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Everything Charlotte Homeowners Need To Know About Energy Efficiency For Their Home’s Windows

Explore Our 2018 Window Energy Efficiency Guide To Get

The Answers You Need To Make The Right Buying Decision.

If you’re looking for energy efficient replacement windows for your Charlotte home, you have a lot to consider. Energy efficiency can vary wildly from window to window, and there is a surprising amount of technical terms and information to know.

To help you choose energy efficient windows for your home, we’ve created the 2018 Window Energy Efficiency Guide. This guide answers the following questions:

  • What makes a window energy efficient?
  • What are window energy efficiency requirements for Charlotte, NC?
  • How much do energy efficient windows cost?
  • Do energy efficient windows save money? And how much?
  • How do you read a window’s NFRC label?

Let’s get started…

How To Read A Window’s NFRC Label

You can find out all you need to know about a window’s energy efficiency by looking at its NFRC label. The NFRC label is a black and white sticker attached on every Energy Star-certified window. Below, we break down what every number and term on the NFRC label means.


U-Factor measures the rate of heat loss between 0 and 1. The lower the U-Factor number, the better the window keeps heat in your home. A well-insulated window with a low U-Factor is going to keep your home a comfortable temperature year round, while cutting your energy costs.

Solar Heat Gain Coefficient

Solar Heat Gain Coefficient (SHGC) measures the fraction of solar radiation admitted through a window and is expressed in a number between 0 and 1. Lower numbers are more desirable EXCEPT in Northern climates due to colder temperatures.

Visible Transmittance

Visible Transmittance indicates the amount of visible light transmitted, and includes the impact of the frame which does not transmit any visible light. Numbers between 0 and1 are possible, with numbers in most windows measuring between 0.3 and 0.7. A high VT is desirable to maximize daylight.

Air Leakage

Air Leakage (AL) measures how much air will enter a room through a square foot of window and is indicated by the amount of air that passes through a square foot of window. The lower the number, the fewer drafts you’ll experience. 1 is considered outstanding; 0.2 is good; 0.3 is average; 0.4 or higher is unacceptable.

Condensation Resistance

Condensation Resistance measures the ability of a product to resist the formation of condensation on the interior surfaces of that product. Higher numbers are desired, and are expressed between 1 and 100. Anything under 50 is unacceptable; 50 to 60 is good; 60 or more is very good.

Do Energy Efficient Windows Save Money?

(And How Much Do They Cost?)

Energy Star—the country’s leading energy efficiency program—researched how much homeowners who replace their old windows can save on bills. Energy Star examined energy savings throughout all regions of the USA. Energy Star concluded North Carolina homeowners can save $280 per year on energy bills when they replace their old single pane windows with Energy Star-certified windows.

To get the most energy efficient windows for your home, you don’t have to spend an arm and a leg. You can get maximum energy efficiency from high-quality vinyl replacement windows for around $499 to $699, installed. The only reason to pay more than this is if you need, say, wood windows specially made for a custom home. On the other hand, make sure you don’t go too “cheap.” Windows in the sub-$400 range are what the industry calls “builder-grade” windows, which are lower quality and provide poor efficiency.

In addition to the long-term savings on your bills with energy efficient windows, you can also take advantage of financial incentives that lower your initial investment. Most energy providers offer these incentives for purchasing Energy Star-certified windows. You can also claim federal tax credits for installing energy efficient windows.

Anatomy Of An Energy Efficient Window

What, exactly, makes a window energy efficient? It’s not just one thing, but multiple features working together. Below, we take a look at the components that determine a window’s efficiency.


Two panes of glass—with air or gas in between them—are much more energy efficient than a single pane of glass. Window can also come with three panes for even greater efficiency, impact resistance, and sound insulation.


Special coatings can be applied to window glass to reflect infrared light, which keeps heat inside your home in the winter and outside in the summer. This coating also reflects harmful UV light, protecting your indoor furniture from fading.


Energy efficient windows have argon, krypton, and other gases between the glass panes. These gases are colorless, odorless, non-toxic, and insulate better than air.


A variety of durable, low-maintenance framing materials reduces heat transfer and improves insulation. For the best efficiency, look for windows that are welded at the corners and have ample insulation within the frame. This will help prevent air leakage and heat loss.


A spacer ensures the glass panes of a window are the proper distance apart. Non-metallic and metal/non-metal hybrid spacers also insulate pane edges, reducing heat transfer through the window.


Windows must be installed tightly, straightly, and to manufacturer specifications to ensure maximum energy efficiency. Poor installation can be hard for homeowners to spot, so do your due diligence on a contractor (i.e., look at reviews, references, certifications, etc.) to ensure you get quality installation.

Get An Emailed Quote On THE Most Energy Efficient Windows In Charlotte

Choosing energy efficient windows is important for your finances and comfort. Not only do energy efficient windows help reduce your utility bills, but they also help keep your home a pleasant temperature all year long. Bottom line: Energy efficient windows can impact your quality of living for decades. So selecting the right brand is crucial.

At Zen Windows North Carolina, we install three exclusive lines of award-winning energy efficient vinyl windows. Here is a look at the why our windows are a fantastic choice for Charlotte homeowners:

  • Our windows have won the Energy Star award for the past three years.
  • Our windows have the lowest air-infiltration rating in the industry. In independent tests, our vinyl double hung window was 23 times more airtight than wood double hung windows!
  • Our windows are packed with features that keep your home a comfortable temperature and your energy bills lower. These features include special glazed and gas-infused glass, double- and triple-pane options, dense foam insulation within the frame, and much more.
  • Even our most modestly priced windows have a state-of-the-art double-insulating Solar LowE glass system and wool-pile weather stripping. You get amazing efficiency no matter what.
  • Depending on the line of windows and type of glass you choose, you can get a U-Factor as low as 0.15—the best U-Factor on the market!

For more info on our windows, visit our Replacement Windows page.

Contact Us Today

At Zen Windows North Carolina, we’ve done away with in-home sales appointments. Simply fill out the quick form here, and we’ll provide you with a rock-solid quote on superior windows for your Charlotte home.

I look forward to hearing from you!

Brian Zimmerman