So you’ve noticed your windows are a little drafty. Sure, you know it’s a problem, but how bad really is it? The effects of water leakage are easy to see, but the invisible impact of air leakage can add up quickly and become costly. From old, worn-out windows to cheaply made, energy-inefficient new windows, air leakage is a problem that can affect anyone.
First, let’s examine what air infiltration is and how it is measured. Air infiltration is air that manages to leak into or out of a room through the gaps in a window. Air infiltration is measured in cubic feet per minute per square foot, so the amount of air in a one foot wide by one foot tall by one foot deep space that can escape through the window in one minute from a one foot by one foot space.
The majority of air leakage occurs through the meeting rail and where the sashes meet the frame. Windows that are fixed, like picture windows, have minimal air leakage. For windows that are able to be opened, air infiltration can be minimized through design features like an integrated meeting rail and premium quality weatherstripping, both featured on ViWinTech windows.
Now, what impact does that have on energy efficiency? When air is able to escape through windows, over time, the temperature in that room either gets warmer or cooler depending on the season. When your thermostat registers this change in temperature, the air conditioner or furnace kicks on to regulate the temperature in the home, using energy. The more quickly air is able to escape, the more quickly temperatures are able to change within your home, and the more often the air conditioner or furnace must turn on to keep the temperature as set on your device. This results in your home using more energy to maintain the temperature set which costs you more money.
Integrated meeting rail and premium quality weatherstripping, both featured on ViWinTech windows
Next, let’s take a look at how to read ratings. The NFRC allows for a maximum air infiltration rate of 0.30cfm/ft^2. The amount of air infiltration through any window will vary based on the size and style of the window. The worst performing ViWinTech windows are rated at 0.15 cfm/ft^2 which is half the limit required by the NFRC, meaning that even the worst air-leakage performing windows are still TWICE as secure as what is required. The very best performing ViWinTech windows on air-leakage are rated at 0.01 cfm/ft^2, which is THIRTY TIMES as efficient at reducing air leakage.
Finally, what are a few other ways the NFRC measures window energy efficiency? Other factors that contribute to the energy efficiency of windows include the U Factor and the Solar Heat Gain Coefficient. What does that mean? The U-factor is the rate at which the window transmits non-solar heat flow. The glass type chosen and glass glaze used can impact this number. The lower the number, the more energy efficient the window is. The Solar Heat Gain Coefficient is the fraction of solar heat radiation admitted through the window into the home. The optimal number for SHGC will depend on the geographical location of your home and the climate of your home’s location.