Energy Efficient Windows

Minneapolis & St. Paul Window Installers

The windows of today are the end results of better science, better materials, and new manufacturing processes that make window units perform very well. Those building new structures or wanting to replace the inefficient windows that have been costing them a great deal on their heating and cooling bills have a lot of information they need to sift through.

The Parts Of A Window

A window has a number of components with three main parts: The sash, the glazing, and the spacer system. When measuring a window’s performance, it is important to look at such factors as how it transmits light and conducts heat. To know what you are getting, you can review the following:

1. Find an Energy Star label – This label confirms that the window’s energy efficiency is based on its impact on heat loss and gain in cold weather and heat gain in warm weather. The labels are specific to the four climate zones in the U.S. Each zone has different types of weather. Some are climates that require mostly cooling and others are climates that require mostly heating.
2. Look at the National Fenestration Ratings Council Label – This independent organization certifies window energy performance. The label lists a number of performance rankings so that specific needs can be met. Your Minneapolis window installer can help you understand what the label means. It includes the following information:
   1. U-factor – How the window conducts non-solar heat flow. The lower the value (between .20 and 1.20) means the window is more efficient.
   2. SHGC – The Solar Heat Gain Coefficient measures how much solar heat gain is allowed through the window and released into the home. The lower the number, the less solar heat is transmitted.
   3. VT – This measures the visible light that comes through the window. If you want a lot of light, then the higher number (0-1) is best.
   4. LSG – Light-to-solar gain is not always available on a label, but it is the ratio between VT and SHGC. It measures the relative efficiency of different glazing or glass types when transmitting daylight while also blocking heat gains. The higher the number, the more light transmission there is without adding to the heat gain.
   5. Condensation Resistance – This rating is also optional and measures the ability of a window to resist condensation on the inside. The number is between 0 and 100 and the higher numbers tend to better resist condensation.
   6. Air Leakage – This is the third optional rating. The lower the number, the less air will pass through.

These ratings are very important so you can see how efficient windows are. In Minnesota, all kinds of weather are experienced throughout the course of a year and that means needing windows that can handle the impacts of heat and cold. Because the cold can be rather intense in the winter, it is imperative that heat stays in or heating bills can skyrocket. The two most important measurements that you are going to look at are the U-factor and solar heat gain coefficient. By paying close attention to these numbers, you can choose a window that works for you and your budget.