Energy efficient windows are often lauded by homeowners and builders as a worthwhile investment, but you may find yourself wondering what the best energy ratings or features work best for your home. While it’s true that the ratings make a big difference, understanding what they mean is easy enough to understand, as the following explanation shows.
Energy Ratings Indicate Efficiency
Windows emit heat outside during the winter and allow heat indoors during the summer. There are two measurements that track the movement of heat and they’re called the U-factor and SHGC. The U-factor describes the solar heat loss coefficient, which is a ratio describing how much heat is distributed across a material. Our recommended threshold for the U-factor is 0.3 or under. For cooler temperate climates, the U-factor is going to be more important than the SHGC, as you’re going to be concerned with how much of the energy that goes into heating your home escapes outwards.
The SHGC describes the solar heat gain coefficient, which can be thought of as the opposite of the U-factor. The SHGC may not always be the same as the U-factor, so in hot climates, pay special attention to the SHGC.
A related measurement is the air leakage coefficient, which indicates how much air will pass through in both directions and it lies between the values 0 and 1. Modern windows will be manufactured well enough to protect the home from draft, but not to the degree to which the seal is airtight. The movement of air leads reduce the effects of air conditioning in the summer and heating in the winter, so the lower the value of the coefficient, the better the window works.
Window Pane Terminology
There are some important categories which form a basic understanding of glass pane production:
- gas filling
Double pane windows use the principle that make down jackets warm. Heat doesn’t travel well through the air, so down coats trap pockets of air. This way, it prevents the heat from easily travelling away from the body. Between two panes of glass is a pocket of air, while three panes of glass has two. Although three pane glass windows or doors are much better at insulation than two pane glass, they are both efficient at insulating the home.
Some manufacturers have engineered the air between the window panes for better energy efficiency. Argon gas is better than regular air, which is a mix of oxygen, nitrogen, and other mixed gasses. Windows filled with argon are usually on the pricier end, but well worth the investment.
Tinted windows will prevent the sun’s rays from entering your home and heating the air. Visible transmission glass has similar properties, but with the added benefit of controlling glare and reflection from outside the house. Low-E coating lowers the U-factor, while Low-E2 glass effects the SHGC value.
There are other non-energy related features including impact resistant glass, which will help you preserve the integrity of the glass. People living in tornado or hurricane prone areas will certainly benefit from this measure.
About The Author
Being a home renovator gives me a great satisfaction. The happiness that you bring into someone’s life, just through your work, can’t be expressed in words. I have been in the home improvement industry since quite a long time and have never felt my work anything other than interesting. I consider being a part in bringing someone’s dream come true, the greatest happiness and virtue. – John Medina