What is Wood Fiber Insulation?

The raw material for wood fiber insulation is residual softwood timber. It has been used in Europe since the 1930s where it compares with expanded polystyrene for price and performance. Companies in North America charge more because it is imported. That is changing because at least three companies are now manufacturing in the US.

Wood Fiber Insulation

How Wood Fiber Insulation Is Made

Most of the raw material for wood fiber insulation is sawdust, wood chips, and offcuts secured from sawmills and other wood processing facilities. The untreated softwood is reduced to fibers; and then formed into batts, blankets, rigid boards, or loose-fill products.

Wood fiber manufacturers always have a ready supply of this waste material. For instance, one Pella window plant in the US cuts over 190 tons of pine every day–a lot of sawdust. Two types of production methods are used–wet and dry.

Types and Uses of Wood Fiber Products

The raw material used to make wood fiber insulation comes from the same base as cellulose. It should not be surprising that they have some of the same types of products and uses in common. All wood fiber insulation has excellent sound attenuation–reducing noise by 36 to over 50 decibels.


Wood fiber batts and rolls are available in various thicknesses and standard stud cavity widths of 16” and 24”. US-manufactured batts have an R-value up to R-4.0 per inch. They are made of up to 95% softwood fibers, a binder, borax, and paraffin wax–either flexible or semi-rigid. There are no toxins or harmful fibers.


Loose-fill wood fiber has an R-value of R-3.8 per inch. It is dense-packed in walls, rafters, and floors with a retention net to hold it in place. It is also used as blow-in attic floor insulation. More R-value with less volume than fiberglass loose-fill insulation. Similar R-value and volume as cellulose loose-fill insulation. It is treated with borate to achieve a Class A fire rating. Borate also repels insects and rodents.

Rigid Boards

Wood fiber rigid board insulation has R-values from R-3.4 – R-3.7 per inch. The boards are 2’ wide, 4’ or 8’ long, and up to 10” thick and available with tongue and groove or butt edges. They are composed of softwood fiber, PMDI adhesive, and paraffin wax. Used for continuous exterior insulation, roof insulation, and for walls, floors, and ceilings.

They cannot be used for exterior insulation below grade and are not recommended for interior basement walls because of possible moisture problems.

Wood Fiber Insulation Uses

Wood fiber insulation is used in the same ways and places as traditional insulation. Use any wood fiber insulation to soundproof interior walls. Especially useful for bedrooms, bathrooms, home theaters, and music rooms.

Batts and Rolls

Batt and rolled wood fiber insulation is used in stud cavities, rafter cavities, and joist cavities. They are also used to insulate attic floors. A double layer of 5.5” material installed perpendicular to each other insulates the attic to R-44.


Loose-fill wood fiber is an excellent option for attic floors. It easily flows around obstructions and fills gaps and cracks. It can be dense-packed into wall, rafter, and floor cavities. It cannot be applied wet like cellulose, so containment netting is required. The borate treatment gives it a Class A fire rating and resists mold, mildew, and pests.

Rigid Boards

Use as continuous exterior wall insulation and roof insulation. It can be attached to the interior faces of studs, rafters, and joists and used to insulate concrete floors. Some manufacturers pre-cut grooves in the board to accommodate in-floor heating. Wood fiber rigid boards cannot be used under concrete slabs like polystyrene because of potential moisture problems.

Benefits of Wood Fiber Insulation

Wood fiber insulation has many attractive qualities. Some of them include:

  • R-values. Compares favorably with traditional insulation products like fiberglass, cellulose, and mineral wool.
  • Moisture Control. Vapor-permeable. Allows moisture in, but it can get back out. Can absorb up to 15% of its weight in moisture without losing any R-value.
  • Environmentally Friendly. Has the same benefits as most wood products–safe, renewable, and natural. Additives are also natural. Biodegradable. Reusable. Compostable.
  • Installation. Easy safe installation. No special safety equipment except a mask if preferred. Will not sag or settle.
  • Stable. Retains its original size. Does not shrink.
  • Soundproofing. Provides exceptional sound attenuation. Noise reduction up to 50 decibels.

Problems with Wood Fiber Insulation

As with many other emerging insulation technologies, cost and availability are problems. Wood fiber rigid boards cost between $4.25 and $6.75 per square foot depending on thickness. This is material only cost.

It is difficult to get because most of it is still imported from Europe. It is often only sold by the pallet. No returns. So if you order too much, you may be stuck with it.

Pricing, availability, and shipping problems should get better as more manufacturers start up in the US. As of this writing, there are only five wood fiber insulation manufacturers in the US–most situated in the northeast. Wood fiber is heavy–making shipping across the ocean and/or county expensive.