Electricity, oil, and gas bills - all homeowners pay for one or
more of these utilities, and wish they could reduce their bills.
We resign ourselves to high bills because we think that is the price
we have to pay for a comfortable home. No matter where you live,
your home will be more comfortable and energy efficient with the
A properly insulated home reduces heat flow, using less energy
in the winter for heating and less energy in the summer for cooling.
Simply put, insulation helps reduce the costs of heating and cooling
your home because heat travels. Heat flows naturally from a warmer
to a cooler space. In the winter, heat flows out; in the summer,
heat flows in.
In the winter, this heat flow moves directly from all heated living
spaces to adjacent unheated attics, garages, and basements, or to
the outdoors; or indirectly through interior ceilings, walls, and
floors - wherever there is a difference in temperature.
During the cool season, heat flows from outdoors to the house interior.
To maintain comfort, the heat lost in winter must be replaced by
your heating system and the heat gained in summer must be removed
by your air conditioner. Insulating ceilings, walls, and floors
decreases this heat flow by providing an effective resistance to
the flow of heat. Insulation can be just as effective in helping
cut air-conditioning costs during the hot summer months by slowing
the transfer of summer heat entering the home.
The term "home insulation" generally means the practice of providing
a barrier of some kind to prevent the transfer of heat either in
or out of the home. This is called thermal insulation, though this
type of insulation can also help to reduce unwanted sound. In addition
to structural insulation, it can include insulation of portions
of a house, such as windows, and even objects within the home, such
as hot water heater insulation, for instance, or pipes, which can
help prevent pipes from freezing in winter. Reasons for insulating
include increased comfort, energy efficiency and cost savings.
The effectiveness of insulation is usually expressed by what is
called an R-factor or R-value. R stands for heat Resistance. Generally,
the higher the number the greater the resistance, meaning the better
the insulation. For example, R-40 insulates better than R-30. The
resistance, or thermal resistivity of insulation is measured with
an insulation tester, using a reference sample of known conductivity,
with the results expressed in an equation, which is then converted
to the more easily understood R-value.
Many local building codes specify a minimum R-value for ceiling
and wall insulation, but bear in mind those minimums don't necessarily
mean the greatest energy efficiency nor economy. So when deciding
how much and what kind of insulation to get, by all means take local
guidelines into account, but also check with an insulation contractor
who will be able to give you more specific information for your
The amount of insulation you need depends on the climate, type
of heating (gas, oil, electricity) you use, and the section of the
house that you plan to insulate. Generally speaking, most advice
is to first insulate your attic, because it is accessible and therefore
less expensive to insulate.
Each time you double the R-value of insulation, you cut your conduction
heat loss in that area in half.
One other thing to keep in mind is how to evaluate the numbers.
Some builders express R-value in terms of such-and-such a number
per inch, while codes are generally given in total values. So you
might hear that one type of insulation has R-3.8 per inch, while
the code requires R-38. The R-value refers to thickness, meaning
in this case you would need to install insulation 10 inches thick
to equal R-38. You might be able to find insulation that thick already,
or you may need to install 10 layers of it.
Also keep in mind that R-values are cumulative. If your attic insulation
is currently at R-20 and you want to bring it up to R-40, you'd
start from the 20 and add enough to equal 40. R-values are usually
printed directly on the bags or labels of insulation, and also on
the facing of fiberglass batts and rolls.
A computer program is available to help you calculate the amount
of insulation appropriate for your house. The program is called
the ZIP-Code because it includes weather and cost information for
local regions defined by the first three digits of each postal service
zip code. The program also allows you to define your own local costs
and certain facts about your house to improve the accuracy of the
Before getting into the different types and applications of home
insulation, it might be a good idea to understand a bit about some
of the different kinds of materials most often used.
Traditional insulation materials are those that have been used
for many years and proven their value. They include:
- Fiberglass insulation is probably the most common of materials.
It's made of many microfibers spun from molten glass, and is usually
pink or yellow in color.
- Rock wool is actually made from rock, as the name suggests, spun
from molted rock instead of glass, but by a similar process to fiberglass,
and is usually brown or gray in color.
- A variation on these two is slag wool, which is fiber spun from
molten slag, or steel mill residue.
- Cellulose is another common material, made from shredded newspaper
or cardboard, and chemically treated to make it fire and insect
New and alternative insulation materials run the gamut from relatively
common plastics to truly innovative and even resurrected old materials.
