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Spray Foam Insulation in Attic

Posted by cas20 (My Page) on
Wed, May 16, 12 at 8:00

I just moved to coastal Georgia and many of the neighbors have sprayed their attic with open cell insulation foam. Reports are as much as 1/3 to 1/2 savings on the summer electric bill. All were definitely in favor of having done it.
We called the contractor that everyone recommended and got a quote. It was weird as he was a little evasive when I asked him about what kind of open cell foam he uses as I told him i wanted to do some research. He said the company website had lots of links full of information. After he left, i went online and there were no links about specific product information. Then when we got the quote there was no mention of specific product. I finally got an answer from him later that he will be using Certainteed's CertaSpray. The cost is a little under $5000.

I wanted to get a second quote for comparison of price and information about product. Since I didn't know anyone who used a different contractor, I turned to the BBB and found one who had an A+ rating in my area and had him come out. He was upfront from the beginning that his company is 5 years old and never used anything but Icynene. And then without my prompting he said some of his competitors constantly switch brands based on price they can get. He also said he does a lot of work in our neighborhood and can provide me with several names of people who live within a mile or two.

The one other bit is Company #1 the guy is a salesman only and we won't see him again. In Company #2, the guy is owner's son and he is salesman but he comes onto job with the crew and shows them exactly what he told us so there is no confusion on what gets done and how.

I am still awaiting quote #2 (he just came a few hours ago and expect it to be similar to #1). We want to have this done ASAP since we have to leave in a week and will be gone for a month so I thought I'd start to get some input. Here are my questions

1. Is there a difference between Certa Spray and Icynene?

2. What do you think of a contractor who switches product based on best price he can get? I was thinking maybe each one had some sort of learning curve or advantages/disadvantages to the other.

3. If price is similar, would you go with the one all the neighbors like even though he seemed evasive or would you go with the BBB rated one (after checking referrals) who feels strongly about being committed to a product.


Follow-Up Postings:

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RE: Spray Foam Insulation in Attic

many of the neighbors have sprayed their attic with open cell insulation foam.

The floor of the attic or the underside of the roof?

The first is straightforward; the second requires sealing all of the attic from the outside.

Assuming it is the floor that is being insulated and the contractors are selling open cell spray foam versions of the product, either Icynene or Certaspray are acceptable. As you can see in the links, both Certaspray and Icynene come in closed cell versions and Icynene offers a "green" variation.

As a builder, I prefer using closed cell spray polyurethane. But as long as you specify the R-Value you're contracting for, the oc will work--it'll just be a thicker layer.

If it were my home, I'd also compare the cost of combining a "flash" coating of spray foam followed by sprayed cellulose. Or just the cost of sprayed cellulose added to whatever's there to begin with. Plus sealing all air leakage points with caulking or hand held foam.


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Recommended Insulation Levels for New Wood-Framed Houses

The US Department of Energy recommends R30-R60 for attic insulation in most of Georgia.

Here is a link that might be useful: Spray Foam basics


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RE: Spray Foam Insulation in Attic

It is the underside of the roof...between the rafters.


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RE: Spray Foam Insulation in Attic

call guy number two back.
check some of his jobs.
if it is a family business you will
probably get a better job.

guy number one if he has done a lot
of work in your neighborhood..check
out some of his jobs.

things to look for..
insulation should fill rafter bays
and the faces of the rafters. when
you look up there should be no exposed
wood.
insulation should be somewhat level
between rafters. if it sinks in then
the depth of the product is less.
roof to attic floor should be sealed
air tight, no leaks or voids.

ask neighbors about comfort and reduced
utility costs, and see if they line up with
what salespeople are telling you.

in our hot humid climate, we use open cell.
there isn't much difference between brands.

prep work is necessary. guy number two seems
to understand this, but have him walk you
thru what he plans to have done.

here are some pictures of a top notch
open cell install:

http://www.slickpic.com/s/NNzDxGNIUxgNzZ/OpenCellUnventedAttic/photo?&play#285991

keep in mind that open cell is about R-4 per inch.
to meet code you need 6"
3" is R-12..it is worth the added product cost to upgrade
to a thicker depth. contrary to what people think
it does not double the price.
the company is already on site, so added cost is just product & time to install.

best of luck.


