Spray Foam (open And Closed Cell) Versus Combo - Insulation - Contractor Talk

Spray Foam (open And Closed Cell) Versus Combo

 
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Old 11-28-2007, 10:01 PM   #1
 
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Spray Foam (open And Closed Cell) Versus Combo


I am working on a custom build house with a foam insulation budget and wanted to get your advice.

Original specs called for 4" Iceyene (open cell 1/2 lb) foam on all exterior walls and roof deck. FYI - this is about 3x the price of batt. I have talked to 4 different foam companies and they all give me a different story and dog on other people's foam solutions, so I am having a hard time getting a straight answer.

The latest guy told me that he would recommend a 1 inch closed cell foam application with R-13 batt insulation. The closed cell foam I have read is about 3x more efficient than open cell. The 1 inch closed cell foam would seal up the house with an R-7 rating and still have room for R-13 on top of that.

Can anyone recommend if I should do 4 inch open cell foam or have you had experience with closed cell foam and recommend a lighter application of closed cell foam coupled with batt ?

Thanks!

Last edited by KesslerDweller; 12-02-2007 at 10:32 PM.
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Old 11-28-2007, 10:13 PM   #2
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Re: Spray Foam (open And Closed Cell) Versus Combo


I have always been under the impression that closed cell is better, costs more than open cell, and must be covered with a minimum of drywall. I was also told it could not be used in attics with duct work running through it (in case of fire).

Complete homes I was the super (1 1/2 years ago) on were running $ 2.00 sq.ft. of wall space for 3 1/2" of Demilac open cell, Attic lids (underside of deck) was $ 2.80 sq.ft. (encapsulating the attic space and making it conditioned)

Never tried the combination of the two different products

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Old 12-01-2007, 04:46 PM   #3
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Re: Spray Foam (open And Closed Cell) Versus Combo


I did the 4" full cavity foam in my 150 year old Gothic Seven Gables home. My house was built in 1855 from used lumber so my wall studs are everything from 2 x4's to 2x14 to tree trunks. So using batt was never going to seal up everything. The upside is that there are no drafts and they could have fireworks on my front lawn and I'd never hear it. The downside is that adding any electric, phone line, plumbing or heating or whatever in the future is out of the question.

I am starting another restoration soon and I will most likely do the 1" and batt method. As long as they blow the foam around the plugs and seal the sheathing to the studs, I believe the batt will take care of the rest.
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Old 12-02-2007, 10:34 PM   #4
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


Thanks for the input folks!

Chris - the foam guys have specified 6 inch open cell foam for all roof decks. 1 inch foam goes on all exterior walls creating an air tight house.
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Old 12-04-2007, 03:15 AM   #5
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Re: Spray Foam (open And Closed Cell) Versus Combo


Never, ever spray 1" closed cell foam against an exterior surface the cover with fiberglass/vapor barrier in a cold climate!

Your creating a place for condensation to pool and slowly destroy your house from the inside out. You need 3" of closed cell polyurethane foam insulation to create a vapor barrier effectively replacing the required 6mil plastic you'd otherwise place between framing and SR. Get a second opinion from a different contractor concerning this "one inch" idea. If you live in a cold climate like I do this only sounds like a good idea.

This is the best wall you can Build for the money:
New construction: 2x6 studs, glued osb exterior, vapor barrier where required by local code, then a thermal break between exterior plywood and siding (usually 1/2+" blue board).
Remodel without replacing siding: 3" solid foam Urethane+batt insulation
Remodel and new siding: same as new construction (paying close attention to your draft elimination).

The most important thing is to eliminate drafts, Tyvek alone will not accomplish this. The second point is, very little heat is lost through walls if they are sealed properly, put your money in the roof.

My question to your insulation contractors is: why don't they spray solid foam throughout? It is my understanding there is very little price difference.
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Old 12-04-2007, 09:07 PM   #6
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


Air sealing with a thin layer of foam may sound good as does getting aditional R-value with "cheap" FG, BUT...

