What do you mean by "our AC units require fresh air ventilation"? Fresh air doesn't come from the attic. If there's an atmospheric combustion appliance in the attic, such as an 80 AFUE furnace, then you shouldn't be encapsulating the attic anyway. If that's the case, you don't want spray foam on the roofline at all. You can either change out the furnace to a sealed combustion unit or do your insulating and air-sealing at the flat-ceiling level. Insulation Spray Coating
In recent years, there has been a significant rise in the use of spray foam insulation in construction. Spray foam insulation varies from traditional insulation, such as fiberglass, in many respects. Fiberglass insulation is typically much cheaper than spray foam insulation; however, it is also less effective at insulating your home. Additionally, spray foaminsulation requires professional installation. Though spray foam insulation is on the rise, fiberglass is still the most common form of home insulation used today. Insulation Spray Coating

A rule of thumb puts two thirds of the coating on the substrate and one third in the air. True HVLP guns use 8–20 cfm (13.6–34 m3/h), and an industrial compressor with a minimum of 5 horsepower (3.7 kW) output is required. HVLP spray systems are used in the automotive, decorative, marine, architectural coating, furniture finishing, scenic painting, and cosmetic industries. Spray Coating
×