Best Insulation Types Compared: Cost, R-Value & Performance

Choosing the right insulation type can save you thousands of dollars on energy bills over the life of your home — but with five major categories and dozens of products, the decision isn't straightforward. Each type has different R-values, costs, installation methods, and ideal applications.

In this guide, we compare every major insulation type with 2026 pricing data and practical guidance for homeowners. Whether you're insulating a new build, upgrading your attic, or finishing a basement, you'll find the right choice below. Use our free Insulation Calculator to estimate costs for your specific project.

Insulation Types at a Glance

Fiberglass Insulation

Fiberglass is the most widely used insulation in American homes — it's in roughly 85% of US residences. Available as batts (pre-cut rolls) or blown-in loose fill, it's affordable, non-combustible, and effective.

Fiberglass Batts (Rolls)

• R-value: R-3.2 per inch
• Cost: $0.50–$1.25/sq ft material, $0.75–$1.75/sq ft labor → $1.25–$3.00/sq ft installed
• Best for: Open wall cavities, accessible attics, new construction
• Lifespan: 80–100 years (if kept dry)

Batts come in standard widths (15" and 23") to fit between studs spaced 16" or 24" on center. The main drawback is that batts must be cut carefully around wiring, pipes, and electrical boxes — gaps and compression significantly reduce performance. A poorly installed batt can lose 30–50% of its rated R-value.

Blown-In Fiberglass

• R-value: R-2.5 per inch
• Cost: $0.60–$1.50/sq ft material, $0.75–$1.50/sq ft labor → $1.35–$3.00/sq ft installed
• Best for: Attic floors (over existing insulation), enclosed wall cavities (retrofit)
• Lifespan: 80–100 years

Blown-in fiberglass fills irregular spaces better than batts and doesn't compress the same way. It's the preferred method for adding insulation to existing attics — it's simply blown over whatever's already there. Note the lower R-value per inch compared to batts (R-2.5 vs R-3.2) — the loose fill is less dense.

Cellulose Insulation

• R-value: R-3.5 per inch
• Cost: $0.50–$1.25/sq ft material, $0.75–$1.50/sq ft labor → $1.25–$2.75/sq ft installed
• Best for: Attic floors, dense-packed walls, retrofit projects
• Lifespan: 20–30 years (settles over time)

Cellulose is made from recycled newspaper treated with borate fire retardant — making it one of the most environmentally friendly insulation options. It has a higher R-value per inch than fiberglass (R-3.5 vs R-2.5–3.2) and fills gaps more completely.

The main advantage of cellulose is air sealing. Dense-packed cellulose reduces air infiltration significantly more than fiberglass, which means better real-world energy performance even at the same R-value. The trade-off: cellulose absorbs moisture more readily and settles 15–20% over time, reducing its effective R-value.

Use our Blow-In Insulation Calculator to compare cellulose vs. fiberglass costs for your attic.

Spray Foam Insulation

Spray foam is the premium insulation option — it's the only type that both insulates and air-seals in a single application. It comes in two formulations:

Open-Cell Spray Foam

• R-value: R-3.7 per inch
• Cost: $0.75–$2.00/sq ft material, $0.75–$1.50/sq ft labor → $1.50–$3.50/sq ft installed
• Best for: Interior walls, attic rafters (cathedral ceilings), sound dampening
• Lifespan: 80+ years

Open-cell foam is soft, spongy, and expands to fill the entire cavity. It's excellent for sound reduction and costs less than closed-cell. It does absorb water, so it's not suitable for below-grade or flood-prone areas. At 5.5 inches (a standard 2×6 wall cavity), it provides R-20.4.

Closed-Cell Spray Foam

• R-value: R-6.5 per inch
• Cost: $1.25–$3.00/sq ft material, $1.00–$2.00/sq ft labor → $2.25–$5.00/sq ft installed
• Best for: Basements, crawl spaces, rim joists, exterior, limited-space applications
• Lifespan: 80+ years

Closed-cell is rigid, dense, and acts as a vapor barrier. Its R-6.5 per inch is the highest of any common insulation — just 3 inches provides R-19.5, meeting most wall code requirements in a 2×4 cavity. It also adds structural strength to walls. The downside: it costs roughly 2× more than open-cell and can be over-applied (too much can cause structural issues due to expansion pressure).

Get a detailed estimate with our Spray Foam Insulation Calculator.

Mineral Wool Insulation

• R-value: R-3.3 per inch (batts), R-3.0 per inch (blown)
• Cost: $1.50–$3.50/sq ft installed
• Best for: Fire-rated assemblies, soundproofing, exterior continuous insulation
• Lifespan: 80–100 years

Mineral wool (also called rock wool or stone wool, with Rockwool being the leading brand) is made from basalt rock and recycite steel slag spun into fibers. It's denser and more rigid than fiberglass, offering several unique advantages:

• Fire resistance: Non-combustible up to 2,150°F — dramatically better than any other insulation type. Required for many fire-rated wall and floor assemblies.
• Sound absorption: Dense fibers provide superior acoustic insulation. Standard choice for party walls, home theaters, and recording studios.
• Moisture resistance: Hydrophobic — repels water rather than absorbing it, unlike fiberglass and cellulose.
• Dimensional stability: Rigid batts hold their shape and don't sag or settle over time.

