Title 24 R-Value Requirements
for Bay Area Attics (2025 Energy Code)
What the Code Says, What Most Homes Get Wrong

Title 24 is California's Building Standards Code. Part 6, the California Energy Code, sets minimum energy-efficiency requirements for homes and commercial buildings. The California Energy Commission updates it every three years. The current version is the 2025 California Energy Code, in effect since January 1, 2026.

Title 24 matters to roofing because it applies at permitting. When you pull a building permit for a roof replacement, the permit application triggers an energy compliance review. In most Bay Area jurisdictions, that review includes attic insulation. If your attic insulation is below current code minimums, you may be required to bring it into compliance as a condition of permit approval.

This is not punitive. It is an opportunity. Reroofing is the lowest-cost time to upgrade attic insulation. The attic is open and the contractor is already on site. Adding insulation during a re-roof costs far less than booking a separate project later.

Title 24 and the roofing permit: what to expect

Bay Area cities check energy compliance with different levels of scrutiny. Some require a CF1R form (the standard Title 24 energy compliance certificate) with the permit application. Others rely on a plan checker's review. Brian has pulled permits in Pleasanton, Livermore, Dublin, Stockton, and nearby cities. He knows which ones are strict on insulation and which keep it simple. NuShake handles the Title 24 paperwork as part of any roofing permit.

R-value measures how well insulation resists heat flow, and higher is better. When you add or replace attic insulation, the 2025 California Energy Code sets the level by climate zone. The Bay Area and the Central Valley span several California Energy Commission (CEC) climate zones:

• Climate Zone 3 — coast and bayside (the CEC reference city is Oakland): R-49, but attics that already have at least R-19 are exempt.
• Climate Zone 4 — South Bay and coastal valleys (reference city San Jose): R-49, plus air sealing if the attic has less than R-19.
• Climate Zone 12 — inland valley (reference city Sacramento): R-49, plus air sealing if the attic has less than R-19.

In plain terms: if you add insulation, plan on R-49. Any attic that already has R-38 or more is exempt. Additions use different numbers (R-38 or R-30, by zone). Your exact zone depends on your address; the CEC's climate zone tool looks it up, and NuShake confirms it at the free estimate.

What R-49 means in physical terms

Picture the depth. At about R-2.5 per inch, R-38 of blown-in fiberglass is roughly 15 inches deep and R-49 roughly 20 inches. Most older Bay Area homes have just 3–6 inches of original batts or compacted blown-in, which is R-11 to R-19 at best. The gap between what these homes have and what code now requires is large.

A large share of the Bay Area's housing stock was built between 1950 and 1975. These homes went up before California had meaningful energy code requirements. Attic insulation, if installed at all, was typically R-11 kraft-faced batts laid between the floor joists. Those batts are now 50 years old.

Fifty-year-old fiberglass batts do not hold their original R-value. They compress and settle over time. They may have become damp from attic moisture cycles. In some cases, rodent activity has disrupted or contaminated the insulation. What started as R-11 may now be performing at R-6 or R-7.

The effect on your home is direct. During a hot Tri-Valley summer, attic air temperatures can top 150°F. An R-7 attic floor is a poor barrier between that heat and your living space. Your HVAC system works harder to keep up, and your PG&E bill shows it. Upgrading from R-7 to R-49 cuts that heat gain in a Pleasanton or Livermore home.

The Bay Area has a pronounced climate gradient. Coastal and near-bay areas like San Francisco, Oakland, Richmond, and Fremont stay mild year-round. Summer highs rarely top 70°F and winter lows rarely drop below 40°F. In these zones, insulation matters mostly for moisture control and winter heating efficiency.

Inland East Bay and Tri-Valley zones cover Pleasanton, Livermore, Walnut Creek, Concord, and Discovery Bay. They see real summer heat, with 95–105°F common in July and August. Insulation here is critical for cutting the cooling load. The same R-49 rule applies when you add insulation. But the payback is faster inland, because the heat gap between attic and living space is larger.

Further inland, in Stockton, Ripon, Tracy, and Manteca, summer highs regularly top 100°F. Attic temperatures routinely hit 140–160°F. Here R-49 is the level the code calls for when you add insulation. Consider spray foam that conditions the attic if your HVAC ducts run through the attic. They do in most 1960s–1980s construction.

Blown-in fiberglass: the standard

Blown-in fiberglass is the most common attic insulation for good reason. It installs fast and settles very little over time. It resists fire by nature, with no added fire retardants. And it handles the Bay Area's moisture cycles well. Owens Corning EcoTouch and CertainTeed InsulSafe are the products NuShake uses most. Both run about R-2.5 per inch, so R-49 needs roughly 20 inches of blown insulation.

