I got into a discussion with a college the other day about testing the attic connection to the house.

When the house is depressurized to -50pa wrt outside, and the attic wrt house is -49pa, isn’t the attic more “outside” then “inside”? When the house was depressurized to -50pa I also looked at the attic wrt outside, and got just -2pa. My understanding is that if the Blower Door is putting -50pa on the house interior, and the attic only goes -2pa wrt the outside, the ceiling is pretty darn tight.

Any thoughts on this? We talked zonal pressures until my head got foggy. Any other ways to describe this testing process would be greatly appreciated. I may even get a lunch out of it if I can explain it better!

Views: 393

Replies to This Discussion

If I am understanding this correctly when the house is at 50Pa relative to outside and the attic is at 2Pa relative to outside then there is not much connection between those two zones. The 2Pa in the attic could even be due to stack. Sounds like they have a very tight ceiling.


Silvie Votrubova, Retrotec

Here are a couple of things to remember when measuring zonalpressures.  First is that you want tomeasure the change in pressure caused by the Blower Door, so you will need torecord a baseline attic to outside pressure. Secondly zonal pressures do not tell you the size of the leakage betweenthe house and the attic.  The zonalpressure tells you the leakage ratio between the house and attic compared tothe leakage between the attic and the outside. For example, if the attic to outside number is 25 pa, then the hole sizebetween the house and attic is the same as between the attic and outside.  If the attic to outside number is 2 pa, thenthe ratio is 1 to 8.  It is possible tohave a attic to outside zonal pressure of 2 pa on one house and 25 pa onanother house and have an equal hole size between the house and attic.



  • Add Videos
  • View All


Latest Activity

David N. Armington liked John Poole's discussion Two Part Epoxy and Repair of Structural Wood
23 hours ago
David N. Armington joined John Poole's group

Historic Home

Historic and vintage homes are significant to our cultural heritage, yet often lack energy…See More
23 hours ago
Seth Romme is now a member of Home Energy Pros
John Nicholas replied to Rob Madden's discussion Blower Door Testing on Energy Star v3 home
"So you have a slab on grade home, duct work in the attic?"
Diane Jackson posted a photo

"Drive Home"

Addison Homes spent a fun day with a film crew from the National Association of Home Builders. We…
Paul Raymer posted a blog post

Healthy Home Evaluator Training

Fall River, MA     October 13, 2016…See More
Diane Chojnowski updated an event

Better homes video series at Seventhwave

October 24, 2016 to January 26, 2017
Profile Iconseoeleczo and Parfait Pouliotte joined Home Energy Pros

© 2016   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service