Some residential buildings have areas of other occupancies, such as retail or office, in the same building. An example of this might be a three-story building with two floors of apartments above ground-floor shops and offices. The first thing to consider when analyzing the energy compliance of a mixed occupancy building is the type and area of each occupancy type.
Depending on the area of the different occupancies, you may be able to demonstrate energy compliance as if the whole building is residential for the space-conditioning and water-heating requirements. This is allowed if the residential occupancy accounts for at least 80 percent of the conditioned floor area of the building (or permitted space). Lighting compliance must be based on the requirements for each actual occupancy type.
Note: Mandatory measures apply separately to each occupancy type regardless of the compliance approach used. The residential envelope is subject to §150.0(a), (b), (c) and (d), while nonresidential envelope is subject to §120.7(a), (b) and (c).
For example, if complying under the mixed-occupancy exception, both residential and nonresidential documentation for mandatory measures must be submitted with other compliance documentation.
If the building design does not fit the criteria described above for a dominant occupancy, then the low-rise residential occupancy type must be shown to comply by itself. The remaining occupancy types must be shown to comply separately either by independent compliance for each occupancy or (for the nonresidential performance approach) by combining nonresidential occupancies in accordance with the rules of the Nonresidential ACM Reference 'Manual. This may be done by using any of the approved prescriptive or performance methods available for each occupancy type. As a result, documentation for each occupancy type must also be considered separately, and a certificate of compliance must be submitted for each occupancy type. Mixed high-rise and low-rise residential occupancies will not occur in the same building because the designation applies to the building.