.....Moisture & Vapor Retarders

Moisture is one of the more
misunderstood aspects of building-shell
performance. Different insulation materials exhibit different moisture handling characteristics. These characteristics must be considered in designing insulated assemblies.

​Glass fibers do not absorb moisture, however, moisture can condense within the insulation and migrate to parts of the insulated assembly that may be damaged. Fiberglass insulation is very susceptible to air ex filtration, the major cause of moisture migration into walls and ceilings.

Ex filtration of moisture-laden air into walls 
and ceilings is the major moisture transfer mechanism. The low air permeability of

cellulose all but eliminates this means of
moisture movement. Cellulose insulation
demonstrates the ability to control moisture
migration by eliminating air movement,
making vapor retarders unnecessary when
cellulose insulation is installed.

Therefore, the Cellulose Insulation
Manufacturers Association does not
recommend use of a polyethylene vapor
retarder with any cellulose wall installation,
unless there are specific extraordinary
conditions indicating that a vapor retarder
would enhance the moisture performance
of the wall. Increasingly, building science
is coming down against prescriptive use of polyethylene vapor retarders.

.....Air Infiltration

Uncontrolled leakage of air through exterior
walls and ceilings of homes is almost
as important as R-value in determining how
much energy will be required to heat and cool
a building. This factor is all too often totally
ignored in specifying insulation.

Fiberglass is used as air filter media, and
fiberglass in walls and ceilings behaves much
as the fiberglass in an air filter. Air rushes 
right through it. During remodeling when old
fiberglass-insulated wall cavities are opened, the batts are usually found to be covered by dust, just as an air filter would be.

Cellulose insulation is very effective at
sealing buildings against air infiltration. Controlled air infiltration is one of the most important factors for energy efficiency in the
thermal performance of a building.

Research shows cellulose to be up to 40% 
better than fiberglass at controlling air infiltration.

Standard Specifications

LICENSE #C32145
P.O. Box 4546
Kailua Kona, HI 96745

(808) 325-5888
mark@ecopacificinsulators.com
ecopacificinsulators.com


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