how to input infiltration or ACH

[F Zahed]

Hello everyone

I wanted to know how can I enter the building infiltration (m3/h.m2) as input for a zone. I just observed that it is possible to enter the amount of leakage or flow for each flow path , but I don't know how I can enter the air exchange rate or infiltration for the whole apartment, as a single zone. in fact, I want to check how the infiltration of PM2.5 from outdoor to indoors differs at different airtightness levels ( 9,4.5, and 2 m3/m3.h@50pa) which are recommended by building codes.

[William Dols]

If this in fact how you wish to proceed, then you must convert you desired airtightness level into a leakage area element for input into CONTAM.
The attached spreadsheet provides the means to do so for a simple, one-zone example.
Refer to the QREFtoELA page of the spreadsheet.
Note the value entered for Q50 of 9.0 m3/h-m2 and see how it is converted to an ELA of 2.131 cm2/m2 at a 4 Pa for the particular dimensions of this example building.
This is based on setting the orifice equation equal to the powerlaw equation used by CONTAM.
This is also outlined in the ASHRAE Handbook of Fundamentals.

The attached PRJ implements several methods of defining airflow elements to obtain the desired results.
You would likely focus on the element named "ELAnorm" for normalized leakage element for which you would then define airflow paths with wall area multipliers which should all sum to the total building surface area (5 sided in this case).
Note that this PRJ is for demo purposes only, and has the zone pressure set to be constant at 50 Pa to verify the results are correct.

You can also refer to the online tutorials and accompanying spreadsheet for related content.

- Stuart

[F Zahed]

Thank you so much for the detailed explanation.