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ENERGY STAR Policy For Attached Housing

Attached housing is defined as one dwelling that shares a common floor, ceiling, or wall with one or more adjacent dwellings. Common examples include condominiums, apartments, townhomes, and duplexes.

This sector of housing has certain characteristics that make it unique with consideration to energy policy. First, the common surfaces are generally adiabatic, making the homes more efficient than an equivalent detached home. Second, due to fewer windows, smaller conditioned floor areas, and the common surfaces, HVAC loads are typically small, making high-efficiency HVAC systems less cost-effective.

To address these unique characteristics, EPA has developed the following modified performance and prescriptive path for qualifying such homes with the ENERGY STAR mark. For more information about multifamily housing, please review EPA's policy on qualifying units in multifamily buildings.

ENERGY STAR Attached Housing Performance Requirements:

To qualify an attached house in the performance path, the house must meet the minimum requirements specified in the ENERGY STAR New Homes National Performance Path Requirements, with the one following exception — all dwellings on the same level and within the same structure may be qualified if the following conditions are met:

  1. The dwelling with the highest percentage of exposed wall area meets the required HERS index, and;
  2. The other dwellings have equal or lesser window area to floor area ratio, and;
  3. The other dwellings use the same, or more stringent, energy efficiency features as the dwelling identified in item 1, and;
  4. All dwellings are verified in accordance with EPA verification requirements for ENERGY STAR Qualified Homes, and;
  5. The entire structure falls within the scope of the residential code where it is built. Most residential building codes apply to structures up to threes stories tall. However, depending on the jurisdiction where the building is constructed, apartment or condominium buildings up to five stories tall may be constructed using the residential building code and be eligible to use this policy.

For example, for a row of five townhomes, all five townhomes shall meet the ENERGY STAR attached housing performance requirements if the townhome with the highest percentage of exposed wall area meets the required HERS index; the other four townhomes have equal or lesser window area to floor area ratio; the other four townhomes use the same, or more stringent, energy efficiency features as the townhome with the highest percentage of exposed wall area; all townhomes are verified and field-tested in accordance EPA verification requirements.

As another example, for a three-story building with condominiums, all condos on the same level shall meet the ENERGY STAR attached housing performance requirements if the condo with the highest percentage of exposed wall area on that level meets the required HERS index; the other condos on that level have equal or lesser window area to floor area ratio; the other condos on that level use the same, or more stringent, energy efficiency features as the condo with the highest percentage of exposed wall area; all condos are verified and field-tested in accordance EPA verification requirements. Note that the condo with the highest percentage of exposed wall area on the top level cannot be used to qualify condos on the first or second level and vice versa.

ENERGY STAR Attached Housing Prescriptive Requirements:

To qualify an attached house using the prescriptive path, the house must meet the minimum requirements as specified in the ENERGY STAR Qualified Attached Homes National Builder Option Package (BOP) PDF (135KB). This BOP is very similar to the one developed for detached housing, but allows builders to select additional energy efficiency features in exchange for not installing a high-efficiency HVAC system.

This policy is effective as of January 1, 2007. The exception noted in the performance path will be revisited if modifications to the HERS guidelines render it unnecessary.