ICF + water repellent in the stucco

[Alberto Morales]

Hi,

In my ICF wall where i have:

Lime render
EPS
Concrete
EPS
Gypsum

I defined a 1% rain leakage in the outside of the external wall. Whether I add a water repellent in my facade but I get the same results (following the procedure that you have in the website-download) than with no water repellent.

1- Do i have to put rain absorption equal to 0 or remove the 1% rain leakage?

Regards

[Christian Bludau]

Hi Albert,
in which material did you place the source?
Is there rain in the climate file you use?
You must not have to put rain absorption to 0. If you have a water repellent layer you set an a-value for the surface. This "controls" the uptake of rain water.
Regards
Christian

[Alberto Morales]

hi

thanks for your feedback

you are right it does not make sense to set the rain absorption to 0

i place the 1% rain in the outside part of the EPS (outermost one)

yes , my weather file contains rain


another question;

if I place the rain leakage in the position where we should install the window (see below)

11111.png (7.33 KiB) Viewed 5515 times

1- when i do a wufi graph, will the values of RH in the window position be realistic? becuase the temperature in the model will be higher (insulation position 1D) instead of exterior temperatures so there is more risk of condensation?

and i do a VTT model for this case i get the next one (see below)

222.png (38.11 KiB) Viewed 5515 times

but ,


2-does the model understimate the mould index because the temperatures that choose are higher than in the reality (window frame colder-1D analysis). is it right to do this type of analysis for external layer using VTT and simulation window leakage? (i guees it is more appropiate WUFI 2D for this cases)

Regards

thanks

[Alberto Morales]

Any reply for this topic please

[Daniel]

Hi Alberto,

1. The rain water leakeage source shall be placed in a material, which can absorb this moisture - behind a cladding or behind an EIFS. In your case normally on top of the WRB. But for sure not in the middle of the EPS which is not absorbing and water tight.

2. If the real temperature is lower, the RH is higher. Of course that influences also the mould risk. However: lower temperature reduces the risk hihger RH increases the risk.

3. If you want to analyze that more in detail you're right: that's more a 2D topic. But like mentioned above: in your case the reain leakage could be deposited on top of the WRB

best regards
Daniel

[Alberto Morales]

thanks Daniel for your quick answer.

i tried to simulate a window leakage in the sill position to stress out the wall and simulate what can happen in a retrofit house scenario so i wanted to know if it is correct to do like my idea in WUFI PRO (not WUFI 2D that can be more right to do it) and if the results taht i will get can be realistic so i asked about temperatures in that position of he insulation where in reality is the window installed.

let me know please

i placed a leakage in the positio you mentioned

11111.png (18.44 KiB) Viewed 5450 times

Relative Humidity in EXT INSULATION for Cladding & WRB FOR 3 types of Rain leakage.png (42.89 KiB) Viewed 5450 times

and here you go my results i got, i hope it makes sense them


Alberto

[Daniel]

The WRB should be installed in a way, that rain water from the window sill cannot run behind the WRB bot in front of it. Therefore the source can be deposited in the air on top of the WRB - not in the insulation behind it. That should improve the situation.

[Alberto Morales]

thanks Daniel

then, should I do it like in the image? unless you could draw a sketch to helo me to understand you

Captura de pantalla 2022-12-09 192848.png (8.09 KiB) Viewed 5440 times

but the thickness of that layer is 1mm as the common practice indicate (1 mm air layer moisture capacity-48 mm air layer no moisture capacity + 1 mm air layer moisture capacity)

in my case i tried to simulate the case where the WRB could have been teared due to poor workmanship or penetration,...? then in this case, is it correct to do it behind the WRB in the outermost side of the insulation?

Regards

[Daniel]

Hi Alberto,

Yes - normally I'd deposit it like in your figure in the 1 mm air layer - however, here it will normally cause no problems. That's exactly the idea of the WRB.

If you want to show the effect of imperfections in the WRB you can also put it behind the WRB in the first mm of the insulation. That's a bit untypical and 1 % is maybe a bit too much in that case. But as far as the WRB is vapor permeable it shouldn't be a problem.

Daniel