The most eco friendly insulation for most US homes is blown cellulose: it is 82% to 85% recycled paper (DOE), costs $0.60 to $2.30 per square foot installed (Angi, 2026) and has among the lowest embodied carbon of any insulation. Wood fiber, hemp, sheep’s wool and recycled denim are also low-carbon choices, but they cost more. The products to avoid on climate grounds are foams made with older HFC blowing agents.
This guide compares the main insulation materials on R-value, recycled content, cost, health and carbon. It also covers attic R-value targets, energy savings, the 2026 tax credit, a payback example and when to hire a contractor.
What makes insulation eco friendly?
Any insulation cuts emissions once installed. EPA estimates that air sealing plus insulation saves an average of 15% on heating and cooling costs, or 11% of total energy costs (Energy Star methodology, modeled on a 1,700 sq ft home built 1970 to 1989). Savings range from 5% to 16% of total energy costs depending on climate zone.
So the “green” question is mostly about what it took to make the product. Four things matter:
- Embodied carbon: emissions from raw materials, manufacturing and blowing agents, measured in CO₂e.
- Recycled or renewable content: newspaper, denim, glass, slag, wood, hemp, wool or cork.
- Health: what installers and occupants breathe during and after the job.
- Performance per dollar: a thin layer of a premium product can save less energy than cheap cellulose at full depth.
Eco friendly insulation products compared
R-values come from DOE Building America guides (2009 and 2012) or manufacturer pages. Costs are installed prices from Angi (May 2026) unless noted. A board foot is one square foot, one inch thick.
| Material | R-value per inch | Recycled or renewable content | Typical cost | Health, fire and moisture notes | Embodied carbon |
|---|---|---|---|---|---|
| Cellulose (blown) | R-2.9 to R-3.8 (DOE, 2012) | 82% to 85% recycled paper (DOE) | $0.60 to $2.30 per sq ft (2026) | Borate treated for fire and pests. Dusty to install. Must stay dry. | Among the lowest (Efficiency Vermont, 2022) |
| Wood fiber | R-3.7 to R-4.0 (TimberHP batt) | Wood fiber, renewable | $4.25 to $6.75 per sq ft (2026) | Borate treated, ASTM E84 Class A, no added formaldehyde per maker. Vapor open. | Among the lowest (Efficiency Vermont, 2022) |
| Hemp | R-3.7 (Hempitecture HempWool) | 90% hemp fiber, 10% binder | Quote only, not verified | Maker says VOC free and safe to handle without gloves. | Maker claims net carbon storage. Check the EPD. |
| Sheep’s wool | About R-4.0 (Havelock R-14 batt at 3.5 in) | 100% wool, renewable | About $2.83 per sq ft, material only (see note) | Buffers humidity, self-extinguishing per maker. New Zealand wool. | Not verified here |
| Cotton / denim | About R-3.7 (UltraTouch R-13 at 3.5 in) | 80% post-consumer denim (Henry) | Not verified | No itch, borate treated (DOE). | Not verified here |
| Cork board | R-3.6 (GreenBuildingAdvisor, 2012) | Bark harvested without felling the tree | About $5.50 per sq ft for R-19 (2012, dated) | Bound by its own natural resin. | Not verified here |
| Mineral wool | R-3.7 (DOE, 2012) | About 75% post-industrial content (DOE) | $1.40 to $4 per sq ft (2026) | Non-combustible, flame spread 0 (Rockwool). Does not support mold. | Not ranked in the source used |
| Fiberglass | R-2.9 to R-4.3 batts, R-2.2 to R-2.7 loose (DOE, 2012) | 40% to 60% recycled glass (DOE) | $0.30 to $1.50 per sq ft (2026) | Skin and lung irritant during install. | Middle (Efficiency Vermont) |
| Spray foam, open cell | R-3.6 (DOE, 2009) | None stated | $0.44 to $0.65 per board foot (2026) | Isocyanate exposure during install. Not for below ground (DOE). | Middle. Blown with air or water, not HFCs (DOE). |
