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?

Spray Foam Attic Insulation

Today, each of the 50 states follows a different set of building codes making navigating these codes confusing, particularly for architects or builders that have projects in multiple states. In some cases, the building code changes significantly between the state and certain cities or counties within the state. For example, at the time of writing Arizona had adopted the 2015 IRC Building Code, however, Phoenix was on the 2012 IRC, IBC and IECC code. With the majority of states either on the 2009, 2012 or 2015 code, below are some high-level points to consider and about how spray foam insulation contributes.
The United States has adapted to using sprayfoam insulation and a new technology called Wall Injection to retrofit existing wall construction by drilling small holes between wall studs in the structures framing and filling the void with a less aggressive expanding water based foam. This allows existing home and business owners to conserve energy by creating a thermal envelope in their existing structure.

I recently did a remodel project for my basement using spray foam insulation. The original builder has used fiberglass, but I wanted the best insulation i could find. We chose closed cell foam because it blocks moisture from getting into the house. It took one day to install and was fumey for about 3 hours. It was pretty cool watching it being done. It comes out as a liquid and then expands rapidly into a foam. It's quick! Then they took a types of saw to shave it flat with the wall studs so we could then go ahead and drywall.

Roof Coating Denver Colorado