
Figure 5.3 – Typical Failure Mode of Foam Fillet Specimens (Phase 1).........................24
Figure 5.4 – Typical Failure Modes for Configuration B on Phase 2 Testing ..................26
Figure 5.5 – First Failure Mode of Configuration C (Phase 2).........................................28
Figure 5.6 – Foam Residue Levels on Wood Members at Failure for Configuration C
(Phase 2).........................................................................................................................28
Figure 5.7 – Second Failure Mode of Configuration C (Phase 2) ...................................28
Figure 5.8 – Third Failure Mode of Configuration C (Phase 2) .......................................29
Figure 5.9 – Fourth Failure Mode of Configuration C (Phase 2) .....................................29
Figure 5.10 – Wood Member Initially Twisted on Test Specimen #9 ..............................30
Figure 5.11 – Failure of Wood Member Initially Twisted on Test Specimen #9 ..............31
Figure 6.1 – Comparative Boxplot of Configuration B Showing the Difference in the Fillet
Application.......................................................................................................................33
Figure 6.2 – Boxplot of Configuration C Test Specimen Groupings................................34
Figure 6.3 –Boxplots of Failure Pressure of the Combined Data for All Panel
Configurations .................................................................................................................35
Figure 7.1 – Comparing Mean Failure Pressure and “Nail” Failure Mode (Tick marks
show the 95% confidence intervals for the mean failure load) ........................................38
v
Figure 8.1 – Components and Cladding Roof Zones for 7º ≤ Θ ≤ 27º and h ≤ 60 ft
(excerpted from ASCE 2006 Figure 6-11C) ....................................................................43
Figure 8.2 – MWFRS Loading Patterns from ASCE 7-05 (ASCE 2006) .........................44
Figure A.1 – Vented and Unvented (Sealed) Attic Concepts (from Hendron et al. 2004)
........................................................................................................................................51
Figure A.2 – Traditional U.S. Climate Zone Regions for Energy-Efficient Building Design
(2002)..............................................................................................................................53
Figure A.3 – Map of DOE’s Proposed Climate Zones (Briggs et al. 2002) .....................54
vi
LIST OF TABLES
Table 2.1 – Average Racking Load (lbs) of Each Wall Panel Configuration (excerpted
from NAHB 1992)..............................................................................................................4
Table 2.2 – Maximum Racking Load of Wall Panels (lbs) (NAHB 1996) ..........................6
Table 2.3 – Summary Results of Using Adhesive as a Retrofit for Roof-to-Wall
Connections (Jones 1998) ..............................................................................................10
Table 4.1 – Pertinent Pump Specifications .....................................................................13
Table 4.2 – Properties of Nails Used in Test Panel Specimens......................................15
Table 4.3 – Test Specimen Configurations .....................................................................17
Table 5.1 – Ultimate Failure Pressures of Test Specimens (Phase 1)............................22
Table 5.2 – Phase 2 ccSPF Uplift Testing Conducted July 2007....................................25
Table 5.3 – Phase 1 Configuration C Specimens Tested July 19-20, 2007....................31
Table 6.1 – Combined Data Summary Statistics for All Panel Configurations ................35
Table 8.1 – ASCE 7-05 Design Wind Pressures for Roof Sheathing Uplift* (psf) ...........43
Table 8.2 – Maximum Design Uplift Force for Roof-to-Wall Connections Using MWFRS*
........................................................................................................................................44
Table A.1 – Global Advantages and Disadvantages of Vented and Unvented Attics .....52
Table A.2 – Climate Zone Definitions (2002) ..................................................................54
vii
1.
INTRODUCTION
This report details methods, results, and conclusions of engineering investigations to
investigate the use of closed-cell Spray-applied Polyurethane Foam (ccSPF) in structural
retrofit applications of residential construction in high-wind areas.
The research
consisted of three primary phases:
(1) Wind uplift tests of wood framed roofing panels representative of typical pre-2000
residential building construction and similar panels retrofitted with ccSPF;
(2) Design wind load analysis to determine the wind uplift capacity of a roof truss-towall connections retrofitted with ccSPF;
(3) Literature reviews of sealed versus vented attics in residential construction and
the racking strength potential of ccSPF-retrofitted wall panels.
The main deliverable from this research is this report documenting the test methods,
results and findings on the use of ccSPF in structural retrofits of residential construction.
1.1
Background
Spray-applied Polyurethane Foam (SPF) is a foam product originally developed for use
as an insulating material in building (exterior wall and roof) construction. SPF can be
spray-applied to the undersides of roof decks and to wall cavities to act as a thermal
break between the exterior environment and the temperature controlled interior spaces.
SPF has been used in two formulations, namely “open-cell” and “closed-cell” foams. A
typical open-cell SPF (ocSPF) has a density of approximately 0.5 pcf, and it is used
mainly in filling cavities inside a building. During installation, the chemical undergoes
significant volumetric expansion (increasing by about 120 times its liquid volume) making
ccSPF Test Report
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31 August 2007
it ideal as spray-applied insulation for use within wood-framed cavities. Open-cell SPF
has an R-value of about 3.6 per inch.
Closed-cell SPF (ccSPF) on the other hand, undergoes far less expansion (only
increasing by 30 times its liquid volume), and it was developed specifically for its high
thermal insulating properties (typical closed-cell SPF has an aged R-value of 6.2 per
inch). Closed-cell SPF is used as exterior roofing insulation for low-sloped roofs (once it
is protected from ultra-violet light that rapidly degrades the product). Closed-cell SPF is
manufactured with a density of 1.7 to more than 3.0 pcf and previous experiments have
shown that ccSPF rapidly develops high and tenacious bond (25-40 psi) to many
construction materials. Throughout this report, the term spray polyurethane foam or
ccSPF will imply closed-cell spray polyurethane foam.
Despite the measured strength and stiffness of closed-cell SPF, it has not been used as
a structural building material in the United States and there are no available design
guidelines relating to its structural properties. Experimental studies and analysis are
needed to understand the structural behavior of ccSPF products.
Because of the
method of ccSPF application (spray-applied), it was felt that a potential structural usage
for ccSPF may be as a structural adhesive retrofit for existing residential houses.
2.
LITERATURE REVIEW
The literature reviewed is on the use of ccSPF in building components and on the
subject of structural adhesives used in construction. Appendix C contains a literature
review of sealed versus vented attics in residential construction.
ccSPF Test Report
2.1
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Using SPF to Improve In-Plane Racking Strength of Wood-framed Walls
Experimental studies (NAHB 1992; NAHB 1996) investigated using the structural
properties of SPF to improve the in-plane racking strength of wood-framed and light
gauge steel-framed shear walls. The National Association of Home Builders (NAHB)
conducted tests sponsored by the Society of the Plastics Industry, Inc. (SPI)
Polyurethane Foam Contractors Division.
The focus of these experiments were to
determine if SPF can provide racking resistance against wind loads instead of using
traditional bracing techniques, i.e. panel or diagonal bracing.
A brief summary of the test method is provided here (excerpted from NAHB 1992).
Thirty (30) panels measuring 8 ft by 8 ft panels were constructed using 2 in. x 4 in. wood
studs and clad on one side using ½ in. thick by 4 ft by 8 ft gypsum drywall sheets
fastened to the framing. The horizontal joint between drywall sheets was taped and
finished with drywall compound. The other side of the wall framing was clad with one of
three different materials:
1. vinyl-clad panels,
2. 5/8-in. thick T 1-11 plywood siding panels, and
3. “conventionally clad” panels
Conventionally clad panels consist of drywall sheet on one side and on the other, a ½-in.
thick full plywood sheet (placed vertically) adjacent to a ½ in. by 4 ft by 8 ft fiberboard
sheet nailed to the framing members. This sheathing is covered with either the vinyl
siding or the T 1-11 siding. The “conventional cladding” simulates the plywood corner
shear bracing that is common in residential construction and the fiberboard sheathing is
a non-structural sheathing used on the remainder of the structure.
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Racking tests were performed according to ASTM Standard E72, “Standard Methods of
Conducting Strength Tests of Panels for Building Construction,” Section 14 , which
evaluates the racking load of sheathing materials on a standard wood frame (8 ft by 8 ft).
Following this procedure, each wall panel has a 3.5 in. by 3.5 in. timber bolted through
the top plates and the racking load is applied to one end of this timber. The wall panel is
braced so that the wall only deflects in the plane of the load.
For each configuration, three wall samples were built and tested and the mean ultimate
failure loads are shown in Table 2.1. Tests were conducted on three (3) wall panels for
each configuration. Note that in the SPF-retrofitted panels, panels made with four wood
stud spacings (16 in., 24 in., 32 in., and 48 in. on center) were tested. The density of the
SPF used was 1.5 pcf.
Table 2.1 – Average Racking Load (lbs) of Each Wall Panel Configuration (excerpted
from NAHB 1992)
Stud Spacing
SPF Panels
Non-SPF Panels
Vinyl
T 1-11
Vinyl
T 1-11
16”
2,800
5,300
913
2,890
24”
2,420
6,387
--
--
32”
2,588
--
--
--
48”
2,298
--
--
--
16” Conventional
--
--
3,853
5,262
From the results, the NAHB study found that SPF retrofits significantly increased the
ultimate racking strength of the vinyl-clad and T-1-11 clad wall panels. In addition, the
racking resistance of SPF-retrofitted panels constructed with vinyl siding varied from
60% to 72% of the ultimate racking strength of the “conventionally clad” wall panels.
ccSPF Test Report
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31 August 2007
Improvement was also observed in racking strength of the SPF-retrofitted T1-11 wall
panels with 16 in. and 24 in. stud spacing, with ultimate racking strengths respectively
equaled and exceeded (21%) the performance of the conventionally-clad un-retrofitted
wall panel.
The variation in stud spacing with SPF-filled wall cavities does not appear to be a major
factor in the racking strength. Since the racking strength is within 25% of each other for
all SPF filled wall specimens regardless of stud spacing, it seems as if the composite
action between only the SPF and the studs is not a major factor in developing the
racking strength. Instead, the composite action of the SPF and sheathing and/or the
effects of the individual components such as the sheathing and drywall and their
fasteners are resisting the racking load.
In 1996, the NAHB conducted racking strength tests on light-gauge steel framed walls
insulated with conventional batt insulation and with SPF (NAHB 1996). The average
density of the SPF used was 2.26 pcf. Only one test was conducted for each of the four
wall configurations listed below, following the ASTM E72 test protocol:
1. 7/16” OSB (front side) and ½” drywall (back side) with R-19 batt insulation in wall
cavities.
2. ½” drywall (both sides) with R-19 batt insulation in wall cavities.
3. 7/16” OSB (front side) and ½” drywall (back side) with SPF in wall cavities.
