Insulated, Enclosed, Unventilated Attic Question

[dfogleman]

Joe, I worry about the use of spray foam insulation such as this. I understand the comments about the insulating factor and the attic being treated as living space however I cannot help but wonder...what about condensation. As this is a newer practice I believe that time will tell and it will do so at someones expense.

What if leaks is a great question too, if the foam is closed cell then it should contain any water leaking in allowing the wood to rot before any indications of a problem are visible.

Word it well and CYA!

[cbuell]

I am pretty sure it is not closed cell. In fact, it is good at dealing with roof leaks because it doesn't "hide" them----it just leaks straight through (making finding the leak behind easier) and supposedly is "good-as-new" when it drys out. There is only going to be condensation if there is air movement. Because there is NO air movement with this type of insulation, condensation isn't "theoretically" possible. It puts the dishes away when it is done too

[jkormos]

http://www.guardianpolymers.com/

[alarsen1]

Originally Posted by tdietrich1

imho:

If the underside of the sheathing is insulated, then the attic has become part of the houses environmental envelope. So you wouldn't ventilate a room, you don't ventilate the attic space.

tom

My thoughts (okay... "guess" too). As the roof sheathing is insulated, for all intents and purposes there is no attic. Any windows?

[wforsyth]

Originally Posted by alarsen1

My thoughts (okay... "guess" too). As the roof sheathing is insulated, for all intents and purposes there is no attic. Any windows?

See, that's what I was thinking. It's not an attic right unless they put the ceiling/flooring in, insulated or not. That space, that would be considered the attic, is not enclosed, therefore does not exist.

The insulation on the roof sheathing is all that is necessary for the entire space.

Does any of that make sense, or did I stay up too late again?

[David P. Valley]

I haven't ran into foam insulation yet, but a lot of foam insulation companies state that attic vents are not necessary.

http://www.builderonline.com/industr...ticleID=250986

http://www.nrel.gov/docs/fy01osti/30909.pdf

[John Nosworthy]

Here's a link to an article in the current issue of Journal of Light Construction
titled "Insulating Unvented Attics with Spray Foam". A different way to do things.

http://www.jlconline.com/cgi-bin/jlc.../View/0703insu

[Barry Adair]

Or you can use the Arkansas chicken farm method!

Closed attics have been around for a few years and the foam has been around even longer. New ways to reinvent the wheel and find a new market niche. I'd like to see them catch on as soon as possible. The last one I did it was 100*F outside a balmy 80* in the attic. Quite the opposite of what is normally encountered.

"Does any of that make sense, or did I stay up too late again?"
Wendy, you know the answer to this, just think a little harder.
NO, wait, not that hard I can smell them burning from here.

[alarsen1]

Originally Posted by jnosworthy

Here's a link to an article in the current issue of Journal of Light Construction
titled "Insulating Unvented Attics with Spray Foam". A different way to do things.

http://www.jlconline.com/cgi-bin/jlc.../View/0703insu

Great article! I grew up on a farm and my dad had a 100 ton walk-in freezer that was completely insulated... floor, sides, and ceiling... with about 10" of sprayed-on foam.

I watch Holmes on Homes once in awhile and he's gone to insulating basement exterior walls with this same method as it's an insulation and vapour barrier all-in-one... and because the foam bonds directly to the concrete, with no "pockets of air" behind, there's no chance for mould to grow in cavities.

[John Nosworthy]

Arne,
I'm glad you thought so highly of the article. For those who are unfamiliar with the Journal of Light Construction, its a GREAT magazine and I continue to find its archived articles a great help explaining technical dwelling matters to the average home owner. I'd recommend all members give jlconline a test drive and see for themselves.

[Todd Stromdahl]

Starting to this in north florida with SIP wall construction. Very strong roof, great insulation, vapor barrier all in one. Keeps the AC ductwork inside the house envelope, saves alot of money on cooling bills. Needs to have an Air to air exchanger to let fresh air in and moist air out, or the house will stew in its own juices.

[gbeaumont]

Originally Posted by tstromdahl

Starting to this in north florida with SIP wall construction. Very strong roof, great insulation, vapor barrier all in one. Keeps the AC ductwork inside the house envelope, saves alot of money on cooling bills. Needs to have an Air to air exchanger to let fresh air in and moist air out, or the house will stew in its own juices.

Hi to all,

I agree with you Todd, I believe this is the future of insulation, I attended a very thought provoking presentation by Mark Cramer (ITA Tampa) a couple of weeks ago where he was discussing the benefits of foam in place insulation. I also wonder if this would also cure some of our wind uplift and building pressure issues down here, in particular I was wondering what the shear resistance of that foam is, as it connects the rafters to the underside of the sheathing I am guessing that it offers a lot of wind lift resistance.

Regards

Gerry

[Marcel R. Cyr]

Right here Gerry on page 8.

http://www.sprayfoam.com/cnt/docs/Honey_ClosedFacts.pdf


Marcel

[Roy D. Cooke, Sr]

Originally Posted by mcyr

Right here Gerry on page 8.

http://www.sprayfoam.com/cnt/docs/Honey_ClosedFacts.pdf


Marcel

Great site thanks Marcel

Roy Cooke

[gbeaumont]

Originally Posted by mcyr

Right here Gerry on page 8.

http://www.sprayfoam.com/cnt/docs/Honey_ClosedFacts.pdf


Marcel

Thanks Marcel,

The link you sent was to the closed cell foam, it is my understanding that it is the open cell that is normaly used for this application (at least down here in the sun drenched south ) I would imagine that the open cell version would be weaker in this area.

Regards

Gerry