Renovation - Spray foam or Batt Insulation! Advice please!

nolaswede said
We will have 2 different A/C systems. One upstairs in the attic, and one brand new downstairs. The addition is about 1/3 of the house(total 2500sqft with the addition).

The addition is facing west and will get a lot of sun/heat in the summer months. Want to make sure that the systems don’t have to work too hard and that spray foam makes sense to have both in attic and in the walls of the new addition.

The price will not be cheaper if we go regular insulation. So trying to see if there is any reason not to go with spray.

Rock wool would be too expensive in our opinion and we wouldn’t be doing it in the entire house anyway!

Thanks!

It doesn't matter how hard the ACs work. I mean they're either on or off unless you have variable speed fans and compressors which is what I'd suggest. Still, the AC is most efficient when it's running and the longer it runs the better so the variable speeds running at low capacity for long intervals is the most efficient.

It makes no sense to me that it wouldn't be cheaper to do batts vs foam so make the builder spend his money and install the foam which is obviously what he likes. Sounds like he's done the math for AC size based on foam and it won't make you any savings to skip it so let him do what he's planning.