Knee-Wall Presentation

1/5/2012
Treating Knee-Walls and Attic Hatches
Adrian Scott, WECC, Madison, WI
Nate Byrnes, UMDWTC, North Dartmouth, MA
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1/5/2012
O
Overview
i
•
•
•
•
•
•
•
What is a Knee-Wall Anyway?
Gaining Access
Working in the Kneewall
Insulation Choices
Effectiveness of Insulation
Attic Hatches and Stairways
Chimney Chases and Attic Dams
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Wh t iis a K
What
Knee-Wall?
W ll?
• A short bearing wall intended to support roof rafters in
balloon framed homes.
• In
I platform
l tf
construction
t ti it can bbe a bbearing
i wallll or usedd to
t
eliminate unusable space in a room
• This creates a space that can be used for storage that can
be heated or unheated.
• If it is unheated this space becomes a outer joist beam attic
and a buffer zone even if used for storage
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K
Knee-Wall
W ll Diagram
Di
Diagram excerpted from the Wisconsin Weatherization Field Guide
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C
Common
Northeastern
N th t “C
“Cape”” St
Style
l H
House
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U h t dO
Unheated
Outer
t JJoist
i tB
Beam Atti
Attic Knee
K
Wall
W ll
• Defines the pressure and thermal boundary
• The knee-wall itself must be air sealed and insulated
• Any access through the wall must be insulated and sealed
and mechanically fastened
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G i i O
Gaining
Outer
t JJoist
i tB
Beam Atti
Attic A
Access
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Attic Access
Atti
A
- Scuttles
S ttl andd Doors
D
Scuttles
S ttl or Hatch
H t h
(Horizontal Access )
• Need to be insulated to the same r-value as surrounding
insulation or maximum structurallyy allowable
• Must have a insulation dam surrounding scuttle
• Made of material that allows repeated access (plywood
lumber)
• Must have air seal and be mechanical fastened
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Atti Scuttles
Attic
S ttl or Hatch
H t h (Vertical
(V ti l Access
A
)
• Need to be insulated to the same R-value as surrounding
insulation or maximum structurally allowable
• Must have air seal and be mechanical fastened
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V ti l Attic
Vertical
Atti A
Access
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V ti l Attic
Vertical
Atti A
Access
Using R-11 duct wrap
Using R-11 unfaced fiberglass batt
and house wrap
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Access Doors
• Insulated to the R-value of
the surrounding insulation
• Must be weather stripped
pp
and mechanically fastened
• May use a plug if access
does not allow you to
attaché insulation to door
Using R10 Polystyrene foam board
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Alt
Alternative
ti M
Methods
th d off Atti
Attic A
Access
• Using gable and roof vents
• Removing siding
• Creating access thru knee wall
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Th
Through
h a Gable
G bl Vent
V t or R
Rooff V
Ventt
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C tti Th
Cutting
Throughh K
Knee-Wall
W ll
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R
Remove
Siding
Sidi andd Replace
R l
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D li with
Dealing
ith Knee
K
walls
ll
•
•
•
•
Need to be air sealed first
Fiberglass needs to be covered on all six sides
Dense pack insulation works the best
Don’t forget get the critical junctures
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Eff ti
Effectiveness
off IInsulation
l ti iis R
Reduced
d d bby:
•
•
•
•
•
Gaps
Voids
Compressions
Air flow within the insulation
Misalignment
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Effectiveness of Insulation
• Insulation installed with approximately 5% voids and
gaps will result in approximately a 17% reduction in
effectiveness.
ff
• R19 insulation compressed into a 3 1/2 inch cavity will
have an R-value of approximately R16.
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Eff ti
Effectiveness
off IInsulation
l ti (cont.)
( t)
• Continuous exterior (foam) insulation is more beneficial
than cavity insulation (approximately 25% of wall area is
framing about R 4 – 7).
7)
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A Blank
Bl k Sl
Slate
t
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Insulating and Sealing Knee Walls Using
Polyisocyanurate Board
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Insulatingg and Sealingg Knee Walls
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I l ti with
Insulating
ith TTwo-Part
P tF
Foam
Photo courtesy of the US Department of Energy
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D ill andd Bl
Drill
Blow
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I
Increase
Effectiveness
Eff ti
bby:
• Prevent wind washing of attic insulation by installing
blocking and baffles at perimeter.
• Cover batts on all six sides to prevent air movement.
