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.