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.  https://www.youtube.com/v/ggLAUsiuI_o&feature=share

Allison--would be very interested in your take on the GHG issues of foams, which have received lots of smart commentary recently. To highlight a few: architect Jesse Thompson's comments on Tom's Good vs Bad post on Energy Circle, the very thorough piece by Alex Wilson on Green Building Advisor and Michael Anschel's cautionary diatribe on Remodeling. 

How Much Does Spray Foam Insulation Cost


In the early days of insulating attics, people believed the insulation was a heat source. That’s not the case, as the insulation is actually a barrier between two areas of different temperatures. As for the “hot roof” theory, the unvented attic system could make the temperature of the roof go up a little, but this increase won’t cause damage to your shingles.
We have a 1950's ranch in Atlanta and are interviewing foam contractors to spray open cell under the roof, with an "ankle wall" out towards the eaves to seal the attic. My wife and daughters are chemically sensitive, so I'm trying to figure out how to minimize the fumes coming into the house. Additionally, at least one contractor has offered (for > $900) to remove our existing rock wool & R-13 fibreglass from the attic floor to "increase cross-ventilation into the attic". Seems to me I can't both minimize fumes AND increase cross-ventilation. They also offered to spray a fire-retardant on for >$600. Would ventilation during installation help any or woud the retardant seal off the foam and help that way? Thanks...

My other question was gonna be this. We ripped all the drywall out after Hurricane Harvey and we found some latent termite damage from some time back. One of the common studs in one corner is pretty well eaten to shreds. I was gonna brace it but then I read about more modern framing practices and I read how each stud is a thermal bridge. So now I'm thinking that I won't bother with it because the house hasn't fallen down and the foam might help a little. Unless you say to brace the stud. Then I'll do it, Martin! :)

How Much For Spray Foam Insulation


Warning: EnergyGuard™ Elastomeric Roof Coatings can freeze below 32° F. This is because the product is water based. In case of freezing temperatures, stop the application process. After application, you must allow the product time to dry before exposing the elastomeric roof coating to foot traffic or water. You should also cover the containers and dispose them responsibly after application. In case you or someone else i.e. a child ingests the coating seek immediate medical attention. Don't induce vomiting. https://www.youtube.com/embed/ggLAUsiuI_o
Most closed-cell spray foam is now formed using hydrofluorocarbon (HFC) blowing agents that have high global warming potential, partially or completely offsetting the climate benefits of the energy savings they can offer. In the United States, HFCs are scheduled to be phased out by January, 2021. A few spray foam suppliers have started supplying spray foam blown with hydrofluoroolefin (HFO) blowing agents without this problem as of early 2017.[14]
Closed-cell foam has a higher density and offers a higher R-value per inch. It also adds strength to walls, ceilings and roofs and can contribute to a structure’s overall durability. Additionally, closed-cell foam’s low water vapor permeability offers protection from moisture when installed in places where high humidity—from climate, occupants, or flooding—meets the structure. 

These coatings are emulsified asphalt and consist of asphalt particles dispersed in water; they utilize clay as the emulsifying component. These coatings also contain many types of organic and/or inorganic fibers and fillers to provide extra strength to the coating. These coatings are available in black, brown, or as a reflective coating when titanium dioxide or aluminum pigments are added.
ACRO, Active Ventilation, AES Epoxies, AES Raptor, AJC, Albion, Alcoa/Marson, All Line, Alpha ProTech, American Sealants, Applied Technologies, ASI Products, Attic Breeze, Aztec Washer, Babcock- Davis, BAK Welders, BASF, Berger, Berry Plastics, Biltrite, Brentwood, Brewer, CEP, Chem Link, Cleasby, CME Manufacturing, CPR, Deks, Dow, Eagle, EagleView, Erin Rope, ES Products, Eternabond, Everhard, Falltech, Flame Engineering, Flashco, Foxy, Franklin / Titebond, Fry Reglet, Greenstreak, GSSI, Guardian, Harpster, HY-C, Interwrap, ITP, ITW, Jaaco, JL Industries, Josam, Karnak, Levis, LionGuard, LSP, Lucas, Luco, Makita, Marathon, Marshalltown, Maze Nails, MEC, MFM, Miro, MM Products, National Nail, Natural Light, Newborn, OMG, Pam Fasteners, Pearl, Polar Blox, Polycoat, Portals Plus, Powers Fasteners, Prime Source, ProTech, Protecto Wrap, Pylex, Quarrix, QuickMount, RHH Foam, Robetex, Roofmaster, RoofTop Products, Senco, SFS Intec, Sievert, Simpson Strong-Tie, Smith, Sno Gem, Solomon, Sonneborn, Steelhead, SunRise Solar, Sunset, Super Anchor, Surebond, Swan Secure, TRA, Trufast, United / Quest, Vulcan, Wade, Watts, Weatherbond, Werner, Western Colloid, Winco, Zurn
I am an Architect in Toronto. I am designing a new roof addition to a row house building. Because of existing conditions and the shape of the new roof. It may be easiest to use closed cell spray foam within the areas of the joists. My question is when spray foam is used in this situation do I need to worry about how the joist members may be thermal bridges? It is not common to provide a little bit of rigid insulation to protect the joist members? The additional layer of outboard insulation will require an extra layer of plywood above the insulation which will add to cost.
I've seen this only once, and it was with closed cell foam, but I've heard of it happening with open cell foam, too. I don't know the details, but I've heard it could result from a bad batch of chemicals, improper mixing, or too high a temperature. Whatever the cause, it's not a good thing. The photo below shows how the spray foam pulled away from the studs. A little bit of uninsulated area like that adds up to a lot of heat loss/gain when the whole house has that problem, as it did here. 

How Much To Spray Foam Basement

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