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Seal Before Batt Insulation
• If installing fiberglass, seal
seams and around outlets at
the pressure boundary
• In this case, seal from the attic
side where no one will see
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U i Insulweb
Using
I l b andd Blown
Bl
C
Cellulose
ll l
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T
Tyvec
andd D
Dense Pack
P k Cellulose
C ll l
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B ilt i B
Built-in
Bookk Sh
Shelves
l
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Unheated Finished Attic
Open Unfloored
Floored
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Knee Wall Attics
MAIN ATTIC
Open Wall Cavities
KNEEWALL ATTIC
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B k
Background
d
From small straw cans to
truck-mounted rigs and
everything in between
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Ad t
Advantages
•
•
•
•
•
•
High R-value per inch
Compatible with existing fiber insulation
Closed cell structure
Disposable kits in a variety of sizes
Expands
R d
Reduces
energy lloss (i(insulates
l t andd airi seals)
l )
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Di d t
Disadvantages
High cost
Ultraviolet light destroys exposed foam
Storage temperature and application restrictions
Local building code regulations (manufacturer
specifications)
• Health hazards (more on this later)
•
•
•
•
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Closed Cell vs.
vs Open Cell
Closed
•
•
•
•
•
•
Higher R-value per inch
Lower moisture permeability
Higher strength and rigidity
More dense
Higher resistance to air flow
Higher cost per R
Open
•
•
•
•
•
•
Lower R-value per inch
Higher moisture permeability
Lower strength and rigidity
Less dense
Lower resistance to air flow
Lower cost per R
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G
General
l Guidelines
G id li
GAPS ≤ 1/4”
Caulk
The Daily Green
GAPS 1/4” – 3”
Spray foam
OTHER
Foam board,
fiberglass in
plastic bags, etc.
Energy Blast Services
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Di d t
Disadvantages
High cost
Ultraviolet light destroys exposed foam
Storage temperature and application restrictions
Local building code regulations (manufacturer
specifications)
• Health hazards (more on this later)
•
•
•
•
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C
Coverage:
One-part
O
t
• Lineal foot
• Number of feet in a straight line
• One-part
One part foam yield is described in lineal feet
• Example: a 24 ounce can of one-part foam may yield 2200
lineal feet at a ¼ inch bead
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High Temperature Issues
Recessed Light Fixtures
Flues
High-temp caulk
IC Rated Fixture
Maintain appropriate clearances
Non-IC Rated Fixture
Photos courtesy of the US Department of Energy
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Ab t S
About
Spray F
Foam
Spray foam insulation is modified polyurethane foam plastic.
•It is used primarily to seal air leaks in building cavities.
•It may be used to insulate vertical or horizontal surfaces.
surfaces
- Knee walls
- Under floors
- Attic hatches
•Due to fire rating,
rating it may not be left exposed in living areas.
areas
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1/5/2012
P d tO
Product
Options
ti
Available in a variety of shapes, sizes and uses
Froth-Pak, Dow Chemicals
http://building.dow.com/na/en/products/sealants/index.htm
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1/5/2012
Product Options
Available in one-part and two-part formulas
One-part:
Two-part:
•
Spray cans
(e.g., Great Stuff)
•
Portable 2-tank kits –
small, medium, and large
•
Spray guns with
screw-on cans
•
Truck-mounted rigs
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SPRAY FOAM INSULATION
O Partt Spra
OneS y Foam Opti
O tions
Non-adjustable
canisters
Adjustable
Gun-type applicators
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One-Part
One
Part Foam: Advantages and Disadvantages
ADVANTAGES
DISADVANTAGES
•
Quick and easy for small
holes and gaps.
gaps
•
Set up time can exceed
2 hours.
•
Creates an effective seal
for small holes.
•
Not cost effective for
large jobs.
•
Lightweight and portable.
•
Freshly gunned product
will not adhere on
overhead surfaces.
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Two Part Foam Kits
Two-Part
Photo courtesy of Dow Chemicals
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SPRAY FOAM INSULATION
Two Part Foam: Advantages and Disadvantages
Two-Part
ADVANTAGES
DISADVANTAGES
•
More thorough sealing.
•
•
Significantly reduced labor
costs.
Expensive; hazardous
materials shipping
pp g fees.
•
Easy to waste material.
•
Motivates workers.
•
•
Good adhesion.
•
Quick cure time.
Restrictive dispensing
temperatures.
((around
around 75˚
75 F recommended
recommended))
•
Specialized and expensive
personal protection
equipment required.
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Safe Use of Spray Foam Insulation
Material Safety Data Sheet (MSDS)
• Must have at job site whenever spray foam is used.
• Follow precautions for safe handling and use.
• Lists emergency and first aid procedures.
Use in well-ventilated area
• Provide ventilation fans to exhaust fumes and ensure
cross-flow of fresh air.
W personall protection
Wear
t ti equipment
i
t
• Coveralls, rubber/latex gloves, eye protection.
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Atti A
Attic
Access S
Scuttles
ttl or Hatch
H t h (Horizontal
(H i t l Access)
A
)
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Atti A
Attic
Access S
Scuttles
ttl or Hatch
H t h (Horizontal
(H i t l Access)
A
)
• Must have insulation damming
• Sturdy enough to allow repeated entry
•
•
•
•
Mustt be
M
b to
t the
th finished
fi i h d R-value
R l off th
the surrounding
di attic
tti
Must be weather-stripped
Must be mechanical fastened
Same level as pressure boundary
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I l ti D
Insulation
Dam
Material strong enough to
handle repeat entry
Seal
Mechanical Fawners
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Diff
Different
tW
Way to
t W
Weather
th St
Strip
i
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I l ti Horizontal
Insulating
H i t lA
Access
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F
Foam
Board
B d
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O C
One
Correctt W
Way with
ith Fib
Fiberglass
l andd H
House W
Wrap
• Insulation to correct R-value.
