Jens Lüder Herms

1. ...and the insulation
is perfect
Performance and effectiveness
of humidity-variable vapour retarders
in Latvia
...and the insulation
is perfect

2. The perfect component
Why are we building airtight?
Luftströmung (Konvektion)
Experiment set-up
Construction of insulating
material
Gap in the vapour seal
(air-tightening).
Frame conditions:
Inside temperature +20° C
Outside temperature -10° C
Pressure difference 20 Pa
= wind force 2-3
Measurement:
Institute of building physics, Stuttgart
Source: DBZ 12/89, page 1639ff
Heat losses – due to air movements
Without gap: U-Value = 0,3 W/m2
K
1m
14 cm
1m
1,44 W/m2
K
Performance down by factor 4,8
With 1 mm gap: U-Value =
Structual damages due to moisture?
Luftströmung (Konvektion)
a
a
Principals of humidity and moisture of the air
max. H2O
[g/m³]
Temperature ° C
3.3
6.8
9.3
12.9
17.3
23.1
5
10
15
20
25
-5 0 5 10 15 20 25
2.1
-10
2.5
Total moisture load at different temperatures (Riga):
-10 °C / 80 % rel. air hum. = 2,1 g/m³ * 0,8 = 1,68 g/m³
20 °C / 50 % rel. air hum = 17,3 g/m³ * 0,5 = 8,65 g/m³
Diffusion:
warm  cold

3. Possibilities for moisture load to the constrution
.......how can we control
diffusion?
Insulation  = 1
(mineral wool)
Air µ = 1
Resistance against diffusion  - value
Diffusion resistance µ - value
Vapour retarder  = 10.000
PE vapour barrier  = 100.000
 Example: OSB board
 Resistance against vapour penetration: µ = 250
 Thickness: s = 1,2 cm (0,012 m)
 Equivalent thinckness of air layer sd-value :
 sd = µ • s
 sd = 250 • 0,012 m
 sd = 3,0 m
sd = µ • s [m]
Diffusion resistance sd - value
e = 0,012 m
sd = 3 m
Diffusion resistance sd - value
Possibilities for moisture load to the constrution
... .what is convection?

4. a
Without gap: 0,5 g water/m2
x24h
Possibilities for moisture load to the constrution
1m
14cm
1m
1.) Diffusion
a
Without gap: 0,5 g water/m2
x24h
Possibilities for moisture load to the constrution
1m
14cm
1m
800 g water/m²x24h
Performance down by factor 1600
With 1 mm gap:
2.) Convection
Possibilities for moisture load to the constrution
.......why do older existing
construction do not collaps?
Air convection due to stack, wind or unbalanced ventilation system
Small leaks pose higher condensation risk than open gaps or joints
Moisture problems due to air flow may be caused by air exfiltration in
heating climates and air infiltration in cooling climates
Energy leak Moisture leak
Possibilities for moisture load to the constrution
Building operation at
small positive pressures
in cooling climates helps
to avoid problems
Structual damage due to moisture Structual damage due to moisture

5. Structual damage due to moisture
Construction process Construction process
Materialfeuchte durch falsche Lagerung Materialfeuchte durch falsche Lagerung

6. Materialfeuchte durch falsche Lagerung An absulute moisture protection is impossible
• Reduction of moidsture entry
• A high drying potential
D
s
L
D
D
s
L
D
Wirkungsweise herkömmlicher Dampfbremsen

7. Bauschäden durch Feuchtigkeit Intelligent vapour retarders
• kein Schimmel innerhalb
der Konstruktion
• feuchte Baustoffe wie
Holz oder Dämmstoff
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70 80 90 100
sd-value[m]
Sd-value in different humidity levels
Average humidity level [%]
Savety in new build houses
HYDO SAFE value - savety in new build houses
sd-Wert[m]
sd-Mittelwert bei unterschiedlichem
Feuchteeinfluss
0
1
2
3
4
5
6
7
50 55 60 65 70 75 80 85 90 95 100


sd-value[m]
Sd-value in different humidity levels
Average humidity [%]

8. Savety in new build houses Modeling with WUFI
Modeling with WUFI Calculation of thermal and moisture transports
Climate: Riga – temperature/air humidity Climate: Riga – surface temperatures tiles
orientation: south
surface colour : black
orientation: north
surface colour : red

9. Calculation – roof constructions
1. Bitumous membrane
2. Timber cladding 20mm
3. Insulation material 240 mm
4. a.) pro clima INTELLO
b.) PE sheet sd 100m
5. Fermacell 10 mm
Moisture 16,7 kg/m³ = 4,0 l/m²
Pitched roof 40°
nord orientation
Riga roof – calculation freedom from structual damage
pro clima INTELLO
app. 1.100 g/(m²*a)
PE sheet
app. 20 g/(m²*a)
No securities agains unforseen
moisture
High security against unforseen
moisture
Calculation freedom of structual damage
1. Bitumous membrane
2. Timber cladding 20mm
3. Insulation material 260 mm
4. INTELLO / PE sheet
5. Installation layer 20mm
6. Fermacell 10 mm
Pitched roof 40°
nord orientation
Black surface
Convection
Good airtigthness n50 = 3
Heigth of construction = 5m
Area of condensation
risk – moisture of the
timber cladding must be
below 20% to avoid
damages!
Pro clima
INTELLO
PE sheet
Water content
timber cladding [%]
Total water
content kg/m²
Riga – consequences of convection
19,1 %
51,5 %
Protection against
structural damage
Calculating Potential Freedom from Structural
Damage
• No mould within the
construction
• Protection against summer
condensation
• Unexpected moisture load
e.g. due to careless and
faulty processing
0
2
4
6
8
10
12
14
16
0 10 20 30 40 50 60 70 80 90 100
sd-value[m]
sd-mean value at varying humidity levels
Average air humidity [%]
• Controlling diffusion in Winter
Drying reserve > moisture load
= freedom from structural damage
No construction damage with sufficient reserves
Vapour membranes with humidity-variable diffusion resistance
offers an ideal protection of the construction
Calculating Potential Freedom from Structural
Damage

10. Performance and effectiveness
of humidity-variable vapour retarders
in Latvia