| Spray foam, closed cell | R-6.1 (DOE, 2009) | None stated | $1 to $1.50 per board foot (2026) | Same isocyanate hazard. Needs a half-inch drywall thermal barrier (DOE). | Highest with HFC-245fa (GWP 1,030). Low with HFO (GWP about 1). |
| Rigid foam (EPS, XPS, polyiso) | EPS R-3 to R-4, XPS R-5.0, polyiso R-5.6 to R-8 (DOE, 2012) | None stated | EPS $0.25 to $0.35, XPS $0.40 to $0.50 per board foot (2026) | Must be covered for fire safety. | XPS with HFC-134a (GWP 1,430) is highest. EPS and polyiso use pentane (GWP about 7). |
| Aerogel blanket | About R-9.6 (calculated below) | None stated | Not verified | Thin: 5 mm or 10 mm. | Not verified here |
Two notes. The sheep’s wool price comes from one retail listing (Source 2050, October 2026): $2,035 per pallet ÷ 720 sq ft = $2.83 per sq ft, before labor. The aerogel R-value is converted from the Aspen Aerogels Spaceloft datasheet: 0.0254 m ÷ 0.015 W/m·K = 1.69, × 5.678 = about R-9.6 per inch.
Most eco friendly insulation: the honest ranking
Our criteria: lowest embodied carbon first, then cost, then health. Efficiency Vermont’s 2022 analysis found that wood fiber and cellulose have the lowest embodied carbon, and closed-cell spray foam and XPS have the highest. Fiberglass, polyiso, EPS and open-cell foam sit in between.
On that basis, cellulose is the best eco friendly insulation for most budgets. It is the cheapest low-carbon option and works in attics and closed walls. Wood fiber, hemp, wool and denim are good products, but wood fiber costs several times more, so they make sense mainly when health or moisture buffering is your priority.
Fiberglass and mineral wool are not greenwashed: both contain real recycled content. If fiberglass is the only bid you can afford, take it and insulate to the full recommended depth.
How much CO₂ is behind your heating and cooling bill? Enter your kWh and country to see the emissions in seconds. Open the free kWh to CO₂ Calculator
Is spray foam eco friendly?
It depends on the blowing agent. BuildingGreen reports that HFC-245fa, long the standard in closed-cell spray foam, has a global warming potential of 1,030, and HFC-134a in XPS board is 1,430 times as potent as CO₂. In its Boston wall model, XPS took 36 to 65 years to pay back its own climate impact at 1 to 4 inches thick. Pentane-blown polyiso took 2.7 years at 4 inches.
Newer HFO blowing agents have a GWP of about 1. EPA’s Technology Transitions rule set a GWP limit of 150 for polyurethane and extruded polystyrene foams manufactured or imported from January 1, 2025. Still, ask the installer for the data sheet and confirm the foam is HFO-blown.
Health is the other issue. EPA says isocyanates, a main ingredient, are a leading chemical cause of work-related asthma. Stay out of the house during spraying and until the installer says it is safe to return.
Is fiberglass eco friendly?
Partly. Most fiberglass contains 40% to 60% recycled glass (DOE), it is the cheapest material in the table, and it sits in the middle on embodied carbon. Its weak points are irritation during installation and the fact that it does not stop air leaks.
Eco friendly insulation for attic, walls and whole houses
The attic is usually the cheapest place to add R-value. Energy Star’s recommendations for existing wood-framed homes are based on the 2021 IECC:
| Climate zone | Uninsulated attic | Attic with 3 to 4 inches existing | Floor |
|---|---|---|---|
| 1 | R-30 | R-25 | R-13 |
| 2 | R-49 | R-38 | R-13 |
| 3 | R-49 | R-38 | R-19 |
| 4A and 4B | R-60 | R-49 | R-19 |
| 4C, 5 and 6 | R-60 | R-49 | R-30 |
| 7 and 8 | R-60 | R-49 | R-38 |
Attic
Blown cellulose is the natural fit. At the upper DOE value of R-3.8 per inch, R-49 needs 49 ÷ 3.8 = about 13 inches. At R-2.9 it needs about 17 inches. Ask the installer which depth the bid assumes.
