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James Dulley's
House Insulation Guide
Checking your home's insulating system is one of the fastest and most cost-
efficient ways to use a whole-house approach to reduce energy waste and
maximize your energy dollars. A good insulating system includes a combination
of products and construction techniques that provide a home with thermal
performance, protect it against air infiltration, and control moisture. You can
increase the comfort of your home while reducing your heating and cooling needs
by up to 30% by investing just a few hundred dollars in proper insulation and
weatherization products.
Adequately-insulated homes save money for homeowner's every month. It helps
us conserve vital energy resources for our children and for the future.
Energy-efficient houses help the environment through lower rates of air
pollution emissions from plant and on-site combustion of fuels for heating,
air-conditioning and ventilation.
Where to Insulate
Adding insulation in the attic, to walls, floors, basements and crawl spaces
may be the best way to improve your home's energy efficiency.
Insulation
First, check the insulation in your attic, ceilings, exterior and basement
walls, floors, and crawl spaces to see if it meets the levels recommended for
your area. Insulation is measured in R-values – the higher the R-value,
the better your walls and roofs will resist the transfer of heat. The U.S.
Department of Energy (DOE) recommends ranges of R-values based on local heating
and cooling costs and climate conditions in different areas of the nation. The
map and chart show the DOE recommendations for your area. State and local codes
in some parts of the country may require lower R-values than the DOE
recommendations, which are based on cost- effectiveness.
Although insulation can be made from a variety of materials, it usually
comes in four types – batts, rolls, loose-fill, and rigid foam boards.
Each type is made to fit in a different part of your house. Batts are made to
fit between the studs in your walls or between the joists of your ceilings or
floors. Batts are usually made of fiber glass or rock wool. Fiber glass is
manufactured from sand and recycled glass, and rock wool is made from basaltic
rock and recycled material from steel mill wastes. Rolls or blankets are also
usually made of fiber glass and can be laid over the floor in the attic.
Loose-fill insulation, usually made of fiber glass, rock wool or cellulose, is
blown into the attic or walls. Cellulose is made from recycled materials
treated with fire-retardant chemicals.
Rigid foam boards are made of polyisocyanurate, extruded polystyrene (XPS or
blueboard), expanded polystyrene (EPS or beadboard), or other materials. These
boards are lightweight, provide structural support, and generally have an
R-value of 4 to 7 per inch. Rigid board insulation is made to be used in
confined spaces such as exterior walls, basements, foundation and stem walls,
concrete slabs, and cathedral ceilings.
Should I Insulate my Home?
The answer is probably “yes” if you:
Have an older home and haven't added insulation: in a recent survey, only
20% of homes built before 1980 were well insulated;
Are uncomfortably cold in the winter or hot in the summer — adding
insulation creates a more uniform temperature and increases comfort;
Build a new house or addition, or install new siding or roofing;
Pay excessive energy bills;
Are bothered by noise from the outdoors — insulation helps to muffle
sound;
Are concerned about the effect of energy use on the environment.
Insulation Tips
Consider factors such as your climate, building design, and budget when
selecting insulation R-value for your home.
Use higher density insulation, such as rigid foam boards, in cathedral
ceilings and on exterior walls.
Ventilation plays a large role in providing moisture control and reducing
summer cooling bills. Install attic vents to help make sure that there is one
inch of ventilation space between the insulation and roof shingles. Attic vents
can be installed along the entire ceiling cavity to help ensure proper airflow
from the soffit to the attic, helping to make a home more comfortable and
energy efficient.
Do not block vents with insulation, and keep insulation at least 3 inches
away from recessed lighting fixtures or other heat-producing equipment unless
it is marked “I.C.” — designed for direct insulation contact.
As specified on the product packaging, follow the product instructions on
installation and wear the proper protective gear when installing insulation.
The easiest and most cost-effective way to insulate your home is to add
insulation in the attic. To find out if you have enough attic insulation,
measure the thickness of insulation. If there is less than R-19 (6 inches of
fiber glass or rock wool or 5 inches of cellulose) you could probably benefit
by adding more. Most U.S. homes should have between R-19 and R-49 insulation in
the attic.
If your attic has ample insulation and your home still feels drafty and cold
in the winter or too warm in the summer, chances are you need to add insulation
to the exterior walls as well. This is a more expensive measure that usually
requires a contractor, but it may be worth the cost if you live in a very hot
or cold climate.
(a) These recommendations are based on the assumption that no structural
modifications are needed to accommodate the added insulation.
(b) For new construction, R-19 is recommended for exterior walls. Jamming an
R-19 batt into a 3-1/2-inch cavity will not yield R-19 because compression
reduces the R-value.
