[Greenbuilding] insulation vs. air sealing

[David Wentling]

Blower door saw the increase in "holes", because the roof was air tight (3" of 
asphalt) when we started and we added two 18" x 18" holes (venting caps) when we 
left! This was standard practice for many years and no one measured performance 
of the practice until we did a research project.

If one plans to ventilate a roof, then be sure to airseal at the ceiling level 
COMPLETELY first. There are many photos of dirt lines, through the insulation, 
above top plates due to leakage along the sides of the plate, behind the wall 
surface (lath & plaster, wall board etc.) and penetrations in the plate. Dr 
Joe's ADA approach highlighted this many years ago.

With the airseal measures in place, and the moisture contribution from 
ex-filtration to the attic eliminated, the question is do you need to ventilate?

 David Wentling

From: Futureship <futureship0000 at hotmail.com>


I have a question with regard to 
Your results:

In the first case you described that "Results were 15% higher energy usage with 
10% greater leakage."

How does a blower door measurement
Tell you 10% greater leakage? The 
Blower door measures holes in 
The building envelope . Assuming no
Air sealing was done the blower door 
Would not measure a 10% greater leakage. I would argue the increase in stack 
effect In this case caused an increase in pressure thru the same holes therefore 
causing more airflow thru the same holes.