Question: Why not heat the non vented attic? | Insulation/Energy/Building Envelope Q&A | Spray Foam Technical Questions and Answers | SprayFoam Magazine Q&A Forums

Q&A Forums

Question: Why not heat the non vented attic? Post New Topic | Post Reply

Author	Comments
Posted: Apr 26, 2007 05:11 PM	Question: Why not heat the non vented attic? We are building our home on the Washington Coast where temps are very mild (35 to 70 degrees year round), but we have lots of misty, wet and windy weather on the shoreline. The roof will be a 2 and 12 pitch and after the open cell foam is installed there will be scant little air volume left. With no roof vents or bird block vents and a heat pump heating system, I thought I would consider adding a small supply vent to the attic and a small return air pipe from the attic to the airhandler return. My thought being this would help circulate and disperse any latent moisture accumulating in the attic from the living space via the wallboard ceiling below? Stupid idea? Colin
Posted: Apr 26, 2007 09:33 PM	Colin, If your weather is misty, wet, and windy, why don't you use a closed cell foam?
Robert Dossett Posted: Apr 27, 2007 01:05 AM	Greetings from the wet side. Depending on your jurisdiction, you may not be able to vent the sealed attic in conjunction with the living space. The only reason to vent it would be if there was an unusually high moisture drive from one direction, like from a pool or spa. As long as your HVAC is designed right, there should be no worries with latent moisture accumulations. Look me up if you have any questions, I may be able to help you. Grays Harbor Insulation and Contracting, Aberdeen, WA
Posted: Apr 27, 2007 02:54 PM	Actually, I had to push my installer a bit to even give me a quote for the closed cell. He insisted that our zone did not require it and it was more expensive than open cell anyway. I have been reading all the conversations here and reading everything else about the open versus closed cell. The building department in Pacific County will permit either and like the fellow in Chicago I have heard all the "reasons" why open cell is better, why closed cell is bad. There are very few installers out here and I was able to locate one that will do either, but does 93% of his jobs open cell and hasn't done a closed cell in several years. He did agree to do closed cell if we framed with 2x6 studs so that his installers did not have to deal with overflow foam remove after the R19 was achieved because the County wanted the entire stud void filled. I have furnished the building department the ASTM C518 Acceptance Criteria for the 2 pound closed cell at 6.3 R per inch and asked them if they will allow a partial file of the 2x6 voids to an R22/R25 rating. If they OK that, then the closed cell with add about $2,500.00 to the total job and I will pay the extra. I posted my attic heat question because I was worried that I might have to stick with open cell and its claimed absorbtion of water vapor. I am also foaming the floor joists in crawl space and with the open foundation vents there is always dampness. Here on the coast you have to use plastic strapping to hold the floor insulation in place because the salt air disolves any metal exposed to it. My query about providing some air movement was a general fear of the open cell with regard to moisture. This is our future retirement home and I don't want to be dealing with problems down the road when I am more of an old fart then I am now. :)
Posted: Apr 27, 2007 03:18 PM	Thanks for the offer. I really hate to fess up about the HVAC issue as I will probably get beat up pretty bad on this forum :( When I got my bids on the foam and a bid for a 3 ton Heat Pump system from a local installer, I knew that the budget wasn't going to handle the impact of both. I am reasonably handy, having done just about every aspect of the building trade for my own personal homes over the years and decided I would tackle the (yikes!) installation of my heat system all by my lonesome. I am still doing the research but figure I can buy the units on the internet and I got a wholesale supplier of the ductwork to let me buy from them "if I produce a specific and correctly termed order list". Geez, it is like being back in school and having 3 tons (pun intended) of homework. The savings from this 'adventure' into the world of HVAC is how I am able to justify the expense of the foam installation. The dollar amounts I have seen occassionally on this forum are so much lower than the kind of numbers I get out here, it is almost unbelievable. The only two vendors I found were $5,000.00 apart in their quotes for open cell on a brand new construction home. That was a 60% jump from one to the other. Yikes ! again. My email is listed on my profile info, should you wish to discuss things further. Colin

Author

Comments

Posted: Apr 26, 2007 05:11 PM

Question: Why not heat the non vented attic?