If you ad FG and avapry barrier you trap any moisture that gets in the walls. If you don't the warm moist room air can reach the dew point in the FG and saturate it reducing its R value to nearly nothing and rotting your house from the inside out.

The only exception I have seen to this is air sealing the lids with 1 1/2" in of hard foam(vapor barrier) and insulating above that with cellulose to an R-50 (14"). At least with this the vapor barrier is on the warm side.

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Old 12-16-2007, 11:10 PM   #7
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


I am spraying 1 inch (R7) closed cell foam from the inside of the house to the OSB. The house is wrapped on the exterior with Tyvek. We are using a combination of stucco, brick, and treated and sealed spruce wood siding on the exterior.

I am in Texas so not in a cold weather environment.
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Old 03-18-2008, 10:15 PM   #8
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


Quote:
Originally Posted by Griffino View Post
Never, ever spray 1" closed cell foam against an exterior surface the cover with fiberglass/vapor barrier in a cold climate!


Hi all, I happened upon this site when doing some research on insulation. Great site with wealth of information!

I have a couple of quick questions concerning the quote above. I am also considering 1" closed cell foam spray against the OSB sheathing (interior) and add FG batt for a 2x6 wall.

Would it be OK if you installed the FG batt with the vapor barrier against the foam? Or must I install batt without the vapor barrier?

Also, would the 1" foam be sufficient as a vapor barrier by itself?

FYI, region is upper Midwest...super hot and humid summers and quite cold winters.

Thanks in advance for your help!

Last edited by Green_2; 03-18-2008 at 10:18 PM. Reason: Removed incorrect quote
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Old 03-19-2008, 12:20 AM   #9
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Re: Spray Foam (open And Closed Cell) Versus Combo


I think more research needs to be done before we start mixing FG and spray foam. I won't trust it for now.

Where are you at Green 2? I'm in the midwest too. Shty winters, eh?

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Old 03-19-2008, 09:35 AM   #10
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


Yeah Mark, crappy winter this year. I'm near the Chicago area. Potholes galore because of the freeze and thaw cycles we had this year.

What I mean in my question was to apply the 1" foam, then add in the batt with the vapor barrier against the foam (instead of facing the drywall).

And if that is not a good idea, then I will have to remove the vapor barrier on the batts. But then I am worried that the 1" foam may not be enough as a vapor barrier.


Any thoughts?
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Old 03-21-2008, 01:03 PM   #11
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


Quote:
Originally Posted by KesslerDweller View Post
I am working on a custom build house with a foam insulation budget and wanted to get your advice.

Original specs called for 4" Iceyene (open cell 1/2 lb) foam on all exterior walls and roof deck. FYI - this is about 3x the price of batt. I have talked to 4 different foam companies and they all give me a different story and dog on other people's foam solutions, so I am having a hard time getting a straight answer.

The latest guy told me that he would recommend a 1 inch closed cell foam application with R-13 batt insulation. The closed cell foam I have read is about 3x more efficient than open cell. The 1 inch closed cell foam would seal up the house with an R-7 rating and still have room for R-13 on top of that.

Can anyone recommend if I should do 4 inch open cell foam or have you had experience with closed cell foam and recommend a lighter application of closed cell foam coupled with batt ?

Thanks!
I would stick with what the house was specked at

I think you will be very happy with the results. Yes, it is more expansive but you will have a much healthier and quieter home and you will save plenty of money in the long run. Send me a email if you have any specific questions on icynene.
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Old 04-08-2008, 01:41 PM   #12
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


One of the reasons you are always told or quoted 1" of "closed cell " is because the open cell expands so much more that the finshed aplication isn't as smooth and can't be as thin of a layer.
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Old 01-16-2010, 05:48 AM   #13
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Re: Spray Foam (open And Closed Cell) Versus Combo


Quote:
Originally Posted by Griffino View Post
Never, ever spray 1" closed cell foam against an exterior surface the cover with fiberglass/vapor barrier in a cold climate!

