Quick answer: The three most common attic insulation choices are blown-in fiberglass, blown-in cellulose and spray foam. Each has trade-offs in cost, R-value per inch, air sealing and how it handles moisture. The best choice depends on your attic, your HVAC setup and your budget.
What are the main types of attic insulation?
For most homes, it comes down to blown-in fiberglass, cellulose or spray foam. The choice affects energy efficiency, comfort and indoor air quality (IAQ). Below, we compare Owens Corning ProCat® blown-in fiberglass, cellulose and spray foam. As an Owens Corning partner, Gold Eagle Services installs ProCat blown-in fiberglass, but every material here has its place, and knowing the trade-offs helps you pick with your eyes open.
How does fiberglass compare to cellulose?
Fiberglass and cellulose are the two most common materials for blown-in attic insulation. Both perform well when installed to the right depth. They differ in what they’re made of, how they settle and how they react to moisture.
| Aspect | Owens Corning ProCat® Blown-in Fiberglass | Cellulose Insulation |
| R-Value Stability | Owens Corning designs ProCat to resist settling so it holds its installed R-value. It is backed by a manufacturer warranty – ask us for the details. | Settles somewhat after installation; installers typically blow in extra depth so the settled insulation still meets the target R-value. |
| Moisture Resistance and Air Quality | Glass fibers are inorganic and don’t absorb much water. Insulation that gets wet from a roof or duct leak should still be dried or replaced. | Made largely from recycled paper and treated with borates for fire and pest resistance. It can absorb water if there’s a leak, so leaks should be fixed quickly and wet material replaced. |
| Installation Process | Blown in with a machine. Crews use protective gear and keep the work contained to the attic. | Blown in with a machine; can be dusty during installation, so containment and cleanup matter. Also commonly used as dense-pack insulation in walls. |
Why choose fiberglass?
Because it’s stable and straightforward. Owens Corning ProCat® blown-in fiberglass is designed to resist settling, so it holds its installed R-value over time, and it’s backed by a manufacturer warranty. Ask us for the details. Glass fibers don’t absorb much water, which makes it a practical fit for attics where keeping insulation dry and stable matters.
Why choose cellulose?
For recycled content and dense-pack wall jobs. Cellulose is made largely from recycled paper, which appeals to many homeowners, and it’s widely used both in attics and as dense-pack insulation in walls. It does settle after installation, so a good installer blows in extra depth to allow for it. Like any insulation, it should be kept dry: fix roof or duct leaks promptly and replace any material that gets soaked.
How does fiberglass compare to spray foam?
Fiberglass and spray foam differ in cost, installation and how they change the way your attic works. Here’s a closer look.
| Aspect | Owens Corning ProCat® Blown-in Fiberglass | Spray Foam Insulation |
| R-Value Stability | Moderate R-value per inch. Higher R-values are reached by adding depth, which is straightforward in most open attics. Backed by a manufacturer warranty – ask us for the details. | High R-value per inch, especially closed-cell foam. Performance depends on correct thickness and quality installation. |
| Moisture Resistance and Air Quality | Doesn’t stop air movement on its own, so air sealing the attic floor first is important. Works in a vented attic, where the attic itself stays outside the conditioned space. | Acts as an air barrier. Applied to the roof deck, it creates a sealed (unvented) attic, which usually calls for an HVAC design that manages humidity and fresh air. |
| Installation Process | Loose fiberglass is blown over the attic floor; most attics can be done quickly with little disruption. | Two components are mixed and sprayed on site by trained crews. Manufacturers specify ventilation and how long occupants should stay out while it cures. |
| Cost Efficiency | Typically a lower upfront cost for insulating an attic floor. | Typically a higher upfront cost. Because it can bring ducts inside the conditioned space, some homeowners find the added cost worthwhile. |
When is spray foam worth the higher upfront cost?
When you want the attic sealed and the ducts inside the conditioned space. Spray foam’s biggest strength is air sealing combined with a high R-value per inch. Applied to the underside of the roof deck, it makes the attic part of the conditioned space, which can be a real advantage in Central Texas, where ducts in a hot attic lose a lot of cooling. The trade-offs are a higher upfront cost and the need for an HVAC design that handles humidity and fresh air in a tighter house. It also has to be installed by trained crews following the manufacturer’s curing and ventilation instructions.
Blown-in fiberglass keeps the traditional vented-attic setup. It typically costs less up front, and with good air sealing at the attic floor and well-sealed, insulated ducts, it delivers strong performance for many homes.
Which insulation is right for your home?
It depends on your attic and your plans. You’re balancing long-term performance, energy savings, indoor air quality and budget. For many Austin homes with a vented attic, Owens Corning ProCat® blown-in fiberglass installed to R-49 or higher (Austin’s current code minimum for attics) is a cost-effective choice. For others, such as homes planning a sealed attic or a major HVAC redesign, spray foam may be worth considering, and cellulose remains a solid option with many experienced installers.
If you’re weighing your options, Gold Eagle Services can look at your attic, your ductwork and your HVAC system together and walk you through which approach fits your home.
Related guides: Choosing the Right Insulation Level for Your Climate (R-Value), How Insulation Helps Control Noise in Your Home and How Insulation Affects Indoor Comfort Levels.
About Gold Eagle Services: This guide comes from the team at Gold Eagle Services, a family-run Austin HVAC, indoor air quality and mold remediation company founded in 2017. We’re licensed (TACLA119235 and RCO1783), insured and bonded, and we serve homes across the greater Austin area.
Need help with this in your home? Learn about our HVAC and home performance services, or call 512-489-4653 to schedule a visit.
