How much insulation do you need?
| Climate zone 3 (DFW, Los Angeles, Pasadena, San Diego) | ENERGY STAR recommendation |
|---|---|
| Attic with no insulation | R30 to R60 |
| Attic with 3 to 4 inches already | Add R25 to R38 |
Source: ENERGY STAR recommended home insulation R-values by IECC climate zone.
How to check your attic
- Look across the attic floor: if you can see the tops of the ceiling joists, you almost certainly need more.
- Measure the depth: blown fiberglass gives roughly R2.5 per inch and cellulose roughly R3.5 per inch, so R38 is about 15 inches of fiberglass or about 11 inches of cellulose.
- Hot upstairs rooms, an air conditioner that runs nonstop, and dust streaks on the insulation (a sign of air leaks) all point to the attic.
Air sealing comes first
Insulation slows heat but does not stop air. Gaps around light fixtures, plumbing and wiring holes, the attic hatch and duct chases let hot attic air into the house. The U.S. Department of Energy recommends sealing those leaks before adding insulation, so we do.
Fiberglass or cellulose?
| Blown fiberglass | Blown cellulose | |
|---|---|---|
| R-value per inch | About 2.2 to 2.7 | About 3.2 to 3.8 |
| Made from | Spun glass | Recycled paper treated for fire resistance |
| Good to know | Light, does not settle much, resists moisture | Denser, fills gaps well, settles some over time |
Insulation and your roof
A roof replacement is a good time to fix attic ventilation and insulation together: the crew is already working on the roof deck, and balanced intake and exhaust ventilation keeps a well-insulated attic from trapping heat and moisture.
Frequently asked questions
How much attic insulation do I need in Texas?
In North Texas (IECC climate zone 3), ENERGY STAR recommends R30 to R60 in an uninsulated attic, or adding R25 to R38 if you already have 3 to 4 inches.
Does attic insulation help in the summer?
Yes. In summer the attic can get far hotter than the outdoors; insulation slows that heat from reaching your rooms, so the air conditioner works less.
How long does it take to add attic insulation?
Most attics are air sealed and insulated in a single day.
Is there a federal tax credit for insulation?
The federal Energy Efficient Home Improvement Credit (25C) does not apply to work placed in service after December 31, 2025. Ask your tax professional, and check your electric utility for current rebates.
Can I finance insulation?
Yes, qualified homeowners can finance insulation alone or together with a roof or other exterior work. See how financing works.