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RE: Spray Foam Insulation in Attic

Open cell polyurethane spray on the underside of your roof will be way below the minimum recommended R Value for new wood framed homes, according to the US Department of Energy. If you have typical 2x6" rafters, you will only be getting R20 vs. the minimum recommended R30.

Plus, unless the job includes sealing all the openings into the attic from the exterior, you will not be getting the full benefits of the insulation. (See linked document.)

Only if you have those leaks sealed and use closed cell foam does spraying the underside of the roof make economic sense.

Unless you have HVAC in your attic, you will likely be getting a much better return by insulating the attic floor as suggested above.

Spraying R20 under your roof on the Georgia shores and calling that fine and dandy? I wouldn't have anything to do with either of these contractors.

If you want an impartial assessment, read the linked materials or contact an energy consultant in your area.

Here is a link that might be useful: Building Science Corp. on Unvented Roof Systems


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RE: Spray Foam Insulation in Attic

Open cell polyurethane spray on the underside of your roof will be way below the minimum recommended R Value for new wood framed homes, according to the US Department of Energy. If you have typical 2x6" rafters, you will only be getting R20 vs. the minimum recommended R30.

actually 2x6 rafters are 5.5" filling the rafter bay with
6" of open cell foam meets the catherdalized insulation standard. foam covers faces of 2x's to minimize thermal bridging. see pictures linked in my previous post.


Plus, unless the job includes sealing all the openings into the attic from the exterior, you will not be getting the full benefits of the insulation. (See linked document.)

document linked is promoting rigid foam sheathing to exterior of roof. OP is applying foam to interior of
attic at roofline.
when roofline is foamed the air and thermal barrier is now at the roofline not the attic floor. leakage sites that
were problematic with insulation at attic floor are no
longer sucking (negative pressure) from the conditioned space below.

Only if you have those leaks sealed and use closed cell foam does spraying the underside of the roof make economic sense.

open cell is used in hot humid climates. not closed cell.

Unless you have HVAC in your attic, you will likely be getting a much better return by insulating the attic floor as suggested above.

Unless being the operative word...
90% of homes in the south have hvac in attic. and ductwork
in the attic. putting equipment and ductwork under the insulation (foam on roofline) allows equipment and ducts
to perform.
putting foam on attic floor still puts equipment and ducts
in 130 degree attic.

Spraying R20 under your roof on the Georgia shores and calling that fine and dandy? I wouldn't have anything to do with either of these contractors.

If you want an impartial assessment, read the linked materials or contact an energy consultant in your area.

Resnet is a good source for an independent energy rater.

best of luck op


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RE: Spray Foam Insulation in Attic

Thanks for pointing out that the Building Science Corporation (BSC) article I linked to deals with XPS sheathing on the roof--another approach that also works well in all climates--rather than spray foam under the deck.
Here is a BSC article detailing the use of spray foam in creating an unvented attic. In it, building enclosure expert Chris Schumacher observes that "Unvented roof assemblies with ccSPF work well in all climate zones."

Icynene technical notes state that : "Average insulation contribution in a full fill stud wall:-2"x6" = R20."

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Source: Buildlng Science Corp. BSD-149

Foam board insulation bridging over wood members yields a higher R value for the whole wall than insulation only between the studs or rafters. However, R values are not measured that way; nor, AFAIK, are such structures accepted by Code officials as having a higher R Value than conventional wall or roof sections. Foam at the roof-- especially ccspf which is an air barrier at as little as 1" thickness--will seal most of the air leaks into the attic. But it doesn't seal where it's not sprayed.

If HVAC equipment is in the attic--one of Dr. Joe's Ten Dumb Things to do in the South--an unvented attic with insulation at (or over) the roof deck is the best way to go.