- Plastic fiber made of mainly recycled plastic milk bottles
- Polyurethane has the highest R-value of any other material for
- Polystyrene also has a high R-value, good moisture resistance,
and high structural strength, but has the disadvantages of being
rather expensive and flammable therefore requiring a flame retardant
coating. It can also degrade in sunlight or high temperatures.
- Concrete block insulation combines concrete with a variety of
other materials, including polystyrene beads, perlite beads (expanded
volcanic glass), or wood chips. An easy type is to simply have the
holes in a concrete block filled with foam insulation.
- Natural fiber insulation is most often used in countries that
are not heavily industrialized, though it is gaining in popularity
elsewhere as a "green" choice. Fibers used include wool, hemp, flax,
- Straw bales were popular over a century ago and are enjoying renewed
interest, as are straw panels made from a process invented in the
1930s, in which straw is fused into flat panels without the use
Types of Insulation
There are a number of different types of insulation, which can
be made from one or more of several kinds of materials. These include:
" Rigid Board Insulation: also known as slab, board, or foam board
insulation is made to be used in confined spaces like basements,
foundation slabs, crawl spaces or exterior walls. As its name implies,
it comes in rigid boards, which are then permanently fastened to
the surface. It's often easier and sometimes only possible to install
this type of insulation during the construction process, as for
example when it's installed horizontally beneath a foundation slab,
or on an exterior wall before the siding is applied. However, it
is possible to add to an existing structure in crawlspaces, inside
foundation walls, or inside exterior walls if the wallboard is removed.
It may also be installed to cover wood framing rather than having
to fit into spaces between studs. Another place it's popularly used
is in cathedral ceilings.
" Board insulation: is usually made of either fiberglass, polystyrene,
or polyurethane and comes in a selection of thicknesses ranging
from about R-4 to R-8 per inch, which is a very high value. Semi-rigid
fiberglass panels are used most often for below grade foundation
applications. When used on the interior of a structure, it must
be covered with gypsum board or some other approved material for
fire prevention. When used in exterior applications, it must be
weather-proofed to prevent deterioration.
" Batts and Blankets: are different words for essentially the same
product. Batts are insulation blankets that have been cut to a certain
size, while blankets refer to the uncut rolls themselves. As their
names imply, these are flexible sheets or blankets of insulation
that is most often used to insulate floors, walls, ceilings, and
attics - where it can be laid down or placed flat. It comes either
faced or unfaced. That is, it may have paper on one side that acts
as a barrier to vapor. Batts and blankets are most often made of
woven or matted fiberglass fibers, though they also come in other
fibers, such as cellulose. Since fiberglass can be irritating to
skin, most of these types come with some sort of paper or plastic
covering to reduce skin contact.
" Loose Fill Insulation: is most often used as attic insulation
in unfinished attics. It is often blown in with a blowing machine,
or for smaller spaces, can be poured directly from the bags. Made
of loose fiberglass, rock wool, cellulose or other fibers, it's
best used in areas where there is unlikely to be any activity or
use, such as attics
" Spray Foam Insulation is one of the best forms of insulation
available as far as R-value. Though it's been around awhile for
use in appliances like hot water heaters and refrigerators, it's
also used as thermal insulation for a home that is fairly new. Its
biggest advantage is that it can seal and fill all the tiny little
cracks, virtually eliminating any air infiltration. However, spray
insulation is more expensive than traditional methods of insulation,
and is quite messy. It may also cause some delays if other subcontractors
such as electricians or plumbers are not accustomed to working around
it. But the increase in R-value and ultimate energy and cost savings
can make it worthwhile to foam insulation use despite its drawbacks.
" Radiant Barrier Insulation works by reflecting heat or thermal
energy either away from a structure to keep it cool, or attracting
it to keep it warm. For summer heat problems, radiant barriers can
be installed on roofs or in attics to reflect solar energy away
from the home. For colder weather, these barriers can be turned
around to reflect heat back into the home and help prevent it from
escaping. Most such barriers are rigid or semi-rigid boards covered
with a thin sheet of reflective material or foil. This type of material
can also be used as window insulation in the same ways.
Where to Insulate
Traditional areas for home insulation are attics, basements, crawl
spaces, roofs, foundations, and exterior walls - the structural
components of a home. But these are not the only places installation
should be installed.