(c) Insulate crawl space walls only if the crawl space is dry all year, the
floor above is not insulated, and all ventilation to the crawl space is
blocked. A vapor barrier (e.g., 4- or 6-mil polyethylene film) should be
installed on the ground to reduce moisture migration into the crawl space.
(d) Thermal response of existing space for cooling benefits does not suggest
additional insulation.
New Construction
For new construction or home additions, R-19 insulation for exterior walls
is recommended for most of the country. To meet this recommendation, most homes
and additions constructed with 2 x 4 walls require a combination of wall cavity
insulation, such as batts, and insulating sheathing, such as rigid foam boards.
You may want to consider building with 2 x 6 framing instead of 2 x 4 framing
to allow room for thicker wall cavity insulation — R-19 to R-21.
When shopping for insulation watch for the ENERGY STAR® label and the
National Association of Home Builders (NAHB) certification.
Go to column 448 for more information about insulation.
| |
|
|
|
|
Ceiling |
|
|
|
|
Basement |
| Zone |
Gas |
Heat
Pump |
Fuel
Oil |
Electric
Furnace |
Attic |
Cathedral |
Wall
(A) |
Floor |
Crawl
Space (B) |
Slab
Edge |
Interior |
Exterior |
| 1 |
x |
x |
x |
|
R-49 |
R-38 |
R-18 |
R-25 |
R-19 |
R-8 |
R-11 |
R-10 |
| 1 |
|
|
|
x |
R-49 |
R-60 |
R-28 |
R-25 |
R-19 |
R-8 |
R-19 |
R-15 |
| 2 |
x |
x |
x |
|
R-49 |
R-38 |
R-18 |
R-25 |
R-19 |
R-8 |
R-11 |
R-10 |
| 2 |
|
|
|
x |
R-49 |
R-38 |
R-22 |
R-25 |
R-19 |
R-8 |
R-19 |
R-15 |
| 3 |
x |
x |
x |
x |
R-49 |
R-38 |
R-18 |
R-25 |
R-19 |
R-8 |
R-11 |
R-10 |
| 4 |
x |
x |
x |
|
R-38 |
R-38 |
R-13 |
R-13 |
R-19 |
R-4 |
R-11 |
R-4 |
| 4 |
|
|
|
x |
R-49 |
R-38 |
R-18 |
R-25 |
R-19 |
R-8 |
R-11 |
R-10 |
| 5 |
x |
|
|
|
R-38 |
R-30 |
R-13 |
R-11 |
R-13 |
R-4 |
R-11 |
R-4 |
| 5 |
|
x |
x |
|
R-38 |
R-38 |
R-13 |
R-13 |
R-19 |
R-4 |
R-11 |
R-4 |
| 5 |
|
|
|
x |
R-49 |
R-38 |
R-18 |
R-25 |
R-19 |
R-8 |
R-11 |
R-10 |
| 6 |
x |
|
|
|
R-22 |
R-22 |
R-11 |
R-11 |
R-11 |
(C) |
R-11 |
R-4 |
| 6 |
|
x |
x |
|
R-38 |
R-30 |
R-13 |
R-11 |
R-13 |
R-4 |
R-11 |
R-4 |
| 6 |
|
|
|
x |
R-49 |
R-38 |
R-18 |
R-25 |
R-19 |
R-8 |
R-11 |
R-10 |
(A) R-18, R-22 and R-28
exterior wall systems can be achieved by either cavity insulation or cavity
insulation with insulating sheathing. For 2 inch x 4 inch walls, use either
3-1/2-inch thick R-15 or 3-1/2-inch thick R-13 fiberglass insulation with
insulating sheathing. For 2 inch x 6 inch walls, use either 5-1/2-inch thick
R-21 or 6-1/4-thick R-19 fiberglass insulation.
(B) Insulate crawl space walls only if the crawl space is dry all year, the
floor above is not insulated, and all ventilation to the crawl space is
blocked. A vapor retarder (e.g., 4- or 6-mil polyethylene film) should be
installed on the ground to reduce moisture migration into the crawl space.
(C) No slab edge insulation is recommended. |
U.S. Department of
Energy Recommended* Total R-Values
for New Construction Houses in Six Insulation Zones |
 |
| *These recommendations
are cost-effective levels of insulation based on the best available information
on local fuel and materials costs and weather conditions. Consequently, the
levels may differ from current local building codes. In addition, the apparent
fragmentation of the recommendations is an artifact of these data and should
not be considred absolute minimum requirements. |