Windows

Intent

Maximize the energy performance of windows.

Requirements

Prerequisites

4.1 Good windows. Meet all of the following requirements:

1. Design and install windows and glass doors that have NFRC ratings that meet or exceed the window requirements of the ENERGY STAR for Homes national Builder Option Package (Table 1).
2. The ratio of skylight glazing to conditioned floor area may not exceed 3%.3 All skylights must meet the ENERGY STAR performance requirements for skylights, but are exempt from the requirements in Table 1.
3. Homes in the Northern or North/Central climate zones that have a total window-to-floor area ratio (WFA) of 18% or more must meet a more stringent U-factor requirement (also applicable to EA 4.2 and 4.3): U-factor = [0.18 / WFA] * [U-factor from Table 1].
4. Homes in the Southern or South/Central climate zones that have a total window-to-floor area ratio (WFA) of 18% or more must meet a more stringent solar heat gain coefficient (SHGC) requirement (also applicable to EA 4.2 and 4.3): SHGC = [0.18 / WFA] * [SHGC from Table 1].

Note: Up to 0.75% of the window-to-floor area may be used for decorative glass or skylight area that does not meet the U-factor and SHGC requirements above.

Credits

4.2 Enhanced windows (2 points). Design and install windows and glass doors that have NFRC ratings that exceed the window requirements in the ENERGY STAR for Homes national Builder Option Package (Table 1).

OR

4.3 Exceptional windows (3 points). Design and install windows and glass doors that have NFRC ratings that substantially exceed the window requirements in the ENERGY STAR for Homes national Builder Option Package (Table 1).

Table 1 ENERGY STAR Requirements for Windows and Glass Doors

Figure 1 Zones for Window Specifications