San Antonio, TX › Attic Insulation
Why Your San Antonio Attic Is Driving Up Your Electric Bill
San Antonio regularly tops 100°F for weeks every summer. That heat bakes your roof deck and radiates into every room in the house around the clock. Spray foam at the roof deck stops it at the source.
The San Antonio Attic Problem
San Antonio sits at the southern edge of the Hill Country, where summer heat is relentless. The city regularly records 100°F+ days from June through September, and the lack of coastal wind relief means roof decks absorb intense solar radiation for hours each afternoon. Neighborhoods across Bexar County — from the 1604 corridor to Alamo Heights to Stone Oak — face the same problem: an attic that becomes an oven.
The result is attic air temperatures that can exceed 130–140°F on a peak summer afternoon. That heat radiates down through your ceiling into every room in the house. Your AC fights it all day. Even if your thermostat is set to 76°F, upper bedrooms stay warmer, the system runs longer, and your monthly bill climbs.
100°F+
Typical San Antonio summer high — weeks on end, June through September
20–40%
Typical cooling cost reduction after attic spray foam install
1 day
Most San Antonio residential attic jobs are completed same-day
Why Fiberglass Falls Short in San Antonio
Most San Antonio homes were built with fiberglass batts laid on the attic floor or blown-in fiberglass across the ceiling joists. Fiberglass slows heat transfer by trapping air in its fibers — but it doesn’t seal air leaks. In a climate like San Antonio’s, those unsealed gaps are the real problem.
Air Leaks Kill Efficiency
Every gap around a light fixture, wire penetration, or HVAC boot is a path for hot attic air to pour directly into conditioned space. Fiberglass doesn't stop that. Spray foam does — filling and sealing every void in a single application.
Humidity Gets In
While San Antonio is drier than the Gulf Coast, Hill Country humidity during spring and monsoon season can be significant. Without an air seal, warm moist air reaches cold surfaces inside your ceiling assembly — leading to condensation, mold risk, and degraded insulation performance over time.
HVAC Ducts Overheat
If your HVAC ducts run through an unconditioned attic, they're sitting in 130–140°F air. They leak conditioned air out, and that hot attic air radiates in. Moving ducts into conditioned space via spray foam at the roof deck solves this entirely — and extends equipment life.
Older Homes Are Especially Vulnerable
Historic neighborhoods like Alamo Heights, Mahncke Park, and King William were built decades before modern insulation standards existed. Many have little to no effective attic insulation. Spray foam is the most effective retrofit solution for these homes without requiring major structural changes.
How Spray Foam Attic Insulation Works in San Antonio
Instead of laying insulation on the attic floor, spray foam is applied directly to the underside of the roof deck. This creates a sealed, conditioned attic — sometimes called an unvented or encapsulated attic. The attic air temperature drops dramatically (often from 130–140°F to within 10°F of indoor temps), and all ductwork and HVAC equipment is now in conditioned space.
We inspect your attic
Before quoting, we assess attic depth, access points, existing insulation, HVAC duct locations, and any existing moisture or air seal issues. In older Bexar County homes, we also check for knob-and-tube wiring or other historic construction details that affect the approach.
We prep and protect the space
HVAC equipment and any items left in the attic are covered with protective sheeting. We run containment barriers at access hatches to prevent overspray from entering living areas.
Spray foam is applied at the roof deck
Open-cell spray foam is applied in a continuous layer across the entire underside of the roof deck and down the rafters. We hit 5.5–6 inches of open-cell (R-20 to R-22) or 3–4 inches of closed-cell (R-21+) depending on your home's needs and Bexar County code requirements.
We verify cure and ventilate
After application, the foam cures and off-gasses. We ventilate the attic and follow manufacturer-recommended re-entry times before the space is considered safe for family and pets (typically 24 hours).
Open-Cell vs Closed-Cell: Which Is Right for Your San Antonio Attic?
Both work well in San Antonio — the right choice depends on your budget, roof deck exposure, and whether moisture or structural reinforcement is a factor.
Open-Cell Spray Foam
~$1.40 – $2.80 per board foot
- R-3.6 to 3.8 per inch — install at 5.5” for R-20+
- Lighter weight — better for older roof decks in historic SA neighborhoods
- Great sound dampening — useful near Loop 1604 and I-35
- Best choice for most San Antonio residential attics
Closed-Cell Spray Foam
~$2.60 – $4.90 per board foot
- R-6.0 to 7.0 per inch — higher R per inch
- Acts as its own vapor barrier — stops Hill Country moisture cold
- Adds structural rigidity to roof deck
- Best for attics with known leak history or homes near Hill Country moisture zones
Our free estimate includes a recommendation on foam type based on your specific attic conditions, not a sales pitch for the pricier option.
2026 Attic Spray Foam Price Ranges for San Antonio Homes
These ranges cover professional prep, application, cleanup, and standard re-entry protocol. Final pricing depends on your attic’s square footage, access difficulty, existing insulation condition, and foam type.
Small Attic (under 1,200 sq ft)
$1,700 – $3,600
Mid-Size Attic (1,200–2,000 sq ft)
$3,200 – $6,200
Large Attic (2,000–3,000 sq ft)
$5,200 – $9,000
Attic + Rim Joists Combo
$4,000 – $7,800
Closed-Cell Upgrade (same sq ft)
+30–60% vs open-cell
Old Insulation Removal Add-On
$400 – $1,200
San Antonio Neighborhoods We Serve
We install attic spray foam across all of San Antonio and the surrounding communities in Bexar County and beyond — including historic inner-city neighborhoods, suburban growth corridors, and Hill Country communities.
- Alamo Heights
- Stone Oak
- The Dominion
- Helotes
- Boerne
- Schertz
- Cibolo
- New Braunfels
- Converse
- Universal City
- Leon Valley
- Live Oak
- Selma
- Garden Ridge
- Seguin
- Windcrest
- Kirby
- Bulverde
- Spring Branch
- Timberwood Park
- Fair Oaks Ranch
- Floresville
- San Marcos
- Pleasanton
Ready to Stop Paying for a Hot Attic?
Free, no-pressure on-site estimate for any San Antonio home. We assess your attic, recommend the right foam, and give you a clear written quote — no surprise add-ons.