The window to a zero energy home, Richmond, VA style...

When it came to window choices, there was a lot to consider, because as you increase the tightness and the insulation level of your home, the glazing makes a greater impact on energy usage. And our particular home design has a lot of windows! Looking to the Efficient Windows Collaborative (EWC) for guidance, the 2009 Energy Star standards for Virginia suggested windows with a U-factor (the rate of non-solar heat loss or gain
through a whole window assembly) of .40 and a SHGC (the Solar Heat Gain Coefficient is the fraction of incident solar radiation admitted through a window) of <.40. But our EarthCraft builder reminded us that the EnergyStar standards were going to be tightened starting in 2010, so we set out in search of better windows. The new Virginia Energy Star standards are a U-factor of .32 and a SHGC of <.40, but few suppliers had windows available reflecting the new values yet. After some creative searching, Mark found us PlyGem MW Pro Series windows with a U-factor of .29 and SHGC of .25 for only $400 more than 2009 rated windows. These are vinyl clad PVC construction, 20 year, double pane, argon gas-filled, low-E glass windows with a Warm Edge technology ( the Warm Edge glass spacer system reduces thermal transfer around the glass perimeter by utilizing a unique U-shaped channel to separate glass panes and interrupt the natural flow of heat to cold). Hopefully the added insulation they provide will reduce the load on our geothermal HVAC system. We are hoping that the lower SHGC will work well, as we have a lot of southeast facing glazing on the back of our house, which because of solar sighting, has little shade in the summer, making excess heat gain in hot muggy Virginia a potential problem. Oh, and that door you see there, that is the Therma-Tru Classic-Craft® Mahogany(waiting to be stained) fiberglass front door, which is also EnergyStar rated. Have to have all the portals covered...