Spray Foamed attic problems
veloguru
11 years ago
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kirkhall
11 years agoworthy
11 years agoRelated Discussions
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 MoreStrange frost pattern on roof after attic spray foam?
Comments (13)Yes, it's a "conditioned attic", which is why the soffit penetrations (above top-plates) have been foamed shut. They're actually backed with with some of the original fiberglass batting to give the outside surface of the foam something to cure against. I'm in CL3, so recommended ceiling R-value is 30 or 38 depending on which version of the IECC specs you use. Unfortunately, I fell pray to the "foam performs better than permeable insulation, so even 3-4 inches performs better than the most of your neighbors" argument, so strictly speaking, the R-value requirements were likely not met. In fairness, I probably have around R-25 once all is said and done and any inefficiencies are accounted for. I'd love to go back 6 months and pay a little more for the extra pass (1-2 inches) to bring it up to the rafter surface and all the rafters, but I didn't. Thankfully, the argument that the biggest benefit is the near perfect air sealing is still true and I will get the lion's share of the benefits even if it's slightly below the recommended thickness. If I ever have my other roof elevation sprayed (over the garage, still a "vented attic"), then I may have the contractor "skim" another inch on top of the existing job. The cost of getting them out there to set up the job is most of the cost. $/foot goes down somewhat as the job gets bigger, so it'll only make financial sense to add foam if there's other work being done. Thanks for all the comments! Dan...See MorePutting attic AC unit in insulated enclosure vs. spray foam
Comments (31)The moisture problem on the roof deck may occur when the deck is colder than the air rising into the attic. How is a whole house dehumidifier going to solve this problem in the winter. During the winter houses in SE PA are struggling to raise their humidity level to 40%. Many are running humidifiers in the winter which will further aggravate the problem. I have looked at a lot of new houses in the NJ and PA area. I can't recall any having HVAC equipment in the attic. I have never seen a house with a spray foamed roof deck either. I am skeptical you will find an insulation contractor who has experience doing this in a new residential home. If you do find one, you know the questions to ask. See if his answers make sense....See MoreMongoCT
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