Windows allow natural light and air to enter your home, but they also play a crucial role in keeping your energy bills low. That’s why properly installed, energy-efficient windows are so important for your home. They help to reduce heat loss in living spaces. In the long term, they will help to save money, making window replacement one of the best investments you can make.

You might be wondering which windows are the best to install in your residence. We’re happy to shed some light on energy efficiency in windows.

Always Check the Energy Rating Label

What is an Energy Rating Label? These are explicit and colorful stickers that provide an easy way to differentiate window products and compare their energy efficiency. They integrate a rainbow design and are used in many energy-based home appliances such as washing machines and refrigerators just to mention a few.

It is important to point out; that there are many energy-rating schemes for windows across the world. However, the most common labels in the US include:

  • The National Fenestration Rating Council Label– NFRC is a US-based NGO that has made its life purpose to sponsor energy efficiency labeling and certification programs.
  • The Energy Star Label– this label explicitly indicates that the appliance/structure has met all the preset energy criteria laid down by The US government. It also compliments the NFRC label.

How Do NFRC Labels Work?

The NFRC labels use letters and numbers to help people determine the energy performance of windows and other structures. To determine this, they consider many aspects such as frame design, frame material, and glass type just to mention a few.

If you intend to carry out a window replacement, you should know an A+ rated window is more energy efficient than a C rated.

The formula NFRC uses to come up with these letters and numbers take into account solar heat gain coefficient, air leakage, overall thermal efficiency, U-value, condensation resistance, and visible transmittance.

To grasp the concept better, let us look at each variable.


This defines the rate of heat transfer through one square meter of a window/structure, where a thermal gradient exists. It is also referred to as U-factor. NFRC range is 0.20-1.20. The lower the number, the better the insulation of the window.

Solar Heat Gain Co-efficient

This defines the correlation of thermal increase of a space as it absorbs incident solar radiation. NFRC range is 0-1. The lower the number, the less radiation the window will allow in the living spaces.

Air Leakage

These entail air barriers that help in the regulation of air leakages in enclosed living spaces. They can be self-adhered or mechanically attached membranes amongst many others. There is no specific range, but 0.3 is the recommended standard.

Visible Transmittance

This entails surface transmittance. In simple, a window surface can transmit radiant energy. NFRC range is 0-1. A lower value signifies a dimmer room and vice-versa. In this case, when choosing, it will depend on whether you want your living space dimmer or brighter.

Condensation Resistance

CR determines how well a window resists the formation of water droplets (condensation) on the inside surface. The NFRC range is 1-100. The lower the number, the more condensate it will form.

Reliable Window Replacement

It is always good to do your research before buying Windows, but if you’re confused, our team at Schmidt Roofing can help you make the best decision possible. Contact us today for an honest quote on window replacement.

company icon