CHOOSE WINDOWS THAT SUIT YOUR CLIMATE AND LOCATION

When you’re window shopping, understanding these terms will help you find windows that will perform well in your climate. For in-depth, location-specific information for your house, use the window selection tool from the National Fenestration Rating Council at efficientwindows.org. What is “fenestration,” you ask? Generally, it means any opening in a surface, such as a wall. 1 INSULATING GLASS

Insulating glass adds a layer of energy efficiency and comfort to your living space. Most new windows have two panes of glass with gas— typically argon—in between the panes.

2 U-FACTOR

The U-factor tells you a window’s rate of heat loss. The lower the number, the better the window will keep heat in. Because our Getaway is in a cold climate, we chose windows with a U-factor of 0.27, which meets Energy Star ratings for northern zones. If your windows have a higher U-factor number, you’ll want to increase the solar heat gain coefficient (see #6).

3 VISIBLE TRANSMITTANCE

Expressed as a number between 0 and 1, visible transmittance signifies the fraction of the visible sunlight spectrum allowed through a pane of glass. The higher the number, the more light the window lets in. Generally, most people prefer to let in all the light they can, so be aware that a lower solar heat gain coefficient typically means a slight reduction in visible transmittance.

4 CONDENSATION RESISTANCE

The higher this number, the better your windows are at resisting condensation. This is greatly affected by interior relative humidity.

5 COATINGS

A low-E coating is standard on most windows. The coating is transparent to allow in all the light, but it reflects heat. In warm climates, it’s applied to the outer glass to keep heat out. In cold climates, it’s applied to the inside glass to retain heat.

6 SOLAR HEAT GAIN COEFFICIENT

Typically a bigger concern in warm climates, solar heat gain is also a consideration here in Wisconsin where summers are hot. The lower the number, the better the window is at blocking heat from the sun. Most people buy windows with the same ratings for the whole house, but it’s possible to fine-tune your windows to suit your needs. For example, you can choose windows with a lower number for your south-facing windows and windows with a higher number for your north-facing ones.

Some people even buy two sets of sashes for their windows and change them seasonally.

7 AIR LEAKAGE RATING

An air leakage rating from 0.10 to 0.30 is good; most new windows easily meet that standard.

MEET THE EXPERT

STEVE URICH IS THE SENIOR DIRECTOR OF PROGRAMS AT THE NATIONAL FENESTRATION RATING COUNCIL.