MousepadMarauder said:
1 story.
Ceilings are all at least 10, some 12, living room vaulted to 24.
No large trees providing any shade.
13 windows.
Dark shingle roof.
Don't know about decking.
The Builder had the system "engineered" by an HVAC engineer, so I assume he did the J calculation? Thanks for all of the replies.
Engineered means one thing in the state of Texas... that means stamped by a licensed, professional engineer.
Since home HVAC plans do not require professional design or stamping by state law, this is where you really need to actually start asking questions.
My builder brought me two of his HVAC subs and it was obvious that they had no clue about foam insulation with respect to HVAC.
I went and found an HVAC contractor with a lot of commercial experience who employed competent HVAC engineers and they did an excellent job.
I am an engineer. I have specified and had direct oversight over dozens of HVAC systems the past 25 years.
A manual J is an absolute requirement, it will ensure your HVAC system is not undersized.
The concerns are the following:
Residential HVAC contractors do not typically employ engineers. I would ask a lot of questions... It isn't hard to tell when they start bs'ing.
Manual J software is only as good as the data input. The key input has to do with ventilation / infiltration. Air cannot get into and out of a foamed house the way it can a traditionally insulated house. Ventilation and dehumidification become the most important factors.
As mentioned, no vents in soffits. Vents in soffit allow hot humid air into your attic to ventilated it in traditional systems. For foam systems, the attic is part of the air conditioned space. Allowing the free exchange of hot humid air into the attic is a disaster.
There is a fresh air source required at the unit in the attic.
A dehumidification system is very useful if not a requirement for houses with foam insulation. It does in ahead of the return air.
Foam, just like other building materials is tested to ensure it does not propagate a fire. It is not fireproof, but it does not propagate a fire. Walls with insulation and gypsum board on the inside form the required fire barrier. Since foam is sprayed to the underside of the roof instead of ceiling joists, there is no barrier. Reputable installers use a different fire resistant foam in this area.
Choosing foam insulation directly impacts home construction and HVAC design. Do not treat them separately as they are intertwined.
Had I trusted my builder, our HVAC would have likely been a disaster.