Attic insulation guide: types, R-values, and contractor tips

Your attic is the most important area in your home to insulate properly. Heat rises, and an under-insulated attic can account for up to 25% of your home’s total heat loss. Whether you are dealing with sky-high energy bills, rooms that never feel comfortable, or ice dams in winter, an attic insulation upgrade is often the single best investment you can make.

This guide covers the types of attic insulation available, recommended R-values for your climate zone, cost expectations, and how to find the right contractor for the job.

Why attic insulation matters

Heating and cooling account for 50% to 70% of the energy used in the average American home. The attic sits directly above your living space, and without adequate insulation, conditioned air escapes through the ceiling year-round.

In winter, warm air rises and passes through a poorly insulated attic floor, forcing your furnace to run longer and harder. In summer, a sun-baked roof heats the attic to 150 degrees or more, and that heat radiates down into your living space, making your air conditioner work overtime.

Proper attic insulation creates a thermal barrier that keeps conditioned air where it belongs. The Department of Energy estimates that upgrading attic insulation can reduce heating and cooling costs by 15% to 30%, which translates to hundreds of dollars in annual savings for most households.

Types of attic insulation

Three insulation types dominate attic applications. Each has strengths that make it better suited for certain situations.

Blown-in insulation

Blown-in insulation is the most popular choice for attic floors. A machine blows loose fiberglass or cellulose fibers across the attic floor, filling gaps and settling around obstructions like wiring, pipes, and junction boxes.

Cellulose (R-3.2 to R-3.8 per inch) is made from recycled paper treated with fire retardants. It packs densely and resists air movement well. Fiberglass (R-2.2 to R-2.7 per inch) is lighter, resists moisture better, and does not settle as much over time.

Blown-in insulation works well for both new installations and topping off existing insulation. A professional crew can insulate a standard attic in two to four hours. For detailed pricing, see our blown-in insulation cost guide.

Fiberglass batts

Fiberglass batts are pre-cut panels sized to fit between standard ceiling joists (16 or 24 inches on center). They provide R-2.2 to R-2.7 per inch and are the most affordable insulation option at $0.50 to $1.50 per square foot.

Batts work best in attics with uniform joist spacing and few obstructions. The downside is that batts leave gaps around wiring, pipes, and irregular framing. These gaps allow air to bypass the insulation, reducing its real-world performance.

If you choose batts, proper installation matters enormously. Compressed batts, gaps at edges, and batts stuffed around obstacles all reduce performance. For this reason, blown-in insulation typically outperforms batts in real-world attic conditions.

Spray foam insulation

Spray foam is applied as a liquid that expands and hardens, creating a continuous air and thermal barrier. Closed-cell spray foam delivers R-6.0 to R-7.0 per inch and also acts as a vapor barrier. Open-cell spray foam provides R-3.5 to R-3.7 per inch and is better for sound dampening.

Spray foam is the premium option. Closed-cell costs $1.50 to $3.50 per square foot, and open-cell costs $0.75 to $2.00 per square foot. It is the best choice for:

• Attics being converted into conditioned living space
• Homes with HVAC ductwork in the attic
• Situations where air sealing is a top priority
• Low-slope roofs where space is limited and high R-value per inch matters

For a detailed comparison, read our spray foam vs. fiberglass guide.

Recommended R-values by climate zone

The Department of Energy divides the country into seven climate zones, each with recommended minimum R-values for attic insulation. Meeting or exceeding these recommendations ensures your insulation performs effectively.

To translate R-value into insulation depth, divide the target R-value by the material’s R-value per inch. For example, reaching R-49 with cellulose (R-3.5/inch) requires roughly 14 inches of depth. Reaching R-49 with fiberglass (R-2.5/inch) requires about 20 inches.

For a complete breakdown of R-values by material, see our R-value guide.

Signs you need more attic insulation

Not sure if your attic insulation is adequate? These warning signs point to an insulation problem.

High energy bills

If your heating and cooling costs are significantly higher than neighbors with similar-sized homes, insufficient attic insulation is one of the most common causes. Compare your energy usage year over year. Steady increases that are not explained by rate hikes suggest declining insulation performance.

Uneven room temperatures

Rooms directly below the attic that are noticeably hotter in summer or colder in winter indicate inadequate insulation above. Second-floor bedrooms are the most common trouble spots.

Ice dams in winter

Ice dams form when heat escaping through the attic melts roof snow, which refreezes at the eaves. If you see icicles or ice buildup along your roofline, your attic insulation and ventilation need attention.

Visible floor joists

Open the attic hatch and look across the attic floor. If you can see the tops of the floor joists above the insulation, your coverage is too thin. Insulation should be level with or above the joists.

Your home is more than 20 years old

Building energy codes have improved significantly over the past two decades. Homes built before 2000 often have attic insulation that falls well short of current recommendations. Even homes built to code in the 1990s may have only R-19 to R-30 in the attic, compared to today’s R-49 to R-60 recommendation for cold climates.

HVAC system runs constantly

When your furnace or air conditioner seems to run nonstop without reaching the set temperature, inadequate insulation is a likely contributor. The system is working against constant heat gain or loss through the attic.

Attic insulation cost breakdown

Understanding costs helps you budget for your project and evaluate contractor quotes. Here is what to expect for common attic insulation scenarios.

Additional costs to budget for

• Old insulation removal: $1.00 to $2.00 per square foot if existing insulation is damaged or contaminated
• Air sealing: $350 to $600 for sealing gaps around wiring, plumbing, and ductwork penetrations before insulating
• Attic access improvements: $200 to $500 if the existing hatch or stairway needs modification for equipment access
• Baffles and ventilation: $2 to $4 per vent bay for rafter baffles that maintain proper attic ventilation

Air sealing before insulating is one of the most impactful steps. Sealing gaps around penetrations can improve insulation performance by 15% to 25% because it stops warm air from bypassing the insulation entirely.

How to choose an attic insulation contractor

Hiring the right contractor ensures your insulation performs as intended and lasts for decades. Here is what to look for.

Verify credentials

Confirm that the contractor holds a valid license in your state and carries both general liability insurance and workers’ compensation coverage. Ask for certificates of insurance and verify them independently.

Look for energy efficiency certifications

Contractors certified by the Building Performance Institute (BPI), ENERGY STAR, or insulation manufacturers (Owens Corning, CertainTeed, Johns Manville) have completed specialized training in proper insulation and air sealing techniques.

Ask about air sealing

A good insulation contractor will recommend air sealing as part of the project. Sealing gaps around wiring, plumbing, recessed lights, and ductwork penetrations before insulating dramatically improves results. If a contractor does not mention air sealing, that is a red flag.

Get detailed quotes

Request itemized quotes from at least three contractors. Each quote should specify the insulation material, target R-value, total square footage, preparation work (removal, air sealing), and warranty terms. This makes it easy to compare quotes fairly.

Check references

Ask for three to five references from recent attic insulation projects. Call them and ask about the quality of work, cleanup, communication, and whether the contractor stayed on budget and on schedule.

For a comprehensive checklist of what to look for, read our guide to choosing an insulation contractor.

Find attic insulation contractors by state

Get free quotes from qualified insulation contractors in your area:

• Utah | Salt Lake City
• Idaho | Boise
• Colorado | Denver
• Oregon | Portland
• North Carolina | Charlotte | Raleigh
• Tennessee | Nashville
• Florida | Tampa
• Arizona | Phoenix
• Ohio | Columbus

Frequently asked questions

For more on insulation types and costs, visit our insulation contractor hub, explore our blown-in insulation cost guide, or read our wall insulation retrofit guide.