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A Guide to Energy Efficient Windows

Did you know that heat gain and loss through windows are responsible for 25% to 30% of residential energy expense? It’s important to choose the most efficient windows you can afford that work best in your climate. This not only saves you money on bills but will aid in comfort by regulating the temperature inside your home.

So let’s say you already know what you want your windows to look like and you are ready to look at the specs of each option. To save the most money you’ll want to look for the Energy Star or NFRC label and review your ratings listed on the label.

Reading your energy labels:

NFRC stands for The National Fenestration Rating Council. An NFRC label helps compare energy efficiency in windows, doors, and skylights by providing ratings in multiple categories.

4 Categories on a Window Label

U factor- Measures how well a product can keep heat from escaping the inside of a room. The lower the number, the better the product is at keeping heat in. This number ranges from 0.2 to 1.2, you want a rating as close to 0.2 as possible for maximum energy efficiency.

Visible Transmittance- Measures how well a product is designed to effectively light your home with natural outside light, assisting in saving the home owner money on electric. This one isn’t necessarily related to heat energy but we wanted to include this saving tip. The higher the number, the more natural light the window is letting in. This number ranges from 0 to 1. For more natural light, get products with ratings as close to 1 as possible for the most amount of natural light.

Solar heat gain coefficient- Measures how well a product can resist unwanted heat gain, which is especially important during summer. The lower the number, the less you'll spend on cooling costs. This number ranges from 0 to 1 as well. The lower the number, the more resistant to summer heat.

Air leakage- Measures how much air will enter or leave a room through a product. The lower the number the fewer the drafts. This number ranges from 0.1 to 0.3. the closer to 0.1, the less drafty the window.

NFRC also has a condensation rating. This rating is optional for manufacturers to include so it doesn’t always appear on the label. The higher the number, the better the product resists condensation.

Other things to look for when shopping for energy efficient windows:

How many panes does your window have? Windows with only one pane barely separate the inside and outside of your home, thus, less insulation. Look for windows with two or three panes instead.

Glass Coatings will help block out solar rays, similar to the effect of sun glasses. Look for Low-E glass coatings to keep your home protected from both heat, and fading effects of UV rays on furniture and carpet. Milgard has their SunCoat® line offering various levels of protection. Another option is a 4th surface coat. 4th surface glass coatings are for double pane windows and offer an enhanced U-factor effect, meaning the heat is kept inside the home. This is good for cold climates.

The area between the panes is important as well. You want a spacer that will properly insulate and reduce air flow to keep the heat in or out, where it’s supposed to be. The gas between your windows, usually Argon and Krypton gas, is another feature that maintains heat levels in the home.

Several Brands have these features, and you can also add some of these options as upgrades if the window you want doesn’t come with an extra energy saving feature. For questions you can talk to a professional from Z Double B at 303-997-8168. Inquiries are always free and we can also provide free estimates and quotes as we guide you through your energy efficient window search.

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