4. ½” drywall (both sides) with SPF in wall cavities.
The four test panels were framed using 20-gauge steel studs placed vertically at 24 in.
on center. One or both sides of the panels were clad with ½ in. thick drywall sheet. As
ccSPF Test Report
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31 August 2007
before, all drywall joints were taped and finished with drywall compound. Results are
shown in Table 2.2.
Table 2.2 – Maximum Racking Load of Wall Panels (lbs) (NAHB 1996)
R-19 batt
insulation
SPF
insulation
% Increase
in racking
strength
OSB & drywall
4,800
6,000
25%
Drywall & drywall
2,400
5,380
124%
Front & back
cladding materials
Insulation
The 1996 NAHB report notes that the SPF-insulated wall panels failed by buckling of the
steel framing whereas the batt insulated wall panels had sheathing failure. The racking
strengths of both of the SPF insulated wall panels increased over the corresponding batt
insulated panels. The racking strength of the SPF insulated panels was close (within
700 lb of each other).
2.1.1
Discussion of NAHB Results
The 1992 NAHB test series showed that SPF insulation provided an overall
improvement in the racking strength of non-structural cladding wall panels as shown in
the results. SPF insulation increased the racking strength of these wall panels by 207%
and 83% respectively for the vinyl and T1-11 systems.
SPF-insulation is shown to have a beneficial impact on the racking strengths of
conventional walls as well as walls having non-structural cladding installed on one side.
The SPF-insulated panels also appear relatively insensitive to changes in wall stud
spacing as changing the stud spacing from 16 in. o.c. (7 studs) to 48 in. o.c. (3 studs)
only reduced the racking strength by 18 %. This result suggests there are structural
ccSPF Test Report
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31 August 2007
benefits of the composite action of the SPF and sheathing that outweigh the effect of
different sheathing materials.
The results of the 1996 NAHB tests also suggest that SPF-insulation has positive
benefits to the racking strength of wall panels. However, these results are less reliable
than the earlier experiments as only one test was performed for each wall configuration
thereby the results are susceptible to experimental error. Limited value can be derived
since only one test was conducted on each panel configuration.
While the results show significant improvements in racking strength performance in the
experimental wall panels, it is uncertain how well these can be extrapolated to an actual
building. Since the tested wall panels were only 8 ft long, the plywood bracing panel
occupied 50% of the wall length, whereas in a typical wall of a residential building, the 4
ft wide plywood sheet is more likely to represent a smaller fraction of the overall wall
length. No tests provide data on how varying the percentage of structural sheathing
would change the results but this researcher suspects that racking strengths for a long
wall section is likely to be lower than the values reported in the NAHB studies.
2.2
Using Adhesives as a Retrofit Measure for Roofs in High Wind Areas
The use of structural adhesives as a retrofit measure to mitigate hurricane damage to
house is not new. Currently, there are structural adhesives on the market that have been
used
in
this
manner
(e.g.
Alpha
Foamseal
Hurricane
Adhesive)
[http://www.alphafoamseal.com/index.html]. The Alpha Foamseal website claims that
this structural adhesive, which was tested at Clemson University, hardens to create a
watertight seal that acts as a secondary water barrier in wood roof structures.
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Jones (1998) conducted wind uplift tests using several roof sheathing materials panels
to evaluate the effectiveness of the adhesive for retrofit and new construction of wood
roofs.
Jones’ tested SPF adhesives in two areas, a) sheathing-to-wood member
connection and b) roof member-to-wall plate connection, which are discussed in the
following sections.
2.2.1
Retrofit Structural Adhesive of Sheathing-to-Wood Member Connection
Jones (1998) conducted suction tests on 4 ft by 8 ft roof sheathing panels in a pressure
chamber loading the panels monotonically until failure. The sheathing used was 19/32
in. OSB and 15/32 in. 3-ply CDX plywood. Power-driven 8d common nails were used for
all of the specimens with a 6 in. on center nailing pattern along the edge wood members
and 12 in. on center along interior wood members. Jones tested a total of 97 panels
with 11 configurations including a control set of 19 panels. Retrofitted panels had a twopart foaming adhesive sprayed continuously along the sheathing-to-wood member joints.
Jones found that the sheathing type affected the uplift capacities.
Using the CDX
plywood (15/32 in.) the adhesive along with the nails provided about a 200% increase in
the uplift capacity of the sheathing over using just nails. Using the OSB (19/32 in.) the
adhesive along with the nails provided 100% to 300% increase in the uplift capacity of
the sheathing over using just nails depending on the amount of adhesive used. Jones
also found specimens constructed using southern yellow pine (SYP) wood members had
approximately 15% lower ultimate failure capacities than those constructed using
spruce-pine fir wood members. Jones suggested that higher wood density (of the SYP)
hinders absorption of the adhesive into the wood. Jones did not consider in-plane shear
forces along the wood members that are resisted by the roof diaphragm and transferred
through the roof member-to-sheathing connection to the roof members.
ccSPF Test Report
2.2.2
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Retrofitting Roof Truss-to-Wall Plate Connections
Jones (1998) also considered using adhesives as a retrofit measure for the toe-nailed
roof-to-wall connections. This type of connection is known to be a weak one that is
responsible for hurricane damage to roof structures in past storms. In much of the older
residential construction the roof-to-wall connections were made using 2 or 3 nails toenailed (driven through side of one member into a supporting member) into a connection.
As a result, under wind uplift loads these nails are placed in withdrawal and they have
very low capacities.
Several retrofit techniques are available for these connections
including metal straps (i.e. Simpson Strong-Tie H2.5 and H10 hurricane straps). Using
structural adhesives is another possible approach.
Jones constructed four configurations of retrofitted roof-to-wall connections retrofitted
with a one-part polyurethane adhesive that was applied between the roof and wall
members and the wood blocks (Figure 2.1). The results were compared with failure
loads of non-retrofitted roof-to-wall connections that were fastened only with three 8d
common nails. Table 2.3 provides a summary of the results.
Toe-nailed connections had average uplift capacities of 429 lbs and 343 lbs for SYP and
spruce-pine-fur wood members, respectively. Jones found that when using the adhesive
connections made using SYP had higher uplift capacities (15-40% more) than sprucepine-fur connections. In addition, when more adhesive was used (double pass) the uplift
capacity of the connection increased.
Jones also found that the blocks with more
surface area contact with the wood members produced a higher ultimate uplift capacity
(i.e. Block D uplift capacity was larger than Block E).
ccSPF Test Report
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31 August 2007
(a) Block A – 3.5”x1.5”x1.5”
(b) Block C – 0.75”x1.5”x3.5”
(c) Block D – 3.5”x1.5”x3.5”
(d) Block E – 3.5”x1.5”x1.5” with notch
Figure 2.1 – Roof-to-Wall Connection Retrofit Methods Using Adhesives (from Jones 1998)
Table 2.3 – Summary Results of Using Adhesive as a Retrofit for Roof-to-Wall
Connections (Jones 1998)
Connection
Configuration
Southern Yellow Pine
Mean
% Increase
Sample
(psf)
Over Control
Size
Mean
(psf)
Spruce-Pine-Fir
% Increase
Sample
Over Control
Size
Control (nails
only)
429
N/A
20
343
N/A
20
Block A, single
pass of adhesive
1146
167
20
1000
192
20
Block A, double
pass of adhesive
1891
341
20
1513
341
20
Block C, single
pass of adhesive
700
63
20
N/A
N/A
N/A
Block D, double
pass of adhesive
1691
294
18
832
143
19
Block D, no toenails
3475
710
20
2959
763
20
Block E, toenails
3246
657
19
2365
590
20
ccSPF Test Report
2.2.3
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31 August 2007
Discussion of Roof Truss-to-Wall Plate Retrofits
It appears that the amount of surface area between the block and the wood members
has a significant influence on the ultimate capacities of these connections as well as the
amount of adhesive used. Increasing the wood block surface area increases the uplift
capacity.
In addition, increased the amount of adhesive also increases the uplift
capacity. The amount of adhesive is also dependent on the amount of surface area.
Blocks D and E have the highest uplift capacities due to large amount of surface area
and subsequent larger amounts of adhesive.
Jones noted that in order to achieve a strong adherence between the wood components,
the adhesive must be applied to clean surfaces, free of dust and particles. For a retrofit
application in an older, existing home, this may be difficult (or sometimes impossible) to
achieve. In addition, the ease of placement of these retrofits in the confined space of a
residential attic with typical sloping roofs could also be problematic. In some cases, the
the ceiling or the roof sheathing may have to be removed and replaced in order fully
access and clean the location, which increases the retrofit cost. As a result, the use of
spray-applied adhesives to retrofit the roof truss to wall plate connection may not be
suitable for all residential buildings. However, if the retrofit can be installed without major
work to get access, the additional uplift capacity of this critical connection would be
significant.
ccSPF Test Report
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31 August 2007
3.
EXPERIMENTAL INVESTIGATION of ccSPF RETROFITTED PANELS
3.1
Research Objectives
This research and experimental program consists of three primary phases:
1. Experimental Tests to Determine Wind Uplift Resistance of Wood-Framed
Roofing Panels – Investigate the structural benefits (if any) of ccSPF in improving
uplift resistance of wood-framed residential roofing.
2. Design Wind Load Calculations of ccSPF Adhesive – Illustrate by structural
analysis calculations the potential benefits (if any) of ccSPF adhesive in retrofit
application to improve wind uplift capacity of roof truss-to-wall plate connection.
3. Literature Review
•
Research through existing scientific literature and reports the benefits (if any)
of sealed attics versus vented attic construction for residential construction.
•
Determine based on NAHB racking test data the benefits (if any) of ccSPF
applied to a wood-framed/plywood shear wall to improve the shear capacity
of the wall.
4.
MATERIALS AND METHODS
University of Florida civil engineering undergraduate and graduate students fabricated
the test panels.
Xtreme Foam, Inc., a spray-foam applicator installed the ccSPF.
Xtreme Foam Inc., located in Orlando, FL, is a professional spray foam contractor that
installs InsulStar®, a 2.0 pcf closed-cell spray foam formulated by NCFI Polyurethanes.
24 of 34 panels that were constructed on March 12, 2007 were sprayed with NCFI
InsulStar® ccSPF on March 15, 2007. A second set of 15 panels was fabricated on
June 17, 2007, 10 of which were sprayed with ccSPF on June 29, 2007.
ccSPF Test Report
13
31 August 2007
The testing procedure followed a modified ASTM E330-02 procedure (Standard Test
Method for Structural Performance of Exterior Windows, Doors, Skylights and Curtain
Walls by Uniform Static Air Pressure Difference) (ASTM 2004) where the pressure
application was limited to only one direction (suction within the chamber) and no
deflection readings were measured.
