With this home insulation guide, we will look at
the basics of insulating your home and how it can save you a lot of money.
Insulation is the process of separating an area
that is warm from an area that is cold. This is accomplished by trapping air in
tiny pockets. Air is a poor conductor of heat therefore these tiny pockets help
to resist heat flow. This resistance to heat flow is known as R-VALUE.
The R-VALUE of a product is set in the
manufacturing process and is determined by the type of material as well as its
thickness. There are factors which can cause this value to change after it is
installed.
Settling is the process where the insulation
material is compressed over time. This process means that less air is trapped
in the pockets and therefore it is easier for the heat to flow. (The R-VALUE is
lower.)
Another factor that can change the effectiveness of
the insulation is moisture. Unlike air, moisture is an excellent conductor of
heat. Therefore, any time that moisture is held in a material, more heat is
transferred through that material. (The R-VALUE is lower.)
Types of insulating
materials
There are four traditional types of materials used
in home insulation.
Cellulose is basically recycled paper that is
treated to resist pests and fire. It is typically blown loosely into attic
spaces or combined with a glue/water mixture and blown into walls. The main
advantage of this material is that it is the least expensive. A disadvantage is
that it has a high rate of settling (typically 20%). Therefore, it can lose a
significant part of it's R-VALUE over time. Another disadvantage is that, when
it is blown wet into the walls, time is required before covering it with
drywall so that it can dry out. If this is not done, mold and other indoor air
quality issues can occur.
Fiberglass is the most common material used in home
insulation. Although it is more expensive, it tends to settle less (typically
only 1-3%) and therefore it retains it's R-VALUE better and longer than
cellulose. Another advantage is that, the material does not retain moisture
like cellulose. Therefore, if the material becomes wet, it will dry out and
return to it's original R-VALUE. The product is available in blankets which are
long rolls that can be cut to a desired length. Blankets are typically used in
attics. When these blankets are precut into lengths that fit into wall spaces
they are referred to as batts. This material is also available in bags for
loose fill. This is typically blown into attics with a machine. (The machine is
avaialable for rent at most home centers.) An advantage of this form is that it
can fill in hard to reach areas.
Foam is another material commonly used for home
insulation. This is available in rigid board form which can be used on the
exterior of a home, basement walls, or walls in an unconditioned crawlspace.
The spray foam (polyisocyanurate) is a combination of a resin, hardener, and
air. It is typically mixed on site and blown into walls and attics. The main
advantage is that the material expands when applied and is good at making an
air barrier. The product also does not settle and is not affected by moisture.
The main disadvantage is it is the most expensive.
The final material is known as a radiant barrier or
reflective insulation. This is typically an aluminum foil that is incorporated
with a foam board or a bubble wrap type material. Unlike the other materials,
this product reflects infrared heat. This material is normally used in attics
and on hvac ducts.
Non-traditional types of
insulation
The latest innovation is commonly referred to as
"blue Jean" insulation because it is produced from recycled denim and
cotton. The 90% post consumer recycled fibers are bonded together and formed
into a batt for installation. The batts contain a fungal inhibitor to protect
against moisture and mold. This is a very environmentally friendly product as
there are no chemicals added and therefore no volatile offgassing. Another
advantage is that it does not not irritate the skin and therefore is easier to
install as no special protective equipment is required.
For situations where traditional forms of
insulation are not practical, you can insulate your home by simply painting the
walls and ceilings. This can save you money by insulating without the expense
of remodeling as well as lowering your utility bills.
How much is needed?
The amount of insulation in a new home is usually
regulated by local building codes. These codes typically give the minimum that
is acceptable in an area.
In the absence of codes, the following recommendations
are generally the most cost effective:
Ceilings should be insulated to achieve an R-49
rating.
Floors over non conditioned spaces should have an
R-25 rating.
Exterior walls should have an R-value of 18-22.
(typically R-19)
Unconditioned basement or crawlspace walls should
be insulated to achieve an R-11 to R-19 rating.
With the rising costs of energy, adding home
insulation can be an investment that pays huge dividends.