Spray foam is a fully adhered insulation that is spray applied into wall cavities, providing a continuous air and moisture barrier. Spray foam allows efficient use of your HVAC system and helps regulate the temperature fluctuations and humidity in your home. Spray foam effectively seals the building envelope, filling in any cracks and crevices, the common source of air and moisture infiltration as well as temperature variations. http://youtube.com/watch?feature=player_embedded&v=ggLAUsiuI_o
Thank you, Allison. We have a split system unit (actually 5) with the heat being propane. The foam guy said that it needed ventilation, so completely sealing the attic wouldn't be a good idea. It sounds like you are saying that the systems need to be vented out of the attic or replaced with some type of closed system. But I shouldn't bother spraying if the plan is to leave the soffet vents open. Is that correct?
once the foam is installed correctly, it is a inert plastic not much different than the foam cushions you sit on. there is not a health rick unless you have off ratio uncured foam that has not mixed properly. the foam is absolutely a health risk in its raw forms before it is mixed and cured. You should not be in the building without proper respirators and eye protection. The spray foam industry should be controlled and regulated by the same standards, testing and inspections that framing ,electrical and plumbing are. until that happens then you will have idiots with spray rigs ruining peoples homes and ruining the market for honest foam contractors that know how to price a job fairly and complete it correctly.

How Much Is Open Cell Spray Foam Insulation

I don't even want to ask this question but... several years ago we hired a local contractor to spray high density foam on the roof deck and walls of our unfinished 2nd floor. We realized that the job was done poorly and cut an access into the attic space to assess things. We realize now that they spray foamed directly to the chimney (no flashing). The chimney is currently used for a woodstove and DHW venting. The DHW will go away but wood stove will remain. My question is, how bad (unsafe) is this? I have found information on foam exposure to fire but have not been able to find anything about temperature ratings in general (i.e. what happens on prolonged exposure to high temperatures).
Steve: If your spray foam installer leaves the vents open, he will be committing the 2nd of the 4 problems I described above. You will most likely have comfort and efficiency problems. You may well have condensation problems. You will be spending a lot of money on a product that likely won't perform as it should. Don't let him leave the vents open. If the installer you've chosen doesn't understand this, you may want to choose someone else. 

Spray Foam Garage

That’s $58.3 Billion dollars. That’s roughly how much money we wasted in 2010 in the US according to the Department of Energy because of air leaking out of our building envelopes. If your building leaks energy, you’re paying more for energy than you need to. Clearly you’re not alone. If you’re ready to claim your share of the savings, it’s quicker and easier than you think.

Roof Coating Seal