Insulating the attic - spray foam?
8 years ago
last modified: 8 years ago
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Spray Foam in Cathedral Ceiling and Attic Floor Joists question
Comments (6)you are correct....open cell is the cheaper, less R and higher perm (allows more water through) then closed cell. Closed cell will be a added cost, but would probably be worth it in the basement at least. Closed cell, in general, will seal up your entire house better then open cell, as well as add structural rigidity to your 2x4 framing making your house stronger. Open cell does not. Closed cell is not water proof, as it seems your questions are hinting toward. Cellulose is just fine for the attic, and going with more closed cell is a waste of money IMO. An animal can rip apart open cell just as easy as getting into cellulose. Besides, if something gets in there you have bigger issues anyway! Also, your roof is suppose to be water proof....not your insulation. If your roof is failing, you do NOT want a water proof insulation anyway. This traps water and allows wood to rot, thus a possible structural failure in your roof without you really even knowing. You may also be money and r value ahead to practice air sealing your walls with caulk and then using a blown fiberglass or dense packed cellulose in your walls. A side note...spray foams are THE most expensive possible way to insulate a home, and most cases you will never see a ROI compared to dense packed cellulose and blown fiberglass with air sealing especially in your climate. (note, I never mentioned batts)....See MoreSpray Foam(hard foam) or Radiant Barrier to Attic Ceiling
Comments (2)There is no question that you will see a benefit from having the attic sealed with spray foam... the question is it worth the cost? From a study: FSEC-CR-1220-00 http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1220-00-es/ "Roof and attic thermal performance exert a powerful influence on cooling energy use in Florida homes. Unshaded residential roofs are heated by solar radiation causing high afternoon attic air temperatures. The large influence on cooling is due to increased ceiling heat transfer as well as heat gains to the duct systems which are typically located in the attic space (Figure E-1)." My summary: Sealed attic construction as promoted by spray-foam installers is not as big a benefit in primarily cooling climates as they promote. If you start with black asphalt shingles, switching to white asphalt will save 4% the spray foam sealed attic will save 9%. White metal, however can save 20-23%! So do you need a new roof? The selection there can surpass any savings you would get from a sealed attic. Of course, if your ducts are leaking, having them sealed would be smart as well, no matter which path you take. Andy Here is a link that might be useful: Comparative Evaluation of the Impact of Roofing Systems on Residential Cooling Energy Demand in Florida...See MoreType of spray foam/sealant to be used for air sealing attic
Comments (3)Thanks for the feedback. Worthy, We'll ask the insulation company to remove the foam that could possibly be affected by the chimney heat. Even though we don't use the fireplaces we want to keep the option open. Energy rater, I should have been more specific in my posting. The foam was just used for air sealing the leaky areas and not the entire attic. Also, the foam was applied only to the perimeter of the housing of the recessed can(may be about 1/2 inch think) and not completely over the housing. The reason for foaming around the cans was because there was a possibility that the holes cut for the cans were slightly larger than the cans. I am assuming that this shouldn't cause problems with the holes in the housing. Please correct me if I am wrong. My only concern was if the housing will get hot enough to make the foam on perimeter burn. BTW, we use CFL bulbs. You are right about the flue vents, For the gas furnace and water heater. We asked the guy doing the air sealing to remove the foam around them. Should we be concerned about the dryer vent though? Other than the chimneys, flue pipes, kitchen and dryer vents we couldn't think of any other places which might get warm/hot. Should we worry about anything else?...See MorePolyurethane foam insulation recommendations
Comments (8)A cathedral ceiling with only 2x4 rafters? It must be a fairly small room. Is it uninsulated now? Is it vented? We've used Tiger Foam for some jobs, and it performs great but is a royal pain to work with overhead. It is super sticky and gets everywhere. It is also very touchy, in that it needs to be right around 80 degrees when you use it. Spray-in foam is very expensive, probably the most expensive insulation out there, whether you do it or have it done. That's why for the last two similar jobs we ended up using solid blocks of foam, which we can cut to size and fit between the rafters. It has the highest R-value per inch, is very reasonably priced for the performance you get, and is friendly for the DIYer. I'd say that unless you are very adventurous and handy, spray foam is not a good DIY project. Also, are you doing this with a permit? R38 is the code for California ceiling insulation, which I believe would be essentially impossible in your situation without making the rafter bays deeper. Solid foam will give you the most bang for your buck, and would get closest to the R38 requirement. Code also says you must have a ridge vent, which helps prevent overheating of the roof, causing the adhesive an asphalt shingles to fail, among other things. We no longer work in the Bay Area, so I'm sorry I don't know any contractors to recommend there....See MoreRelated Professionals
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