Understanding Energy Efficiency Ratings for Windows

Understanding Energy Efficiency Ratings for Windows

Nowadays, there is so much talk about the energy efficiency of windows and doors. Of course, this is for a good reason as energy efficiency can be instrumental in making your home comfortable and saving you lots of money. But before selecting energy-efficient windows and doors, you must first understand what energy efficiency ratings mean.

In general, energy rating (ER) is the most essential figure that helps in determining the energy efficiency rating of a window. Nonetheless, this figure depends on other factors that are explained below:

  • U-Value/U-Factor

Other known as U-value, U-factor measures the ability of a window to resist heat loss. The lower the U-factor of a window, the better its ability to prevent heat from escaping your room. Therefore, if you are looking for a window with exceptional insulation, its U-factor must be lower.

U-value is particularly crucial if you stay in a region with extreme colder months. It will save you lots of money on energy bills as your heating system will not be operated at a high level.

It should be noted that there is also R-value which is associated with U-value. R-value determines the ability of a window to retain heat. If a window is energy-efficient, it will have a high R-value and low U-factor.

  • Solar Heat Gain Coefficient (SHGC)

Generally, a window allows some amount of solar radiation to be transmitted into a house. Solar heat gain coefficient is the factor that measures the specific amount of radiation transmitted through this means. SHGC is usually measured as a number between 0 and 1. A lower number shows that less solar heat is transmitted through the window.

When it comes to SHGC, glass type will determine its specific value. Because of its additional protective coating, Low-E glass is popular for its ability to lower solar heat gain. Notably, both lower and higher SHGC can be useful based on the level of surrounding shade, climate, as well as orientation of the room.

  • Air Leakage

Air leakage determines the amount of air that goes through the cracks that a window has. A window with a higher air leakage rate will experience lots of heat gain and loss. Resultantly, the energy efficiency and interior comfort of a building with such a window will be significantly lower than they should be.

In some cases, poor installation is responsible for air leakage.

  • Visible Transmittance

This is the amount of visible light that a window allows to come into the interior part of a building. Visible transmittance is usually indicated as a percentage. A lower percentage shows that the window allows less light to get into the building while a higher percentage means that lots of light will come into the house. Notably, the higher the percentage of visible transmittance, the more comfortable the house will be.

While it is easy to understand the energy efficiency ratings of a window, you should note that there is no one-size-fits-all standard for them. This is because climate zone is the major factor for determining the standard for energy ratings. So, check energy rating standards in your zone before choosing windows and doors for your home.