Dense-Pack Insulation Tool User Guide
Red Calc Tool User Guide
What this tool can do for you
This tool will help determine the information you need for installing dense-pack
insulation, including the number of bags of insulation and the installed density.
A choice of two framing options are given, hidden and exposed, to help you
accurately calculate the framing-factor and the fenestration and penetrations.
Installed density or bag count.
Clicking the label for any input or result will cause a
popup help box to appear. This help box includes the
allowed and normal ranges (for inputs).
This tool is for dense-packed insulation only.
Wood framing is assumed, rather than metal framing.
Inputs and field measurements
Insulation bag weight - from insulation manufacturer.
Framing - select hidden or exposed.
Gross area or cavity area to be insulated, from
Fenestration/penetration area - windows, doors and
other openings, from field measurements.
Assembly type - select ceiling, wall, or floor.
Cavity depth, from field measurements.
Installed density - desired final density, from insulation
Bag count - bags of insulation used for project.
Densely packed cellulose and fiberglass are the favored methods if insulating
walls and other closed cavities in existing dwellings. Dense packing is
also gaining favor in new construction. Dense-pack methods have the advantages of
preventing insulation from settling, completely filling the
cavities, consistent insulating values, and the ability to slow airflow.
Cellulose is the favored type of dense-pack insulation used for the DOE-funded
low-income weatherization programs. This fire-retardant insulation is made
from recycled newspaper and boxes. Advantages include the ability to store small
amounts of water and, because it is usually manufactured locally, it is not
shipped long distances. Cellulose has the disadvantages of braking
down when it gets saturated with water. Its R-value per inch
is from 3.2 to 3.5 (0.222 to 0.2428 RSI per cm).
Fiberglass is lighter than cellulose and will not be permanently damaged
if it is saturated with water. Currently, about 20 to 40
percent of the fiberglass sold as insulation is recycled. This is a significantly
lower percentage than cellulose, but the fiberglass industry continues to make
gains. Its R-value per inch is 4.2 (0.29 RSI per cm).
Dense-pack insulations should always be installed at the manufacturer's
recommended densities. In the Dense-Pack Insulation tool, include this
density as the "Installed density" when solving for "Bag count". The
recommended dense-packed density for cellulose is 3.5 to 4.5 lb/ft3
(56 to 72 kg/m3) and for fiberglass 1.8 to 2.6 lb/ft3
(29 to 42 kg/m3).
Installing dense-pack insulation properly requires the proper knowledge
and "feel", this only comes from experience. In addition to the skill of
the installer, the insulation blowing machine must have the proper capacity
to install the insulation productively. The static pressure at the takeoff
of the blowing machine should be at least 2.9 pounds per inch2
or 80 inches of water column (722 pascals). Blowing machines should be kept
in good working order.
Periodically the installed density should be verified. There are a number
of ways to do this, including core sampling (see Related external resources
below, Karg 2007, for cellulose) or the use of this tool to calculate the
overall insulation density of fiberglass or cellulose.
Related RED Calc Free tools
Parallel-Path Equivalent R-Value:
Determine the overall equivalent R-value of an area made up of smaller
areas, each with a different R-value.
Surface Heat Transfer:
Determine the heat transfer through a surface area with a given R-value
and temperature difference across the surface.
Determine the required bags of insulation or the installed depth when
blowing loose-fill insulation in attics.
Related external resources