The big disadvantage with spray foam is cost.
Spray in the attic.
Choose from two types.
Earlier this year i got a question about a home that had spray foam insulation in the attic.
Nothing unusual about that.
Spray foam attic insulation.
Spray foam offers the best attic insulation performance available.
However in a vented attic situation it will become approximately 130 degrees in the summer.
The practice of foam insulating the attic has raised eyebrows in the building industry because standard roofing techniques call for the attic to be ventilated.
Spray foam installers may miss some of the air leakage sites in the attic which can lead to problems in the insulation of the attic.
They sport insulation values of approximately r 6 5 and r 3 6 per inch respectively.
A lot of builders and homeowners are going with spray foam insulation because of the airtightness benefits but then the questioner mentioned that the spray foam contractor had intentionally left big holes to the outside by not sealing the gable vents.
There s no reason for an air conditioning and vent ductwork to have to work in that type of severe conditions.
If you don t have hvac and ducts in the attic spray foam on the roofline isn t really necessary.
It s generally 3 to 4 times what you ll pay for blown cellulose or fiberglass.
I d blow insulation on the attic floor after air sealing of course.