We are building our home on the Washington Coast where temps are very mild (35 to 70 degrees year round), but we have lots of misty, wet and windy weather on the shoreline. The roof will be a 2 and 12 pitch and after the open cell foam is installed there will be scant little air volume left. With no roof vents or bird block vents and a heat pump heating system, I thought I would consider adding a small supply vent to the attic and a small return air pipe from the attic to the airhandler return. My thought being this would help circulate and disperse any latent moisture accumulating in the attic from the living space via the wallboard ceiling below? Stupid idea? Colin

Posted: Apr 26, 2007 09:33 PM

Colin,
If your weather is misty, wet, and windy, why don't you use a closed cell foam?

Robert Dossett

Posted: Apr 27, 2007 01:05 AM

Greetings from the wet side. Depending on your jurisdiction, you may not be able to vent the sealed attic in conjunction with the living space. The only reason to vent it would be if there was an unusually high moisture drive from one direction, like from a pool or spa. As long as your HVAC is designed right, there should be no worries with latent moisture accumulations. Look me up if you have any questions, I may be able to help you.

Grays Harbor Insulation and Contracting, Aberdeen, WA

Posted: Apr 27, 2007 02:54 PM

Actually, I had to push my installer a bit to even give me a quote for the closed cell. He insisted that our zone did not require it and it was more expensive than open cell anyway. I have been reading all the conversations here and reading everything else about the open versus closed cell. The building department in Pacific County will permit either and like the fellow in Chicago I have heard all the "reasons" why open cell is better, why closed cell is bad. There are very few installers out here and I was able to locate one that will do either, but does 93% of his jobs open cell and hasn't done a closed cell in several years. He did agree to do closed cell if we framed with 2x6 studs so that his installers did not have to deal with overflow foam remove after the R19 was achieved because the County wanted the entire stud void filled. I have furnished the building department the ASTM C518 Acceptance Criteria for the 2 pound closed cell at 6.3 R per inch and asked them if they will allow a partial file of the 2x6 voids to an R22/R25 rating. If they OK that, then the closed cell with add about $2,500.00 to the total job and I will pay the extra.

I posted my attic heat question because I was worried that I might have to stick with open cell and its claimed absorbtion of water vapor.

I am also foaming the floor joists in crawl space and with the open foundation vents there is always dampness. Here on the coast you have to use plastic strapping to hold the floor insulation in place because the salt air disolves any metal exposed to it.

My query about providing some air movement was a general fear of the open cell with regard to moisture. This is our future retirement home and I don't want to be dealing with problems down the road when I am more of an old fart then I am now. :)

Posted: Apr 27, 2007 03:18 PM

Thanks for the offer. I really hate to fess up about the HVAC issue as I will probably get beat up pretty bad on this forum :(

When I got my bids on the foam and a bid for a 3 ton Heat Pump system from a local installer, I knew that the budget wasn't going to handle the impact of both. I am reasonably handy, having done just about every aspect of the building trade for my own personal homes over the years and decided I would tackle the (yikes!) installation of my heat system all by my lonesome. I am still doing the research but figure I can buy the units on the internet and I got a wholesale supplier of the ductwork to let me buy from them "if I produce a specific and correctly termed order list". Geez, it is like being back in school and having 3 tons (pun intended) of homework. The savings from this 'adventure' into the world of HVAC is how I am able to justify the expense of the foam installation. The dollar amounts I have seen occassionally on this forum are so much lower than the kind of numbers I get out here, it is almost unbelievable. The only two vendors I found were $5,000.00 apart in their quotes for open cell on a brand new construction home. That was a 60% jump from one to the other. Yikes ! again. My email is listed on my profile info, should you wish to discuss things further. Colin

You need to login to reply to this topic. Please click here to login.