Spray Foam Insulation

[EddieWalker]

Will Open-Cell Spray Foam Insulation Really Rot Your Roof?

I read the article and think it's pretty good about the issues with open cell foam and what has happened to houses that use it, but I also think it's a bit slanted in making excuses for those issues. I think that the one thing that we can all agree on when discussing open cell foam is that there have been issues with it and there is a gamble that is taken when using it. The more you search about it, the more you will read both sides of the debate, and for those that support it, the blame is always on the install.

 

[dieselscout80]

I saw this wall design and it seems interesting. What do you guys this of it?

‘Extended Plate and Beam’ Walls - GreenBuildingAdvisor

https://www.homeinnovation.com/~/me...Guide Extended Plate and Beam Wall System.pdf

 

[EddieWalker]

Remind me of an overweight guy that I used to work with that spent $600 on a titanium bicycle seat because it was lighter then his original seat. He rode twice a month and drank beer afterwords. You can spend a lot of money and never see an improvement or return on your investment.

 

[goeduck]

Heat gain and loss is almost exclusively controlled by how well the attic area, or roof, is insulated. This is where foam really shines. Nothing is better then closed cell foam. I would never use open cell and personally think it should be banned from being used in homes. For less money, blown in insulation will give you the same results if you have it applied deep enough to achieve the same R value. It's all about the R value and how much room you have to obtain it. I have 2 feet of blown in Atticat in my house and it's awesome. When I build my shop, I will have a ceiling so I can do the same in there. When I add on to my house, I will have a vaulted exposed beam ceiling with no room for blown in insulation, so I will use closed cell foam for there.
.

So for inside walls and valulted ceilings you would go with closed cell but in a traditional attic you would go with blown in Atticat? I have fiberglass bats between ceiling joists up to joist height and there are a number of gaps from work up there over the years that I am losing heat through. I am wanting to add to or re-do my attic insulation and am curious what you would do in a retrofit, including how to protect the soffit ventilation air path.

 

[Grumpycat]

If you are building, here is something new to consider, insulated 2x6 studs. Wood only has an R value of 1/inch. You may have R19 in the walls, but with 10% of your wall being studs with only an R value of 6, the overall wall R value is about 12. You need to do something to break the thermal bridge that the 2x6 creates. I have no affiliation with this company, I just stumbled upon them a few weeks ago when researching building materials.
Tstud

1.5" stud every 24" is 6.25% not 10%.

 

[EddieWalker]

So for inside walls and valulted ceilings you would go with closed cell but in a traditional attic you would go with blown in Atticat? I have fiberglass bats between ceiling joists up to joist height and there are a number of gaps from work up there over the years that I am losing heat through. I am wanting to add to or re-do my attic insulation and am curious what you would do in a retrofit, including how to protect the soffit ventilation air path.

Both Lowes and Home Depot sell Rafter Vents that fit between the Rafters so you will have open air from the vents up past the insulation. https://www.lowes.com/search?searchTerm=rafter+vents

Home Depot will let you use the machine for free to blow in the AttiCat if you buy 10 bags or more.

It takes two people to do this. One to feed the blower, the other to hold the hose up in the attic. Both are easy jobs. Last time we did it was for an addition to our house and my wife fed the AttiCat into the blower while I was in the attic space holding the hose.

Decide how much you want, and figure out where that comes to on the stuff that's up there. If it's a foot thick for R30, mark that on a vent pipe, or AC duct or whatever you have up there. Or two feet for R60. Then just point the hose in that direction and let it build up. Start at the farthest away point and work your way back. Most 2,000 square feet houses will take half a day to spray, so be prepared to be up there for at least that long.

 

[goeduck]

Both Lowes and Home Depot sell Rafter Vents that fit between the Rafters so you will have open air from the vents up past the insulation. https://www.lowes.com/search?searchTerm=rafter+vents

Home Depot will let you use the machine for free to blow in the AttiCat if you buy 10 bags or more.

It takes two people to do this. One to feed the blower, the other to hold the hose up in the attic. Both are easy jobs. Last time we did it was for an addition to our house and my wife fed the AttiCat into the blower while I was in the attic space holding the hose.

Decide how much you want, and figure out where that comes to on the stuff that's up there. If it's a foot thick for R30, mark that on a vent pipe, or AC duct or whatever you have up there. Or two feet for R60. Then just point the hose in that direction and let it build up. Start at the farthest away point and work your way back. Most 2,000 square feet houses will take half a day to spray, so be prepared to be up there for at least that long.

On top of the bats?

 

[Trails2004]

Remind me of an overweight guy that I used to work with that spent $600 on a titanium bicycle seat because it was lighter then his original seat. He rode twice a month and drank beer afterwords. You can spend a lot of money and never see an improvement or return on your investment.

....but he looked cool

 

[jgedmond]

I read the article and think it's pretty good about the issues with open cell foam and what has happened to houses that use it, but I also think it's a bit slanted in making excuses for those issues. I think that the one thing that we can all agree on when discussing open cell foam is that there have been issues with it and there is a gamble that is taken when using it. The more you search about it, the more you will read both sides of the debate, and for those that support it, the blame is always on the install.

Yeah, that's my take as well. Like many things I think that it does come down to details of the installation. The closed cell properties make it more robust to installation errors. Improper curing and such could still screw up a closed cell foam job.

It seems that the key with open cell is to keep the dewpoint of the attic air above the roof deck temperature. If that is done most of the time, then the deck will be dry or have time to dry between wet periods and not rot. Besides attic air dewpoint, sun exposure of the roof will be very important to keep the roof deck above the dewpoint. The small air gap between the metal roofing and OSB will help the decking stay warm overnight after daytime heating.

I probably need to embed some thermocouples in the foam touching the OSB and monitor dewpoint in the attic air to decide if there is a problem.

 

[EddieWalker]

On top of the bats?

Yes. Just think of what you have as a first layer with the existing bats. At R19, you need another 6 1/2 inches to hit R30