Posted on March 29, 2018
If you're a Minneapolis homeowner looking for new double hung windows, it's important to know about air infiltration before you make a buying decision. Poorly-made double hung windows can leak air from several areas, causing uncomfortable drafts and higher energy bills.
Here's what you need to know about window air infiltration—and how our vinyl double hung windows are literally 23-times more airtight than wood double hung windows.
Energy Star is the standard for energy efficient consumer products in America. Energy star measures the efficiency of windows in a number of categories. One of these categories is Air Leakage (AL). As with all of a window's ratings, you can find AL on the window's NFRC label:
The NFRC label with AL circled in red.
AL gauges how much air will penetrate the window itself (this does not include around the frame—we'll get to that in a minute). The amount a window leaks air is represented as a number between 0.1 and 0.3 on the NFRC label; the lower the number, the better a window protects against air leakage. For instance, a window with an AL rating of 0.18 will be more airtight than a window with an AL rating of 0.27.
Here is a simple rule of thumb when examining a window's AL rating:
Poorly-made double hung windows can leak air from numerous areas. These areas include the sash meeting rail, the sill, and the sash perimeter.
Here's a diagram of potential leak areas of a double hung window:
Air can leak through the sash meeting rail, sash perimeter & sill of a double hung window.
Why do substandard double hung windows leak air from these points? For several potential reasons.
The window may be made with inferior parts. Or it could be manufactured poorly. Or it may not contain the necessary features to stop air leaks, such as weather stripping and built-in airlocks. Whatever the reason, it all means a drafty home and higher energy bills for YOU.
Since the best AL rating on the NFRC label is 0.1, it cannot express how much more airtight OUR double hung windows are.
Our lines of vinyl double hung windows have an AL rating between 0.01 and 0.07. Note that extra decimal place—that means our windows are MUCH more airtight than Energy Star's BEST air-leakage rating!
When you see all the air-leak-proofing features packed in our windows, it's easy to see why:
To put in perspective just how much better our windows block out air, let's compare our vinyl double hung windows to other window brands and materials:
Yes. But that is not something expressed on a label in as a numerical value. The NFRC label measures air leakage only through the PRODUCT itself. It doesn't factor in air that may leak around the frame. This means even the window with the best AL rating in the industry can leak air if it's improperly installed.
That's why it's so important to choose an experienced Minneapolis window company with a PROVEN track record to install your double hung windows.
If you'd like to know how Zen Windows Twin Cities can guarantee you superb installation and a completely stress-free experience, visit the Why Choose Us section of this website. Then feel free to get an online quote on our Request A Quote page. We'll provide you with an accurate, ironclad price and the information you need to make the right decision. No pressure. No pricing games. Period.