4.1
Test Chamber
We conducted pressure tests using a 6 in. deep steel pressure chamber that measured
4 ft 6 in. by 8 ft 6 in. in plan. The chamber walls are hot-rolled channel members welded
to each other at the corners and continuously welded to a steel sheet base.
One
chamber wall has a 2.0 in. diameter hole that is connected to a vacuum pump by PVC
pipe.
Two 0.5 in. diameter threaded holes are tapped into the chamber wall for
connecting the pressure gauges.
Two vacuum pumps were used for the testing, as detailed in Table 4.1, because the first
pump failed and had to be replaced. The test setup (for Pump #2) is shown in Figure
4.1. The chamber pressure is adjusted using two valves; a) gate valve to adjust intake
of outside air and b) T-valve that closes off the test chamber or the pump, if needed.
Table 4.1 – Pertinent Pump Specifications
Pump
#
Model #
Serial #
Maximum
CFM
Maximum
Pressure
(psf)
Pump Type
Specimens
Tested
1
Graham
LX180/10/43/
M/K1
066847VP
82
760
Liquid Ring
Vacuum
1-3, 6, 12,
14-36
2
US Vacuum
CP15
8817
15
2100
Rotary Vane
Single Stage
5, 7-9, 11,
13, 1A-5C
ccSPF Test Report
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31 August 2007
Pressure Chamber
Pressure Gauges
Pump
Tee Valve
Atmospheric Air
Intake Gate Valve
Figure 4.1 – Suction Chamber Pump and Controls (Pump #2)
4.2
Roof Sheathing Panel Construction
Roof panel specimens were fabricated using ½” by 4 ft by 8 ft oriented strand board
(OSB) sheathing and Southern Yellow Pine (SYP) 2 in. by 4 in. framing members. The
wood was purchased on March 9, 2007, from Contractor’s Supply, Gainesville, FL.
Norbord, an APA-The Engineering Wood Association certified producer, manufactured
the OSB sheathing for Exposure 1, with a 32/16 rating.
K-D Wood Products Inc.
produced the No. 2 grade SYP wood members.
The OSB sheathing was fastened to the wood using two (2) power-driven nail sizes in
two phases. The first 34 panels used 8d ring shank nails, and the second set of 15
panels used 6d common nails (Table 4.2). We installed the nails using a framing gun,
Bostitch Model No. F21PL (Serial No. N88RH-2MCN) powered using compressed air
supplied at 40-45 psi. All OSB panels were installed with the interior surface in contact
with the framing members.
ccSPF Test Report
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31 August 2007
Table 4.2 – Properties of Nails Used in Test Panel Specimens
UF Test Nails
Quantity
NDS, Appendix L
(AF&PA 2001)
6d
8d
Common Common
ESR-1539, Table 1
(2005)
6d
Common
8d Ring
Shank
Shaft Diameter (in.)
0.112
0.123
0.113
0.131
0.120
Head Diameter (in.)
0.28
0.313
0.266
0.281
n/a
Length (in.)
2.0
2.49
2.0
2.5
2.5
8d Ring Shank
The wood members for each test specimen were 5 ft long so that the edges rested on
the vertical sides of the pressure chamber. Unlike in roof construction, the end members
of each panel were not centered along the edge of the sheathing but instead were
placed with their outer face flush with the edge of the sheathing (Figure 4.2). Care was
taken to consistently install nails true and at the 6”/12” fastening schedule, with nails
spaced 6 in. apart on the exterior members and 12 in. apart along the interior wood
members.
Edge nailing
@ 6" o.c.
6"
Interior nailing
@ 12" o.c.
48"
6"
24"
24"
24"
24"
96"
Figure 4.2 – Test Specimen Layout and Nail Schedule
ccSPF Test Report
4.3
16
31 August 2007
ccSPF Application
During the spray-foam installation, the applicator wore a Tyvex suit, full facemask and a
breathing apparatus (Figure 4.3). The ccSPF is made by combining two chemicals (a
two-part process), Part A and Part B. Part A or “A-side” is an isocyanate liquid (diphenyl methane di-isocynate or MDI) manufactured by Huntsman. Part B or the “B-side”
is a proprietary liquid resin blend manufactured by NCFI Polyurethanes under the
InsulStar® brand. The B-side blend consists of polyester and polyether polyols, blowing
agents, surfactants, catalysts, fire retardants, UV inhibitors and dyes. In this formulation,
Honeywell Enovate® HFC245fa blowing agent is used. When properly applied by a
trained applicator, the foam will have the physical properties defined by the InsulStar®
data sheet (see Appendix B). The two chemical products are transported in separate
containers to the site, and they are mixed using a spray foam machine under high
pressure (1000 psi) during application. The test panels were laid out the ground on a
plastic sheet, OSB sheathing side down and the ccSPF was sprayed to the panels.
Figure 4.3 – Application of Second Lift of ccSPF for the Full Foam Specimens
The 49 test specimens were divided into three treatment groups (Table 4.3), as follows:
•
Configuration A (Control): ½ in. by 4 ft x 8 ft OSB/wood roof panel (described
previously, see Section 4.2).
ccSPF Test Report
•
17
31 August 2007
Configuration B (Foam Fillet): Configuration A, plus an application of a ccSPF
fillet adhesive between wood members and roof sheathing, (see Figure 4.4(a)).
•
Configuration C (Full Foam): Configuration A, plus a 3 in. thick full coverage of
ccSPF foam layer between the wood members (see Figure 4.4(b)).
(a)
(b)
Figure 4.4 – ccSPF Application: (a) Configuration B – Foam Fillet, (b) Configuration C – Full
Foam
Table 4.3 – Test Specimen Configurations
Nail Type
Configuration A
Configuration B
Configuration C
Total
8d ring shank
10
13
11
34
6d common
5
5
5
15
Totals
15
18
16
49
The ccSPF fillets in the Configuration B specimens were sprayed along either side of
interior wood members and on one side of the exterior members (see Figure 4.5). In the
two fabrication phases, different application techniques were used to apply the ccSPF
fillets to the panels. In Phase 1, the rectangular nozzle of the spray gun was oriented
ccSPF Test Report
18
31 August 2007
with the long dimension parallel to the wood member axis (Figure 4.5(a)), whereas in
Phase 2, the nozzle was oriented with its long dimension perpendicular to the wood
member (Figure 4.5(b)). As a result, the Phase 2 fillets were wider and taller than the
Phase 1 fillets, with apparently greater contact area between the ccSPF and OSB
sheathing and wood members.
(a)
(b)
Figure 4.5 – ccSPF Foam Fillets: (a) Phase 1 Fillet and (b) Phase 2 Fillet
The full ccSPF coverage (Configuration C) foam was installed in two layers or lifts as, we
are told, is the practice in residential insulation projects.
Application of closed-cell
ccSPF in two lifts is required to achieve optimum foam properties. If sprayed in a single
pass to achieve a 3.0 in. thickness, the exothermic reaction can negatively affect the
foam properties. The first lift was approximately 1.0 to 1.5 in. thick and the second lift
completed the 3 in. thickness.
The ccSPF rapidly hardens once sprayed onto the
panels. About 15 minutes after spraying, the panels were moved into the dry storage
facility and covered with a tarpaulin to allow the ccSPF to cure for a minimum of 7 days.
4.4
Test Procedure
The testing method is modified from ASTM E330-02 (Standard Test Method for
Structural Performance of Exterior Windows, Doors, Skylights and Curtain Walls by
ccSPF Test Report
19
31 August 2007
Uniform Static Air Pressure Difference) procedure (ASTM 2004). Currently no standard
test procedures exist for the determination of wind uplift performance of wood roof
structures. The main modifications to ASTM E330 test procedure were as follows:
•
pressure is applied in one direction only, i.e. suction or reduced pressure within
the test chamber,
•
no deflection readings are taken to record permanent deformation of the panels,
•
the chamber pressure is reduced in 15 psf increments, applied and maintained
for approximately 10 seconds, and
•
the recovery period for stabilization is not used.
Test specimens were placed on the chamber, sheathing side down, with wood members
spanning the short dimension of the chamber. The test specimen was loosely covered
with a single thickness of 2 mil (0.002 in.) thick polyethylene film so that the membrane
did not prevent movement or failure of the specimen. The polyethylene film had extra
folds at the corners and around the wood members, so that when the pressure is applied
there were not fillet caused by tightness or the plastic. The plastic film was adhered to
the test chamber walls using duct tape (3M L155-XW) to create an airtight seal (see
Figure 4.6).
ccSPF Test Report
20
31 August 2007
Figure 4.6 – Suction Chamber with Roof Panel and Plastic
We reduced the chamber pressure by slowly closing the gate valve at the atmospheric
air inlet.
We reduced the chamber pressure in 15 psf increments, which was held
constant for 10 seconds at each pressure increment.
We measured the chamber
pressure using a general-purpose digital pressure gauge (Omega, Model No. DPG8000VAC; Serial No. 1015044), which is calibrated in inches of mercury (inHg) (1 inHg =
70.73 psf). The test proceeded in this manner until panel failure occurred and the peak
pressure recorded. We removed the plastic sheet and at failure and examined the
specimen to determine its failure mode and other pertinent information.
5.
RESULTS AND OBSERVATIONS
5.1
Failure Modes for ccSPF Retrofitted Roof Panels
We observed five distinct failure modes in the roof panels. This section briefly describes
these failure modes. Failure can occur in the sheathing (nail pull-through), in the wood
member (nail withdrawal or wood fracture) or in the ccSPF itself. For this discussion, the
wood member and sheathing are called the adherents and the ccSPF, the adhesive
(Figure 5.1).
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31 August 2007
Figure 5.1 – Adhesive Failure Modes (from http://wikipedia.org)
•
“Cohesive” Fracture – A crack propagates through the adhesive and
portions of the fractured adhesive remain on the adherent material (wood
members and sheathing).
•
“Adhesive” or “Interfacial” Fracture – Debonding occurs between the
adhesive and the adherent.
For ccSPF application to wood, adhesion is
achieved by mechanical means with the adhesive working its way into small
pores in the wood instead of a chemical bond.
•
Mixed Fracture – Failure occurs if the crack propagates as a cohesive
fracture in some places and as an adhesive fracture in other places.
•
Alternating Crack Path – The crack jumps from one interface to the other
due to tensile pre-stresses in the adhesive.
•
Fracture in the Adherent – The adhesive remains intact but the adherent
fractures due to a tougher adhesive than adherent.
ccSPF Test Report
5.2
22
31 August 2007
Phase 1 Testing
Table 5.1 provides wind uplift capacities of the Phase 1 roof panels tested. Appendix A
provides observations about each individual panel.
