[GSBN] Straw-Bale Blower Door and Infrared Test Results

[David Elfstrom]

The report says that flow was 617 cfm at 50 Pa depressurization.

If the house volume is (900 sqft x 10 ft avg wall height) = 9000 cuft , 
then air changes per hour at 50 Pa depressurization is 617 cfm/9000 
cuft  * 60 min/hr = 4.11 ACH @50 Pa. That is typical for a suburban 
tract home built in Ontario today without any special attention to 
detail, and easily achievable by retrofits.

Even if the volume were doubled (20 ft average wall height) it still is 
considerably more than new home construction to the R2000 standard from 
the 1990's of 1.50 ACH50. Passive House requires a mere 0.60 ACH50 or less.

In the report it states "ASHRAE suggest a minimum natural ventilation of 
950-1200 CFM for a house of this size". I don't think so! That would be 
a seriously leaky house, and would be as dry as a bone in winter. ASHRAE 
actually suggests mechanical ventilation to 7.5 cfm per person + 3 cfm 
/100 sqft, so a four-person 900 sqft home would require a mechanical 
ventilation to achieve a mere 57 cfm for all the fresh air needed.

David Elfstrom

On 24/12/2010 12:42 AM, Dan Smith wrote:
> David and Anni, thanks for sharing this, it is a treat.
>
> What's the air change per hour at 50 Pa?
>
> Happy Holidays,
> Dan
>
> http://greenbuilder.com/mailman/listinfo/GSBN
>