6. Use Highly Insulated Windows and Doors
- Use insulated fiberglass doors with tight air seals.
Aim for a 14% window-to-floor area (WFA) for the whole house, with about 50% of the windows on the south side, where the common living areas should be located. Depending on local circumstances however, more windows on the south side may not always be cost effective. These are all things that should be decided in the design phase. - Use triple-pane windows with approximately 0.2 U-value, such as Harvey Tribute, Thermotech, Atrium Northwest, Cascade, Solar View, Intus, Milgard or Alpen. Some double pane windows such as Milguard’s I-89 StyleLine, are achieving u-values close to 0.20 and should be considered.
Fixed windows and casement windows with multi-point locking hardware are more energy efficient than sliders and single or double hung windows, both of which have leakage issues. - Look for windows that have the smallest frame profile because the frame has a higher thermal transmission than triple pane glazing. It is more energy efficient to use fewer larger windows with the same glazing area as more numerous smaller windows, because larger windows have a higher glass to frame ratio.
- Depending on energy modeling, current pricing and advances in technology, shop for the most cost-effective, energy efficient windows. Less expensive triple pane windows may be the most cost-effective in many applications. In some climates and applications, energy efficient double pain windows may be sufficient.
Twelve Steps to Affordable Zero Energy Home Construction