[Bigbux58]

Gents,
Brand new here. Quick run down on my issue... Had to remove all my attic insulation due to raccoon damage during the time of the previous owner. ( been in the house a few months) my question is... I'm thinking about installing 6in. Of open cell spray foam to the attic floor. Got a few quotes... For 1053sq it's 2000-2500 bucks. Not much online or YouTube of people doing this. Do you think it's the right thing to do? I live in Pittsburgh by the way... Thanks in advance

 

[joecaption]

I'd be using blow in insulation, far less costly, and DIY do able.
Buy 10 bags at Lowe's of HD and they let you use the blower for free.

 

[Bigbux58]

I'd be using blow in insulation, far less costly, and DIY do able.
Buy 10 bags at Lowe's of HD and they let you use the blower for free.

I looked into to that as well. For cellulose. I would need about 85 or so bags for the right r value. With that and other stuff I would need to buy, it would cost around $1000. I know the savings would be more, but is it worth the extra g for a better product/result... I don't know...

 

[jlhaslip]

An issue which might alter your plans is whether there is a vapour barrier installed already. You would not want a closed cell foam over an existing vapour barrier. Condensation would be trapped and cause some grief. If you decide on the foam alternative, spec an open cell foam if there is a vapour barrier in place.

 

[Bigbux58]

An issue which might alter your plans is whether there is a vapour barrier installed already. You would not want a closed cell foam over an existing vapour barrier. Condensation would be trapped and cause some grief. If you decide on the foam alternative, spec an open cell foam if there is a vapour barrier in place.

There is no vapor barrier. Would it be nesisary? Since cellulose or Fiberglas doesn't require it...

 

[joecaption]

There is no location in your profile, this is a class case where a location should be added.
https://www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_insulation_table
Air sealing, proper attic venting is just as important!

 

[Gary in WA]

PA doesn't require a vb in the ceiling if the air space above (attic) is over 12" high. Since you have a vented attic above, most often blown-in FG (low density- so it takes a lot more material-height)/cellulose is used so you reach the required R-value on ceiling per code for location- R-38; http://energycode.pnl.gov/EnergyCodeReqs/index.jsp?state=Pennsylvania It's a good air sealer though. IMO, use rigid XPS for better R-value at the reduced clearance perimeter walls. Cover any exposed Romex with-in 10' of access hole, per code.

Gary

 

[Bud9051]

The numbers aren't adding up for me. You say 1,000 ft² for $2,000 to $2,500. Gary says r-38 is probably required and I agree. Open cell is about 3.6 per inch for r-value. To get to 38 you would need 10 inches + of open cell. At a typical $0.50 per board ft you would be looking at 10,000 bd ft or $5,000.

I don't think their bid was for 10" of foam insulation and if not, how did they plan on meeting code?

Of course I could be lost, it happens. Corrections welcome.

Bud

 

[Bigbux58]

The numbers aren't adding up for me. You say 1,000 ft² for $2,000 to $2,500. Gary says r-38 is probably required and I agree. Open cell is about 3.6 per inch for r-value. To get to 38 you would need 10 inches + of open cell. At a typical $0.50 per board ft you would be looking at 10,000 bd ft or $5,000.

I don't think their bid was for 10" of foam insulation and if not, how did they plan on meeting code?

Of course I could be lost, it happens. Corrections welcome.

Bud

I agree... That's one of the issues I'm having. All 3 of the contractors told me 6in. In fact another told me 4in is fine... I asked them about the r value and they said it's technically not the same cause it is a complete air seal. Anything over that would be redundant. Very little info online about it. Are they lying just to get the work and under insulating my house... I don't know.

 

[Bud9051]

Yes, it is their little white lie and the foam industry has been arguing for years that they should get more credit for their r-value than all other forms of air permeable insulation. But, what they are proposing doesn't meet code, unless you get your local office to accept less than 20 for r-value and (importantly) 5" doesn't make it to the top of the 2x6 joists (assuming ex6) to reduce the thermal bridging.

For that same money you could install those 85 bags of cellulose and cover everything.

The reason for the lie is their product will do a good job, but will not sell at the code level of installation. There are times and places where a foam installation makes sense, but a flat attic floor is not one of them.

Bud

 

[Bigbux58]

Yes, it is their little white lie and the foam industry has been arguing for years that they should get more credit for their r-value than all other forms of air permeable insulation. But, what they are proposing doesn't meet code, unless you get your local office to accept less than 20 for r-value and (importantly) 5" doesn't make it to the top of the 2x6 joists (assuming ex6) to reduce the thermal bridging.

For that same money you could install those 85 bags of cellulose and cover everything.

The reason for the lie is their product will do a good job, but will not sell at the code level of installation. There are times and places where a foam installation makes sense, but a flat attic floor is not one of them.

Bud

Thanks... They are 2x4 joists and he said he would go over the joist to stop the thermal bridging. Would you have any idea what office I would need to call? I have no clue what department I would need to talk to.

 

[Bud9051]

Code enforcement would be a good name to ask for. 99% of the time the front office people are extremely helpful and knowledgeable. I'm sure they will direct you.

Bud

 

[Gary in WA]

They are quoting you the "performance path" correctly, not Code "prescriptive
requirements" (Code). They are confusing what you want or you are not specifying it correctly. Read this; http://www.greenbuildingadvisor.com/blogs/dept/musings/it-s-ok-skimp-insulation-icynene-says

In your attic, SPF WILL stop any convective loops on the attic floor- de-rating any fibrous insulation AND it will air seal the room air/moisture below from reaching the attic to cause ice dams or rot/mold the roof sheathing. They do have some good points; http://www.icynene.com/fbdocs/TheEconomicThicknessofThermalInsulation-April2013.pdf

3" of cellulose also stops convective loops especially after it forms a "crust" on the top few inches years later.

If not following code, there is a cost/value ratio you can follow;http://www.marchandmartin.com/S-Economic Thickness of Thermal Insulation.pdf

Gary