Poorly designed double hung windows are a huge source of air leaks in many Charlotte homes. And that’s really bad news for your energy bills—air infiltration in your windows can run up utility costs in a big way.
In this article, I want to tell you more about air infiltration in double hung windows, how it happens, and why Zen Windows has the most airtight double hung windows in the industry (and it’s not even close!).
First, let’s start with what air infiltration actually is.
Energy Star rates air infiltration of individual windows. You can find this rating on a window’s NFRC label under Air Leakage (AL). Here’s what the label looks like…
The Air Leakage rating measures how much air will enter a room through the product itself (not around the actual frame—I’ll come to that in a second). This rating is expressed as a number between 0.1 and 0.3, with lower numbers being better. The number itself refers to how much air leakage occurs in a window per minute. For example, a window with a 0.23 AL rating will leak air at a rate of 0.23 Cubic Feet per Minute (CFM).
As a rule of thumb: 0.1 is exceptional, 0.2 is pretty good, and 0.3 is average and considered the industry standard. Anything higher than 0.3? Avoid!
Poorly designed double hung windows will leak air because they don’t have the built-in airlocks, weather stripping, and barriers required to stop air from forcing its way into your home. Without these components, air will push between the sash meeting railings and around the perimeter of the sash.
The Air Leakage rating on an NFRC label only goes as low as 0.1. That’s unfortunate because it cannot capture how amazingly efficient our vinyl double hung windows are—0.01 to 0.07!
That’s right. Our vinyl double hung windows are over 10 times more airtight than the NFRC’s best rating.
How? Because our windows specially designed to block air and are packed with weather barriers that go FAR beyond industry standards. These components include…
To put how airtight our double hung windows are into perspective, consider this:
How Does Installation Contribute To Window Air Leakage?
As previously stated, the AL rating measures only the proficiency of the window itself. It does not take into account potential air leakage around the frame. But even the best vinyl double hung windows in the world will leak air if they are not properly installed. If the installation is crooked… or the opening for the window isn’t cut PERFECTLY… or the sill flashing is done wrong… the window WILL leak air. End of story.
This is why it’s best to go with a professional, well-reviewed window company to install your double hung windows in Charlotte. Here are a few things to consider when researching window companies…
At Zen Windows Carolina, our No Deposit protocol GUARANTEES you the absolute best installation. Why? Because you don’t pay us a dime until we’ve installed your windows and YOU are satisfied.
For more reasons why we’re Charlotte’s go-to company for vinyl double hung windows, explore the links below: