Choosing your windows

Windows play a big part in any design project. You want to let views and light in but keep heat gain and loss under control. The newer low-e products use a very thin film of metal on one of the glass surfaces to keep the long wave radiation from passing through. From what I understand, windows designed for cooler climates use the film to keep the heat inside the structure, and windows designed for the south use the film to keep the heat out. Make sure that you get the windows specified for your area of the country. In my project, near Columbia, South Carolina, I used the Anderson 200 series, and here is one of the stickers from the window. There are three numbers on the sticker. The top left one is the U factor and for the southeast it should be a number lower than .40. Mine are.30. Next, the top right number is the SGHF or solar heat gain coefficient, and it should be .40 or less. Here we have a .34. Last number on the bottom is for the Visible Transmittance and it should be as high as you can get. Look for something over .50. All windows with the energy star label should get you the numbers that you are looking for. And as for numbers for your region of the country there is a great website,

http://www.efficientwindows.org/energystar.cfm that has maps and correct values for different regions of the country.