Cellulose insulation and its problems

Tightly packed cellulose insulation is more energy-efficient than fiberglass. But cellulose insulation poses some problems - fluffing, settling, water damages - that should be conveniently addressed and taken into account.

Cellulose composition

Cellulose is mostly made from recycled newsprint, cardboard, paperboard and other waste-paper products treated with chemicals (to make it fire-resistant and insect-resistant).

Cellulose comes as loose-fill or as a wet-sprayed material - which requires adequate pneumatic equipment and a professional installation.

Due to its composition and its high-recycled content, cellulose is a typical “green” insulation material, and an excellent air sealer with superior acoustical properties.

Cellulose insulation Performance

Tightly packed cellulose insulation is thermally more energy-efficient than fiberglass. Although with an insulation R-value very similar to that of fiberglass batts (around 3.7 per inch), loose-fill and wet-sprayed cellulose seals in a much more efficient way any cracks, voids and gaps, and any possible air leaks.

Uses of cellulose insulation

Cellulose is mainly used in attics (dry cellulose fiber, or damp fiber) and walls (usually damp fiber, sprayed into the wall cavities). Dry-blown cellulose is more common in retrofit applications, namely in attics.

cellulose insulation Prices

Cellulose prices are typically higher than those of fiberglass, often close to those of low density (low insulation value) sprayed foams.

Mildew and deteriorations caused by water

Cellulose insulation problems with moisture are well known. In fact, cellulose insulation can absorb more moisture than other types of insulation...

So: do not use cellulose insulation whenever there is a reasonable risk of dampness. When installing cellulose in wall cavities, they should be perfectly dry, and if there is the risk of water leaks and moisture, look for other alternatives...

Cellulose and Fire Risk

Another problem with cellulose insulation is the fire-risk problem. Tests confirm that undeteriorated cellulose is fire-safe, all the more that tightly cellulose fibers prevent air combustion - and, consequently, the spread of fire through walls and other cavities or gaps of the house.

But the risk exists in case of deterioration of the insulation caused by moisture. And since cellulose is to prone to water damages...

Cellulose installation Problems

Surfaces and walls should be carefully sealed before installation.

Dry-loose cellulose demands specific pneumatic equipment and installers should pay attention to the time demanded by the material to attain the required settling-density and R-value. The manufacturer's demands on this issue should be strictly respected.

Damp-sprayed cellulose installation requires a professional. The material is applied into the open wall cavities, which should not be closed before it acquires less than 25% water content (otherwise, walls could get moisture and mildew in the near future).

Cellulose insulation is also prone to problems involving unprofessional and improper installation - not only related with water presence, but also with settling and fluffling, in the case of sprayed-on cellulose. In fact, cellulose settling - much more than fiberglass or rockwool - may amount to 15 to 20%, which can be a huge problem in wall cavities.

That problem can be easily solved by adding more material, in the case of attic insulation, but it is very difficult to overcome in wall cavity insulation.

See, for more details on this issue: Problems with cavity insulation