Walk into your attic on a July afternoon in San Antonio. If your hand sticks to the ladder rungs, your attic is over 140°F. If it feels like a comfortable warm day, your ventilation is working.
Most Central Texas attics fail this test. The consequences are real.
What over-heated attics do to your roof
- Premature shingle aging. Asphalt is petroleum-based. Sustained 140°F+ temperatures accelerate the breakdown of shingle binders, causing curling, cracking, and granule loss years before the warranty cycle.
- Decking damage. OSB and plywood deck materials warp under sustained heat. Bowed decking shows up as visible roofline waves and creates leak opportunities.
- Manufacturer warranty issues. Most major shingle manufacturers require minimum ventilation (typically 1 sq ft of net free area per 150 sq ft of attic floor). If your attic doesn't meet it, your warranty may be invalidated when you need it.
What it does to your home
- AC works 30–50% harder in summer
- Bedrooms over the garage or on second floors get unevenly hot
- Insulation R-value degrades faster
- Moisture builds in winter, causing condensation and mold
How proper ventilation works
A balanced ventilation system has two parts:
- Intake at the soffits (where the roof meets the wall, under the eaves)
- Exhaust at or near the ridge (top of the roof)
Air flows in cool from the soffits, rises as it warms, and exits at the ridge. The math: you want roughly equal net free area (NFA) at intake and exhaust. Imbalanced systems short-circuit and don't actually move air.
Common ventilation mistakes we see
- No soffit vents at all. Common in older Boerne homes. Owners see ridge vents and assume they're working — but with no intake, there's no airflow.
- Painted-over soffit vents. Painters seal them when re-painting. Easy fix.
- Insulation blocking soffit vents. Blown-in insulation drifts and clogs intake. Baffles solve this.
- Mixing exhaust types. Combining a powered attic fan with ridge vents pulls air sideways instead of up. Pick one.
- Inadequate exhaust. Older box vents or turbines may have been correct in 1985 but are undersized for modern requirements.
The replacement opportunity
The single best time to fix attic ventilation is during a roof replacement. The roof is open, the soffits are accessible, the shingles are off the ridge — adding proper ventilation costs a fraction of what it would cost as a separate retrofit.
On every roof replacement we do in the Boerne and San Antonio metro, we calculate net free area requirements, inspect existing intake, and recommend ventilation upgrades. It's not an upsell — it's the difference between a roof that lasts 25 years and one that fails at 14.
What to ask your roofer
If you're getting bids, ask each roofer:
- What ventilation calculation did you run?
- How many square inches of intake and exhaust will the finished roof have?
- Does that meet the manufacturer warranty requirement?
If they can't answer, that's information about their installation quality.
