[Greenbuilding] insulation vs. air sealing

[David]

Ran weatherization program in Baltimore back in the '80s with sealed flat roofs. They cut holes in roof to spray insulation and seal holes with venting caps. Test before and after normalized energy bills and blower door. Results were 15% higher energy usage with 10% greater leakage. These were low income homes being assisted with federal funds. Revised program to cut hole in roof, send in crew to seal top plates and ballon frame chaseways, dense pack low area where could not reach to airseal. Blew R-40 over all other areas then applied sheet metal over the hole before we installed their standard vent cap. Results were 20% energy reduction and 15% airleakage for additional $150 per house installation cost. Other airseal measures were later added to increase savings.

Bottom line, seal top before insulation and no need to ventilate. Ventilation is to remove the moisture from the exfiltration air which was eliminated. 

Hope this helps.  

Sent from my iPhone

On Oct 2, 2010, at 10:49 AM, "Kathy Cochran" <kathys_old_house at goldrush.com> wrote:

Hi all,

I am getting ready to have insulation blown in to my attic.  What exactly is
the "stack effect"

And, now in my county anyway, it is required to have roof caps that are
ventilated.  So, how does this impact on sealing up all "leaks" in the
attic?

Thanks,

Kathy Cochran

-----Original Message-----
From: greenbuilding-bounces at lists.bioenergylists.org
[mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of
Futureship
Sent: Saturday, October 02, 2010 7:03 AM
To: Corwyn; Greenbuild List
Cc: Greenbuilding
Subject: Re: [Greenbuilding] insulation vs. air sealing

Corwyn and Nick,

Do you have a suggestion on
How to test the stack effect ? 
I could do a before and after. 
My hunch is that the stack effect decreases if you air seal attic before
blowing insulation and increases If you do not air seal the attic before
blowing insulation.

Bob Jakaitis aka "Jake"
704-236-3574



On Sep 30 Corwyn wrote:

You certainly shouldn't take mine or Nick's word on it.  Perform an
experiment for yourself.

Thank You Kindly,

Corwyn

--
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.greenfret.com/
topher at greenfret.com
(207) 882-7652


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