10 Fiberglass Insulation Alternatives

There are alternatives to fiberglass insulation that provide better thermal resistance and are safer and more environmentally friendly. Fiberglass is the most popular insulation product because of price and availability but the following types of insulation are gaining traction.

Fiberglass Insulation Alternatives

Why Switch From Fiberglass?

As popular as fiberglass is, it does have a few negatives.

  • R-value. Fiberglass batts have an R-value of approximately R-3.2 per inch. Some competing products provide better R-values.
  • Not as Environmentally Friendly. Can use up to three times more energy during the manufacturing process. Not recyclable. Does not easily break down in landfills. Uses approximately 40% recycled materials.
  • Health Issues. Fiberglass packaged in the US states that there may be health risks associated with the product. May contain formaldehyde. May cause lung and skin irritation.
  • Flammable. Until recently, the paper on faced fiberglass was flammable. The newer products are non-flammable. But fiberglass melts–allowing more oxygen to feed fires.

10 Insulation Options

Insulation is the most important part of home comfort. Yet 90% of US homes are underinsulated. Choosing the best insulation for your needs includes considering factors such as cost, energy savings, ease of installation, health risks, and comfort.

Spray Foam Insulation

Spray foam is considered one of the best insulation options. It has an R-value of R-6.5 per inch, fills and seals gaps and cracks, and wraps around protrusions like wires, pipes, electrical boxes, and framing members. Spray foam is one of the more expensive insulation options. Buying and using DIY kits often costs more than contractor-installed foam.

Spray foam insulation is used on basement walls, living area walls, and vaulted and sloped roofs. Most spray foam is installed by professional contractors. DIY spray foam kits are available for smaller projects. They are perfect for rim joist insulation and jobs in remote areas where travel costs can be prohibitive.

Icynene Spray Foam

Icynene spray foam is relatively new to the US market. It is available in open-cell and closed-cell formulations with R-values up to R-6.75. The cost is comparable to regular spray foam. It is not available in DIY kit form.

Icynene foam is 100% water blown. It contains no volatile organic compounds (VOC). Making for safer installations. Like other spray foam products, Icynene fills all cracks and gaps and eliminates airflow. Mold and mildew will not grow on it because it prevents moisture infiltration and humidity problems.

Aerogel Insulation

Aerogel is also a fairly new insulation product; even if the original invention happened in 1931. It removes the solids from silica and replaces them with air. Dead air is the prime insulator in most products from fiberglass to rigid foam.

Aerogel is produced in thin sheets that wrap around HVAC ducting in place of fiberglass. It is also used to insulate hot water tanks and can be used as wall insulation. Aerogel is highly water-repellent, will not sag, or crack, and can be removed and used again. It costs approximately $3.00 per square foot. The R-value is R-10.3 per inch.

Cellulose Insulation

Cellulose insulation is one of the most versatile products you can use in your home. The R-value is approximately R-3.5 per inch. It is used as loose fill in attics and walls. It is wet sprayed on walls and ceilings. It can be dense-packed in wall cavities that are already drywalled. It is even available in batt form.

Cellulose is made from 85% recycled newspapers and cardboard making it very ecologically friendly. Borates are added as a fire retardant and insect repellant. Most cellulose is installed by contractors but you can rent the equipment for a DIY project. (Wet spray is not a DIY application.)

Mineral Wool Insulation

Mineral wool insulation is produced using lava rock and slag from the iron industry. It does not absorb moisture. It is more rigid than fiberglass. Mineral wool is often specified by architects for use in multi-family buildings because it is fireproof and for its great soundproofing capabilities.

Batts are R-3.0 – R-3.8. Loose fill for blowing into attics is R-2.5 – R-3.7. Batts cost between $1.50 and $2.25 per square foot. Loose fill costs between $1.75 and $2.81 per square foot. Mineral wool insulation is much heavier than fiberglass and cellulose. Loose fill weighs over 2 lbs. per square foot–over one ton on a 1000 square foot attic floor.

Cotton Insulation

Cotton insulation is also known as denim insulation because it is made with recycled blue jeans among other cotton products. It does not contain formaldehyde or VOCs. Denim is an excellent soundproofing insulation material; making it ideal for noisy environments or as insulation for music rooms and theaters.

Cotton insulation has an R-value of R-3.5 per inch. It costs around $1.00 per square foot. Denim insulation may have limited availability due to a lack of raw materials for the manufacturers. It must be installed in sealed environments because it attracts rodents.

Wool Insulation

Sheep’s wool has been used for insulation for centuries. It has the ability to absorb moisture without losing its insulation value. Making it a good option for humid locations. Wool is also a natural fire retardant. It is difficult to light and very slow-burning if it does catch fire.

Sheep wool insulation is available in batt form or as loose-fill blow-in material. It costs between $1.10 and $3.10 per square foot depending on thickness and type. The product will last as long as the structure it is installed in and does not degrade over time. Sheep’s wool meets all US building codes but is not accepted in Canada.

Rigid Foam Insulation

Rigid foam insulation can be installed on interior walls or on the exterior of the building–including below grade. Rigid foam between the studs can replace fiberglass batts. Gluing foam to interior basement walls saves floor space, creates a vapor barrier, and keeps the basement warm.

The three popular rigid foams–expanded polystyrene, extruded polystyrene, and polyisocyanurate–range in R-value from R-3.6 to R-6.5 per inch. The cost is between $0.25 and $0.75 per board foot. (A board foot is one square foot one inch thick.)

Hemp Insulation

Hemp insulation is eco-friendly. It is made from the fast-growing hemp plant–which grows with few or no fertilizers and pesticides–and about 8% polyester. It is non-allergenic and free of VOCs. The R-value is R-3.7 per inch. Hemp costs approximately $1.80 per square foot for 3 ½” thick batts.

Hemp insulation is not widely available. Many states have restrictions on growing it because of its relation to marijuana.

Radiant Barrier Insulation

  • Radiant barrier–or reflective–insulation does not have an R-value. It is made of reflective foil that prevents solar gain in hotter climates. (It has little value in colder climates and may be detrimental.) It is most effective when installed on the undersides of roof rafters–capable of reflecting up to 90% of solar heat.
  • Bubble wrap insulation is also radiant barrier insulation about ⅜” thick that helps keep houses cool. A layer of plastic containing air bubbles–somewhat like packaging bubble wrap–is sandwiched between two layers of reflective foil. Installed under siding, it also reflects heat away from the building. Claims of anything more than R-1.0 are considered wild exaggerations, but it works very well at reducing solar gain.