Code Requirements
In 2001 more stringent residential code requirements went into effect with the adoption of International Residential Code (IRC) as the statewide residential building energy code. The IRC also incorporates the entire International Energy Conservation Code (IECC) as an alternative energy code for homes with glazing areas of 15% and below.
In order to comply with these requirements windows must have U-factors, SHGCs and air leakage ratings that meet or exceed the minimum requirements. These requirements vary according to the climate zone, or package, that applies to the particular county in question, the percentage of window area, and whether it is for a new or existing building:
| Different Climate Zones/Packages for Texas IECC Code Compliance | |
| New Building | Existing Building |
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Solar Heat Gain Coefficient (SHGC)
In general, the residential building energy code in Texas specifies a maximum 0.40 solar heat gain coefficient (SHGC) for fenestration products - windows, glazed doors and skylights. This is true of both new construction and remodeling projects. However, there are several counties in the Panhandle region (specifically zones C&D or G&H shown above) where this requirement is not applicable. See the table below for the specific requirements.
U-factor
Upper limits on U-factor range from 0.37 (zone H; 25% window area) to 0.90 (zone A; 15% window area) in new buildings and from 0.40 (zone D) to 0.75 (zone A) in existing buildings. In general, the U-factor requirements are stricter (lower U-factor) in colder climates like the Panhandle region where heating requirements are greater. See the table below for the specific requirements.
IECC 2000/2001 Solar Heat Gain Coefficient (SHGC) and U-factor Requirements in Texas
Air Leakage
The code requires that windows be labeled to show that they meet the IECC's air infiltration requirements of less than or equal to 0.30 cfm per square foot of window area.
For Background information on Texas energy codes or a Step-byStep Guide on meeting code requirements in Texas, visit the following:
