Roof Insulation Spray Foam

[niceg3s]

Anyone done this? Cost to vacuum out old and spray in new? Was it worth it?

[Txhunter3000]

What insulation could you be vacuuming out of the rafters?

[niceg3s]

It’s blown in circa 1996. That’s all I could tell you.

[TeamAmerica]

Why not just blow some more in there? It is quite a bit cheaper. Is this your forever home and want to do it once right?

[Txhunter3000]

I know I'm nitpicking but if it was blown in the rafters it would fall out. Sooo it seems you could just have it blown in the rafters and keep what you have in the ceiling joists. Just add ventilation in the attic to keep humidity under control. You should get with your HVAC guy and see what he says about bringing in fresh air.

[Strummer]

I’m the attic ? If it’s spray foam leave the old stuff . The foam goes in the roof .

[Kirks55]

What this guy said. When I go to spray foam I will leave blown insulation in place because spray foam will be applied on roof osb

I’m the attic ? If it’s spray foam leave the old stuff . The foam goes in the roof .

[niceg3s]

Has anyone ever been in an attic where it was done? Seems to make a huge difference.

[Rush2Judge]

We did what you are describing to our lake house. Took out all the old insulation and spray foamed the roof and overhangs. We also took the insulation batting out from under the house and sprayed closed cell foam.

I want to say the whole thing was about $12K for a 1500 sqft house. We love it. This Summer in 100 degree afternoons it was high 80's in the attic. House stays cool (warm in Winter) and the humidity stays in the low 40's.

[matagordian]

I know I'm nitpicking but if it was blown in the rafters it would fall out. Sooo it seems you could just have it blown in the rafters and keep what you have in the ceiling joists. Just add ventilation in the attic to keep humidity under control. You should get with your HVAC guy and see what he says about bringing in fresh air.

Pretty sure he is saying he has blown in fiberglass or cellulose on the floor of the attic (joist)

[7sdad]

Has anyone ever been in an attic where it was done? Seems to make a huge difference.

My whole house is spray foam and the attic never gets over 85 or so during the summer.

[Mountaineer]

Has anyone ever been in an attic where it was done? Seems to make a huge difference.

Yes. I’ve seen it done wrong many times. I wouldn’t recommend spray foam modifications on existing homes. Can you do it? Yes. Is it worth it? Probably not depending on the situation.

Replacing blown or batt attic insulation with spray foam is not plug and play. Several modifications need to be made to do it correctly on an existing home.

Attic ventilation (soffit and roof) needs to be sealed and previous insulation needs to be removed. You are turning the attic into a conditioned space and the attic air will mix with the interior of the home. Adding a supply/return duct to the attic may be needed also. If you don’t have electric heat and water heaters, high-efficiency gas furnaces and water heaters need to be installed. Spray foam should not touch standard metal B vent piping for standard gas appliances and these gas appliances need exterior air for combustion. This includes gas fireplaces vents also.

If you have a vented attic now, add more insulation and increase attic ventilation. Homes from the 90s and early 2000s generally have poor attic ventilation and limited insulation.


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[Mission408]

I’m the attic ? If it’s spray foam leave the old stuff . The foam goes in the roof .

Can cause mold under this condition. Attic becomes a "conditioned" space with no place for humidity to go

[RiverRat1]

Has anyone ever been in an attic where it was done? Seems to make a huge difference.

Yes. You're attic can then become a climate controlled storage area.

[Adgerc15]

I've considered a similar solution, assuming he is talking about the attic roof in a current not-conditioned attic. Is another option to spray in radiant barrier?

If so, does radiant barrier reduce air temp in attic and help conditioned space in the ome maintain more moderate temps? My upstairs will get up to 85 degrees in the peak of Summer in DFW. AC just cant keep it cool.

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