Table 5.1 – Ultimate Failure Pressures of Test Specimens (Phase 1)
Date of Test
Configuration A
Configuration B
Configuration C
Sample
ID #
Pressure
(psf)
Sample
ID #
Pressure
(psf)
Sample
ID #
Pressure
(psf)
4/5/2007
27
88
26
158
12
252a
4/6/2007
28
70
22
126
2
285
29
100
24
165
3
267a,b
30
46
1
238
6
180a
4/18/2007
4/20/2007
4/21/2007
5/14/2007
19
154
31
85
21
163
32
85
18
192
17
179
16
106
15
106
14
168
20
168
33
71
23
135
34
90
25
170
35
71
36
71
Mean (psf)
77.7
154.9
244.7
Std. Dev. (psf)
15.16
25.65
39.94
COV (%)
19.5%
16.6%
16.3%
a. Failure occurred at a knot in the wood member.
b. Nail heads removed prior to testing.
ccSPF Test Report
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31 August 2007
The initial specimens were tested in a sequential order (a panel from A then B then C) to
ensure uniformity in the test sequence between panel configurations. On April 20, a
Configuration C panel (#13) was tested but vacuum pressure in the chamber would not
exceed a pressure of 212 psf. The panel did not fail at this pressure. The remaining
Configuration A and B panels were tested since their previous maximum failure
pressures were less than 200 psf. The pump worked correctly for these specimens but
a new pump was ordered that could attain a higher pressure and fail the Configuration C
panels. Specimen #13 was retested with the new pump in July and is recorded in
Section 5.3, Table 5.3.
The typical failure mode for Configuration A (control) panels was nail pull–through. The
ring shank nails remained in the wood members and the OSB sheathing failed locally
around them (see Figure 5.2). For Configuration B, the typical failure mode was the
nails pull-through (described above) and a combination of adhesive/cohesive failure of
the ccSPF at the sheathing and wood member interfaces. (see Figure 5.3). In some
cases, very little ccSPF material remained on the wood, indicating an adhesive fracture.
In other cases, a substantial amount of ccSPF remained on the wood, indicative of a
cohesive failure.
We observed three failure modes in the Configuration C (full coverage) panels:
1. The wood member separated from the foam on both sides leaving the foam
attached to the OSB sheathing. The wood member sometimes had little to
no foam residue remaining on the wood member (adhesive fracture) and
sometimes a significant amount of foam residue was evident (cohesive
fracture).
ccSPF Test Report
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31 August 2007
2. The wood member separated on one side from the foam (usually an
interfacial fracture) and on the other side the foam remained attached to the
wood member but separated from the OSB sheathing (cohesive failure).
Whenever the foam separated from the sheathing, approximately 5-10 inches
of foam would remain on the wood member.
3. One of the wood members would split (adherent fracture) always at a knot in
the wood.
Figure 5.2 – Typical Failure Mode of No Foam Specimens using 8d Ringshank Nails
(Nail Heads Pulled Through Sheathing)
Figure 5.3 – Typical Failure Mode of Foam Fillet Specimens (Phase 1)
ccSPF Test Report
5.3
25
31 August 2007
Phase 2 Testing
Phase 2 of the ccSPF panel tests consisted of a second set of specimens tested July
18-19, 2007, using Pump 2. Fifteen specimens were tested in three configurations (A,
B, and C) with five replicates each. The only difference in these specimens from the
earlier specimens was Configuration B – the foam fillet. The fillet for this set of five was
applied perpendicular to the wood member as opposed to parallel with it as was the
case with the first set (see Figure 4.5, Section 4.3). Table 5.2 shows the data from these
testing days.
Table 5.2 – Phase 2 ccSPF Uplift Testing Conducted July 2007
Date of Test
7/18/2007
Configuration A
Configuration Bb
Configuration C
Sample
ID #
Pressure
(psf)
Sample
ID #
Pressure
(psf)
Sample
ID #
Pressure
(psf)
1A
75.0
1B
194.5
1C
282.9a
2A
105.4
2B
178.2
2C
246.1
3A
71.4
3B
178.2
3C
200.2a
7/19/2007
4A
76.4
4B
146.4
4C
253.9
5A
46.7
5B
177.5
5C
268.8
Mean (psf)
75.0
175.0
250.4
Std. Dev. (psf)
20.86
17.50
31.42
COV (%)
27.8%
10.0%
12.5%
a. Failure occurred at a knot in the wood member.
b. Spray nozzle long dimension held perpendicular to wood member longitudinal axis.
The typical failure mode for Configuration A was nail pull out—nails remaining in the
sheathing and pulling out of the wood members. On one test (#5A), one of the end nails
on the center wood member pulled through the sheathing. It was observed that this nail
was closer to the edge of the sheathing than other end nails. During this test (#5A) slow
ccSPF Test Report
26
31 August 2007
nail withdrawal of the sheathing from the wood members was initiated on the side where
the nail had pulled through the sheathing. By the time the test was stopped, the nail on
the opposite end of the wood member had just started to withdraw from the wood
member evidenced by a small visible separation between the wood member and the
sheathing at the end.
There were two typical failure modes of the Configuration B specimens during Phase 2
testing. The first failure mode was separation of the wood member from the foam on
both sides (see Figure 5.4(a)). This separation from the wood member was sometimes
an interfacial fracture evidenced by no foam residue remaining on the wood member.
Sometimes we observed a cohesive failure evidenced by significant foam residue
remaining on the wood member. The other failure mode was separation of the foam
from the sheathing on one side of the wood member (cohesive failure) and separation
from the wood member on the other side (interfacial fracture) (see Figure 5.4(b)).
(a)
(b)
Figure 5.4 – Typical Failure Modes for Configuration B on Phase 2 Testing
ccSPF Test Report
27
31 August 2007
There were four different types of failure modes for the Configuration C specimens.
1. The wood member separated from the foam completely and the foam remained
intact on the sheathing (see Figure 5.5). The separation from the wood member
was sometimes an interfacial fracture evidenced by no foam residue on the wood
member and sometimes a cohesive failure evidenced by significant foam residue
remaining on the wood member (see Figure 5.6(a)).
Sometimes when
separation occurred from the wood member, approximately half of the wood
member (in the 3.5 in. dimension) would have significant foam residue remaining
and the other half would not (mixed failure) (see Figure 5.6(b)). This is most
likely due to one of the lifts of foam achieving a stronger bond with the wood than
the other lift.
2. The foam separated from the sheathing but remained intact on the wood member
(see Figure 5.7). In this failure mode, the failure was always a cohesive failure
since there was always significant foam residue remaining on the sheathing.
When the foam remained on the wood member and separated from the
sheathing, the amount of foam that broke from the sheathing was nearly
constant. Approximately a 7-8 in. width of foam would remain attached to the
wood member (see Figure 5.7).
3. A combination of failure modes 1 and 2 above (see Figure 5.8).
4. The wood member failed by splitting (adherent failure) and occurred twice in the
five specimens. It was observed that the failure occurred at a knot in both of the
wood members (see Figure 5.9).
ccSPF Test Report
28
31 August 2007
Figure 5.5 – First Failure Mode of Configuration C (Phase 2)
(a) Interfacial failure
(b) Mixed failure
(c) Cohesive failure
Figure 5.6 – Foam Residue Levels on Wood Members at Failure for Configuration C (Phase 2)
~8 in.
~8 in.
Figure 5.7 – Second Failure Mode of Configuration C (Phase 2)
ccSPF Test Report
29
31 August 2007
~8 in.
Figure 5.8 – Third Failure Mode of Configuration C (Phase 2)
Knot in wood member
Figure 5.9 – Fourth Failure Mode of Configuration C (Phase 2)
Several (6) Configuration C specimens constructed at the same time as the original
specimens in March 2007, were tested approximately 4 months after the original
specimen tests. These six specimens were tested on July 19-20, 2007. All of these
specimens had a significant bowing effect.
When laid on the suction chamber, the
exterior wood members did not touch the chamber.
The gap between the wood
ccSPF Test Report
30
31 August 2007
members and the chamber was 0.5 to 1.125 in. These six panels were stacked on top
of one another and stored in the dry storage facility during the four months from
construction to testing. Specimen #9 also had one of the wood members skewed at an
angle of approximately 60º from horizontal (see Figure 5.10). All of the nail heads had
already pulled almost all of the way through the OSB sheathing, yet no visible separation
of the foam from the wood was noticeable. The failure of this member was a cohesive
fracture on one side of the member through the foam since a large section of foam
remained attached to the wood member (see Figure 5.11(a)). On the other side of the
wood member, a mixed fracture was evident due to significant amounts of foam
remaining on the member in some places and little to no foam in other places (see
Figure 5.11(b)). After failure, we observed that a significant amount of foam had actually
been between the wood member and the OSB sheathing (see Figure 5.11(a)).
Figure 5.10 – Wood Member Initially Twisted on Test Specimen #9
ccSPF Test Report
31
31 August 2007
(a)
(b)
Figure 5.11 – Failure of Wood Member Initially Twisted on Test Specimen #9
Table 5.3 shows the raw data from these six tests. The failure modes were similar to
those for the Configuration C specimens sprayed with ccSPF on March 15, 2007.
Table 5.3 – Phase 1 Configuration C Specimens Tested July 19-20, 2007
Date of Test
Sample ID #
Pressure (psf)
7/19/2007
7
178.9
5
240.5
11
237.6
13
253.2
9
139.3
8
269.5
7/20/2007
Mean (psf)
219.8
Std. Dev. (psf)
49.9
COV (%)
22.7%
ccSPF Test Report
6.
32
31 August 2007
DATA ANALYSIS
A statistical analysis of the data gathered on the ccSPF specimens was performed,
assuming a 0.05 (α = 0.05) significance level for all tests. Our F-test on the data set
showed that the variances of each treatment (Configurations A, B & C) from Phase 1
and Phase 2 should be the same. In addition, the Student’s t-test on the mean values of
each treatment did not show any significant differences in means between Phase 1 and
Phase 2 results, despite the fact that physically several specimen characteristics had
changed (nail, type, cupping of sheathing in Phase 2, ccSPF color, cure time of ccSPF,
etc.).
For Configuration B, the mean uplift capacities between Phases 1 and 2 were not
significantly different from each other, despite longer cure time in Phase 1 and
application method of fillet (see Figure 4.5, Section 4.3).
Figure 6.1 shows a comparative boxplot of these two different foam fillets. The top and
bottom of the vertical lines in the boxplot represent the spread of the data, and the
lowest and highest horizontal lines in the boxplot represent the first and third quartiles of
the data respectively. The middle horizontal line represents the median. The results
suggest that the larger fillet (constructed June 2007) has a higher overall resistance and
less variability possibly due to the fact that there is a larger area to which the foam
adheres.
ccSPF Test Report
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31 August 2007
200
Panel Failure Pressure (psf)
190
180
170
160
150
140
130
120
110
100
March/April
June/July
Configuration B Construction/Test Dates
Figure 6.1 – Comparative Boxplot of Configuration B Showing the Difference in the Fillet
Application
We found no statistically significant difference in the uplift capacity between the six
Configuration C specimens that cured for 12 weeks versus those that were only cured
for 3 weeks, although the mean uplift capacity of the specimens that had cured longer
was lower by 25 psf. Therefore, we conclude there is no strength degradation due to
aging at the 0.05 confidence level.
