17 common questions about energy-efficient window treatments

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17 Common Questions About
Energy-Efficient Window Treatments
Craig Birdsong, Jo Ann Less and Mary Mari
Guide G - 523
1. Question: Are the terms window treatments and systems the same?
Answer: Though some people use the terms synonymously, they actually are not the same. Treat
ment refers to a method or technique used to control specific functions of a window. Draperies,
blinds, and shutters, whether conventional or modified to be more energy efficient, as well
as storm windows and most types of moveable insulation, are examples of treatments. A
window system is a total unit concept, in which recognition is given to all components. For
example, a well-sealed, insulated drapery with a vapor barrier, the window frame and glass,
and the add-on storm window would comprise a window system. Because the effectiveness
of R-values in reducing heat loss or gain diminishes in proportion to the increase in R value
(see question 4), it is better to consider the total unit concept or window system, rather than
only one part of the system (a treatment).
2. Question:        What is the most energy-efficient window treatment?
Answer: The most efficient treatments are those with high R-values (ability to reduce or restrict air
flow), the ability to be sealed on all four sides (creating a dead air space between the window
itself and the treatment), and a vapor barrier (preventing moisture in the warm indoor air
from passing through and condensing on the window glass).
3. Question: How energy efficient should a treatment be?
Answer: As efficient as possible. The efficiency of a treatment is determined by the R-value of the
materials from which the treatment is made. The higher the R-value the more effective the
treatment will be, provided all four sides of the treatment are sealed.
Remember that R-values are cumulative. That means the R-values of the various materials
from which a treatment is made can be added together to arrive at the total R-value of the
treatment itself. However, increasingly high R-values may not be cost effective (see question 4).
4. Question: How high an R-value is necessary or desirable for an energy efficient window treatment?
Answer: A window treatment that achieves an R-value of 4 should be considered relatively energy
efficient today. It's efficient because such a treatment reduces the amount of heat lost or
gained through the window by 75 percent, and is easily achieved using materials commonly
available in today's market place.
Many products, if properly installed, can easily bring the standard single-paned window
up to an R-value of 2 and reduce your heat loss or gain by 50 percent. However, the costs
of materials to make insulating window coverings may allow you to achieve an R-4 for about
the same cost as an R-2 (depending upon the cost of the product you choose), making the
R-4 product more cost effective. Because it has a better insulating value for the same price,
it has a shorter payback time. In the future,as more materials having higher R-values are
developed and available at lower costs, the effectiveness of window treatments with reasonable
payback periods will increase.
As indicated in question 3 above, the effectiveness of a treatment in reducing the amount
of heat lost or gained by adding additional R-values decreases in proportion to the increase
in R-value.
•Housing and/or Home Furnishing Specialists in Colorado, New Mexico and Arizona, respectively.