Two ways to insulate an attic
| Spray foam on the roof deck | More insulation on the attic floor | |
|---|---|---|
| Where it goes | Underside of the roof, rafters and gable walls | On top of the ceiling, between the joists |
| What it does | Brings the attic inside the insulated shell; ducts and the AC unit sit in conditioned air | Keeps heat in the attic and out of the rooms below |
| Air sealing | Seals gaps as it expands | Gaps need separate sealing |
| CPS Energy rebate | Usually outside the rebate's rules (it covers insulation between living space and the attic) | Can qualify when the attic goes from R-14 or less to R-38 or more |
| Best for | Homes with ducts or equipment in the attic, rooms over garages, bonus rooms | Simple attics with no equipment and good existing air sealing |
Rebate rules: CPS Energy ceiling and attic insulation rebate page. We confirm eligibility for your specific project before you count on any rebate.
What we check on the site visit
- Current insulation type and depth, and its R-value
- Where the ducts, air handler and water heater sit
- Roof deck condition, leaks and signs of moisture
- Attic ventilation and any combustion appliances that need fresh air
- Rodent damage or old insulation that should come out first (insulation removal)
What you get when we finish
A completion report with the foam type, depth readings across the attic, before and after photos and your re-entry time. If you applied for a CPS rebate, the report has the square footage and R-values the application asks for.
Common questions
Will spray foam in the attic lower my power bill?
Sealing and insulating the attic usually lowers cooling load, but the amount depends on the house, the AC system and how leaky the attic was. We will not promise a percentage we have not measured.
Can you add insulation over what I already have?
On the attic floor, often yes, if the existing insulation is dry and clean. For roof deck foam, old attic floor insulation can stay or come out depending on the plan. We will explain both on the visit.
How long does an attic job take?
Most single-family attics are done in a day. You stay out during the install and for the re-entry period we give you in writing.