Your creating a place for condensation to pool and slowly destroy your house from the inside out. You need 3" of closed cell polyurethane foam insulation to create a vapor barrier effectively replacing the required 6mil plastic you'd otherwise place between framing and SR. Get a second opinion from a different contractor concerning this "one inch" idea. If you live in a cold climate like I do this only sounds like a good idea.
All the classes that I have taken also preach this regarding cold climates. One class the instructor only recommends spray foam for the rim joist. Others pretty much say the same regarding a minimum but no "Skim Coat". Heck spray foam is new to me but it's getting cheaper so people are now looking at it with more vigor. Now I have to learn the pros/cons and put them in place. SO with this said I would like to add a few question to this thread.

1. Does anyone have a link regarding brands, there perm rating (Vapor Barrier Status);
2. Tyveck, yea/na. I'm a fan just to have that additional block for wind driven bulk moisture;
3. Ceiling, catherdal - Vent and spray to the vent or spray to roof decking. My concern here is somewhere the dew point will occur. I would rather vent just in case any moisture is present.

I live at Coastal Alaska so we get plenty of the wet/white stuff.
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Old 01-16-2010, 08:33 AM   #14
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Re: Spray Foam (open And Closed Cell) Versus Combo


ACHOA - www.buildingscience.com is the link you want

Demilic is my favorite brand & I prefer the hot roof system myself (i.e. no vents)
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Old 01-18-2010, 03:19 AM   #15
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Re: Spray Foam (open And Closed Cell) Versus Combo


I passed the question on to UAF - Cold Climate Housing Research Center. I did go to the above site but from what I have found it appears to be applicable for winters that are only 4-5 months long with a real summer that allows time for drying. I can count the days in one year above 70 on both hands so our drying time is minimal. I did research a class I took a few years ago regarding this and the instructor recommended against spray foam applied directly to the underside of the roof decking (Catherdal) due to the above minimal drying time, stating prolong condensation would be inevitable. I'm leaning more towards a cold roof design. I have yet adventure into spray foam roofs, always been R38 or more and cold roof design. Not a lot of SIP homes in my location, (Due to cost of S/H), so unsure how those have done. Have a new customer that would like to spray foam the entire homes so trying to get all my ducks in a row regarding pros/cons and best technique...
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Old 01-18-2010, 08:39 AM   #16
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Re: Spray Foam (open And Closed Cell) Versus Combo


Not positive, as I have never fully researched your environment but...

You might have to go with a 6"+ CC Foam for the roof, make sure you run an HRV(? maybe an ERV) to help control interior moisture & air issues

Run a dehumidifier to fully dry out the interior - make sure wood is considered dry before applying foam, as long as the material is dry, no additional moisture can get to it with CC Foam (Contact whichever companys manufacturer you are going to use for spec sheets, best practices in that enviroment - make sure you post the info as I always love learning how issues are dealt with elsewhere)

Are you using an Ice & Water Membrane on the roof? This should help prevent any moisture getting to the sheathing
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Old 01-19-2010, 10:27 PM   #17
 
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Re: Spray Foam (open And Closed Cell) Versus Combo


Open and closed cell. Open cell foam such as Icynene is an open cell foam. Better than using batt insulation but still requires the use of an air barrier and moisture barrier. Closed cell foam or what is called 2 pound medium density foam can be an all in one product, serving as the thermal insulation, vapour barrier and air barrier. If you are in the USA, look for something like sealection 500 by Demelec. If in Canada, PolarFoam PF 7300-0 Soya. Your air seal is accomplished with 2 pound foam in the first 1/4 inch and to get to a proper moisture barrier, 2 inch. We normally spray 3 inch in walls and 5 inch in attics. Cost is about 2 to 3 times that of batt insulation but when you way the benefits, foam is the only way to go. Stays where it is placed, seals every nook and cranny, no mold or mildew and adds structural strength to the building against rack and shear. Of course the biggest benefit is the saving of energy.

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