Types of Home Insulation: Pros, Cons & Cost per Square Foot

Not all insulation is created equal — and the "best" type depends entirely on where you're installing it, your climate, and whether air sealing is a priority. Here's how every major insulation type compares.

Insulation Types at a Glance

| Type | R-Value per Inch | DIY-Friendly | Best For | Cost (installed) | |---|---|---|---|---| | Fiberglass batts | R-2.9–3.8 | Yes | Framed walls, attic floors | $0.50–$1.50/sq ft | | Mineral wool (Rockwool) | R-3.0–3.3 | Yes | Fire resistance, sound | $0.80–$2.00/sq ft | | Blown-in fiberglass | R-2.2–2.7 | Partially | Attic floors, wall cavities | $0.80–$1.50/sq ft | | Blown-in cellulose | R-3.2–3.8 | Partially | Attics, existing walls | $0.80–$1.60/sq ft | | Open-cell spray foam | R-3.5–3.7 | No | Interior walls, rim joists | $1.50–$3.00/sq ft | | Closed-cell spray foam | R-6.0–7.0 | No | Basements, crawl spaces, roofs | $2.50–$5.00/sq ft | | Rigid foam board | R-3.8–6.5 | Yes | Exterior walls, foundations | $0.50–$1.50/sq ft |

Fiberglass Batts

R-value: R-11 (2×4 wall), R-19 (2×6 wall), R-30/R-38 (attic)

The most common insulation in American homes. Pre-cut to fit 16" or 24" stud spacing. Available in faced (kraft paper vapor retarder) and unfaced versions.

Pros:

• Cheapest option
• Easy DIY installation
• Widely available at any hardware store
• Non-combustible

Cons:

• Doesn't seal air gaps — it filters air, not blocks it
• Performance degrades if compressed or wet
• Must be fitted precisely; gaps reduce effectiveness significantly
• Loses R-value in extreme cold

Best used for: New construction framed walls and attic floors where you'll add a separate air barrier. Less effective as a retrofit without air sealing.

---

Mineral Wool (Rockwool / SAFE'n'SOUND)

R-value: R-15 (3.5"), R-23 (5.5")

Made from basalt rock or steel slag. Denser and more fire-resistant than fiberglass. Doesn't absorb moisture. Popular in commercial and high-performance residential projects.

Pros:

• Fire resistant (melts at 1,800°F vs. fiberglass at 1,100°F)
• Excellent sound attenuation (STC ratings 45–55)
• Moisture resistant — won't support mold growth
• Slightly higher R-value per inch than fiberglass

Cons:

• Costs 2–3× more than fiberglass batts
• Heavier and denser (harder to handle in large quantities)
• Still not an air barrier

Best used for: Party walls, bedroom/bathroom walls for sound control, fire separation assemblies, garages.

---

Blown-In Insulation

Blown-In Fiberglass

Loose glass fibers blown in by machine. Good for attic floors — fills around joists and obstacles easily. Less effective on settling slopes.

Blown-In Cellulose

Made from recycled paper treated with fire retardant. Higher R-value per inch (R-3.2–3.8) than blown fiberglass and better air resistance — cellulose dense-packs into gaps.

Dense-pack cellulose blown into existing wall cavities through small holes is one of the most cost-effective ways to insulate existing walls without major renovation.

Pros (cellulose):

• Better air resistance than loose fiberglass
• Recycled content (85% post-consumer paper)
• Good for attics and retrofit wall cavities
• Cost-competitive

Cons:

• Settles 5–20% over time (installers compensate)
• Heavy — check attic structure before adding thick layers
• Not DIY-friendly (requires rented blower machine)

Best used for: Existing attics needing more R-value, retrofit wall cavities via dense-pack.

---

Open-Cell Spray Foam

R-value: R-3.5–3.7 per inch

Sprayed as liquid that expands 100× and hardens. Open-cell foam is softer and vapor-permeable. Lower R-value than closed-cell but excellent air sealing.

Pros:

• Superior air sealing — fills all gaps, cracks, and irregular shapes
• Soundproofing properties
• Less expensive than closed-cell
• Vapor-open (dries if it gets wet)

Cons:

• Professional installation only
• Needs vapor barrier in cold climates
• Off-gasses during curing (vacate 24–48 hours)
• Not moisture-resistant — not for below-grade

Best used for: Rim joists, interior wall cavities, ceiling/roof deck (interior side), anywhere air sealing is the priority.

---

Closed-Cell Spray Foam

R-value: R-6.0–7.0 per inch

The premium option. Rigid, dense foam that doubles as a vapor barrier and adds structural strength. One inch achieves R-7.

Pros:

• Highest R-value per inch
• Also acts as vapor barrier
• Moisture-resistant — suitable for basements and crawl spaces
• Adds wall racking strength
• Can reduce radon infiltration

Cons:

• Most expensive ($2.50–$5/sq ft installed)
• Professional only
• High global warming potential (HFO-blown versions are better)
• Difficult to remove or modify

Best used for: Basements, crawl spaces, cathedral ceilings (when height is limited), cold climates where maximum R-value per inch is needed, below-grade applications.

---

Rigid Foam Board

R-value: R-3.8 (EPS), R-5.0 (XPS), R-6.5 (polyiso per inch)

Rigid boards cut to size. Three types: EPS (white beads, cheapest), XPS (blue/pink boards, water-resistant), Polyiso (foil-faced, highest R-value).

Pros:

• Can be DIY-installed
• Excellent for continuous insulation (breaking thermal bridges)
• Polyiso achieves high R-value in thin profile
• XPS is moisture-resistant

Cons:

• Rigid — requires careful measuring and cutting
• Needs to be covered (fire code) in occupied spaces
• Joints must be taped for air sealing

Best used for: Basement walls (XPS or EPS with drainage mat), exterior continuous insulation on wall sheating, under slab, attic hatches.

---

Choosing the Right Type by Application

| Location | Recommended Type | Notes | |---|---|---| | Attic floor (accessible) | Blown cellulose or fiberglass batts | Add to R-38 or R-60 minimum | | Attic sloped (cathedral ceiling) | Closed-cell spray foam | Needs 2" minimum for vapor barrier | | 2×4 framed walls (new) | Mineral wool batts + air barrier | Or dense-pack cellulose | | Existing walls (retrofit) | Dense-pack cellulose | Via small holes, patched after | | Basement walls | Rigid foam + closed-cell spray | XPS or EPS with drainage gap | | Crawl space | Closed-cell spray foam | Encapsulation preferred | | Rim joists | Closed-cell spray foam (2") | Best bang for buck on air sealing | | Garage ceiling | Fiberglass batts R-30 | Or blown-in for faster coverage |

---

Tax Credits for Insulation (2025)

Air sealing and insulation added to existing homes qualifies for the Energy Efficient Home Improvement Credit:

• 30% of material and installation costs
• Up to $1,200 per year
• Applies to insulation that meets 2021 IECC standards

This makes high-performance options like closed-cell spray foam much more financially attractive. See our full guide to IRA home energy tax credits for details.

---

Bottom Line

• Tight budget, new construction walls: Fiberglass batts
• Best performance for money in most applications: Dense-pack cellulose
• Air sealing + insulation in one step: Spray foam (open or closed cell)
• Maximum R-value per inch, wet/cold locations: Closed-cell spray foam
• Sound control, fire resistance: Mineral wool

For a full cost breakdown by area and R-value target, see our home insulation cost guide.