Window insulation can supplement your existing insulation by helping
to further prevent heat exchange through the glass. One of the most
common methods of window insulation is double or triple paned glass.
Or take a tip from the past and install storm windows, which are
surprisingly effective at resisting heat exchange. A modern innovation
is the installation of solar screens that filter out sunlight and
its heat. Heavy draperies or other window treatments can also help
to keep summer heat out and winter warmth in.
Pipe insulation can do a lot to help contain energy costs. Wrapping
hot water pipes will help to keep the water hot, conserving water
overall, and reducing the load on your hot water heater. Insulating
water pipes can also help to prevent freezing in the winter, which
can be a costly inconvenience.
Other areas or sites to insulate and/or seal are any and all possible
areas where air can infiltrate from outside, leak from inside, or
through which heat can enter or escape. These include:
- The ribbon plate, or the wooden board going around the base of
the house attached to the floor joists
- Openings for pipes such as those leading to the air conditioner,
electric or other service entries, the clothes dryer vent, stove
vent(s), and cable TV wire entry
- Electric outlets in perimeter (outside) walls
- Window and door openings should be sealed with weatherstripping,
which is just insulation in a long strip form, usually with some
type of adhesive on one side to hold it in place.
- The scuttle hole leading to the attic. Use weatherstripping tape
around the opening, and tape a batt of insulation on the back side
of the cover
- Basement doors and windows are seldom insulated or sealed, but
consider at least adding weatherstripping and at least a plastic
covering if not using storm windows and doors.
- Fireplaces and chimneys are notorious for air leaks. Other than
ensuring the damper is closed during periods of non-use, caulking
or sealing around the edges can also help, as can installing glass
doors for extra insulation
- HVAC ductwork is another overlooked area of heat exchange. First,
be sure to seal any seams to prevent air leakage, and then wrap
the ducts with a layer of insulation, as well as sealing areas around
How to Install Home Insulation
Once you've decided on the type and amount of insulation you need,
you'll need to make up your mind how to install it. There are really
only two choices: do it yourself, or hire a professional to do it
Do it yourself is definitely feasible for a number of different
situations and types of insulation. Larger jobs that lend themselves
well to do it yourself projects include attic, ceiling, floor, and
basement insulation if you're planning to use blanket or batt type
insulation. Even some kinds of rigid board insulation can be fairly
easily done on your own. Of course, smaller jobs like weatherstripping,
or wrapping your pipes or ductwork are also easily done by an amateur.
In general, if you can buy the insulation material at your local
home improvement store, and you can easily reach the area to be
insulated, you can probably do the job yourself.
If you do decide to do your own installation, be sure to install
a vapor barrier if you're using loose fill by stapling or tacking
a plastic or polyurethane sheet under the area you're planning to
fill, toward the heated or air-conditioned part of the home. Blanket
and batt types of insulation usually already have a vapor barrier
of some type attached, but if not, be sure to install one under
these as well. If you're adding new insulation on top of old, be
sure there is no vapor barrier between the new layers.
Another point to keep in mind is to wear gloves and long sleeved
clothing when handling fiberglass, as the fibers can be very irritating
to the skin. Also, make sure you measure your space beforehand as
to how thick a layer it can accommodate, as squeezing the insulation
in will reduce its effectiveness. For best results, make sure it
lies flat, but is not compressed.
Professional installation is definitely required for application
of some types and areas of insulation. For the newer types of foam
installation, you will need to hire a professional insulation contractor.
Not only does the job require specialized equipment and training,
many localities also require that the person installing this type
of material be certified. Loose insulation, except for fairly small
areas, may also require using the services of a professional, as
it is often blown in, using a machine not readily available to the
amateur, or easily operated without specialized training. Also bear
in mind that some places have ordinances governing insulation, which
a contractor is required to know, but which you, as a do-it-yourselfer
may not. For instance, in older homes, many local laws require that
you first isolate, or "box in" wiring and pipes before blowing in
Although it can seem daunting to consider so many options, investing
in good home insulation can be one of the most important steps you
can take to ensure that you and your family not only enjoy a comfortably
cool or warm place to live, but also save money on heating and cooling
costs, and do your part to help conserve energy resources. The good
thing is a good job of home insulation should serve you well for
many years, with little maintenance required, and only occasional