6 Eco-Friendly Insulation Options for Your Tiny Home

Glass wool insulation

Liz Grotyohann and Brian Schulz of Actually Tiny are passionate about sustainable building. For them, eco-friendly isn’t a blanket title. “It all exists on a spectrum of sustainability, and is filled with trade-offs that are going to make different options better or worse for individual projects,” Grotyohann said.

That said, they recommend glass wool or fiberglass as a quality option for someone looking for an environmentally friendly insulation option for their tiny home.

Another name for fiberglass, glass wool is probably what people are most familiar with when they think of insulation. It's cheap compared to other insulations and widely available. It has one of the lowest global warming potential ratings of all batt insulations, Grotyohann said, and it’s made from mostly recycled glass material.

“It can be tricky to install correctly, and respiratory protection while installing is a must,” she said. “A 2x4 wall will only give you R-13 insulation, less if the batts are installed incorrectly and are compressed or slump within the wall cavity.”

R-value is the measurement of an insulation material's effectiveness in terms of its thermal resistance.

Tiny home owners Paul O’Connor and Annett Welss of Living Tiny and Green used glass wool insulation in their build and are happy with the results. 

“The house is nicely insulated from top to bottom which keeps us warm in the winter and cool in the summer,” Welss said.

Mineral wool insulation

Mineral wool is another option that’s often advertised as eco-friendly. It’s also readily available in most building supply stores. Made from igneous rock spun into fibers, it is installed in batts much like fiberglass, Grotyohann said, so respiratory protection is a must when doing the installation yourself. 

It costs around 25 percent more than fiberglass, but you’re gaining a higher R-value (R-15 for a 2x4 wall) for the cost, she said. Grotyohann finds it easier to install than fiberglass and much easier to cut around electrical boxes, wiring and plumbing without losing its full R-value. 

“One of the things I like about mineral wool is that unlike many other insulation products, it is potentially salvageable for reuse at the end of the life of a structure,” Grotyohann said.

Sheep’s wool insulation

Sheep’s wool has a similar R-value to fiberglass, Grotyohann said, and is often marketed as eco-friendly. However, it’s more expensive compared to other insulation options, running two or three times the cost of fiberglass. She also advises people considering sheep’s wool as an eco-friendly insulation option to pay attention to any additives in the material. 

“Keep in mind that flame retardants may be added and pesticides may be added to wool, so if natural fibers are important to you, be sure to look into the additives in the product you’re using and their potential health impacts,” Grotyohann said.

Polyisocyanurate insulation

A rigid insulation option that’s eco-friendly is polyisocyanurate panels, Grotyohann said. For her, they are easy to install and offer a high R-value—sometimes as much as R-21 in a 2x4 wall. Surprisingly it has a global warming potential rating lower than mineral wool despite being made of foam, Grotyohann said.

“But they are quite expensive, and again, you would likely need a flame retardant wall covering like drywall,” she said.

Denim or cotton insulation

Similar to mineral wool, denim and cotton insulation are marketed as eco-friendly options and are comparable in price to mineral wool. The material is mostly made from salvaged and recycled clothes, like blue jeans. However, denim batts have a global warming potential rating a little higher than that of mineral wool, Grotyohann said. 

“Although, that impact is lower if you take into account the carbon sequestered in the denim,” she said.

Similar to sheep’s wool insulation, she advises that people consider that the denim or cotton materials may be treated with a flame retardant to reduce flammability.

Cellulose insulation

Made from recycled newsprint, wood and even corn cobs, cellulose insulation is another eco-friendly option, similar to denim and cotton insulation. The most common type is loose fill cellulose insulation. This is designed to be blown into walls and cavities, much like spray foam insulation. However, cellulose insulation is a dry material. The advantages of cellulose are that the pieces of material can settle around most obstructions, like wires and pipes, within walls and crevices. However, this can also be a drawback because over time it can pack down unevenly and leave air pockets.