Code Requirements

Beginning November 1, 2016, the 2015 International Energy Conservation Code (IECC) went into effect for all construction other than single-family homes. And on September 1, 2016, the 2015 International Residential Code went into effect for one- and two-family homes and low-rise multifamily buildings. The 2015 IECC requirements are presented in the table below or click here for a two page PDF guide to window requirements under the 2015 IECC.

Climate Zones/Packages for Texas IECC Code Compliance

2015 IECC Solar Heat Gain Coefficient (SHGC) and U-factor Requirements in Texas

Solar Heat Gain Coefficient (SHGC)

Texas currently requires a maximum 0.25 solar heat gain coefficient (SHGC) for windows, glazed doors and skylights in all construction in climate zones 2 and 3, and a 0.40 SHGC in climate zone 4. This is true of both new construction and remodeling projects. Builders can incorporate future energy requirements in today’s buildings, providing a good head start on saving homeowners money in energy bills.


U-factor requirements also improved significantly in the 2015 IECC. While low U-factor windows are important in all climate zones, low U-factors are particularly important where buildings are heated more often (as in climate zones 3-4).

Air Leakage

The code requires that residential 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.

Energy Rating Index (ERI) Compliance Path

The 2015 IECC code incorporates a new option for achieving code compliance: the Energy Rating Index or ERI Path. The ERI path provides a wide range of performance options to demonstrate compliance. The ERI scale ranges from 0 (representing zero net energy) and 100 (representing a home built to 2006 IECC). Each point on the ERI scale represents a 1% change in the relative energy efficiency of the building.

In the ERI compliance path, builders may use certain "trade-offs" to achieve the required level of efficiency for code compliance. For example, builders may use the efficiency values from the 2009 IECC for fenestration as long as they make up the difference in other areas such as HVAC, water heating, and installed appliances.

The table below shows the maximum ERI Scores for Texas in each climate zone. The Texas Legislature has established a gradual improvement in the ERI Score over the next 6 years.

Climate Zone Sept. 1, 2016-2019 Sept. 1, 2019-2022 Sept. 1, 2022-2025
Zone 4 69 67 63
Zone 3 65 63 59
Zone 2 65 63 59

For more information on the ERI Compliance Path, visit the Building Energy Codes Program page on the U.S. Department of Energy (DOE) website.