Spray Foam vs. Fiberglass · What You Need to Know
Spray Foam vs. Fiberglass Insulation: Which is Best for Texas Homes?
When it comes to insulating a home or business in Texas, the battle usually comes down to two main contenders: traditional fiberglass and modern spray foam. With summer temperatures consistently breaking the 100-degree mark and energy costs on the rise, having an efficient thermal envelope is no longer a luxury—it is a necessity.
At Weeks Spray Foam, we replace failing, outdated fiberglass insulation with high-performance spray foam every single week. But is spray foam really worth the investment over standard fiberglass? Below, we compare the two materials across energy efficiency, longevity, and performance to help you make an informed decision for your property.
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What is Fiberglass Insulation?
Fiberglass is the traditional “pink fluffy” insulation you see in most older homes. Made from spun glass fibers woven together, it is typically installed as large rolls (batts) or blown in as loose-fill in attics. For decades, it has been the standard building material across the country.
The Pros of Fiberglass:
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Low Initial Cost:
Fiberglass is one of the most inexpensive insulation materials on the market. -
Widely Available:
It is standard at almost every hardware store and lumber yard. -
DIY-Friendly:
While itchy and messy, rolling out fiberglass batts is a common weekend project for handy homeowners.
The Cons of Fiberglass:
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Zero Air Sealing:
Fiberglass filters air; it does not block it. Outside heat, humidity, and allergens can easily pass right through it. -
Degradation Over Time:
Fiberglass batts are prone to sagging, and blown-in fiberglass will settle over the years, drastically reducing its effectiveness. -
Moisture and Pests:
Fiberglass absorbs moisture, which can lead to heavy, matted insulation and potential mold growth. It also makes excellent nesting material for rodents and insects.
What is Spray Foam Insulation?
Spray foam is a liquid polyurethane material that, when sprayed, rapidly expands to fill wall cavities, attic spaces, and crawlspaces. It cures into a solid, continuous layer of insulation. It comes in two forms: open cell (spongy and highly expansive) and closed cell (dense and rigid).
The Pros of Spray Foam:
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Total Air Barrier:
Spray foam expands into every gap, crack, and crevice, creating an airtight seal that physically stops hot air and humidity from entering your home. -
Highest R-Value:
It offers superior thermal resistance per inch compared to fiberglass, keeping your conditioned air inside where it belongs. -
Lifelong Performance:
Spray foam does not sag, settle, or degrade. It is a permanent solution that lasts the lifetime of the building. -
Pest and Moisture Deterrent:
It offers zero food value or nesting appeal to pests. Closed cell foam also acts as a complete moisture and vapor barrier.
The Cons of Spray Foam:
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Higher Upfront Investment:
The premium materials and specialized equipment required make spray foam more expensive to install initially. -
Professional Installation Required:
Spray foam requires highly trained, licensed technicians (like our team at Weeks Spray Foam) to ensure proper mixing, application, and curing.
Spray Foam vs. Fiberglass Comparison
To help you quickly identify the right material for your project, use this side-by-side comparison:
| Feature | Spray Foam | Fiberglass |
|---|---|---|
| Stops air infiltration | Yes — creates an airtight seal | No — air passes through it |
| Lifespan | Permanent — will not settle or sag | 10–15 years — settles and degrades |
| Pest resistance | Excellent — no nesting material | Poor — rodents love nesting in it |
| Moisture resistance | High — especially closed cell | Low — absorbs moisture, risks mold |
| Energy savings | Up to 50% reduction in energy bills | Standard baseline efficiency |
| Initial cost | $$$ | $ |
Why Traditional Fiberglass Struggles in the Texas Climate
In mild climates, fiberglass can get the job done. But in Texas, our extreme heat exposes the biggest flaw in fiberglass: it allows airflow.
Think of a fiberglass-insulated attic like wearing a thick wool sweater on a windy winter day. The sweater is thick, but the wind cuts right through the fibers, making you cold. Fiberglass acts the same way in the summer. 140-degree attic air easily pushes through the fiberglass fibers into your living space, forcing your HVAC system to work overtime.
Spray foam, on the other hand, is like wearing a high-quality windbreaker. It physically stops the air from moving. By applying spray foam to your roof deck, you stop the Texas heat from ever entering your attic in the first place, keeping your ductwork cool and drastically lowering your energy bills.
Spray Foam vs. Fiberglass FAQs — cost, performance & Texas homes
Is spray foam worth the extra cost over fiberglass?
Yes. While fiberglass is cheaper to install on day one, spray foam pays for itself over time. Homeowners who upgrade to spray foam typically see immediate, significant drops in their monthly heating and cooling bills, yielding a fantastic Return on Investment (ROI).
I already have fiberglass in my attic. Can I just spray foam over it?
No. To create a proper, effective air seal, the old insulation must be removed. At Weeks Spray Foam, we offer complete insulation removal services. We will vacuum out the old, dusty fiberglass and prep the area for a fresh, clean spray foam application.
Does fiberglass insulation cause mold?
Fiberglass itself does not cause mold, but because it holds onto moisture and allows humid Texas air to enter your home, it creates an environment where mold can easily thrive on the paper backing of the batts or the surrounding wood framing.
How much faster will my house cool down with spray foam?
Because spray foam seals the building envelope, your HVAC system doesn't have to fight a constant influx of outside heat. Your home will cool down much faster, maintain a consistent temperature, and experience far fewer "hot spots" in hard-to-cool rooms.