The main downside is cost — mineral wool batts are 25–50% more expensive than fiberglass batts. But for fire-rated assemblies, soundproofing, and areas prone to moisture, it's the superior choice.

Rigid Foam Board Insulation

Rigid foam boards are dense, flat panels used where you need high R-value in thin applications — typically on foundations, exterior walls (continuous insulation), and below grade.

XPS (Extruded Polystyrene)

• R-value: R-5.0 per inch
• Cost: $1.50–$4.00/sq ft installed
• Best for: Foundation walls, below-grade, under-slab
• Recognizable by: Blue (Dow) or pink (Owens Corning) color

XPS is the most common rigid foam for residential use. It's moisture-resistant, dimensionally stable, and maintains its R-value when wet — making it ideal for any below-grade application. Standard thicknesses: 1", 1.5", and 2".

Polyisocyanurate (Polyiso)

• R-value: R-6.0–6.5 per inch
• Cost: $2.00–$5.00/sq ft installed
• Best for: Continuous exterior insulation, commercial roofing

Polyiso has the highest R-value per inch of any rigid foam. It comes with foil facers on both sides, which act as a radiant barrier. The caveat: polyiso's R-value drops in cold temperatures (below 50°F, it may perform at R-4.5–5.5/inch), making it less ideal for cold-climate exterior applications. Best used above grade.

EPS (Expanded Polystyrene)

• R-value: R-3.6–4.4 per inch
• Cost: $1.00–$3.00/sq ft installed
• Best for: ICF (insulated concrete forms), under-slab, budget exterior

EPS (white "styrofoam" boards) is the cheapest rigid foam option. It has the lowest R-value of the three but maintains performance in cold weather better than polyiso. Commonly used in ICF foundation systems and under concrete slabs.

Best Insulation by Application

Use our Attic Insulation Calculator to compare costs for attic-specific projects including fiberglass batts, blown-in options, and spray foam.

R-Value Requirements by Climate Zone

The US Department of Energy sets minimum R-value recommendations by climate zone. Here's what you need:

These are minimums — insulating above these values provides additional energy savings, especially in extreme climates. The most cost-effective R-value is typically 10–20% above the minimum for your zone.

Frequently Asked Questions

Frequently Asked Questions

What type of insulation has the highest R-value per inch? +

Closed-cell spray foam has the highest R-value per inch at R-6.5. This means just 3 inches provides R-19.5, meeting most wall insulation requirements. Polyisocyanurate (polyiso) rigid foam boards are second at R-6.0–6.5 per inch, followed by XPS rigid foam at R-5.0 per inch.

What is the cheapest insulation to install? +

Blown-in cellulose and fiberglass batts are the cheapest insulation options, both costing $1.25–$3.00 per sq ft installed. For a 1,000 sq ft attic, that's $1,250–$3,000. Fiberglass batts are the cheapest for DIY installation since the material is widely available at home improvement stores.

Is spray foam insulation worth the extra cost? +

Spray foam is worth it in specific situations: air-sealing is needed (spray foam is the only insulation that air-seals and insulates in one step), space is limited (closed-cell's R-6.5/inch needs less thickness), or you're in an extreme climate. For standard attic insulation, blown-in cellulose or fiberglass is usually the better value.

What R-value insulation do I need? +

R-value requirements depend on your climate zone and where you're insulating. The Department of Energy recommends: Attics — R-38 to R-60 (most US climates). Walls — R-13 to R-21. Floors — R-25 to R-30. Crawl spaces — R-25. Colder regions (Zones 5–7) need higher R-values, while mild climates (Zones 1–3) need less.

Can I install insulation myself? +

Fiberglass batts and blown-in insulation are both DIY-friendly. Batts are cut and placed by hand. Blown-in requires a blowing machine — many home improvement stores rent them free with a minimum insulation purchase. Spray foam is NOT a DIY project — it requires specialized equipment, safety gear, and trained application technique.

What is the best insulation for an attic? +

For most homeowners, blown-in cellulose is the best attic insulation. It's affordable ($1.25–$2.75/sq ft installed), fills gaps and irregular spaces well, provides R-3.5 per inch, and has good fire resistance. Blown-in fiberglass is a close second. For attics that also need air sealing (common in older homes), open-cell spray foam is an excellent choice.

How long does insulation last? +

Fiberglass batts and blown-in fiberglass last 80–100 years if they stay dry and undisturbed. Cellulose lasts 20–30 years before settling reduces its effectiveness. Spray foam (both open and closed cell) lasts 80+ years. Mineral wool lasts 80–100 years. Rigid foam boards last 50–80 years. In practice, most insulation is replaced due to renovations or moisture damage, not age.