Walls
Closed walls can be filled with dense-pack cellulose. In open walls, wood fiber, hemp, wool, denim or mineral wool batts fit standard stud bays. When re-siding, Energy Star suggests adding R-5 insulative sheathing in zone 3 and R-5 to R-10 in zones 4 to 8.
Basements and crawl spaces
Natural fibers must stay dry, so foam is hard to avoid here. Choose EPS, polyiso or HFO-blown products over older XPS. Replacing the roof too? See our guide to eco-friendly roofing.
Cost and payback: a worked example
Angi (2026) puts attic insulation at $1,500 to $6,000, or $1 to $7 per square foot. Here is a simple cellulose example for a 1,000 sq ft attic.
- Cost: 1,000 sq ft × $0.60 to $2.30 = $600 to $2,300. Midpoint: $1,450.
- Energy bill: US households spent an average of $1,884 on energy in 2020 (EIA).
- Savings: $1,884 × 11% = about $207 per year.
- Payback: $1,450 ÷ $207 = 7.0 years. Range: $600 ÷ $207 = 2.9 years to $2,300 ÷ $207 = 11.1 years.
Treat this as a rough guide. EPA’s 11% assumes air sealing plus insulating the whole house to code, not the attic alone. Your bill may differ: check electricity cost by state and how many kWh a house uses.
Is there a federal tax credit for insulation in 2026?
No, not for work done in 2026. The Energy Efficient Home Improvement Credit (Section 25C) covered 30% of insulation and air sealing material costs, up to $1,200 per year. The IRS page (last reviewed April 28, 2026, checked October 2026) says the credit applies only to property placed in service from January 1, 2023 through December 31, 2025. Energy Star gives the same end date.
For 2026 projects, check state and utility rebates, which vary locally.
When to hire a professional
Energy Star rates batts as a basic-skill job, blown-in and rigid board as intermediate, and spray foam as advanced work that needs a certified installer. Hire a contractor for spray foam, dense-pack walls and any home with moisture problems.
A good contractor air seals first, then insulates. Installers typically charge $40 to $80 per hour (HomeAdvisor, 2026). A blower door test, which measures how leaky the house is, costs about $350, and a full home energy audit averages $437 (HomeAdvisor). Questions to ask:
- Are you licensed and insured in this state, and certified for this product?
- Will you seal air leaks before insulating, and is that in the written bid?
- Will you run a blower door test before and after?
- What installed R-value and settled depth am I paying for?
- For foam: which blowing agent, and how long must we stay out of the house?
Frequently asked questions
What is the most eco friendly insulation?
Cellulose and wood fiber have the lowest embodied carbon according to Efficiency Vermont’s 2022 analysis. Cellulose is also 82% to 85% recycled paper and one of the cheapest materials to install.
Is spray foam insulation eco friendly?
Only when it uses an HFO blowing agent with a GWP of about 1. Closed-cell foam made with HFC-245fa (GWP 1,030) has among the highest embodied carbon of any insulation.
Is fiberglass insulation eco friendly?
It is a reasonable middle choice. It contains 40% to 60% recycled glass and is cheap, but it irritates skin and lungs during installation.
How much does eco friendly insulation cost?
Installed cellulose runs $0.60 to $2.30 per square foot and wood fiber $4.25 to $6.75 (Angi, 2026).
Sources
- Energy Star: Recommended home insulation R-values
- Energy Star: Methodology for estimated energy savings from air sealing and insulation
- US Department of Energy: Types of insulation
- DOE Building America: Energy Renovations, Insulation guide (2012)
- IRS: Energy Efficient Home Improvement Credit
- BuildingGreen: Avoiding the global warming impact of insulation
- Angi: How much does insulation installation cost? (2026)
About the author
Georgi Todorov is an eco activist and entrepreneur. He runs Ecoki, where he builds free tools and guides that help small businesses measure and cut their carbon footprint.