Figure 6.2 shows a comparative boxplot of the Configuration C specimens grouped by
both fabrication date and test date for the specimens. The longer cured specimens (the
March/July group) show a larger spread in the data, as well as the lowest failure values
of the three groups.
One of these Configuration C panels actually failed at uplift
pressure of 140 psf or 20 psf lower than mean uplift capacity of the Configuration B
panels. While this is an extreme value, we do not see evidence that this value is an
outlier that should be removed from the analysis. However, the larger spread and low
ccSPF Test Report
34
31 August 2007
failure values suggest that the variability in uplift capacity increases with ccSPF foam
age.
300
275
250
225
200
175
150
125
March/April
June/July
March/July
Configuration C Construction/Test Dates
Figure 6.2 – Boxplot of Configuration C Test Specimen Groupings
We concluded from our t-test analysis that there is insufficient evidence to conclude that
the cure times were a factor in the results and so it was permissible to group together all
data for each treatment (Configurations A, B, and C) tested.
Figure 6.3 shows a comparative boxplot of the combined data sets (ignoring cure time)
for the three configurations. The spread in the data is largest in Configuration C due to
the older specimens.
Table 6.1 gives a summary of our data analysis and the
confidence intervals for each configuration.
ccSPF Test Report
35
31 August 2007
300
250
200
150
100
50
0
A
B
C
Configuration
Figure 6.3 –Boxplots of Failure Pressure of the Combined Data for All Panel Configurations
Table 6.1 – Combined Data Summary Statistics for All Panel Configurations
Configuration
A
B
C
Mean (psf)
76.8
160.5
237.2
Std Dev (psf)
16.55
24.94
41.44
COV (%)
21.6%
15.5%
17.5%
Minimum (psf)
46.0
106.1
139.3
Maximum (psf)
105.4
194.5
285.0
Number of Samples
15
18
16
95% Confidence Level
(psf)
±9.2
±12.4
±22.1
95% Confidence Level as
Percentage of Mean
±11.9%
±7.7%
±9.3%
(Lower Bound) (psf)
67.6
148.1
215.1
(Upper Bound) (psf)
86.0
172.9
259.2
ccSPF Test Report
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31 August 2007
Further, our t-test analyses showed overwhelming evidence that the mean values for the
three configurations differed significantly from each other (with P-values approximately
10-6 to 10-12). In other words, the mean uplift capacity of the Configuration B panels
(foam fillet) was significantly greater than mean value for the Configuration A (no foam)
panels. Similarly, the mean uplift capacity of the Configuration C panels (full foam)
panels indeed is significantly larger than either the Configuration A or B panels tested.
7.
DISCUSSION OF RESULTS
7.1
Nail Pullout
Table 11.2C of the National Design Specification (NDS) (AF&PA 2001) provides
allowable nail withdrawal strengths in wood, which according to McLain (1997) assumes
a factor of safety of 6.0. Ring shank nails have higher withdrawal strengths over the
equivalent size common nail, e.g. the withdrawal strength of an 8d ring shank nail
fastened in southern yellow pine (SYP) is 46 lbs per in. penetration versus a 41 lbs per
in. withdrawal strength for an 8d common nail driven into the same material (using a
specific gravity of 0.55).
It is reported in the technical literature (i.e., McLain (1997)) that ring shank nails can
provide improved withdrawal resistance. This withdrawal strength is highly dependent
on several factors, including geometry of the threads, head size, manufacturing quality,
etc., and there are few standards to ensure uniformity. The NDS does not provide any
values for nail pull-through strengths for any roof sheathing materials. Chui and Craft
(2002) conducted tests that showed nail pull-through strengths need to be accounted for
in the design of fasteners. Using ½ in. thick OSB and Canadian soft plywood (CSP)
ccSPF Test Report
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31 August 2007
their results confirmed that nail head pull-through failures can occur at lower loads than
the nail withdrawal capacities.
In the 2007 UF roof panel wind uplift tests, we observed two failure modes; a) nail
withdrawal from the wood member and b) nail head pull through the OSB roof sheathing.
The first failure mode occurred in configuration panel tests where panels were fastened
with 6d common nails. Nail pull through failures were observed in all other tests (8d ring
shank nails). The mean failure pressures of Configuration A panels fastened with 6d
common and 8d ring shank nails were 75 psf and 78 psf respectively. These failures
values represent two failure modes – nail withdrawal and nail pull-through respectively.
The observed failure mode of the panels fastened with 8d ring shank nails is the nail
pulling through the ½ in. OSB sheathing. There is no statistical difference in the mean
failure loads of the ccSPF retrofitted panels using 8d ring shank or 6d common nails at a
0.05 significance level for the three individual configurations. Figure 7.1 shows a 95%
confidence level interval for the mean failure load of the three configurations tested with
respect to nail failure mode.
ccSPF Test Report
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31 August 2007
300
Pressure (psf)
250
200
150
100
50
0
Pull Through Withdrawal Pull Through Withdrawal Pull Through Withdrawal
Configuration A
Configuration B
Configuration C
Figure 7.1 – Comparing Mean Failure Pressure and “Nail” Failure Mode (Tick marks show the
95% confidence intervals for the mean failure load)
The wind uplift resistance of Configuration A is controlled by the lower withdrawal
capacity of the 6d common nails and not by flexural behavior of the OSB sheathing. The
major factors affecting nail pullout resistance are length of penetration of the fastener
into timber member, the density of wood, fastener diameter, and shank profile. Chui and
Craft (2002) showed that the mean pull through load was the same for ½ in. OSB and
softwood plywood but the variability in the OSB results was much larger.
7.2
7.2.1
ccSPF Foam Retrofit
Configuration B – Foam Fillet
The ccSPF fillet in the Configuration B panels increases the uplift capacity of the roof
panels by 2.1 times the capacity using only nails (Configuration A).
As mentioned
earlier, the foam fillets in the Configuration B panels were applied using two different
techniques (Section 4.3 and Figure 4.5), but the difference in results was not statistically
significant. However, the reader is cautioned that the relatively small sample sizes may
be insufficient to conclusively determine apparent differences.
Further testing is
ccSPF Test Report
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39
31 August 2007
Although the coefficients of variation were almost equal (16.6% versus
15.5%), it appears that ccSPF application is better controlled and more consistent
(visually) when the fillet is applied perpendicularly to the wood member, and a larger
volume of ccSPF is required. We suspect that greater control in application technique
will minimize the variability in the strength of the fillet and hence in uplift capacity.
We also noted that the size of the ccSPF fillet is proportional to the application rate
and/or speed that the spray nozzle moves along the wood member. With slower nozzle
moving speed, more foam is applied in a given area at a given time. Therefore, it should
be no surprise that that the ultimate wind capacity is related to the application technique
and to the skill of each applicator.
7.2.2
Configuration C – Full Foam
Application of a 3 in. thick ccSPF layer (Configuration C) over the panel resulted in a 3.1
time increase in uplift capacity over using just nails (Configuration A). The following
sections describe various points of interest in the failure capacities of these specimens.
7.2.2.1
Wood Member Failure
In five specimens (#3, 6, 12, 1C, and 3C) a wood member failed during testing. Failure
always occurred at a knot in the wood, and all failures (except #3) were at interior wood
members. The average uplift failure load of these five panels is 236.6 psf with a COV of
18.7%. The difference between the two extreme failure loads for these five panels is
more than 100 psf. In fact, three of the five failure loads are greater than 250 psf which
is more than the overall average uplift failure load and the average uplift failure loads of
their respective groups (Phases 1 and 2). The fact that three wood member failure
pressures are greater than the overall uplift failure pressure indicates that the failure of
the wood members does not seem to be an issue with respect to the ultimate failure
ccSPF Test Report
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31 August 2007
loads. In addition, if the five wood member failure loads are removed from the data set,
the overall mean uplift failure loads of the Configuration C panels is 237.4 psf with a
COV of 17.8% compared to 237.2 psf and 17.5% when the panels are included.
Therefore, the wood member failure is not significant with respect to the ultimate
capacity of the ccSPF itself.
7.2.2.2
“No Nail” Uplift Test
Prior to testing Specimen #3, a full foam retrofit panel (Configuration C), we removed the
nail heads using a grinder in order to determine the holding power of the ccSPF itself.
We assumed that the nail without its head provides no resistance to sheathing
withdrawal from the wood members. With this modification, the Specimen #3 failed at
an impressive 267 psf, or approximately 20 psf higher than the mean uplift capacity of
the Configuration C, Phase 1 specimens. The failure mode was not even in the foam
itself, rather one of the exterior wood members failed at a knot. None of the other wood
members separated from the foam or the OSB sheathing.
While this test provided only one data point, which is insufficient to draw any statistical
conclusions, it provides anecdotal evidence of the potential retrofit advantage of the
ccSPF layer. This observation warrants further testing in the future.
7.2.2.3
Aging Considerations
The test specimens tested after curing for four months also exhibited a lower mean uplift
capacity (219.8 psf) than those that cured for only 2 to 3 weeks (244.7 psf and 250.4
psf), even though statistically the mean uplift capacities were not different from each
other. Again, we consider the reduced strength of the older specimens is a cause for
further investigation.
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Strength degradation of structural adhesives with time is a factor that needs to be
accounted for and can be a major issue when using adhesives in structural retrofits.
This phenomenon was discussed in the study (Jones 1998) reported in the literature
review. Until, further studies show otherwise, it is recommended that an “aging” factor of
safety should be used, if ccSPF is to be used as a structural adhesive in long-term (>6
months) applications. The safety factor should be determined through further testing
and/or reliability studies.
7.3
Panel Stiffness
Previous experimenters found that the panel stiffness influences the effectiveness of the
roof sheathing to wood member connection, especially for panels installed using
adhesives (Jones 1998). Excessive panel deflections can cause the adhesive to fail.
The stiffness of a roof panel can be increased in several ways: by increasing the
sheathing thickness, by reducing the spacing between wood members, or by, for
example, adding a structural foam layer, which creates a deeper composite section with
increased section moment. Jones (1998) also cautions that higher construction loads on
the roof after the adhesive is applied can cause the adhesive to crack or fail before uplift
loads are applied to the roof.
We can expect that if we change the roof sheathing material (i.e. using say a 19/32 in.
