|
There are really only two major types of insulation
used in the walls and ceilings of Canadian residential construction.
They are cellulose and glass fibre. Cellulose is produced from
recycled paper and borates. Borates are fire retardant and comprised
of two types of chemicals: borax and boric acid. These are the same
chemicals commonly found in day-to-day items such as beauty
products, laundry soap and fertilizers. Glass fibre is comprised of
sand, boron, phenol formaldehyde and a percentage of recycled glass
product.
Cellulose is a loose-fill, fibrous insulation made
from selected paper stock. Each bag displays Environment Canada's
"Ecologo", classifying it as an "environmentally friendly" product.
Cellulose may be hand poured or applied using a blowing machine.
Machine application ensures that the cellulose is properly
conditioned and placed at the required design density.
The great advantage of cellulose is that it forms
itself to whatever cavity it is injected into. This enables it to
fill the cavity with the most consistency and does not allow any
voids.
Glass fibre batt is the most widely used type of
insulation by contractors because it is cost-effective nature. It is
also more environmentally friendly today, as major manufacturers are
making formaldehyde-free fibreglass insulation.
Typically it is installed in formed batts for the
walls and loose fill for the attic. If not installed properly the
product can leave voids, which cause air gaps leading to increased
heating/cooling costs. Loose fill product is made from the same
material as batts but is left in its fibrous state and must be
blown-in using a machine and delivery hose. Glass fibre is fire
retardant by nature and will not rot or decay over time. The product
is quick and easy to install but offers less thermal value than
cellulose.
Cellulose and glass fibre function under very
different principles. Cellulose is a paper product and derives its
thermal value from the density of the product, which means less air
movement. Glass fibre derives its thermal value from the air, which
it traps within its fibres.
Spray-in-place
Spray-ins of any type has several other advantages.
There is little likelihood of the insulation settling since the
fibres are glued to each other and the cavity sides. It forms a
uniform covering throughout the cavity and forms a good air seal
between electrical wiring, pipes, framing members, and anything else
inside the building cavity.
Blown or sprayed loose fibre glass insulation uses
roughly the same sort of equipment and adhesive that sprayed
cellulose uses, but it doesn't prevent air infiltration as well as
sprayed cellulose does.
There are some precautions to take when using sprayed
fibre insulation. The chemical fire retardant within the products
may corrode metal fasteners, pipes, or structural members that they
contact. Unscrupulous installers can also "fluff" blow-in-blanket
insulation, installing it at lower density than disclosed to the
homeowner. Excessive water content and insufficient drying may
promote fungus growth inside building cavities.
Application and cost
Sprayed insulation is most practical for new
construction or unfinished spaces with exposed studs.
Installations are often messy, since some of the insulation also
adheres to unintended surfaces such as floors and windows. However,
the adhesive binders are water-soluble so it is easily removed.
After application, the stud edges are scraped clean with a special
milling tool. As long as the "salvaged" insulation is free of debris
it can be sent through the blowing machine again for reuse.
Sprayed insulation also
needs time to dry before being enclosed in the building cavity. The
drying time for the insulation varies depending on the type of
insulation material and its moisture content, the moisture content
of the framing members, and conditions such as humidity and
temperature. Two (proprietary) techniques for faster drying times is
to use rockwool, which does not easily absorb moisture, or netting
over the studs to support the insulation, with less water content,
as it dries.
Sprayed insulation
systems cost more than fibreglass batt insulation - about 40 per
cent more. However, it generally is less expensive than sprayed
foam, and performs almost as well in many cases.
A foot of blown-in
loose-fill cellulose yields an R-value of 45, while a foot of
loose-fill mineral fibre would offer an R-33 level, according to a
study by the Canadian Construction Materials Centre. A foot of
fibreglass batt insulation would deliver about R-46. (Since most
batts are 5.5 inches thick, the actual insulation is still a
respectable R-21). R-values are compromised with any insulation if
does not completely fill the wall cavity.
With thanks to Michael DellaFortuna, a product specialist with
Can-Cell Industries Inc., Owens Corning / Johns Manville |
fibreglass batts in 2"x 4” and 2"x 6" walls provide much less than their
stated R-Value. Many builders and homeowners are considering other
insulation systems that deliver substantially better performance.
BETTER CHOICES