Cellulose Fibre

Does anyone have information regarding how much cellulose fibre is expected to compact over the first year.
I did a one year warranty inspection on a house that was supposed to have 12.2" (R40) insulation in the attic. I measured 8-9".


try this

US CIMA info:
Installation standards & practices
Loose-fill cellulose insulation, like all loose-fill
insulation, should be installed in accordance with
ASTM Standard C-1015, Standard Practice for Installation
of Cellulosic and Mineral Fiber Loose-Fill Thermal
In wall applications standard practice is to compact
loose-fill cellulose to a density that will prevent settling.
While this is a matter of some controversy most authorities
recommend a density of at least 3.0 pcf for cellulose
insulation in walls. Materials with high nominal settled
densities (2.0 pcf and higher) should be installed at 3.5
pcf. Research has confirmed that settling is virtually nil
with any cellulose insulation at densities of 3.5 pcf, or
higher. Compacting cellulose insulation may produce a
very slight reduction of R-value.
Specifiers do not need to compensate for settling in
attics since federal law (the CPSC standard and the FTC
R-Value Rule) requires R-value and coverage data to be
stated at settled density. Open blow cellulose installations
do lose R-value as the material settles, however
such installations provide “bonus R-value” until they
reach settled density

Specifiers, installers, and buyers need to understand
that the “minimum thickness” column on cellulose
coverage charts represents settled thickness, if the chart
has only one thickness column.

This is not done to confuse or mislead. It results
from the fact that there is no accepted procedure for
determining blown thickness that has been proven to
correlate with the amount of material, by weight,
required to yield the desired R-value. ASTM is working
on an appropriate procedure. Some manufacturers
provide initial installed thickness recommendations, but
this is only a guideline to aid installers. The bag count
and weight columns are the “official” coverage statements.


I’d look on the certificate or ask builder to prove what the bag count was and calculate from that or contact Energy Auditor with IR for more accurate information.



Industry standard in Canada is blown cellulose:

12" blown thickness for R40 (actually works out to R45.6)
Settles to 10.5"= R40.

14.7" blown thickness for R50 (actually R55.1)
Settles to 13.15" (R50)

R Value 3.8 per inch

Hope this hepls.

You will find some contractors blow the cellulose with too much air. This causes the insulation to “fluff up”. It enables the contractor to install less product for 12" depth, but it can settle to 8 - 9" over time, therfore decreasing the R Value obtained. This is an incorrect and sometimes deliberate installation.

Thanks Barry.
Thanks Rodney. Is this info documented somewhere?