Will
upgrading my attic insulation really
lower my energy bill?
Yes, as much as
30-50%. Adding attic insulation is the
least expensive most cost effective way
to lower your energy bill. Check the
attic to make sure there is at least 12"
of insulation. If not, you are probably
one of the millions of homes in the U.S.
that are under-insulated. Attic
insulation is the one of the most
important things to look for to upgrade
the energy-efficiency of your home. In
fact, heat escaping through the attic
may be responsible for up to one half of
your home's entire heat loss. Homes not
insulated to today's energy standards
can suffer substantial heat loss in
winter and heat gain in summer, forcing
your heating and cooling system to work
overtime, wasting precious energy
dollars.
What is an
R-value?
R-value relates to thermal resistance.
Thermal resistance is the measure of a
material's ability to retard heat flow.
An R-value represents the amount of time
(in hours) that is required for one Btu
to be transmitted through one square
foot of a material (or structure) when
there is a temperature difference of one
degree Fahrenheit between the two
surfaces of the insulation. Since
R-values are a measurement of the
ability to retard heat flow, the higher
the R-value, the higher the insulation
value. Materials which have the same
R-value, regardless of thickness,
weight, or appearance, are equal in
insulation value.
What are the
differences (pros and cons) between
fiber glass and cellulose insulation?
There are three important differences
between fiber glass and cellulose.
Fire Resistance - Fiber glass is
made mostly of inorganic materials and
therefore is naturally non-combustible
and has a low flame spread rating. It
will maintain its fire resistance over
its lifetime. On the other hand,
cellulose is made up of newspaper, which
is organic and naturally flammable.
Therefore, approximately 20% of the
finished cellulose product is comprised
of fire retardant chemicals (80%
newspaper / 20% fire retardant
chemicals). These fire retardant
chemicals may not be applied
consistently and may deteriorate over
time. Smoldering and re-kindling of
fires have been reported with this
product.
Moisture Absorption - fiber glass
is installed dry and does not absorb or
retain moisture. Cellulose is often
installed damp and needs to fully dry
after installation. Even after drying,
cellulose can absorb moisture, which can
lower the R-value of the product and may
promote fungal growth.
Settling - Fiber glass has nearly
no settling (1-3%). Therefore, the
R-value is stable over time. Cellulose
can settle or shrink causing the R-value
to deteriorate over time. Unless 20% or
more extra thickness is installed, you
can't be sure of achieving the desired
R-value.
Insulation Material Comparison Summary:
Fiber Glass vs Cellulose
|
Performance Property |
Fiber Glass |
Cellulose |
|
Thermal Resistance |
Variety of R-values
available in batts, and
loose-fill. Stable over
time. |
Higher loose-fill R/inch
(for tight spaces). R can
deteriorate from
settling/shrinkage. |
|
Ease of Installation |
Batts install fast, except
careful cutting, fitting
required in irregular
spaces. Loose-fill requires
equipment and skilled
installer. |
Equipment maintenance and
skilled installer required.
Voids unlikely with careful
installer. Cleanup takes
time. |
|
Moisture |
Installed dry. Low moisture
adsorption. |
Often installed damp. Should
be allowed to dry. Absorbs
moisture which lowers
R-value and may promote
fungal growth. |
|
Air Flow |
Filled cavities restrict air
circulation. (Infiltration
controlled by other
measures.) |
Likely has higher air flow
resistance depending on
installation. (doesn't
effect home's main leakage
points) |
|
Attic Convection |
Batts not susceptible.
Loose-fill slightly impacted
in some climates. (Example:
$3.92/1500 sq.ft. attic
effect in Denver, Colorado) |
Not susceptible at
traditional densities. |
|
Corrosion |
Non-corrosive |
Corrosion a concern with
retained moisture and some
fire retardants. |
|
Fire Resistance |
Non-combustible, low flame
spread |
Combustible. Fire retardant
treatment may not be
consistent. Smoldering and
re-kindling of fires
reported. |
|
Environmental Benefits |
25% recycled glass, and
light weight so relatively
fewer resources consumed.
Energy savings is big
environmental plus. |
80% recycled paper but 20%
virgin chemicals. More
resources consumed. Energy
savings is big environmental
plus. |
|
Health Impacts |
Skin/respiratory irritation
possible. Long-term effects
have been extensively
studied and safe practices
defined. |
Allergic effects possible
from inks, dust, chemicals.
Long-term effects never
researched but questions
persist. |
|
