It is acceptable to create a HERS Index for the worst-case home among multiple attached single-family homes. The ENERGY STAR for Homes guidelines must be followed, including the worst-case among the units for exposed wall area, window-to-floor area ratio. Performance tests (e.g. blower door test, duct blaster test) must be completed on every home (except where sampling is applicable), and the HERS Index must include the worst-case performance test results from among all homes included in the batch.