Story at a glance:

  • An efficient thermal insulation material can aid in lowering energy bills as well as have a positive effect on the environment.
  • The thermal resistance, or R-value, of thermal insulation materials varies depending on the physical property.
  • The effectiveness of thermal insulation materials depends on climate compatibility.

With the effects of climate change becoming more evident, extreme temperature conditions are more common. Many cities around the world are experiencing variations in weather patterns that they aren’t accustomed to, which has manifested itself in the degradation of infrastructure, like energy demands that can cripple power grids. Many homeowners are feeling the burden, struggling to maintain comfortable home temperatures as high oil prices inflate energy bills.

Whether installing radiant barriers or putting in a few cool walls, homeowners can take many avenues to make their homes more energy-efficient, but insulation is important. Thermal insulation is responsible for making the internal temperature of a building stable, and finding an efficient material can help to reduce the energy required for heating/cooling the house, conversely creating lower energy bills. This can also have a positive effect on the environment by reducing the burning of fuel in power plants, which will reduce the emission of greenhouse gasses.

Thermal insulation plays a key role in making a home more energy-efficient, but finding the right material can be tricky. From bulky blankets of fiberglass to futuristic aerogels, there’s a myriad of options to choose from. Here is our guide to the best thermal insulation materials.


Usually dulled out in batts installed in pieces or rolls, fiberglass remains one of the most common forms of insulation. Photo by Brizmaker

Made up of molten glass and spun into fibers, fiberglass remains one of the most common forms of insulation due to its adaptability, affordability, and effectiveness. Usually dulled out in batts that are installed in pieces or rolls that are rolled out, fiberglass can also come in a loose-fill form blown out using a machine as well as rigid boards and rolls for ducts. Fiberglass thermal insulation is both fire- and moisture- resistant, and much of the material is recyclable.

Due to its commonality, the mass production of fiberglass has made it one of the cheaper options for thermal insulation material, and its adaptive properties make it ideal for DIY projects. The thermal resistance, or R-value, of fiberglass ranges around 2.2 to 2.7 per inch of thickness, but comparatively speaking that’s low when stacked to other available options. Over time that value can decrease due to sagging or settling.

Fiberglass can be hazardous to install due to its natural properties, where slivers of glass can get lodged in skin and cause irritation. If inhaled, it can cause irrefutable damage to lungs. It is the most ubiquitous option out there when it comes to thermal insulation, but it may not always be the best.

Mineral Wool


ROCKWOOL transforms volcanic rock into quality stone wool insulation that’s both performance tested and ranked high in use among the residential construction market. Photo courtesy of Rockwool

Composed of rock or slag, mineral wool consists of mostly post-industrial recycled content. Much like fiberglass, mineral wool thermal insulation can come in many forms, from roll and batts to loose-fill, but its R-value sits around 3.0 to 3.3 per inch of thickness. The thermal performance of mineral wool holds up over time, and its high heat manufacturing process strips it of organic matter—making it a poor medium for moisture and mold.

Mineral wool’s natural components make it extremely durable and a great choice when considering longevity, but it is more costly on the front end. That extensive, high-heat manufacturing process increases the price and uses a lot of energy, but once installed that energy is recuperated within five months. Mineral wool is also heavy, which can make it less ideal for some projects, but its materials are recyclable and inherently non-combustible, adding to the fire resistance of a building.

While not as ubiquitous as fiberglass, a lot of great options for mineral wool exist on the market, including ROCKWOOL, which transforms volcanic rock into quality stone wool insulation that’s both performance tested and ranked high in use among the residential construction market.

“We tend toward ROCKWOOL on all of our projects,” said Chris Laumer-Giddens, vice president of the architecture and construction firm LG Squared, in a previous gb&d article. “They’re making it more accessible to the residential construction market, which is where we spend most of our time. I’ve tried the other stuff, and it just doesn’t have the same performance and usability.”


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Greenfiber’s wall insulation starts as a plant material, is made into paper, and reused as insulation. Photo courtesy of Greenfiber

Cellulose thermal insulation material is growing in popularity due to its highly sustainable nature. Made from primarily recycled paper products reduced to small pieces and fiberized, cellulose typically comes as either loose-fill or dense packed. It has a typical R-value of 3.2 to 3.8 per inch thickness, and its manufacturing process makes it more affordable. Although naturally more flammable, cellulose can be treated with chemicals like boric acid to increase its fire resistance, also making it less desirable to pests and mold.

