Wednesday, May 14, 2008

Energy Efficiency and Hurricane Windows – Part I

Energy efficiency is a "hot" topic today. I will not try to explain everything about energy efficiency on hurricane windows and doors because it will be unrealistic. However, I would like to quickly present to you to the key facts to know about energy efficiency and glazing.

First, we need to briefly define a few terms, including SHGC, U-Factor and VT, which are important to understand energy ratings.

SHGC stands for Solar Heat Gain Coefficient, a number between 0 and 1 that provides a measure of how well a product blocks heat from the sun. The lower the SHGC, the better a specific product is at blocking unwanted heat gain. As an illustration, a window that features a 0.60 SHGC means that it allows 60% of the available solar heat to come through. In warm weather, a low SHGC is desirable. As a point of reference, the National Fenestration Rating Council (NFRC) recommends installing windows and doors with a combine SHGC of 0.40 or lower. In the past, there were not hurricane windows in the market that could match that recommendation. Today, new lines of hurricane windows exceed these requirements.

U-Factor is another important factor for hurricane windows and doors. The U-Factor measures how well a product prevents heat from escaping a property. U-Factor ratings, which range from 0.20 to 1.20, are particularly important in cold weather during winter heating season. The lower the U-Factor, the better a window or door is at keeping heat inside the property.

VT stands for visible transmittance, an indicator of how much light comes through a hurricane window or hurricane door. The higher the VT, which is expressed as a number between 0 and 1, the higher the potential for day lighting.

On the following issue, we will continue expanding our conversation about energy efficient hurricane windows and key indicators.

Visit Astor Impact Windows for information about purchasing impact windows and doors. You can also email us at or call us at 1-800-573-1780.


  1. I am currently collecting bids for impact resistant windows for 2 homes in Volusia County. Although I have asked each contractor for the same information, I sometimes find myself comparing apples to oranges and it is a bit confusing. Some contractors have a "just leave the decisions to us" attitude, which is not helpful. Since I am footing the bill, I want final say in the decisions!

    I've read all your blogs on this site and found them to be very helpful & informative. Thank you.

  2. Thank you for giving us your feedback. I am glad that the information has been helpful.