Configuring air leakage through a wall

[pmpasbl]

Hello,

I'm trying to simulate an air leakage through a wall insulated with 20 cm of cellulose from the inside. The hypothesis is that a hole equivalent to a 2€ coin is observed in the vapor barrier.
I tried to calculate the air flow through the hole, using the equation shown in the attached file.
In this equation :
V is the air flow
Cd is the discharge coefficient depending on the size of the hole. In this case : 0.6
A is the size of the hole in square meter
DeltaP is the pressure balance between the inside and the outside
Roh is air density

Using a 5 cm² coin, I get a 3.05 m³/h air flow.
The woodframe is 0.2 m thick and is insulated with cellulose. Thus, the calculated air volume exchange is 15.2 vol/h.

I created a txt file where this air rate exchange takes different values along the day.
I simulated the case and observed the water content and behaviour of the overall wall and different materials.

My question is the following : does this way of approaching the situation seem good enough or am I missing some variables ?

What effects are being neglicted by doing so ? (I'm thinking of the air flow through the hole being the same as the air flow going outside through the rest of the wall, for example. This is an important hypothesis.)

Thank you for your help.

Best regards

Benjamin

[Manfred Kehrer]

You would need to create a transient input file containg hours since calculation start and air change rate (1/h), which you can easily calculate out of your Volume flow using some geometry.
(F1) should give you some more help.

[Matthew Smith]

Hi Manfred,

I am looking for additional guidance on representative air change rates for small cavities and calculations from volumetric flow rates. Have you removed a link to guidance from your post - F1?

Regards,

Matt

[Manfred Kehrer]

F1 key means the help content specific help system in WUFI