[TRNSYS-users] modeling a passiv haus

Michaël Kummert michael.kummert at gmail.com
Tue Jan 10 07:35:41 PST 2006


> I’m going to model a "15 kWh passiv haus", the first real project of 
> this type in France (!!!).
> I don’t know how to estimate the airchange of infiltration of this type 
> of house. I know it will respect the german specification (0,6 vol/h at 
> 50 Pa) but I don’t know how to traduct this value into “airchange of 
> infiltration”. Does someone have an idea ?

The 2005 ASHRAE handbook of fundamentals (Chapter 27, p.21) lists a rule 
of thumb that is often used: the yearly average infiltration rate is 
taken as the value at 50 Pa divided by 20. This is of course a gross 
simplification since it ignores the variations of infiltration with its 
driving forces (temperature difference and wind). The same chapter in 
the handbook provides references to other methods to use the "50 Pa" 
infiltration value.
The most detailed way to model infiltration in TRNSYS is to use a 
multizone airflow model (TRNFLOW, COMIS or CONTAM), but you may not need 
it in your case since there will be a ventilation system with 
(hopefully) a much larger ventilation rate.
If you are interested in heating energy load and system design I would 
think that the "1/20" rule of thumb is good enough, but of course things 
are different if you are studying summer thermal comfort with operable 
windows or other aspects where (possibly controlled) infiltration is 

I hope this helps,

Michaël Kummert


Michaël Kummert

École Polytechnique de Montréal - Génie Mécanique
Case Postale 6079, succursale Centre-Ville
Montréal   QC   H3C 3A7

Tel: +1 (514) 340-4711, Ext. 3367
Fax: +1 (514) 340-5917
Email : michael.kummert à polymtl.ca

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