OSB or plywood instead of ½ in.), the pull-through resistance will also change (increase)
and once the pull-through resistance exceeds nail withdrawal strength a different failure
mode will occur.
ccSPF Test Report
8.
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DESIGN WIND UPLIFT LOADS ACCORDING TO ASCE 7-05
ASCE 7-05 (Minimum Design Loads for Buildings and Other Structures) (ASCE 2006) is
a standard published by the American Society of Civil Engineers provides baseline
structural loads for design of buildings. This standard is adopted and included in many
building codes across the country. Chapter 6 describes the approach to determine wind
design loads.
8.1
Roof Sheathing Wind Uplift Design Loads
The design loads for roof sheathing wind uplift loads are calculated according to the
(Analytical) Method 2 for Components and Cladding (C&C) described in ASCE 7-05
(Section 6.5). The C&C method divides the roof into three different zones with varying
design uplift pressures to account for the variability in suction loads on a roof (see Figure
8.1 for a description of the zones). The wind uplift loads presented in Table 8.1 are
determined for a building with a 30 ft roof span and roof pitch of 4 in 12 (18.4º). The
mean roof height is less than or equal to 30 ft. The upwind exposure is Category B
(suburban), and the design loads are calculated for wind speeds of 130, 150, and 170
mph. The design wind speed is a 3-second gust speed given at 33 ft above ground in
an open terrain. The building is assumed to be partially enclosed.
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Figure 8.1 – Components and Cladding Roof Zones for 7º ≤ Θ ≤ 27º and h ≤ 60 ft (excerpted from
ASCE 2006 Figure 6-11C)
Table 8.1 – ASCE 7-05 Design Wind Pressures for Roof Sheathing Uplift* (psf)
Design Wind
Speed (mph)
Zone 1
(Interior)
Zone 2
(Edge)
Zone 3
(Corner)
10 square foot effective area
130
-37.3
-57.9
-81.1
150
-49.7
-77.1
-108.0
170
-63.8
-99.0
-138.7
130
-36.0
-54.1
-75.9
150
-48.0
-72.0
-101.1
170
-61.6
-92.4
-129.9
130
-34.8
-45.0
-65.6
150
-46.3
-60.0
-87.4
170
-59.4
-77.0
-112.3
*Based on a suburban exposure with a mean roof height of less than 30 ft.
ccSPF Test Report
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Roof-to-Wall Connection Wind Design Uplift Loads
Design wind uplift loads for the roof-to-wall connection are presented in Table 8.2. The
conditions are the same as for the sheathing uplift loads presented in Table 8.1. The
roof-to-wall connection loads, however, are calculated using the Main Wind Force
Resisting System (MWFRS) method in ASCE 7-05. There are effectively two different
loading patterns for this design (see Figure 8.2).
Table 8.2 shows the maximum
resultant design loads.
Transverse Wind Loading
Longitudinal Wind Loading
Figure 8.2 – MWFRS Loading Patterns from ASCE 7-05 (ASCE 2006)
Table 8.2 – Maximum Design Uplift Force for Roof-to-Wall Connections Using MWFRS*
Design Wind Speed
(mph)
Maximum Design Uplift
Force (lbs)
130
1110
150
1480
170
1910
*30-ft roof span, 4:12 roof slope, <30 ft mean roof
height, suburban exposure, partially enclosed
It is immediately obvious comparing these results with Jones (1998) findings that toenailed connections of SYP wood members to walls with ultimate wind uplift capacity of
429 lbs are woefully inadequate (by a factor of 2.6 for SYP in 130 mph zones) to resist
uplift forces.
Generally, the recent building codes have been revised to reflect this
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knowledge, and toe-nailed connections are not allowed to be used in residential
construction. However, there remains a substantial inventory (the majority) of existing
homes that have not been retrofitted and are, therefore, susceptible to roof blow off.
Jones (1998) results showed that spray-applied structural adhesives used in
combination with wood blocking can increase the wind uplift resistance of the roof-to-wall
connections. Since the wind uplift capacities of the ccSPF-retofitted roof panels in these
tests provided a similar increase in uplift capacity as the earlier Jones tests, it is likely
that using ccSPF and wood blocking will also improve the uplift capacity of toe-nailed
roof-to-wall connections. However, to achieve consistent capacities in field application
as observed in the laboratory tests, the devil may be in the details. Issues such as
accessing the joints in confined attic spaces, preparing the wood surfaces and applying
the adhesive must be considered and tested.
9.
•
CONCLUSIONS
Experimental results have shown that applying a ccSPF fillet along wood roof
member can increase the wind uplift capacity of ½” thick OSB roof sheathing panels
by more that two times the uplift capacity of the a control panel fastened using only
nails. The results further also showed that a continuous 3 in. thick ccSPF layer can
increase the wind uplift capacity by as much as three times that of the control roof
panel.
•
The use of SPF as a retrofit technique for roof member-to-wall connections needs
further validation through experimental studies, (listed below in Future Work). An
analytical model of the ccSPF retrofit will enhance its use as a structural adhesive.
However, extensive finite element modeling and testing is needed to make this so.
ccSPF Test Report
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31 August 2007
The performance of aged ccSPF may be a factor in the uplift capacity of the
retrofitted roof panels suggested by the increased variability in wind uplift capacity
results for the “aged” ccSPF-retrofitted panels.
•
Nail selection (6d common versus 8d ring shank) did not appear to have an effect on
the uplift capacity of the ½” thick OSB retrofitted roof panels. The uplift capacity may
be increased by using thicker sheathing panels or selecting a different sheathing
material (i.e. plywood).
10.
FUTURE WORK
The experimental work and results presented in this report about using ccSPF as a roof
retrofit technique in high wind areas provide a good start to understanding the behavior
of retrofitted roof sheathing panels.
However, to fully understand the behavior and
interaction of the SPF with the roof sheathing panels, several other factors should be
considered. While, the potential is good the following lists potential areas for research:
•
Flexural stiffness of roof sheathing – can this affect the uplift capacity of ccSPF
retrofitted panels
•
Compatibility of roof sheathing in contact with ccSPF
•
Aged performance of ccSPF – long-term durability of ccSPF.
•
Analytical design methods for using ccSPF as a structural adhesive
•
Relation of uplift capacity to application technique, pattern or foam volume
•
Trapped water and moisture content variations of sheathing and wood members
– effect of ccSPF in limiting drainage
•
Repairing/removing ccSPF retrofitted panels and roof members
•
Effectiveness of ccSPF as a secondary waterproofing layer in roof construction
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Effect of insulation on underside of roof structure – effect of ccSPF insulation
raising the temperature of asphalt roof shingle
•
Comparison of ultimate capacity of field-applied vs. laboratory-prepared
specimens roof panels
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REFERENCES
AF&PA. (2001). National Design Specification for Wood Construction ANSI/AF&PA
NDS-2001, American Forest and Paper Association, Washington, D.C.
ASCE. (2006). Minimum Design Loads for Buildings and Other Structures (ASCE/SEI
Standard 7-05), American Society of Civil Engineers, Reston, VA.
ASTM. (2004). "E 330-02 Standard Test Method for Structural Performance of Exterior
Windows, Doors, Skylights and Curtain Walls by Uniform Static Air Pressure
Difference." Annual Book of ASTM Standards, American Society for Testing and
Materials.
Briggs, R. S., Lucas, R. G., and Taylor, Z. T. (2002). "Climate Classification for Building
Energy Codes and Standards." Pacific Northwest National Laboratory,
downloaded July 26, 2007, from
http://www.energycodes.gov/implement/pdfs/climate_paper_review_draft_rev.pdf
.
Chui, Y. H., and Craft, S. (2002). "Fastener head pull-through resistance of plywood and
oriented strand board." Canadian Journal of Civil Engineering, 29(3), 384-388.
DOE. (2003). "Map of DOE's Proposed Climate Zones." Downloaded from
www.energycodes.gov/implement/pdfs/color_map_climate_zones_Mar03.pdf
July 26, 2007.
Hendron, R., Farrar-Nagy, S., Anderson, R., Reeves, P., and Hancock, E. (2004).
"Thermal performance of unvented attics in hot-dry climates: Results from
building America." Journal of Solar Energy Engineering, Transactions of the
ASME, 126(2), 732-737.
ICC-ES. (2005). "ESR-1539 - Power-Driven Staples and Nails." ICC Evaluation Service,
Inc., Whittier, CA.
Jones, D. T. (1998). "Retrofit Techniques Using Adhesives to Resist Wind Uplift in Wood
Roof Systems," MS Thesis, Clemson University, Clemson, SC.
Lstiburek, J. W. (2006). "Understanding attic ventilation." ASHRAE Journal, 48(4), 36-45.
McLain, T. E. (1997). "Design axial withdrawal strength from wood. II. Plain-shank
common wire nails." Forest Products Journal, 47(6), 103-109.
NAHB. (1992). "Testing and Adoption of Spray Polyurethane Insulation for Wood Frame
Building Construction Phase 2 -- Wall Panel Performance Testing." Prepared for
The Society of the Plastics Industry, Inc., Polyurethane Foam Contractors
Division by the NAHB Research Center, Upper Marlboro, MD.
ccSPF Test Report
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31 August 2007
NAHB. (1996). "Communication between Bob Dewey of NAHB and Mason Knowles of
The Society of the Plastics Industry, Inc., Spray Polyurethane Foam Division."
National Association of Home Builders.
Rose, W. B. (1995). "Attic construction with sheathing-applied insulation." ASHRAE
Transactions, 101, 789-798.
Rose, W. B., and TenWolde, A. (2002). "Venting of attics and cathedral ceilings."
ASHRAE Journal, 44(10), 26-33.
Rudd, A. (2005). "Field performance of unvented cathedralized (UC) attics in the USA."
Journal of Building Physics, 29(2), 145-169.
TenWolde, A., and Rose, W. B. (1999). "Issues related to venting of attics and cathedral
ceilings." ASHRAE Transactions, 105(pt 1), 851-857.
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LITERATURE REVIEW OF SEALED AND VENTED ATTICS
In traditional residential construction, attics are constructed with openings in the soffits
and near ridges of roof structures. Building codes suggest attic venting for several
reasons. In hot climates, openings allow venting to occur which allows heated air in the
attic to escape to the exterior, thereby maintaining a cooler attic space. On a typical
summer day in Florida, the roof temperatures can exceed 180º F with attic temperatures
well over 100º F. The high temperatures radiate through the ceiling down to the
occupied space resulting in additional heating load on the HVAC systems. Venting also
reduces moisture accumulation on the underside of the roof sheathing is also listed as a
benefit to venting.
In cold climates, attic ventilation is used to maintain a cold roof temperature, thereby
minimizing the ice dam formation on the roof. If snow accumulates on a warm roof
surface the roof temperature can melt a layer of snow adjacent to the roof. This water
(snow-melt) flows down the roof and refreezes on colder roof overhangs (eaves) area.