Blown-in cellulose: the dense-pack option

Cellulose is denser than fiberglass and slightly better at air-sealing in tight spots. It is made from recycled paper and carries fire retardants. The tradeoffs: it settles 10–20% over time, which lowers its R-value, and it takes on moisture more easily than fiberglass. For open, ventilated attic floors, fiberglass is the usual pick in the Bay Area's damp coastal zones. Cellulose can still make sense for certain jobs or homeowner preferences.

Spray foam: the premium option

Closed-cell or open-cell spray foam goes on the underside of the roof deck, not the attic floor. This seals the attic and brings it into the conditioned space. It is the top-performance option when HVAC ducts run through the attic, because it brings the ducts inside and ends duct loss entirely. Cost is roughly 3–4x blown-in. For homes with attic ducts and high cooling loads, the energy savings often justify the premium in 5–10 years.

Batts: DIY-friendly but limited for upgrades

Kraft-faced or unfaced fiberglass batts are familiar and easy to handle, which makes them popular for DIY projects. For whole-attic upgrades, blown-in is almost always more practical. It fills around joists, blocking, and obstructions without cutting and fitting each piece. Batts work well in specific cases, like adding a second layer in a regular joist pattern. But blown-in wins for speed, coverage, and cost on a full upgrade.

R-values add up. Stack new insulation on top of old, and the numbers combine. Here is how to find what you need, in three steps.

1. Find what you have now. Measure how deep your current insulation is. Then multiply by its R-value per inch. Old, compressed fiberglass is about R-2 per inch. So 4 inches gives you roughly R-8.
2. Find the gap. Subtract that number from your target. R-49 is the code level when you add insulation in most zones. If you have R-8 and need R-49, the gap is R-41.
3. Turn the gap into inches. Divide the gap by the R-value per inch of the new material. Blown-in fiberglass is about R-2.5 per inch. So R-41 means roughly 16 inches of new blown-in on top.

NuShake measures your existing insulation and confirms the depth you need during the free estimate. You do not have to run these numbers yourself.

PG&E participates in California's statewide energy efficiency programs. The Energy Upgrade California and TECH Clean California programs both offer rebates for qualifying attic insulation upgrades. Typical rebate amounts run 10–30% of project cost for Title 24-compliant work.

Rebate eligibility has three requirements. A licensed contractor must do the work. The materials must meet set performance standards. And documentation must be submitted through the program portal. NuShake provides the product data sheets, installation records, and any compliance forms your rebate application needs.

Rebate programs change. Funding is set aside each year and can run out before the year ends. Brian confirms what is available at the time of your project. The general rule holds: Title 24-compliant insulation work by a licensed contractor usually qualifies for some level of PG&E incentive.

PG&E rebates stack with the savings from bundling. Do a roof replacement and add attic insulation at the same time, and the insulation portion costs less because the crew is already on site — no second mobilization. You may also qualify for PG&E rebates on the same work. That combination cuts the real cost of the insulation upgrade substantially.

NuShake offers insulation as part of roofing work because the roof and the attic insulation are the same thermal envelope. A roofer who sees the attic during a re-roof and does not address the insulation is leaving unfinished business. The customer pays for two mobilizations, two permits in some jurisdictions, and misses the window when the work is cheapest.

Brian has worked every role: tear-off crew at 18, crew lead at 20, lead salesman at 21, licensed owner at 23. He knows what degraded insulation looks like. He knows what ventilation problems look like. In a single inspection visit, he can tell you what your attic actually needs, not what a sales-first pitch would push. Insulation and airflow work as a pair. Our attic ventilation guide explains why one without the other can trap moisture and shorten the life of your roof deck.

The insulation service page covers the full scope of what NuShake installs. For solar insulation interaction (the cool-roof connection), see the solar roofing hub.

When you replace your roof and upgrade your attic insulation as a single NuShake project, the insulation portion costs less. The reason is simple. A second trip out means a second round of trucks, crew time, and staging equipment, and the bundle removes all of that. We are already on site, so the added cost of the insulation work drops sharply.

That saving only exists when the two are contracted together — it comes from the shared trip out, so scheduling insulation separately loses it. Most homeowners who hear the economics do not choose to separate the projects.

Now add PG&E rebate eligibility. Between the shared mobilization and the rebates, bundling can meaningfully lower the real cost of the insulation work versus hiring a separate contractor for it later.