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Question DetailsAsked on 5/23/2011

Lack of ventilation with spray foam insulation

I am planning on reroofing and redoing the insulation in my home in the Central Valley of California. The spray foam insulation salesman says they would seal up the attic and enclose the attic space with insulation so that it will be the same tempurature as the interior of the house. He also says the foam will block moisture so you don't need ventilation to remove moisture to prevent rot in the roof. The roofer says sealing off the vents will void the roof warrenty. The foam insulator responds that the roofer doesn't know his technology. Where is the source that can be trusted to resolve this? The spray foam insulation seems better than fiberglass in other respects so if this could be resolved I'd go with spray foam.

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5 Answers


To answer your question, " Where is the source that can be trusted to resolve this?" There isn't one. Which salesman do you want to believe?

The roofer is going on the manufactures guide lines and your foam guy is going on a kinda out there principle of building science.

Think about this! "The spray foam insulation salesman says they would seal up the attic and enclose the attic space with insulation so that it will be the same tempurature as the interior of the house.".

Do you live in your attic? If not, why should you expend resources/money on heating/cooling it?

There are better ways to effectively and economically improve the comfort and safety of a home.

Answered 9 years ago by Frank


honestly the source to be trusted is almost any trade manual the city building inspector or architectural engineer .. the roofer is pretty much right too most material warranties would be void if that roof was sealed up thats why rafter vents are installed befor sealing and insulating rafters there are reliable builders with years of experience even education the indutry spends billions of dollars every decade developing material which determines trade practices based on that science frank mentioned your insulation guy was a tin man

Answered 9 years ago by ahrextreme


geeze i cant sleep thinking about jgdeans kids growing up with birth defects because of his insulation salesman.. dont forget heat rises an unventilated attic can get to temperatures in excess of 1400 degrees as it heats the entire house heats your air conditioner loses effectiveness and breaks down the exterior of your house then suffers as the heat transfers it melts shingles siding and engineered flashings etc.. spray foam is used in commercial application to not only insulate but often help fire block the high exposed well ventilated underside of the roof whoever is trying to get you to seal up your attic should be arrested for misrepresentation and reckless endangerment theres just so many things wrong about this entire situation I am a 20 year builder restoration contractor propery claims adjuster with considerable education in all trades as well as engineering and if you are even slightly leaning towards what you suggested please consult and architectural engineer he will verify everything i am telling you.. remember..Jesus was a carpenter

Answered 9 years ago by ahrextreme


what the hell is frank talking about?? frank seems to be on the right track but missing the point just a little bit spray foam s used mostly for repairs and remodeling fairly new to the construction industry especially new construction . has many good uses but the point is your friggen house need to breath or youll give yourself and children sinus and respiratory problems maybe even die when the microbes enter your bloodstream and react with the drugs that you took the day you decided to seal up your house like a tupperware container.. god bless you frank i was just kidding

Answered 9 years ago by ahrextreme


A house needs ventilation for moisture control and a few other reasons you seal it up your material sweats mechanical equipment oxidizes and microbes grow creating an unsafe unhealthy environment for you and your children .. Do you want your children to grow up as an active bacterial culture or as a human being?Your roofer is right as a 20 year restoration general contractor property claims adjuster and trade school instructor i pretty much agree . you need ventilation so the moisture will continually leave or you can die... Is there something you dont understand about that? does the g in jgdean stand for gilligan? Pleas let your roofer take care of this anyone can be a home inspector it costs two hundred dollars and you take an on line test in most states that roofer had to learn his trade in the field he knows best a home inspector is for little more than you having a third opinion to make you feel good about buying a place and in most cases have very little practical experience or education thats why they do what they do

Answered 9 years ago by ahrextreme

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