The process of choosing the most suitable choice between two different windows can be a bewildering whirlwind of terms, amounts and rival claims of efficiency. Standard rating systems decrease a few important characteristics of windows to simple measurements, which makes it a lot easier to directly compare two different windows from two different manufacturers — so long as you understand which characteristics are significant and what the amounts should be.
U-Factor
Windows are a significant source of unwanted heat loss and gain in your house, so a fantastic place to start comparing two different windows would be in how well they insulate against the transport of heat. A window insulating capability is quantified in a number called the U-factor; the lower the U-factor amount, the better the window’s insulating capacity. Window U-factors typically vary between 0.25 and 1.25, but a few extremely efficient windows can attain a score of 2 or 3. In Northern California, a window with a U-factor of 0.5 is generally efficient enough. Windows with multiple panes of glass and gas-filled spaces between the panes are able to attain increased U-factor ratings.
Solar Heat Gain
Since the sun shines on window glass, the glass does a fantastic job of transmitting solar power into your house in the kind of heat, and this can be a problem in warm climates. A window’s solar heat gain coefficient measures how well the window protects against solar heating; the lower the number, the less solar heat the window transmits. Typical SHGC ratings vary from 0.25 to 0.8; in Northern California, an SHGC amount below 0.3 is greatest. Windows with low-emission glazing offer enhanced resistance to solar heat transport.
Visible Transmittance
Whether you want heat to maneuver through your windows depends on where you are and also the time of year, but you’re going to want light to maneuver through your windows easily. A window visible transmittance rating measures how much light passes unobstructed through the window glass, and it’s influenced by the thickness of these panes; a greater VT rating means the window lets more light into your house.
Frame Material
The material where the window frame is constructed affects not only its efficiency, but also its physical appearance and ease of upkeep. Conventional timber frames are appealing, but they’re also typically less effective than newer substances, and they require routine maintenance. Vinyl- or aluminum-clad wood frames give the structural stability of timber as well as the maintenance, durability and efficiency benefits of these tougher cladding materials. Fiberglass frames are durable, effective and low-maintenance. All-vinyl frames are cheap and low-maintenance, but they also tend to be less effective and less appealing compared to other framework options.