3_ Kehl wooden beam end CESBP 2013

Faculty of architecture, Institute of Building Climatology
Hygrothermal Behaviour of Wooden Beam Ends
literature review, decay model and convection at the beam end
Dipl.-Ing.(FH) Daniel Kehl
Vienna, CESBP 09.09.2013
Content
1. Causes of decay at
wooden beam ends
2. Field tests of different
wooden beam ends
(literature review)
Decay (brown rot)
of a wooden beam
end before renovation
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© picture TUD – Daniel Kehl
3. Simplified decay model
4. Convection at the beam end
5. Future work
EnOB-Project (Energy-Efficient Buildings)
Assessment of existing buildings with wooden beam ceilings
3D simulation
3D material properties of wood
Convection model
field tests
field tests
decay model
field tests
Funded by
Federal Ministry of Economics and Technology
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1.1 Causes of decay at wooden beam ends
• Long construction time
• High moisture content of the
beams at the beginning
> 30 M-%
Long period of high moisture
content is expected
The risk of decay is high
1908 construction site Leipzig
1937
amount of wooden beam ceilings: ~ 80 %
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© picture: Kalender 2013 LTM GmbH, Adolf Deininger, 1908
1) At the beginning of the
building:
1.2 Causes of decay at wooden beam ends
2) Lack of maintenance
• downpipes
• leaking roofs
• lack of protection against wdr
The wall is wet and …
© picture TUD – Daniel Kehl
… the beam end has decay
no downpipe before
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2. Field tests - literature review / own measurments
1
2
3-5
6
7
8
9/10
11
13
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12
no.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
town
D-Hamburg
D-Berlin
D-Drebkau
D-Senftenberg
D-Brieske
D-Dresden
D-Wassenberg
D-Wiesbaden
D-Ludwigshafen
D-Ludwigshafen
A-Waidhofen
A-Graz
CH-Zürich
wooden beam end – Dipl.-Ing. Daniel Kehl
research institut
TUHH
TUD
BTU
BTU
BTU
TUD
TUD
IWU
PHI
PHI
TUW
TUG
City Zürich
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2.1 class of wind driven rain (cwdr)
CWDR = class of wind driven rain (DIN 4108-3)
I = low
II = average
moisture load
III = high
1
2
3-5
7
6
8
9/10
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2.2 Wiesbaden – Lehrstraße (IWU)
W
Source: [Loga 2005]
N
E
S
Cardinal direction of the facade
South-West
CWDR II + cardinal direction
average moisture load
outside: new plaster and coating
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picture: Institut Wohnen und Umwelt,, Darmstadt
building from 1890
after renovation (2002)
NEW
Linoleum
Wooden floor
4 cm
Moisture content
picture: Institut Wohnen und Umwelt,, Darmstadt
„water
repellent
plaster“
Source: [Loga 2005]
2.2.1 Wiesbaden – Lehrstraße (IWU)
beam
plaster
interior insulation:
55 mm EPS (expanded polystyrene)
+ 5 mm wood wool cement bonded board
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2.2.2 Wiesbaden – Lehrstraße (IWU)
moisture content at the wooden beam end
25
Holzfeuchte [%]
20
15
10
Nr. 1 (3. OG Wohnraum) - Balkenkopf in innenged. Fassade / Balkenzwischenr. gedämmt
Nr. 4 (3. OG Wohnraum) - Balken im Gebäudeinneren
Nr. 5 (2. OG Küche) - Balkenkopf in innengedämmter Fassade
Nr. 6 (2. OG Wohnraum) - Balkenkopf in innengedämmter Fassade
0
Okt
02
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Dez Feb
02
03
Apr
03
Jun Aug Okt
03
03
03
Dez Feb
03
04
Apr
04
Jun
04
Jul
04
Sep Nov Jan
04
04
05
wooden beam end – Dipl.-Ing. Daniel Kehl
Mrz
05
Mai
05
Jul
05
Nr. 10
Source: [Loga 2005]
5
Nr. 2 (3. OG Wohnraum) - Balkenkopf in innengedämmter Fassade
Nr. 3 (3. OG Wohnraum) - Balkenkopf in innengedämmter Fassade
2.3 Ludwigshafen – Limburger Straße (PHI)
Building from 1890
After renovation (2002)
N
W
E
S
Very low moisture load of wdr
front site (North-East)
outside: facade was hydrophobed
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Source: [Ratzlaff et.al. 2005]
Cardinal direction of the facade
North-East
CWDR I + cardinal direction
2.3.1 Ludwigshafen – Limburger Straße (PHI)
