Selection and Buying
Windows, Skylights & Doors
When shopping for windows, doors and skylights, pay close attention to…
NFRC, Energy Star or the European BFRC labels …
Compare different window, doors or skylights taking into account
their overall ratings for insulation, thermal resistance (and
eventually visible transmittance, condensation resistance or air
leakage performance). Use, for that effect the NFRC, Energy Star
or the European BFRC labels …
Insulation ( U-factor)
Insulation provided by doors, windows and skylights is
fundamental and it’s measured through the U-factor coefficient.
In the case of windows, the overall U-factor (glaze + frame +
sash…) should be below 0.4 for maximum energy savings.
Cooling performance
In hot climates low SHGC coefficients (linked to low E2 glass)
is essential: the SHGC is the coefficient of the solar radiation
transmitted through the glaze. SGHC below 0.4 or 0.3 are common
and desirable in hot climates.
Rating coefficients
The U-factor and the
SHGC coefficient are the main indicators of the energy-efficiency of
windows, doors and skylights. But there are other coefficients
you may ponder: visible transmittance, condensation resistance
and air leakage performance
Rating of the overall windows, doors and skylights
Ratings should apply to the entire product: the glazing, but
also the frame and the other elements of windows, doors or
skylights. It shouldn’t involve just the glass element. Take it
in consideration when buying and selecting windows, doors and
skylights.
Labels from the manufacturer
Labels from the manufacturer should be analyzed with cautious.
Do the U-factor, the SHGC and other coefficients apply to the glazing only or to the entire unit? If it
involves the entire unit, that’s ok. If they are for the glazing
only, then the real coefficients are considerable different due to
frame and spacer impacts…
Panes, glass and gas fills
Single-pane windows are a bad option. Multiple-pane, low-E
(or low-E2, in hot climates) windows are much better options.
Low-E glass panes and gas fills are now a common option:
manufacturers have introduced the use of argon and other gases
fills, with considerable improvement in thermal performance.
Climate impact & windows, doors and skylights selection
When buying and selecting fenestration, you should demand products that are qualified for your specific
climate zone. The
Energy Star ratings (or the European BFRC and other ratings) for
doors, skylights and windows are valid and applied to specific
climate zones...
Frames
Common aluminum-frame windows aren’t a good option. Select the
best frame materials for maximum insulating value: wood, vinyl,
and fiberglass. Aluminum-frame windows should only be bought with
well designed thermal breaks in mild climates.
Manufacturers
Most manufacturers have different quality levels of windows,
doors and skylights. The popularity and rating of the
manufacturer is important, but when buying and selecting
fenestration it may be more important to take
into account the specifications of each particular product.
Long warranties
Long warranty periods are an indicator of sound design and
construction, and lower probability of insulating glass seal
failures or gas leakage… So, select and buy windows, doors and skylights
with longer warranties.
Day-lighting
In order to implement day-lighting you
should locate and dimension your windows correctly. And consider
skylights, clerestories, sunrooms... You may also
bet on windows, glazed doors and skylights with an high visible
transmittance coefficient.
Tinted windows
Tinted glazings for windows, such as bronze and green, provide lower
solar heat gain coefficients. But low-E coatings glasses (or a
combination of low-e coating and tinted glazings) are
usually a better buying option.
See also:
Windows, Doors and Skylights basics
Labels and ratings
Windows and climate
Windows, doors and
skylights manufacturers
Daylighting
Frames and sashes
Advanced Doors
Skylights
Rebates and Tax Credits
NFRC
Energy Star
Energy Saving
Trust UK
British Fenestration Rating
Council
Australia Windows & Doors Labeling
Australian GreenHouse Office
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