INSULATION TYPES
A guide to common home insulation materials
Choosing the Right Insulation
No single insulation material is best for every part of a home. The right choice depends on where it will be installed, the available space, your budget, and the performance you need. R-value — a measure of resistance to heat flow — is one factor, but air sealing, moisture control, and proper installation matter just as much.
Below is a plain-language overview of the most common insulation types used in American homes, including where each works best and the trade-offs to consider.
Understanding R-Value
R-value measures how well a material resists heat transfer. Higher R-values mean better insulating power. Importantly, R-value is rated per inch of thickness, so a thicker layer of a lower-R material can outperform a thin layer of a higher-R one. The U.S. Department of Energy recommends higher total R-values for cold-climate states like Vermont — for example, an attic retrofit range of roughly R-49 to R-60.
R-value alone does not guarantee comfort or savings. Gaps, compression, and air leakage can dramatically reduce real-world performance, which is why professional installation and air sealing are part of most weatherization projects.
Common Insulation Materials
Fiberglass
✓ Advantages
- Affordable and widely available
- Non-combustible and moisture resistant
- Easy to install in standard cavities
✗ Considerations
- Can leave gaps if poorly fitted
- Lower R-value per inch than foam
- Irritant during handling — requires protective gear
Cellulose
✓ Advantages
- Made from recycled paper — eco-friendly
- Fills gaps and around obstructions well
- Treated for fire resistance
✗ Considerations
- Can settle over time, reducing coverage
- Sensitive to moisture if not properly sealed
- Dense-pack requires professional equipment
Spray Foam
✓ Advantages
- Highest R-value per inch
- Acts as both insulation and an air barrier
- Closed-cell adds structural strength and moisture resistance
✗ Considerations
- Most expensive option
- Requires professional installation
- Improper installation can cause off-gassing issues
Mineral Wool (Rock / Slag Wool)
✓ Advantages
- Excellent fire resistance and sound dampening
- Naturally water repellent
- Maintains R-value even when damp
✗ Considerations
- More expensive than fiberglass
- Heavier and denser — harder to cut
- Can be irritating to skin during installation
Rigid Foam Board
✓ Advantages
- High R-value per inch with continuous coverage
- Reduces thermal bridging when applied outside framing
- Moisture resistant and durable
✗ Considerations
- Must be sealed at joints to prevent air leaks
- Some types can absorb moisture over time
- Requires careful detailing around windows and doors
Reflective / Radiant Barriers
✓ Advantages
- Reflects radiant heat rather than absorbing it
- Thin and lightweight
- Useful in combination with other insulation
✗ Considerations
- Little benefit in cold Vermont winters on its own
- Must face an air space to work
- Not a substitute for thermal insulation
Where Insulation Is Typically Installed
- Attic / ceiling: Usually the most cost-effective place to add insulation. Loose-fill fiberglass or cellulose is common; deeper coverage raises total R-value.
- Exterior walls: Dense-pack cellulose or blown-in fiberglass is often used in retrofit projects. Spray foam is an option where air sealing is a priority.
- Rim joists & foundations: Closed-cell spray foam or rigid foam board help control air leakage and moisture in basements and crawlspaces.
- Floors over unconditioned spaces: Batts or rigid foam can reduce drafts and improve comfort above garages and vented crawlspaces.
Air Sealing Matters
Insulation slows conductive heat flow, but it does not stop air leaks. Gaps around plumbing, wiring, chimneys, and attic hatches can let warm air escape and cold air in — undermining even high-R-value insulation. Most professional weatherization projects pair insulation upgrades with air sealing and a blower-door test to measure the improvement.
Vermont Considerations
Vermont's cold climate makes high total R-values and thorough air sealing especially valuable. Local programs like Efficiency Vermont's Home Performance with ENERGY STAR® may offer rebates for qualifying professional weatherization work. The right material and scope depend on your home's construction, existing insulation, and applicable Vermont energy requirements — a professional assessment is the best way to confirm what applies to you.
Need Help Choosing?
This guide is for general planning only. A professional insulation assessment can evaluate your home's current condition, recommend the right materials and R-values, and identify available rebates. Request a free local assessment to get started.
Information is for general educational purposes only and does not constitute professional advice. R-values, material availability, and program details vary by project and location. Actual performance depends on proper installation, air sealing, and your home's construction.