I'm looking to build pretty soon. We are in superhot, superhumid houston. I think I have a builder. He has done spray foam insulation before but not much.
I am looking for someone who can expertly answer questions on spray foam AND how it ties in with hvac and attic ventilation, especially in humid climates (miami, houston, etc). Willing to pay a reasonable fee. Probably a half hour of time, but you tell me.
Post here and i'll get my contact info to you.

Go to sprayfoam.com there you can register and ask questions of foam applicators directly

Homes in hot humid climates like Houston benefit from sealing the attic from outdoor air in several ways. The humidity brought into the attic from traditional venting schemes represents a much larger latent load to the AC than the sensible load it might experience from higher temps. But if you insulate at the roof deck, even the sensible load from the attic is lower (important for system efficiency if the HVAC ducts &/or air handler are in that attic.)

Insulating the roof deck raises peak roofing temps somewhat, reducing the lifespan of shingles slightly, but the energy cost savings will typically pay for that reduction in roofing lifecycle cost on the roofing several times over.

I think its a non-issue, dont waste your money on a consultation. All you need to do is make sure you dont hire hackers, people fail to realize how important this is. If you get in touch with a quality HVAC contractor they will size your system perfectly with a heat loss analysis taking the r value of your insulation (and many other things) into account. Worry most about the kind of job your general contractor will do, and make sure he does not scrape the barrel with his subs...

If you have contractors that understand the difference in heating/cooling loads between a vented attic and non-vented (foamed) attic you should have no problems. Please DO NOT use R-values for load calculations. Foam works much better than any other type of insulation, (it's why they used it in spacecrafts, yes, spacecrafts!) R value will WRONG SIZE your A/C units.

If R values are not used to determine value, what is the alternative. That statement made no sense to me.

Spray foam kits are quicker and easier to use plus you get a seamless air barrier and high r-value in just 1 inch.

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