two types of interior insulation
The facade was hydrophobed
• 80 mm mineral wool with
humidity variable vapor barrier
respectively
• 80 mm expanded polystyrene
beam
source: [Ratzlaff et.al. 2005]
relative humidity
temperature
sketch
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Ludwigshafen – Limburger Straße
(Passivhaus-Institut)
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graphic: Passivhaus-Institut, Darmstadt
rel. humidity [%]
Source: [Ratzlaff et.al. 2005]
relative humidity between wall and interior insulation
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2.3.2 Ludwigshafen – Limburger Straße (PHI)
relative humidity at the beam end
RH - beam end OG1
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source: [Ratzlaff et.al. 2005]
relative humidity
umidity [%]
RH - beam end OG2
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2.4 Brieske - (Gnoth, Stopp, Strangfeld 2005)
N
W
E
S
old
plaster
picture / source: Gnoth et.al. 2005
Cardinal direction of the facade
North-West
CWDR I/II + cardinal direction
low moisture load of wdr
25 mm calziumsilicat board
direction:
North-West
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2.4.1 Brieske - (Gnoth, Stopp, Strangfeld 2005)
Relative humidity in the air gap
65 %
45 %
Moisture content M-%
graphic / source: Gnoth et.al. 2005
15 M-%
9 M-%
Temperature at the beam end
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2.5 Conclusion of the literature review
Wooden beam end will keep dry, when …
1.
2.
The moisture load of wind driven rain is low
The wall is protected against wind driven rain
- low AW-value (water absorption coef.) and a vapour open surface
Other protection (no measurements were found in the literature, but
well known constructions):
- cavity wall – attention old masonry with header bricks
- ventilated cladding
Special and risky:
bare brick walls (without plaster outside) treated with water repellent
fluids (check is necessary!)
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3. Decay of wood - When it starts?
Moisture
content
Wälchi
1980
Minium %
Cartwright
& Findlay
1958
Theden
< 20
No growth
28
1941
Viitanen
Ritschkoff
1991
a / 28b
>2626
M-%
Results
Huckfeldt
Laboratory
Results
Huckfeldt
in buildings
26,2
28
Optimum %
4 weeks
30-40
hypoth.
-
-
-
35-55
-
Optimum %
40-60
30-40
ab 40
bis 55
45-90
40-70
Maximum %
119
-
180
90
225
224
a)
b)
Spruce
Pine sapwood
… but decay depends on temperature
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Source: T. Huckfeldt; O. Schmidt; H. Quader 2005
Minimum – Optimum – Maximum
of moisture content M-% (serpula lacrymans – „dry rot“)
3.1 Decay – model of Hannu Viitanen
Brown rot (0 % mass loss)
1. „Activation“
2. Mass loss
month
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constant boundary
conditions
12 month no mass
loss was detected
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3.2 From Viitanen to a simplified model - suggestion
relative humidity
moisture content
DIN 68800
Easy to measure
Well known value
Well known value
pay attention:
Measurement of the resistance
is inaccurate ± 1,5 M-%
Simulation: the result depends on
sorption curve in the program
pay attention:
High fluctuation
in comparison to moisture content
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Sorption isotherms of spruce
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4. Example – simulation of a wooden beam end
climate Essen
west = a lot of wdr
Indoor climate
normal moisture load
EN 15026 (30 % / 60 %)
How much air will flow?
plaster
Aw = 0,0083 kg/m²√s
36,5 cm
brick
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10 cm
Multipor
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4.1 Driving force for convection:
pressure difference as a result of the stack effect
pressure difference
height of the building 12 m
Overpressure
h
Underpressure
Wind effect and underpressure in summer is ignored
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4.2 Convection Delphin 5.8 – 2D / laminare convection
Airtightness of masonry and plaster?
