Frequently Asked Questions
Responses
What are “low-e” windows?
Low-e windows are windows that are coated with microscopically thin,
virtually transparent coatings that help to control heat and light transfer.
Most low-e coatings cut heat loss significantly, reducing energy bills,
significantly improving comfort when you’re near a window, and reducing the
potential for condensation. Some low-e coatings are specifically designed to
significantly reduce the amount of the sun’s heat that can pass through them –
these are sometimes called “solar-control” coatings.
Low-e windows are recommended for all new Colorado homes. Solar-control low-e
windows are recommended for windows that have the potential to gather more solar
heat than desired in winter or summer.
For more information, see the Windows fact sheet on this web site and visit the
web site of the Efficient Windows Collaborative.
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Should basements be insulated on the outside or
the inside?
Basement walls can be insulated on either side – or both! Interior insulation
is generally easier to accomplish and can tie in well with interior finish. It
has a disadvantage of potentially trapping moisture, though, because it makes
the concrete foundation colder. It also takes up valuable space inside your
basement.
Exterior insulation is a good choice because it warms the concrete foundation,
reducing the potential for moisture problems, and because it keeps the extensive
“thermal mass” of the foundation inside the insulated shell of the home. The
challenges with exterior insulation are an adequately strong mechanical
attachment of the insulation to the concrete wall and weather protection for the
insulation exposed above grade at the top of the wall. These challenges can be
overcome with attention to the details of design and construction.
“Insulated concrete forms” (ICF) are an altogether different type of building
system – a great option that provides insulation on both sides of the wall.
For more detailed information on basement insulation options see
EEBA’s
Builder’s Guide / Cold Climate.
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What problems are created with crawl spaces?
Crawl spaces have been challenges in the past because of uncertainty about
whether a crawl space is “inside” or “outside” the house. Moisture control has
been poorly understood. Many building code regulations, based on outmoded
assumptions, have contributed to this confusion. Surprisingly, performance
testing has shown that vented crawl spaces are much more closely connected to
the house than to outdoors. Many vented crawl spaces have problems with heat
loss, moisture and radon.
Another problem with crawl spaces is that they are “out-of-sight, out-of-mind.”
Homeowners rarely poke their head into a crawl space. In the past, crawl spaces
have often received too little attention during the construction process, with
hasty work and little quality control. This has further compromised crawl space
performance.
“Deep” crawl spaces – built below suspended basement floors in areas with
expansive soils – are often in wetter soils than traditional “at-grade” crawl
spaces. Again, moisture control has been poorly understood. Deep crawl spaces
have been prone to moisture, mold and decay.
The good news is that improved understanding of how crawl spaces work has led to
solutions that perform much better than traditional crawl spaces. The important
elements are to (1) bring the crawl space unambiguously inside the shell of the
building (no vents to outdoors – make it part of the conditioned space); (2) use
simple approaches to keep moisture out of the crawl space; (3) pay close
attention to the details.
For more details on crawl spaces, check the
EEBA’s Builder’s Guide /
Cold Climate and the Moisture Management Task Force’s “Guidelines for Design and Construction
of New Homes with Below-Grade Under-Floor Spaces.”
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Should the door between a crawl space and basement be
left open?
If the crawl space is vented to outdoors, leave the door closed. If the crawl
space is NOT vented to outdoors, it doesn’t matter whether the door is left open
or closed.
The more important answer is that the smart way to design and build a crawl
space is as intentionally conditioned space. Then it makes no difference how the
basement / crawl space door is managed. See the response to another FAQ about crawl spaces
for more information.
Back to Top What is “glare?”
“Glare” refers to too much light in your field of view – so much that your
eyes are strained in as they try to adapt to it. Glare often results from too
much contrast in brightness between adjoining areas within your field of view.
Avoid glare with careful attention to both daylighting design and electric
lighting design.
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What contributes to effective daylighting?
Daylighting means bringing “natural” light from the sky into your home. It
can provide very attractive lighting and reduce your electric bills by
minimizing the use of electric lighting. Factors contributing to effective
daylighting include:
- Reflected light. The disc of the sun is so bright that it causes
uncomfortable glare. Effective daylighting primarily relies on reflected light
from the rest of the sky. Think about the sun’s path in all seasons to avoid
bringing in too much direct sunlight.
- Balanced lighting. Bringing in daylight from at least two sides of
every room helps eliminate glare and dark corners. Think about windows,
skylights, partial height walls, windows.
- Light-colored finishes. Lighter walls, ceilings, floor coverings
and furnishings do a much better job of distributing light indoors than darker
surfaces.
- Appropriately sized windows. Careful placement of windows is more
important for daylighting than window size. Large windows can bring in too
much light and heat from the sun.
- Window placement. Place windows near corners and/or near ceilings
so that adjoining walls and ceilings can help distribute the daylight.
- Keep the heat out. A challenge with daylighting is to bring in
enough light without bringing in too much of the sun’s heat. Think about the
sun’s path, exterior shading and solar-control windows.
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How will I know if a compact fluorescent light bulb
(CFL) will produce the right amount of light?
The amount of light produced by any light bulb is measured in “lumens.” The
lumen rating is always listed on the packaging and/or in the catalog. You can
directly compare the rated output of the CFL versus the rated output for the
familiar incandescent bulb that you’re replacing.
The light output of a CFL falls off somewhat, very gradually, over the long life
of the bulb. Therefore you may wish to buy a CFL with a rated initial lumen
output 10-15% higher than the lumen rating for the incandescent bulb you’re
replacing.
The great news about CFLs is that, compared with incandescent bulbs, they put
out many more lumens of light per watt of electricity you have to buy. You get
the same amount of light while using 65% to 80% less electricity.
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Is there more that could be done from a code
perspective to increase the supply of high-performing homes?
Building code typically sets minimum standards for the individual parts that
make up a home. It defines “the worst house you can legally build.” It is an
important lower limit for new construction. In contrast, high-performing homes
are the result of putting the pieces together, using a whole-house approach, in
a way that meets performance goals that are usually much higher than the
minimum.
Occasionally, approaches that can lead to better whole-house performance run
into conflicts with code requirements that were based on a component approach or
that rely on an outmoded understanding of building science. In these cases,
builders and code officials need to work together to resolve the issue.
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What could be done to improve the performance of
existing homes?
There is a wealth of opportunities to reduce energy costs, increase comfort,
and improve indoor air quality and durability in existing homes. Because of the
diversity of the existing home stock, it’s hard to make generalizations. In some
homes, the improvements are easy and inexpensive to capture; in others they may
well be prohibitively expensive. The place to start is by getting an
understanding of where the problems and opportunities lie. Then make a game
plan, making sure not to ignore interactions among the things you want to
change. A good place to start is with an energy rating.
A skilled “whole-house” contractor can be very helpful.
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