Well you do have two options:
- they can drill holes in the drywall and dense pack the area with cellulose or
- they can drop the drywall and spray the floor with closed cell foam.
Personally I would opt for the closed cell option as that should also help stop air leaks which would include CO and other exhaust fumes from the garage.
One of the biggest items to watch out for (especially in the Phoenix market) is what type of wiring was used in your house. If it was aluminum that will rule out using dense pack unless it is changed out.
You may also wish to consider having an energy audit done and having them check your attic to make sure the work was done properly.
- An infrared camera can help a lot in this regard though there are some typical problem areas that are near impossible to correct.
- You should also make sure they check your ducts as this could be why those rooms are not cooling down properly.
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