construction or layer
airtightness
q50 [m³/m²h]
Cement plaster
0,001 – 0,002
Lime- cement-plaster
0,002 – 0,05
„soft“ lime-interior plaster (1928)
0,02 – 0,6
Plaster with coating (distemper)
airtight
Bare masonry wall
2,1 – 15
Masonry with interior plaster
0,1 – 2,0
plaster: q50 von 0,1 m³/m²h
brick q50 von 2,0 m³/m²h
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table: IWU 1995
Model
for convection
4.3 Convection simulation – results
Model
for convection
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Moisture content
for beam end (5 mm)
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4.4 Convection – simplified decay model
evaluation of the simulation results
Wall without insulation
with convection
Wall with insulation
with convection
Daily average values
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4.5 Convection – simplified decay model
evaluation of the simulation results
Wall without insulation
with convection
Wall with insulation
without convection
Daily average values
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5. Future work
• Measurements in double climate chamber to
validate the new material data (Frank Meissner)
(radial, tangential, longitudinal)
• Implement a 3D model in Delphin
(Stefan Vogelsang)
• Measurements of the permeability of masonry,
wooden beam end in an pressure chamber
(Daniel Kehl)
• Implement an improved convection model in
Delphin
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5.1 Convection at the wooden beam
Test chamber
∆P = 0… 100 Pa
LFE
V [m³]
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5.2 Permeability of masonry – first step (2013)
Test chamber with 11.5 cm Brick-Wall
no beam / no plaster inside
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… then you will sleep dry
pictures: [IBA 1985]
Pay attention to
(wind driven) rain and convection
Thank you for attention
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Other investigations on decay
growth
20 °C
95 % RH
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Other investigations on decay
Holzart: Japanese red pine
Holzzerstörer: Braunfäulepilz
Fomitopsis palustris
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Strömung am Holzbalken - Stufe 1
Erste Messungen bis Herbst 2013
Fall 1: beiseitig unverputzt
Fall 2: oben/unten innen verputzt
Fall 3: Fläche innen verputzt
Fall 4: Nur Holzbalken (inkl. „Riss“)
Messung von
• Abklebung
• Abdichtungen
• Rissen
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Literature
[Gnoth et.al. 2005]
[Huckfeldt, Schmidt 2005]
[IBA 1985]
[Loga 2005]
[Ratzlaff et.al. 2005]
[Viitanen 1996]
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Gnoth, S.; Strangfeld, P.; Stopp, H.: Hygrothermisches
Verhalten eingebetteter Holzbalkenköpfe im innengedämmten Außenmauerwerk, Beitrag in der Zeitschrift
Bauphysik, Verlag Ernst und Sohn, Berlin 2005
Huckfeldt, T.; Schmidt, O.: Hausfäule- und Bauholz-pilze –
Diagnose und Sanierung, Rudolph Müller Verlag, Köln 2006
Hrsg.: Internationale Bauausstellung Berlin, Sanierung von
Holzbalkendecken, Verlag Ernst und Sohn, Berlin 1985
Loga, T.: Energetische Modernisierung eines Gründerzeithauses in Wiesbaden, Beitrag zum 6. Leipziger Bauschadenstag 2005, MFPA Leipzig GmbH, Eigenverlag, Leipzig
Ratzlaff, M.; Schnieders, J.: Mehrfamilienhäuser in
Ludwigs-hafen, Beitrag in Arbeitskreis kostengünstige
Passivhäuser, Protokollband 32, Eigenverlag, Darmstadt 2005
Viitanen, H. Factors affecting the development of mould and
brown rot decay in wooden material and wooden structures.
Effect of humidity, temperature and exposure time. Doctoral
Thesis. Uppsala. The Swedish University of Agricultural
Sciences, Department of Forest Products
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Measurements from Hannu Viitanen (VTT Helsinki FIN)
since 1990
Investigations:
a. Wood species:
Spruce
Pine sapwood
b. Test samples were inoculated with
Coniophora puteana and serpula
lacrymans (both brown rot)
Test samples were put into
different constant RH with
different temperatures
d. The mass loss of the samples
were measured
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picture: Hannu Viitanen 1996
c.
Nr. 36
Contact
TU Dresden
Institute of building climatology
Daniel Kehl
[email protected]
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