Replies

1. GBA Editor
   Martin Holladay | Oct 17, 2012 03:05pm | #1

   Roger,
   I don't know of any way to convert cfm per square foot @ 75 Pascals pressure difference to ach50.

   Do you know cfm/sq.ft. @ 50 Pascals -- otherwise known as cfm50?

   To calculate air changes per hour at 50 Pa (ACH @ 50 Pa or ach50), multiply cfm50 by 60 minutes per hour and divide the product by the building volume, including the basement, measured in cubic feet.

2. 
   user-1061844 | Oct 17, 2012 06:04pm | #2

   you can't...... if you don't know the envelope area of the building and the volume of the building.....

   if you do, you can figure it out - although you would need to use an approximate conversion factor to account for the pressure difference. Infiltec list this as a 1.30 factor to convert the flow rate (cfm)
   http://www.infiltec.com/inf-larg.htm

   Keep it tight!

3. 
   eyremountllc | Oct 18, 2012 09:03am | #3

   Thanks Martin and Floris! That's what I thought after doing some research too.

   Thanks