The problem was that the installer was doing his first spray foam job ever, and the thickness of the insulation varied from zero (visible roof deck) to about 9". Unfortunately, good average thickness doesn't cut it. The coverage needs to be uniform because a lot of heat will go through the under-insulated areas. (See my article on flat or lumpy insulation performance.)
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Spray foam insulation or spray polyurethane foam (SPF) is an alternative to traditional building insulation such as fiberglass. A two-component mixture composed of isocyanate and polyol resin comes together at the tip of a gun, and forms an expanding foam that is sprayed onto roof tiles, concrete slabs, into wall cavities, or through holes drilled in into a cavity of a finished wall.
While coatings may potentially stop minor leaks, the roof should be properly repaired and dried prior to coating application. Coatings may be able to seal pinhole leaks, which are leaks not visible to the naked eye. If the roof is leaking, the roof leak will need to be identified and repaired prior to any recoating; do not expect the coating to find and seal the leaks.
Before you decide on spray foam or another method of insulation, it's important to understand the superiority of spray foam compared to traditional materials. When compared to fiberglass batts, spray foam offers nearly double the R-value per inch, achieves air-sealing and insulation in one step, won't be damaged by mold or moisture, and won't settle, compress, or otherwise be damaged to the point it needs replacement.

For large jobs, professionals such as Dr. Energy Saver use two-part foam, which comes in larger containers. With 2-part spray foam, it's necessary to mix separate resin and catalyst compounds at the application nozzle. Combining these ingredients starts a chemical reaction that creates expanding foam. Contractors use small 2-part foam "kits" to air-seal an attic or to seal and insulate ductwork. To insulate an entire attic or wood-framed wall with spray foam, the resin and catalyst compounds are pumped to the application nozzle from 50-gallon drums in a specially equipped truck.


Spray foam insulation, when properly installed is both an air barrier and when closed cell foam is used at the proper depth a vapor barrier!  Before hiring any contractor you should establish the brand of foam being used and verify that with the named manufacture.  Please ask for ESR reports and MSDS sheets on any foam being installed in your home. A couple areas where you might consider spray foam insulation include:
Jennifer, I'm not an expert on the health effects of closed cell foam. A lot of people live in houses with closed cell foam and have no health problems from it, at least not short-term, acute problems. I do know of one person who had it removed from her crawl space because she was convinced it caused her dog to get sick, but I know only what she told me.  
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We have a 22 year old home located in southeastern georgia where the humidity is very high. In the past 2 weeks our floors have started buckling all over. We have a vented crawl space and the old insulation is drooping from moisture and the wood is wet. We are debating between the "encapulation" method or the spray foam method to repair this issue. Which would you recommend?
Spray foam is a chemical product created by two materials, isocyanate and polyol resin, which react when mixed with each other and expand up to 30-60 times its liquid volume after it is sprayed in place. This expansion makes it useful as a specialty packing material which forms to the shape of the product being packaged and produces a high thermal insulating value with virtually no air infiltration.
To avoid the expense re-roofing a house that is simply suffering from nail fatigue, and to obtain optimum insulation, an 85mm layer of polyurethane foam can be sprayed onto the underside of the slates or tiles of a pitched roof. This stabilises and weatherproofs the roof by fixing the nails, battens and roofing felt. As the foam is a superior insulant, coupled with just 100mm of insulation at joist level, your roof will also meet the stringent thermal performance standards required for a new home. A typical roof can be insulated using the polyurethane treatment for around half the cost of re-roofing.
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Apply coating when the roof is dry and the sealant has set. You will be using a 9-inch heavy-duty frame, ½-inch paint roller for spreading coating on roof or 1-1/4-inch roller for dipping in pail, and a 5–to-6-foot extension pole. Use a 3/4-inch roller with basecoats and emulsions. Map out your roof and make each pail fill that area. See Elastek Product Sheets for recommended coverage. An inexpensive 3-inch or 4-inch brush should be used to reach areas not possible with a roller. Use a stiff paintbrush for applying 103 Crack & Joint Sealant.
If you cut the nails holding one of the corner studs to the bottom plate and the top plate with a Sawzall, you can use a flat bar (or a flat bar plus a wrecking bar) to pull the stud off the sheathing nails. Either re-use the stud, or buy a new stud, and install the stud with toenails as shown in the link I provided in Comment #51 (this link: Outside corner detail).

How Much Will Spray Foam Save Me

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