That being said, cellulose is more prone to moisture absorption, so very humid climates might not be the environment for the material. An additional installation of a vapor barrier will also be needed, and sagging and settling can also be an issue, decreasing the R-value over time. Regardless, cellulose is one of the most sustainable options on the market, and companies like Greenfiber have embraced that concept, taking steps to help the environment by using less energy consumption in the manufacturing process.

“Greenfiber uses a low-energy manufacturing process that results in materials with the least-embodied energy of most major insulation products. The production process generates little no waste or byproducts because we leverage recovered material to start with,” said Jason Todd, the director of market development and building science at Greenfiber, in a previous gb&d article.


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Polystyrene boards are lightweight and water-resistant, and their low water absorption helps to prevent mold. Photo courtesy of ISI Building Products

Polystyrene is a versatile material made up of colorless, transparent thermoplastic. Usually provided in its rigid foam board form, this thermal insulation material’s R-value ranges around 3.6 to 4.0 per inch of thickness and its foam board form makes it easier to install and less hazardous than fiberglass or mineral wool.

Polystyrene boards are lightweight and water-resistant, and their low water absorption helps to prevent mold. Foam boards can be brittle though, and their upfront costs are more than fiberglass, making them riskier. Their chemical makeup isn’t biodegradable and can create toxins when burning, but their high R-value and sound dampening properties makes polystyrene an attractive option.

Polyurethane Foam

dupont froth-pak sustainable products for home renovation

Froth-Pak is an all-in-one kit for contractors to quickly and efficiently seal out moisture, dust, and allergens and improve energy efficiency, building resilience, and comfort. Photo courtesy of DuPont

Polyurethane foam, more commonly marketed as spray foam, is an insulation material that contains low-conductivity gas in its cells. Spray foam comes in two types, open-cell and closed-cell, and the R-value depends on what kind is used. Closed-cell spray foam typically has an R-value around 6 to 7 per inch of thickness. It works well in climates with high humidity due to its tendency to expand and solidify, making it impermeable to moisture. DuPont offers an array of insulating foams through their Great Stuff product line, one of which is their closed-cell polyurethane spray foam, Froth-Pak.

“Froth-Pak is an all-in-one, self-contained, easily portable kit for our professional contractors to quickly and efficiently fill larger gaps and penetrations to seal out moisture, dust, and allergens while improving energy efficiency, building resilience, and comfort for homeowners,” said Amy Radka, DuPont’s retail marketing director, in a previous article for gb&d.

Open-cell spray foam, on the other hand, is less dense, and the air-filled cells give the material a spongier texture. Open-cell spray foam has a typical R-value of 3.6 to 3.9, and it’s not as moisture-resistant as closed-cell, but it is the cheaper of the two options with a greater expansion rate.

Regardless of the form, polyurethane spray foam is considered eco-friendly, as it is one of the most energy-efficient insulation materials on the market with its high R-values and penance for longevity. Over time production of polyurethane foams has been refined to decrease the amount of damage that it once had on the environment, and while the verdict is still out on its potential health risks, polyurethane spray foam continues to grow as a popular option for energy-efficient renovations.

Cementitious Foam

Similar to closed-cell polyurethane spray foam, cementitious foam thermal insulation material becomes rigid and solid after being sprayed in.

These cement-based, foam-in-place insulation materials are nontoxic, nonflammable, and can have typical R-values of 3.9 per inch of thickness.

While they may not be the best for colder environments, cementitious foams are moisture- and mold-resistant, cost-effective, and can provide additional structural support.


Aerogels have a high gas content that gives them an impressive R-value of 10.3 per inch of thickness. Photo courtesy of The National University of Singapore

Moving into more innovative territory, aerogel thermal insulating materials aren’t necessarily new, but their growing availability has increased their ease of application over the years. Usually composed of silica, aerogels are generally transparent in appearance and have a high gas content that gives them an impressive R-value of 10.3 per inch of thickness. This incredible propensity for low thermal conductivity makes it the most energy-efficient insulation material out there but also the most expensive. Aerogels can also be very brittle, which can make them more difficult to use in areas with higher tension.