Why Spray Foam Insulation Beats Fiberglass (And Why It Costs More)

Spray Foam vs. Fiberglass: Which Insulation Is Better?

Both spray foam and fiberglass insulate your home. But they work differently. Here’s the truth about both, and why spray foam is worth the extra cost for most Peoria homes.

How Fiberglass Insulation Works

Fiberglass batts are sheets of fluffy pink or yellow insulation that fit between studs and joists.

• Cost: $0.50–$1.00 per sq ft (cheap)
• R-value: ~3.2 per inch
• Installation: Fast, DIY-friendly
• Air sealing: Minimal. Air leaks around edges and penetrations.
• Durability: 80+ years if dry, but degrades if wet
• Moisture resistance: Poor. Can absorb water and lose effectiveness.
• Soundproofing: Moderate

The Problem with Fiberglass

Fiberglass has major limitations:

• Air leaks: Gaps around batts allow cold/hot air to bypass insulation completely
• Settling: Over time, fiberglass compresses and loses R-value
• Moisture issues: In basements or humid spaces, fiberglass absorbs water and fails
• Rodent access: Mice love nesting in fiberglass
• Installation quality: Poorly installed fiberglass performs way worse than specifications claim

How Spray Foam Insulation Works

Spray foam is liquid that expands to fill cavities completely.

• Cost: $1.50–$3.00 per sq ft (expensive)
• R-value: Open-cell ~3.5/inch, Closed-cell ~6–7/inch
• Installation: Professional-only, requires special equipment
• Air sealing: Excellent. Creates a continuous seal across all penetrations.
• Durability: 80+ years, extremely stable
• Moisture resistance: Closed-cell is a moisture barrier; open-cell allows vapor permeability
• Soundproofing: Excellent

The Advantage of Spray Foam

• Complete sealing: No gaps, no air leaks. Every cavity is filled.
• No settling: Foam hardens immediately. R-value stays constant.
• Moisture barrier option: Closed-cell foam prevents water damage in basements.
• Rodent prevention: Hard foam is difficult for mice to penetrate.
• Consistent performance: Professional installation = guaranteed R-value.
• Structural benefit: Spray foam adds slight rigidity to walls and roofs.

The Head-to-Head Comparison

When to Choose Fiberglass

Fiberglass makes sense if:

• You’re on a tight budget and can accept lower R-value
• You’re insulating a dry attic with good ventilation
• You want to DIY (saves labor cost)
• You don’t care about air sealing perfection

When to Choose Spray Foam

Spray foam is better if:

• You want the best thermal performance and energy savings (most people)
• You’re insulating a basement or crawl space (moisture risk)
• You want superior air sealing and no drafts
• You’re renovating and want maximum performance
• You plan to stay in your home 10+ years (payback period)
• Energy efficiency tax credits offset some cost

Real-World Energy Savings

Peoria home with old fiberglass attic insulation + air leaks:

• Current energy loss: 30–40% of heating/cooling escapes through attic
• Heating bill: $2,000–$3,000/winter
• AC bill: $1,500–$2,000/summer

After spray foam retrofit:

• Energy loss reduced to: 5–10%
• Heating bill: $1,400–$2,100 (25–30% savings)
• AC bill: $1,200–$1,600 (15–20% savings)
• Annual savings: $800–$1,600
• Payback period: 5–8 years

Our Recommendation

For most Peoria homes, spray foam is the smarter investment. Yes, it costs more upfront. But the energy savings, comfort improvement, and durability make it worth it, especially if you’re planning to stay long-term.

Call now for a free energy assessment: 309-491-4457