Spray Foam vs. Fiberglass Insulation: Which Is Right for Your Illinois Home?

When it comes to keeping your home comfortable and your energy bills under control in Oak Lawn, IL, insulation is one of the most important investments you can make. But not all insulation is created equal — and choosing the wrong type for your home can mean paying more to heat and cool it than you should.

Two of the most common options homeowners ask about are spray foam and fiberglass insulation. Both work, but they perform very differently in the kind of climate Illinois dishes out. At Swiftguard Enterprises LLC, we help homeowners throughout Oak Lawn and the surrounding Chicagoland area make this decision every day. Here’s what you need to know.

What Is Fiberglass Insulation?

Fiberglass insulation is the pink or yellow fluffy material most people picture when they think of home insulation. It’s made from extremely fine glass fibers and is one of the most widely used insulation materials in the U.S.

It comes in two main forms:

• Batts and rolls — pre-cut panels sized to fit between wall studs and attic joists
• Blown-in fiberglass — loose material blown into attics or wall cavities for fuller coverage

Fiberglass is affordable, widely available, and effective when installed correctly in the right areas of the home.

What Is Spray Foam Insulation?

Spray foam insulation is applied as a liquid that expands and hardens into a solid foam. It comes in two types:

• Open-cell spray foam — softer and more flexible, expands significantly, and is better for interior applications
• Closed-cell spray foam — denser and more rigid, with a higher R-value per inch and a moisture barrier built in

Spray foam is more expensive than fiberglass, but it offers performance advantages that make it a strong choice for specific situations.

R-Value: How Well Does Each Insulate?

R-value measures how effectively insulation resists heat transfer. The higher the R-value, the better the insulation performs. In Illinois, the U.S. Department of Energy recommends attic insulation of R-49 to R-60 for most homes.

• Fiberglass batts: R-2.9 to R-3.8 per inch
• Blown-in fiberglass: R-2.2 to R-2.9 per inch
• Open-cell spray foam: R-3.5 to R-3.7 per inch
• Closed-cell spray foam: R-6.0 to R-7.0 per inch

Closed-cell spray foam delivers the highest R-value per inch, which matters when you have limited space to work with, such as in wall cavities or a shallow attic.

Air Sealing: The Hidden Performance Factor

R-value alone doesn’t tell the full story. One of the biggest sources of energy loss in Illinois homes isn’t inadequate insulation — it’s air leaks. Cold air infiltrating around gaps, cracks, outlets, pipes, and attic hatches can undermine even well-insulated walls and ceilings.

• Fiberglass insulates but does not seal air gaps. It needs to be paired with separate air sealing work to perform at its best.
• Spray foam expands to fill gaps and cracks as it’s applied, creating an air barrier and insulation layer in one step.

This is one of spray foam’s most significant advantages in the Chicago area, where winter wind and cold temperatures relentlessly find every gap in a home’s envelope.

Moisture Resistance

Illinois humidity and freeze-thaw cycles mean moisture management matters as much as temperature control.

• Fiberglass can absorb and hold moisture if exposed to water intrusion or high humidity, which reduces its effectiveness and can contribute to mold growth over time.
• Closed-cell spray foam acts as a vapor barrier, actively resisting moisture infiltration — a major advantage in attics, crawl spaces, and exterior walls in the Midwest climate.
• Open-cell spray foam is not a vapor barrier and can allow moisture to pass through, so it’s less suited for below-grade or high-moisture applications.

Cost Comparison

Budget is a real factor for most homeowners, and fiberglass and spray foam differ significantly in cost.

• Fiberglass is one of the most affordable insulation options, both in material cost and installation labor
• Spray foam costs significantly more upfront — closed-cell spray foam in particular can cost two to three times more than fiberglass for the same area

However, spray foam’s superior air sealing and higher R-value per inch often translate to greater long-term energy savings, which can offset the higher initial investment over time, especially in an energy-intensive climate like Illinois.

Which One Is Right for Your Home?

The best choice depends on where you’re insulating, your budget, and your home’s specific needs.

Fiberglass is a strong choice when:

• You’re insulating a large attic with plenty of depth for blown-in material
• Budget is the primary concern and air sealing will be addressed separately
• You’re insulating interior walls where moisture is not a concern

Spray foam is the better option when:

• You need maximum R-value in a limited space, such as a shallow roof deck or wall cavity
• Air sealing and insulation need to be done together efficiently
• You’re insulating a crawl space, rim joists, or areas prone to moisture
• You want the longest-lasting performance with minimal maintenance

Many Oak Lawn homeowners end up with a combination — spray foam in high-priority areas like rim joists and attic hatches, and blown-in fiberglass for the broader attic floor — which delivers strong performance while keeping costs manageable.

Signs Your Home May Need Insulation Upgrades

Not sure if your current insulation is keeping up? Watch for these warning signs:

• Energy bills that are consistently higher than your neighbors’ in similar-sized homes
• Rooms that are difficult to keep warm in winter or cool in summer
• Drafts near windows, outlets, or baseboards
• Ice dams forming along your roofline in winter
• Moisture or condensation in your attic

If any of these sound familiar, a professional insulation assessment can identify exactly where your home is losing energy and which solution makes the most sense.

Get the Right Insulation for Your Oak Lawn Home

At Swiftguard Enterprises LLC, we assess your home’s existing insulation, identify gaps and inefficiencies, and recommend the right solution — whether that’s fiberglass, spray foam, or a combination of both. We serve homeowners throughout Oak Lawn, IL and up to 60 miles surrounding the area.

Ready to lower your energy bills and improve your home’s comfort? Contact Swiftguard Enterprises LLC today to schedule your free insulation assessment.