Spray Foam vs. Fiberglass: What South Texas Homeowners Need to Know

Let’s not sugarcoat this: if you live in South Texas and your home is insulated with traditional fiberglass batts, you are losing money every single day between May and October.

When homeowners in Schertz and San Antonio start complaining about $400 electric bills, master bedrooms that never cool down, and AC units that run 20 hours a day, the conversation almost always leads back to the attic.

You’ve probably heard that spray foam insulation is the gold standard, but you’ve also seen that fiberglass is the industry default. So, what’s the real difference? Here is the blunt, honest comparison between spray foam and fiberglass insulation, and why you should seriously consider making the upgrade.

Why Do Builders Use Fiberglass?

Let’s address the elephant in the room first. If fiberglass is so bad at handling the Texas heat, why is it installed in 90% of new homes in Guadalupe and Bexar counties?

Because it is cheap.

That’s it. That’s the secret. Production home builders operate on incredibly tight margins. To keep the final sale price of the house competitive, they have to use the cheapest materials that legally meet the minimum local building codes.

Fiberglass is cheap to manufacture, cheap to buy, and extremely fast to install. A crew can roll out fiberglass batts or blow a few inches of loose-fill cellulose into an attic in a matter of hours. The builder checks the "R-value" box for the city inspector, closes the drywall, and hands you the keys. They don’t have to pay the massive CPS Energy bills the following August—you do.

The Flaw of Fiberglass in Extreme Heat

Fiberglass insulation is not inherently "bad," but it is designed for moderate climates, not the brutal extremes of South Texas.

Here is the fundamental flaw: Fiberglass is a filter, not a barrier.

Think about the air filter in your HVAC unit. It is made of woven fiberglass or pleated paper. Air easily passes right through it, leaving the dust behind. Traditional attic insulation works the exact same way. It provides some thermal resistance (R-value), but it does absolutely nothing to stop air movement.

When your dark-colored roof bakes in the 105-degree sun, your attic temperature skyrockets to 140°F. Because fiberglass is porous, that superheated, humid air pushes right through the pink fluff and down into your ceiling joists, light fixtures, and wall cavities. Your air conditioner is forced to constantly fight the hot air bleeding into your home.

Why Spray Foam Actually Works

Homeowners eventually upgrade to spray foam for one simple reason: it solves the problem permanently.

Spray foam insulation doesn’t just slow down heat transfer; it provides an absolute air seal.

When we apply open-cell spray foam to the underside of your roof deck, it expands massively, filling every tiny crack, gap, and crevice in the wood framing. Once it dries, it becomes a solid barrier. It is the equivalent of putting a Yeti cooler lid on your house.

The Spray Foam Advantage:

1. It Stops Air Leaks: The 140-degree air is locked out of your attic entirely.
2. It Protects Your AC: With spray foam, your attic temperature drops by 30 to 40 degrees, meaning your AC ductwork is no longer sitting in a 140-degree oven. The air pumping into your bedrooms actually stays freezing cold.
3. It Blocks Dust and Pests: Because we seal the attic vents, we block the main entry point for South Texas dust, pollen, and rodents.
4. Massive ROI: Because your HVAC unit doesn't have to work nearly as hard, most homeowners see a 30% to 40% reduction in their summer energy bills. Over a few years, the foam pays for itself.

The Bottom Line

Fiberglass is a budget material used to pass inspections. Spray foam is an engineered performance upgrade used to actually protect a home.

Yes, spray foam requires a larger upfront investment. It requires specialized equipment and trained professionals to install correctly. But the payoff—in sheer comfort, indoor air quality, and drastically lower utility bills—is unmatched.

If you are tired of overpaying to cool your attic and want to feel comfortable in your own living room again, it’s time to ditch the pink fluff. Contact Schertz Spray Foam Insulation today for a free estimate. We’ll show you exactly what it takes to seal your home and beat the Texas heat for good.