Spray foam covering attic rafters. (And then some.) Source: Insulationcavity.com


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RE: Spray Foam Insulation in Attic

so what happens when the roof leaks and the closed cell
traps water between foam and roof decking?
understanding that at some time in the life of the
house the roof leaks..fact of life.

this was the question we put to Joe Lstbruk (sp)
at the classes we attended.

his words were:
in the south WHERE HOUSES DRY TO THE INSIDE
use of open cell foam is recommended.
up NORTH where HOUSES DRY TO THE OUTSIDE
closed cell foam is recommended.

not to argue with you worthy.
you know lots of stuff.
we face this same argument with each
new foam company that comes to town.

OP ..best of luck.


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RE: Spray Foam Insulation in Attic

"High density spray foam insulation due to its impermeability properties can be installed directly under roof decks in any climate zone without any additional provision for vapor diffusion resistance - including Climate Zones 5 or higher (see Map 1)." (emphasis added) Building Science Digests 102 Joseph Lstiburek

By contrast, open cell spray foam requires a vapour retarder in cooling climates.

In fact, in the North, buildings dry both to the inside and the outside. That's why those absurd poly vapour barriers on the inside of walls, especially basements, were so disastrous in Northern climates, where the temperature can range from -40˚ to 120˚. Winnipeg anyone?

so what happens when the roof leaks and the closed cell
traps water between foam and roof decking?

The leak takes longer to show up, but the damage is confined.

Very long term, when roof sheathing has to be replaced, so will any spf on the underside.

Another serious concern is that hidden voids and other defects in the spf insulation may render it ineffective.

Disclosure: I've repeatedly used ccspf on garage ceilings, rim joists and foundation walls (inside)but have backed away from under roof applications. But, then, we don't put HVAC and water tanks in our attics.


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RE: Spray Foam Insulation in Attic

ok worthy lets just agree to disagree.
is it possible for you to do that?

its really frustrating to try to advise
someone in a similar climate and
have to argue with you.

if you look at the R-value for zone 2/3
where I am located you will see that
cathedral ceiling values are 22-38.
open cell will meet that code requirement.

if you have no experience with open cell,
hot humid climates or hvac, ductwork & water
heaters in attics...why do you feel the need
to interject your other climate experiences?

you admit that you back away from under roof
applications. fine. then let the people who
understand and have experience deal with it.

I just don't get it. geeze man..

sorry OP that once again a thread has been
shot to crap by such bs.

best of luck


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RE: Spray Foam Insulation in Attic

Sorry, I didn't know this was an argument.

Three points.

1) I've quoted Building Science Corp.'s publications word for word with citations that contradict your recall of Dr. Lstiburek's comments. Perhaps he has changed his mind. I will post this point on a professional forum that thrives on discussion. In any case, either type of foam will work in the South, according to Building Science Corp.

2) I realize Code requirements are lower than US Department of Energy recommendations. But many consumers are looking for something more than the minimum.

3) I also have experience with open cell foam. But, in any case, I try not to base my comments on personal anecdotes. This is the Net and I could claim anything with anonymous authority. Instead, I rely on the findings, commentary and conclusions of building scientists, engineers and materials experts. I try to apply these to the individual situations that people bring up here. Even if some consider me garrulous and pedantic.

I hope the OP will continue with his/her research and not act hastily succumbing to the first (or second) slick salesman with a clipboard and a hardhat.


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RE: Spray Foam Insulation in Attic

Hi cas20,

Very good questions.

1. Is there a difference between Certa Spray and Icynene?

Minor differences, all spray foam products are designed and tested to fall within certain design parameters. Just different icing on the cake as far as vendors names go.

2. What do you think of a contractor who switches product based on best price he can get? I was thinking maybe each one had some sort of learning curve or advantages/disadvantages to the other.

If the contractor said they would use product X, they should stick to that product regardless if they perform the same or not, regardless of industry.

3. If price is similar, would you go with the one all the neighbors like even though he seemed evasive or would you go with the BBB rated one (after checking referrals) who feels strongly about being committed to a product.

Above all I would go with whom you feel most comfortable with. Spray Foam Insulation is a very technical install, so choosing the right contractor is very important.

Here is a link that might be useful: Spray Foam Insulation Information


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