519.1 All occupied conditioned spaces in the Prototype, Reference and Proposed Design Buildings in all climates shall be simulated as being both heated and cooled. The assumptions in this subsection are prescribed assumptions. If the Proposed Design does not include equipment for cooling or heating, the Design Energy Consumption shall be determined by the specifications for calculating the Energy Cost Budget as described in Table 517.4.1 HVAC System Description for Prototype and Reference Buildings. Exceptions to 519.1 are as follows:

519.1.1 If a building is to be provided with only heating or cooling, both the Prototype or Reference Building and the Proposed Design shall be simulated, using the same assumptions. Such an assumption cannot be made unless the building interior temperature meets the comfort criteria of RS-2 (incorporated by reference, see § 434.701) at least 98% of the occupied hours during the year.

519.1.2 If warehouses are not intended to be mechanically cooled, both the Energy Cost Budget and Design Energy Consumption shall be modeled assuming no mechanical cooling; and

519.1.3 In climates where winter design temperature (97.5% occurrence) is greater than 59 °F, space heating need not be modeled.

519.2 Space temperature controls for the Prototype or Reference Building, except multi-family high-rise residential buildings, shall be set at 70 °F for space heating and 75 °F for space cooling with a deadband per subsection 403.2.6.3. The system shut off during off-hours shall be according to the schedule in Table 515.2, except that the heating system shall cycle on if any space should drop below the night setback setting of 55 °F. There shall be no similar setpoint during the cooling season. Lesser deadband ranges may be used in calculating the Design Energy Consumption. Exceptions to 519.2 are as follows:

(a) Setback shall not be modeled in determining either the Energy Cost Budget or Design Energy Cost if setback is not realistic for the Proposed Design, such as 24-hour/day operations. Health facilities need not have night setback during the heating season; and

(b) Hotel/motels and multi-family high-rise residential buildings shall have a night setback temperature of 60 °F from 11:00 p.m. to 6:00 a.m. during the heating season; and

(c) If deadband controls are not to be installed, the Design Energy Cost shall be calculated with both heating and cooling thermostat setpoints set to the same value between 70 °F and 75 °F inclusive, assumed to be constant for the year.

519.2.1 For multi-family buildings, the thermostat schedule for the dwelling units shall be as in Table 519.1.2, Thermostat Settings for Multi-Family High-rise Buildings. The Prototype Building shall use the single zone schedule. The Proposed Design shall use the two-zone schedule only if zonal thermostatic controls are provided. For Proposed Designs that use heat pumps employing supplementary heat, the controls used to switch on the auxiliary heat source during morning warm-up periods shall be simulated accurately. The thermostat assumptions for multi-family high-rise buildings are prescribed assumptions.

519.3 When providing for outdoor air ventilation in calculating the Energy Cost Budget, controls shall be assumed to close the outside air intake to reduce the flow of outside air to 0 cfm during setback and unoccupied periods. Ventilation using inside air may still be required to maintain scheduled setback temperature. Outside air ventilation, during occupied periods, shall be as required by RS-41, (incorporated by reference, see § 434.701) or the Proposed Design, whichever is greater.

519.4 If humidification is to be used in the Proposed Design, the same level of humidification and system type shall be used in the Prototype or Reference Building. If dehumidification requires subcooling of supply air, then reheat for the Prototype or Reference Building shall be from recovered waste heat such as condenser waste heat.