I'm considering having vinyl siding installed on my home. Will this reduce my
heating and cooling costs?
Q. What does the term "R-value" mean?
A. R-value is a measure of how well a material resists the passage of heat. The higher
the R-value the more effective insulation is in keeping the home warm in winter
and cool in summer. Insulation should always be judged by R-value rather than
inches, as different insulation materials have different R-values per inch of thickness.
Q. How much insulation should I have in my attic?
A. Attics should be insulated to R-38 whenever possible.
Q. If I install more insulation in my attic, what type should I use?
A. Most homeowners find it easiest to use batt insulation. Always use unfaced batts,
as the paper of foil vapor retarder can trap water vapor in the original insulation,
causing moisture problems. If possible, install the new insulation perpendicular to
the attic floor joists to reduce heat loss through the joists. Loose fiberglass or
cellulose can also be used, by pouring it and leveling it with a board or other implement.
Q. If I install more insulation in my attic, what type should I use?
A. Exterior walls in new homes should be insulated to R-15 or higher. In existing
homes, insulation can be blown into uninsulated walls. Have a qualified contractor
check the walls and determine the feasibility of blowing in insulation.
Q. How much insulation should I have under my floor?
A. Floors over unheated crawlspaces or basements should be insulated to R-19, while
floors over open air (such as overhangs) should be insulated to R-30 if possible. If
your home has a basement containing your heating system or other sources of
heat, you should insulate the basement walls to R-11, rather than insulating the
floor above.
Q. My home is built on a slab - is there a way to insulate my floors?
A. With slab construction, there is no way to insulate under the floor. In new
construction, the perimeter of the slab should be insulated to several feet below
ground level. This can also be done in an existing home, but the cost and difficulty
of trenching around the perimeter often makes it impractical.
Q. Is it better to insulate the attic floor, the roof, or both?
A. Unless you are finishing the attic for living space, you should insulate the attic
floor to contain the heat within the living space.
Q. Is it a good idea to add additional insulation to my walls, and how is this done?
A. If your walls currently have no insulation, insulation can be blown into the cavities
through holes drilled through the exterior of the home. This should only be done
by a reputable, qualified contractor. If there is already some insulation in the
walls, you should not attempt to add any more.
Q. Can I compress 6" R-19 batts to fit into a 2"x 4" cavity, and will
it be more effective than 3 1/2" batts?
A. While insulation batts are easily compressed, the R-value will be significantly
reduced - it is best to use the correct thickness and not compress the insulation.
You should also avoid storing heavy materials on top of attic insulation for the
same reason.
Q. I've always heard that "heat rises". Why do I need to insulate my floors?
A. Actually, heat moves from warm to cold. If your home is built over a crawlspace
or unheated basement, you can lose a lot of heat downward through the floors.
Insulation will help reduce that loss and also make your floors feel warmer in the
winter.
Q. If the walls and ceiling of my home are well insulated, do
I really need to insulate my basement?
A. The importance of basement insulation depends on whether the basement is heated.
If you heat your basement, or if your furnace or other sources of heat are
in the basement, you should insulate the basement walls to contain the heat. If not,
you should insulate the basement ceiling to reduce heat loss to the basement and
keep your floors warmer.
Q. What is a "vapor retarder" and how important is it?
A. A vapor retarder is a material which resists the passage of water vapor (the paper
or foil facing on batt insulation is a vapor retarder). A properly installed vapor
barrier (facing the warm-in-winter side) can minimize the chance of water vapor
condensing inside your wall insulation, which not only reduces the insulation's
effectiveness but can also cause damage to your home.
Q. I've heard that you can make a home "too tight" - should I be
concerned about this?
A. With new construction, it is possible, although unlikely unless extraordinary
measures are taken to eliminate air leakage. For an existing home, basic air sealing
measures like caulking and weatherstripping will save energy dollars without making the
home too tight for acceptable indoor air quality.
Q. What is the best type of insulation to use in my attic?
A. Either loose fill (typically fiberglass or cellulose) or batt insulation (usually
fiberglass) will work well. Batts are easier to install yourself, while many
contractors find loose fill easier and less expensive to install.
Q. Which type of batt insulation is better - foil faced or paper faced?
A. The foil or paper facing is a vapor retarder. There is no difference in R-value
between foil or paper faced batts. While the foil is a somewhat more effective
vapor retarder, it is also more expensive and less widely available.
Q. Is it better to caulk my windows and doors on the inside or the outside?
A. Any large gaps on the outside should be weatherproofed to keep rain out, but the
inside is generally the best place to caulk to keep the heated air inside, along with
any water vapor that could condense in a cold wall cavity.
Q. How much ventilation should I have in my attic?
A. In most cases, you should have one square foot of net free vent area for each 150
square feet of attic floor area. Net free area is the actual area that air can flow
through. With screens and louvers, you can assume that is roughly half the gross
area. If you have a properly installed ceiling vapor retarder, you can reduce the
vent area to one square foot per 300 square feet of attic floor area.
Q. How much ventilation should I have in my crawlspace, and should the vents be
closed in the winter?
A. If the crawlspace has a dirt or gravel floor, you should have one square foot of
vent area for each 150 square feet of crawlspace area, unless you have a waterproof
ground cover, in which case one square foot for each 1500 square feet is recommended.
Vents should not be closed in winter. If the floor over the crawlspace is uninsulated,
you should have it insulated to reduce heat loss through your floors.
Q. What is the best way to ventilate a cathedral ceiling?
A. Cathedral ceilings should have continuous soffit vents and a ridge vent to allow air
circulation between the insulation and the underside of the roof. Insulation should
be installed with at least 1 inch of clearance from the underside of the roof. There
are plastic baffles available that can be used to maintain this air space. A
continuous vapor retarder is also recommended to minimize migration of water
vapor into the insulation.
Q. Can I insulate over recessed lighting fixtures?
A. Only if the fixtures are designed to be covered with insulation (these fixtures are
referred to as "IC Rated"). Otherwise you should maintain three inches of
clearance around the fixtures and leave the top of the fixture uncovered to avoid
potentially hazardous heat buildup within the fixture.
Q. What is a "thermopane" window, and how does it work?
A. A "thermopane" or double-paned window has two panes of glass, separated by a
trapped air space. The trapped air acts as an insulator, reducing heat loss through
the glass.
Q. My home has single-paned windows - would it be better to
replace them with double-paned windows or to add storm windows?
A. Both double-paned or thermal windows and storm windows work by creating an
insulating air space between the panes of glass. If your existing windows are in
good shape, storm windows will usually be more cost-effective. If your existing
windows are damaged or if you are replacing them for aesthetic reasons, you
should install good quality double-paned windows.
Q. Why does moisture form on the inside of my windows in winter,
and how can I minimize the amount of moisture?
A. Condensation will occur whenever warm air hits a cold surface because warm air
can hold more water vapor than cold air. If you have single-paned windows,
adding storm windows will keep the inner pane of glass warmer and reduce the
amount of condensation. Monitoring your indoor humidity and keeping it in the
range of 40 - 50% will also help.
Q. What are "Low-E" windows?
A. "Low-E" windows incorporate a microscopically thin layer of a metal oxide which
reduces the amount of heat transferred through the glass without reducing the
amount of light. This coating is only used with double-paned windows.
Q. I'm considering having vinyl siding installed on my home.
Will this reduce my heating and cooling costs?
A. Vinyl siding is typically installed over a thin layer of foam insulation material.
Although this material has some insulating value, it is minimal. You should be
skeptical of any claims of substantial energy savings. The main benefits of vinyl
siding are enhanced appearance, reduced maintenance and potentially increased resale value.