• Is not compressed and is
covered on all six sides.
• Fits into insulation dam
touching sides – allowing
minimal air movement.
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Thi D
This
Does Not
N tW
Workk
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Diff
Different
t St
Styles
l off H
Horizontal
i t lA
Access
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Atti Stairs
Attic
St i
•
•
•
•
Are large and heavy
May need to be adapted to home owner
Must be to same R-value as surrounding insulation
Hole may be reduced to attic access if no storage is
provided
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Atti St
Attic
Stairs
i (Coffin
(C ffi Dam)
D )
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A th Option
Another
O ti
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I l ti Access
Insulating
A
Dos
D andd D
Don'ts
't
• Do
• Should be as close to the attic pressure boundary as
possible
• Should be the same R-value as surrounding attic insulation
• Fills insulation damming as much as possible still allowing
for easy removal
• Fiberglass should touch sides of insulation damming
• Foam board should be within ¼ inch of the sides
• Insulation should be covered on six sides
• Insure insulation is anchored for repeated removal
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1/5/2012
I l ti Access
Insulating
A
Dos
D andd D
Don'ts
't
• Don’ts
• Do not compress fiberglass
• Do
D nott allow
ll airi movementt aroundd or through
th
h insulation
i l ti
• Don’t make it so tight that it can’t be removed
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Chi
Chimney
Dams
D
•
•
•
•
Must be non-combustible
3 inch clearance
Need to air seal first
Higher than surrounding insulation
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Treating the Chimney Chase
Photos courtesy of The US Department of Energy
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HOUSE AS A SYSTEM
Chi
Chimney
Chases
Ch
Photo courtesy of The US Department of Energy
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S l d Chimney
Sealed
Chi
Bypass
B
Sealed chimney
bypass…
with insulation
barrier.
Photos courtesy of The US Department of
Energy
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1/5/2012
A Alternative
An
Alt
ti Method
M th d
Detail for Sealing Thermal
Bypass Around Chimney
Photos courtesy of The US Department of Energy
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M t lD
Metal
Damming
i
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D
Damming
i Round
R d Flue
Fl
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PRESSURE & THERMAL BOUNDARIES
Photo courtesy of NRCERT
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P
Proper
Vents
V t a.k.a.
k Eve
E Ch
Chutes
t
• Needs to be in to eave
• Needs insulation stop
• Ned s to be mechanical fasten
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E
Eave
Sh
Shute
t
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N
Now
W
We C
Can St
Startt IInsulating
l ti
• Blower-door/IR scan guided to find condition of
key junctures, interstitial spaces, hidden interior
holes
• Devise a plan; some drilling may be visible and
done from the interior
• Identify thermal boundaries
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D li with
Dealing
ith C
Critical
iti l JJunctures
t
• It is important to seal the critical junketers before insulation
the knee-wall or the outer joist beam attic
• Must identify what the pressure and thermal boundaries
are
• Insulating only slows down heat loss air sealing stops heat
loss
• The golden rule is seal first than insulate
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1/5/2012
The M
Main
i C
Critical
iti l JJunctures
t
A
Are
•
•
•
•
•
The floor line
The ends of slants
The knee wall to floor connection
The ends of knee wall to exterior wall
The outside wall to outer joist beam attic floor
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1/5/2012
S li the
Sealing
th Critical
C iti l Junctures
J t
andd P
Penetrations
t ti
M
Methods
th d
•
•
•
•
•
One Part Foam
Two Part Foam
Bag Method
Foam Board
Dense pack cellulose
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1/5/2012
Th Critical
The
C iti l Floor
Fl Li
Line
Open floor joist cavities
A good candidate for the BAG method
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1/5/2012
D li with
Dealing
ith th
the floor
fl liline
• Bag Method
• Onion bags
• Insulwepp
I l
B
Bags
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Fi Crucial
Five
C i l Junctures
J t
off the
th St
Story andd a H
Halflf
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ROOF
AIR LEAKAGE OCCURS AT
THE OPEN JOIST AREA
WOOD
FRAMED
WALL WITH
CAVITY
INSULATION
FLOOR JOISTS EXTEND
PAST WALL TO FORM
PORCH CEILING
Dense PackCellulose
Air-Seal While Insulating
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S l Penetrations
Seal
P t ti
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T
Tops
off Exterior
E t i Walls
W ll
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1/5/2012
T
Tops
off Exterior
E t i Walls
W ll
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Wh t are you going
What
i to
t do
d
Built in
Dresser
Access
Floor
pockets
empty
91