The refreezed snow-melt forms ice which dams further water flow causing the ice layer
to build up, adding weight and damaging the roofing materials.
Attic venting can be accomplished by (a) natural convection - with openings in soffits and
vents near the ridge and (b) mechanical methods - using exhaust fans to create the
airflow (see Figure A.1(a)). Vented attics have insulation installed on the attic floor to
provide a thermal barrier between the attic and the conditioned air space below. Batt
insulation or “blown” insulation is typically used for this purpose.
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(a) Vented Attic
31 August 2007
(b) Unvented (Sealed) Attic
Figure A.1 – Vented and Unvented (Sealed) Attic Concepts (from Hendron et al. 2004)
Current building codes prescribe a minimum opening size for attic ventilation, called the
ventilation ratio (ratio of vent opening to attic floor area). Typically the codes prescribe
attic ventilation ratios ranging from 1:150 to 1:600 with a ventilation of 1:300 being the
most common (Lstiburek 2006). Tenwolde and Rose (1999) note that although this
ventilation ratio was first proposed by the Federal Housing Administration in 1942, there
is no supporting research basis for this ratio.
Tenwolde and Rose identified three important parameters in regulating moisture
conditions in cold climates: (1) indoor humidity, (2) ceiling air tightness and air pressure,
and (3) attic ventilation.
Although data to support the 1:300 ventilation ratio was
inconclusive, attic ventilation was suggested as a means to regulate moisture conditions
in the attic in cold climates. Because of the increasing complexity and geometry of
residential roof shapes, effective attic ventilation is sometimes improbable in all or part of
the roof (Lstiburek 2006).
A sealed, or unvented, attic, lacks air vents to allow airflow of attic air to the outside (see
Figure A.1(b)). Instead, sealed attics are insulated directly below the roof sheathing and
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at the soffits forming a partially “conditioned” air space. Batt insulation or spray applied
foam insulation can be used for this installation. Table A.1 provides a list of advantages
and disadvantages of sealed attics versus vented attics.
Table A.1 – Global Advantages and Disadvantages of Vented and Unvented Attics
Attic Type
Unvented
(Sealed)
Attic
Vented Attic
Advantages
Disadvantages
1. Energy transfer through the
ductwork is no longer a loss to the
exterior (Rose 1995).
2. Freezing of water pipes in the attic
is eliminated.
3. Air tightness requirements for the
ceiling plane are reduced or
eliminated.
4. Renovation and rewiring involve no
disturbance to the insulation layer.
5. Attic storage is easier since no
insulation is placed on the attic
floor (Lstiburek 2006).
6. Prevent or minimizes water
leakage of water into the building.
7. May prevent roof pressurization
and roof blow off
1. Residential contractors are more
familiar with construction methods
and sequencing.
2. Relatively easy to inspect roof
structure and replace sheathing.
3. Roof structural or moisture damage
easy to inspect.
1. Requires greater technical and
coordination of construction during
installation.
2. More difficult to install insulation on
roof than on top of ceiling.
3. Poor detailing at roof to wall
corners can create thermal bridges.
4. Insulation likely to conceal roof
sheathing damage or moisture.
1. Allows water leakage through
soffits and ridge vents into the
building during high wind events
(Lstiburek 2006).
2. Soffit collapse can lead to internal
pressurization and roof blow off
(2002).
It has been suggested that one possible advantage to using sealed attics in high wind
zones is that sealing the soffits can prevent or reduce high wind flow into the attic which
can cause attic pressurization and roof blow off (Rose 1995). However, experimental
investigations have not yet determined if this is so.
At the same time, it is likely that
similar attic pressurization can occur when a window or door is broken in the home. The
wind design code takes this into consideration through the internal pressure coefficient
for partially enclosed buildings.
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Two issues to consider in the choice of sealed versus vented attics is attic moisture
content and roof shingle temperature. Climate is a major factor in determining the need
for attic venting to control moisture content. The climate of the United States can be
divided into five zones separated by arbitrary boundaries, shown in Figure A.2.
Figure A.2 – Traditional U.S. Climate Zone Regions for Energy-Efficient Building Design (2002)
Briggs et al. (2002) proposed a more detailed climate map, reproduced below Figure A.3
that met several qualifications:
•
Offer consistent climate materials for all compliance methods and code sections;
•
Be technically sound;
•
Map to political boundaries;
•
Provide a long-term climate classification solution;
•
Be generic and neutral; and,
•
Offer a more concise set of climate zones and presentation formats.
Using 30 years of weather observations from 237 U.S. weather stations obtained from
the National Climatic Data Center (NCDC), Briggs et al. (Briggs et al. 2002; DOE 2003)
developed a new climate zone map. Three major climate subdivisions are shown on the
map: (a) Moist, (b) Dry, and (c) Marine. Table A.2 briefly describes the different zones
shown in Figure A.3.
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Figure A.3 – Map of DOE’s Proposed Climate Zones (Briggs et al. 2002)
Table A.2 – Climate Zone Definitions (2002)
Zone No.
Climate Zone Name and
Type
Representative U.S.
City
1A
Very Hot, Humid
Miami, FL
1B*
Very Hot, Dry
--
2A
Hot, Humid
Gainesville, FL
2B
Hot, Dry
Phoenix, AZ
3A
Warm, Humid
Memphis, TN
3B
Warm, Dry
El Paso, TX
3C
Warm, Marine
San Francisco, CA
4A
Mixed, Humid
Baltimore, MD
4B
Mixed, Dry
Albuquerque, NM
4C
Mixed, Marine
Salem, OR
5A
Cool, Humid
Chicago, IL
5B
Cool, Dry
Boise, ID
5C*
Cool, Marine
--
6A
Cold, Humid
Burlington, VT
6B
Cold, Dry
Helena, MT
7
Very Cold
Duluth, MN
8
Sub-artic
Fairbanks, AK
*Defined but not used in the United States
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The testing of moisture control and attic ventilation was performed in cold climates, and
Rose and Tenwolde (2002) state that “no scientific claims have ever been made that
attic ventilation is needed for moisture control in hot, humid climates.” In fact, in hot,
humid climates attic venting tends to increase moisture levels in attics (Rose and
TenWolde 2002; TenWolde and Rose 1999).
Rudd (2005) observed several different unvented houses in three cities in a hot, humid
environment (Houston, TX – one house, Jacksonville, FL – one house, and Lake City,
FL – two houses). He found that the roofs with sealed attics and netted and blown-in
cellulose insulation and fiberglass insulation under the roof sheathing needed a vaporretarding barrier installed directly under the asphalt composition shingles. This was
necessary to prevent the sheathing from absorbing moisture that condensed on the roof
shingles overnight.
Rudd observed that houses without the vapor barrier had higher moisture levels in the
attic during the day and this placed a higher moisture load on the space cooling system
than is necessary even though overnight the moisture content was equalized with the
living space.
Attics with open-cell foam insulation also showed lower resistance to
condensation during winter months if the outside air fell below the dew point temperature
of the attic air due to the higher airflow resistance of open-cell foam.
Rudd also
observed that in two Lake City, FL, homes that had sealed attics (open-cell, low-density
foam insulation sprayed to the underside of the roof sheathing) the roof sheathing
showed no signs of moisture condensation, mold, discoloration, delamination, or
deterioration. Wood moisture content ranged from 7-16% for the roof sheathing with the
median at 10% and 7-12% for the roof-framing members with the median about 9%,
which fall within normal moisture content ranges for wood construction materials.
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Researchers (Lstiburek 2006; Rose and TenWolde 2002) have found that shingle
temperatures installed over unvented attics tend to be about 2-3º F higher than roof
shingles installed over vented attics. This temperature increase is small as compared to
other factors that affect shingle temperature, such as geographic location, the direction a
roof surface faces, and shingle color, which can increase shingle temperature up to 54º
F higher depending on the color.
Observations by Rudd (2005) of attics in hot, humid climates show that summertime
average daily temperatures of roofing materials is nearly equal whether installed over
vented or unvented attics, however the short-term peak temperatures are increased by
about 7º F for roofing installed over unvented attics. TenWolde and Rose (1999) also
believe, due to the lack of strong evidence, that attic ventilation has insignificant to no
relation to shingle durability due to temperature and moisture concerns.
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APPENDIX A – DAILY TESTING REPORTS FROM SPF ROOF PANEL TESTING
Failure Load
inHg
psi
psf
Panel
ID #
Config.*
Test
Date
27
A
4/5
1.24
0.610
88
26
B
4/5
2.24
1.100
158
12
C
4/5
3.57
1.753
252
28
A
4/6
0.98
0.483
70
22
B
4/6
2.12
1.041
150
2
C
4/6
4.03
1.979
285
29
A
4/6
1.42
0.697
100
Comments/Failure Modes
• Nail heads pulled through OSB at the
center wood member.
• Initial failure at one of the first interior wood
members by separation of wood member
from foam on both sides.
• Foam remained attached to OSB.
• Nail heads pulled through OSB.
• Plastic tore at 2.39 inHg (169 psf) so
procedure stopped and tear fixed then test
was restarted.
• Failure at one of the first interior wood
members by splitting at a knot in the wood
member.
• This caused the other two interior wood
members to fail by separation of the wood
members from the foam on each side while
the foam remained attached to the OSB.
• Nail heads pulled through the OSB at the
center wood member.
• Evidence of separation of foam from both
the wood member and sheathing near end
of one of the first interior wood members.
• Failure at the same interior wood member
by separation of wood member from foam
on one side and separation of foam from
sheathing on the other end where it was
observed before testing leaving a
significant amount of foam attached to the
wood member.
• Failure first occurred at the center wood
member by separation of wood member
from foam on one side and separation of
the foam from the OSB on the other side
leaving a significant amount of foam
attached to the wood member.
• One of the adjacent trusses failed in a
similar manner as the center truss.
• On one of the first interior wood members,
the three center nail heads pulled through
the OSB while the two nails near the ends
of the wood member remained so the OSB
was still attached to the wood member.
ccSPF Test Report
Panel
ID #
Config.*
58
Test
Date
Failure Load
inHg
psi
psf
24
B
4/6
2.33
1.041
158
3
C
4/6
3.78
1.857
267
30
A
4/18
0.65
0.319
46
1
C
4/18
3.37
1.655
238
19
B
4/20
2.18
1.071
154
6
C
4/20
2.55
1.252
180
13
C
4/20
N/A
N/A
N/A
31
A
4/21
1.2
0.589
85
32
A
4/21
1.2
0.589
85
31 August 2007
• Observed initial separation of foam from
exterior wood member at 1.91 inHg (135
psf).
• Failure occurred at center wood member
by separation of foam from wood member.
• Nail heads pulled through sheathing.
• Nail heads were removed from all nails
using a grinding wheel.
• One of the exterior wood members split at
a knot.
• The adjacent interior wood member then
failed by separating from the foam on both
sides.
• On one of the first interior wood members,
the three center nail heads pulled through
the OSB while the two nails near the ends
of the wood member remained so the OSB
was still attached to the wood member.
• The center wood member separated from
the foam on one side and the foam
separated from the OSB on the other side.
• An adjacent wood member then failed in
the same manner.
• Nail heads pulled through the OSB.
• Center truss separated from the foam on
both sides.
• An adjacent wood member then failed in
the same manner.
• Nail heads pulled through the OSB.
• Center wood member split at a knot.
• An adjacent wood member then failed by
separating from the foam on one side and
the foam separating from the sheathing on
the other side.
• Panel was tested but pump reached
capacity at 3.00 inHg (212 psf) without
panel failure.
• Retested at a later date (7/20) when a new
pump was ordered.
• Three interior nail heads pulled through
OSB on center wood member.
• Similar nail head pull through on both
adjacent wood members.
• Nail heads pulled through OSB on center
wood member.
• An adjacent wood member then pulled
nails through OSB.
ccSPF Test Report
Panel
ID #
Config.*
59
Test
Date
Failure Load
inHg
psi
psf
21
B
4/21
2.3
1.130
163
18
B
4/21
2.72
1.336
192
17
B
4/21
2.53
1.243
179
16
B
4/21
1.5
0.737
106
15
B
4/21
1.5
0.737
106
14
B
4/21
2.38
1.169
168
20
B
4/21
2.37
1.164
168
33
A
5/14
1.01
0.496
71
34
A
5/14
1.27
0.624
90
31 August 2007
• Center wood member separated on both
sides from the foam which remained in
place on the OSB.
• The two adjacent wood members then
failed in a similar manner.
• One of the first interior wood members
separated on both sides from the foam
which remained in place on the OSB.
• The other two interior wood members then
• Observed initial separation of foam from
the OSB on one of the first interior wood
members prior to testing.
• Failure occurred first at center wood
member by separation of the foam from
both sides of the wood member.
• The two adjacent wood members then
• Nail heads pulled through OSB on one of
the first interior wood members.
• The center wood member then failed in a
similar manner.
ccSPF Test Report
Panel
ID #
Config.*
60
Test
Date
Failure Load
inHg
psi
psf
36
A
5/14
1
0.491
71
23
B
5/14
1.91
0.938
135
25
B
5/14
2.4
1.179
170
1A
A
7/18
1.06
0.521
75
1B
B
7/18
2.75
1.351
194
1C
C
7/18
4
1.965
283
2A
A
7/18
1.49
0.732
105
2B
B
7/18
2.52
1.238
178
31 August 2007
• Only the three center nails pulled through
the wood member.
similar manner.
similar manner.
• Nails pulled out of the center and one of
the adjacent wood members. The nails
remained in the OSB.
• The center and one of the adjacent wood
members separated from the foam on both
sides of the wood member.
• Nails pulled out of the wood members and
• Center wood member split at a knot about
1 ft from one end.
• The other two interior wood members
separated from the foam.
• Nails pulled out of the wood members that
failed and remained in the OSB.
• Nails pulled out of all three interior wood
members and remained in the OSB.
failed by separating from the foam on both
sides of the member, but the member was
still attached to the panel.
• Nails pulled out of this member as well and
ccSPF Test Report
Panel
ID #
Config.*
61
Test
Date
Failure Load
inHg
psi
psf
2C
C
7/18
3.48
1.709
246
3A
A
7/18
1.01
0.496
71
3B
B
7/18
2.52
1.238
178
3C
C
7/19
2.83
1.390
200
31 August 2007
• The center wood member and one of the
adjacent members separated from the
foam on one side and the foam separated
from the OSB on the other side (~7-8 in.).
• On the other interior wood member, the
foam separated from the OSB (~7-8 in.) on
both sides of the member.
• Nails pulled out of all three wood members
as well and remained in the OSB except for
one nail each on both the center and one
adjacent wood member at the end of the
member which pulled through the OSB.
• Nails pulled out of the center and one
adjacent wood member and remained in
the OSB.
adjacent wood members separated from
the foam on one side and on the other side
there the foam separated from the OSB
and remained attached to the wood
members.
• There was little to no residual foam left on
the wood members where the foam
separated from the members.
• Nails pulled out of these members and
• This specimen had a little thinner
application of the full foam than the other
specimens (approximately 2.5-3.0 in.).
the foam on one side with significant foam
residue remaining on the member (upper
half of the 3.5 in. dimension). On the other
side, the foam separated from the OSB
(~6-8 in.).
• One of the other interior wood members
split at a knot approximately 12 in. from
one end.
• The other interior wood member separated
on one side some from the foam at one
end but not completely along the whole
length of the member.
A crack was
observed that cut diagonally across the
foam out to about 10 in. from the wood
member. On the other side there was
noticeable separation of the foam from the
OSB but the board remained firmly
attached at the other end to the panel.
• Nails pulled out of the two members that
failed completely and remained in the OSB.
ccSPF Test Report
62
Panel
ID #
Config.*
Test
Date
Failure Load
inHg
psi
psf
4A
A
7/19
1.08
0.530
76
4B
B
7/19
2.07
1.017
146
4C
C
7/19
3.59
1.763
254
5A
A
7/19
0.66
0.324
47
31 August 2007
• Nails pulled out of the three interior wood
members and remained in the OSB.
the foam on one side completely with little
to no foam residue remaining on the
member. On the other side, 2/3 of the
foam separated from both the wood
member and the OSB and on the other 1/3
of the member, the foam separated from
only the OSB and remained attached to the
member.
• On one of the adjacent wood members
separated from the foam on one side
completely with little to no foam residue
remaining on the member. On the other
side, 1/3 of the foam separated from both
the wood member and the OSB and on the
other 2/3 of the member, the foam
separated from only the OSB and
remained attached to the member.
• The other interior wood member showed
signs of foam separation from the OSB but
the member was still firmly attached to the
panel.
• The center and one adjacent wood
member separated from the foam on one
side and approximately 6 in. of foam was
separated from the OSB on the other side
but the boards remained attached to the
panel.
• Nails pulled out of these members and
• Nails pulled out slowly from the center and
one adjacent wood member.
• On the center wood member, one of the
end nails actually pulled through the OSB.
ccSPF Test Report
Panel
ID #
Config.*
63
Test
Date
Failure Load
inHg
psi
psf
5B
B
7/19
2.51
1.233
178
5C
C
7/19
3.8
1.866
269
7
C
7/19
2.53
1.243
179
31 August 2007
the foam on one side with little to no foam
residue remaining on the member. On the
other side, half of the wood member
separated from the foam and on the other
half the foam separated from both the
wood member and the OSB (~6 in.).
• On one of the adjacent wood members, the
foam separated from the wood member on
both sides except ~6 in. at one end on one
side where the foam separated from the
OSB. There was little to no foam residue
left on the wood member.
• On the other interior wood member, one
side completely separated from the foam
and on the other side the foam separated
from the OSB along most of the length
even though the board remained attached
to the panel.
the
foam
on
both
sides
along
approximately 2/3 of the length and the
foam separated from the OSB and
remained attached to the wood member
along the other 1/3 of the length. Little to
no foam remained on the wood member on
the bottom half of the 3.5 in. dimension and
significant residue remained on the upper
half.
• On both of the other interior wood
members, the foam separated from the
members on one side and from the OSB
on the other side (~7-8 in.). On one of the
members, there was significant foam
residue remaining on about half of its
length and on the other little to no foam
residue remained along the entire length of
the member.
• One of the first interior wood members had
foam remaining on both sides of the
member but separated from the OSB on
both sides.
• The nail heads pulled through the OSB.
ccSPF Test Report
Panel
ID #
Config.*
64
Test
Date
Failure Load
inHg
psi
psf
5
C
7/19
3.4
1.670
240
11
C
7/20
3.36
1.650
238
13
C
7/20
3.58
1.758
253
31 August 2007
• A significant bow in the panel was
observed (deflections at the ends were
0.75-0.875 in.).
adjacent members separated from the
foam on one side and 7-8 in. of foam
and remained intact on the member.
• The wood member did not have much if
any foam residue left on the wood member
itself on the one side that the foam
separated.
observed (deflections at the ends were 0.50.75 in.).
the foam on one side (through observation
of a large crack in the foam along the wood
member) and a noticeable separation from
the OSB on the other side of the wood
member (~5”) even though the board did
not separate from the panel.
• One of the adjacent wood members
exhibited the same failures as the center
member except the separation from the
OSB was about 10 in.
• Retested from earlier date (4/20) after new
pump ordered.
0.875-1.06 in.).
• The center and one of the adjacent wood
members separated from the foam on one
side with varying amounts of foam residue
remaining although the top half of the 3.5
in. dimension seemed to consistently have
more.
On the other side, the foam
separated from the OSB (~5 in. except
near one end which was about 10 in.).
• The other interior wood member split at a
knot about 16 in. from one end.
ccSPF Test Report
Panel
ID #
Config.*
65
Test
Date
Failure Load
inHg
psi
psf
9
C
7/20
1.97
0.968
139
8
C
7/20
3.81
1.871
269
31 August 2007
0.75-1.125 in.).
• One of the first interior trusses was twisted
significantly (approximately at a 60º angle
from horizontal) prior to testing. All of the
nail heads had pulled though most of the
OSB as well. There appeared to be no
separation of the foam from the wood
member, though, prior to testing. This
wood member separated from the foam on
one side but the other side had a
significant amount of foam still attached
even though the foam did not separate
from the OSB.
• The center and other interior wood
members separated from the foam on one
side and the foam separated from the OSB
on the other side of the wood member (~46 in.).
0.75-0.875 in.).
• The center wood member and one
adjacent wood member separated from the
foam on one side with little to no foam
residue remaining especially on the bottom
half of the 3.5 in. dimension. The foam
(~4-6 in. on the center member and ~5-12
in. on the other member).
• The other interior wood member split at a
knot approximately 12 in. from one end.
ccSPF Test Report
66
31 August 2007
APPENDIX B – INSULSTAR® BROCHURE
The following brochure is for the spray-applied polyurethane foam (ccSPF) product used
in the experimental testing outlined in this report. The Insulstar® foam is manufactured
by NCFI (see Section 4.3).
ccSPF Test Report
67
31 August 2007
ccSPF Test Report
68
31 August 2007
ccSPF Test Report
69
31 August 2007
ccSPF Test Report
70
31 August 2007

- Spray Polyurethane Foam Insulation South Africa

Transcription

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