Our project is a hospital addition in Sarnia, Ontario. The minimum ventilation requirements for hospitals are defined in the mandatory Canadian Standard (CSA Standard CAN/CSA-Z317.2-01. Special requirements for heating, ventilation, and air conditioning (HVAC) systems in health care facilities.) According to ASHRAE 62 (referenced in ASHRAE 90.1), "Special requirements or codes... may determine minimum ventilation rates," which we understand indicates we should follow the CSA standard for our Budget case. Our interpretation request relates to our Design case ventilation rates. According to the ASHRAE 90.1 User\'s Guide, "The minimum ventilation rates designed for the proposed building... must also be modeled in the budget building design... and ventilation is energy neutral as far as trade-offs are concerned." The LEED Reference Guide and ASHRAE\'s User\'s Guide both state that, "Outdoor air ventilation can be a major contributor to building energy consumption, but it is not considered an opportunity for energy savings under the Standard." It is our understanding that the intent of these stipulations is to avoid accruing energy savings by sacrificing fresh air and therefore indoor air quality. In a hospital designed to meet our CSA standard, moving and conditioning ventilation air accounts for more than half of the energy consumption. We have developed a strategy that delivers increased fresh air at higher efficiencies than a conventional design and wish to confirm that this opportunity for energy savings associated with the building ventilation system meets the intent of ASHRAE 90.1 and LEED. For each hospital room type, the CSA standard specifies a minimum total air change rate and a minimum fresh air component. For example, a typical patient room is to receive 6ACH total, 2ACH of which must be fresh. Our strategy, which has been reviewed by the chair of the CSA technical committee, is to provide lower total volumes of air that is 100% fresh and deliver this air with a high level of ventilation effectiveness (0.9). In the patient room example above, the room will receive 4ACH, 100% fresh. This strategy allows us to: - effectively utilize heat recovery - reduce duct and fan sizes - reduce fan energy - improve infection control with recirculated air eliminated As a result, we are providing larger volumes of fresh air to the building at reduced capital and operating costs. We propose using the CSA standard ventilation requirements for minimum ventilation and outdoor air requirements for our Budget case. The Budget case will also include heat recovery where required by ASHRAE 90.1 Section 6.3.6.1. For our Design case, we propose using our increased outside air volumes and increased heat recovery. By saving energy while increasing fresh air supply we find that this approach is not in conflict with the intent of this credit. Please advise us whether this interpretation is acceptable.
The use of the CSA standard\'s hospital ventilation requirements for the budget building is acceptable. ASHRAE 62 defers to special requirements, and CSA-Z317.2-01 has been adopted by the Standards Council of Canada. The Energy Cost Budget Method in ASHRAE 90.1 and the LEED Energy Modeling Protocol do not allow the modification of schedules or ventilation rates between the proposed and budget buildings. The models must be run with the same ventilation rates and schedules. The proposed building energy model should be modeled with the code compliant ventilation rates. Energy cost savings as described above must be determined using the Energy Cost Budget Method, 11.5 Exceptional Calculation Methods of ASHRAE 90.1. Be sure to carefully explain the methodology used to determine energy savings for these measures as a part of the submission for LEED Certification. The proposed HVAC design modifications necessary to model the changes are fairly extensive. A revised proposed building will have to be created with changes to the amount of outside air, total amount of air, fan sizes, and the addition of heat recovery. It may be necessary to also modify the budget building if ASHRAE 90.1 would require additional heat recovery due to the modified system design. The resulting savings are then subtracted from the DEC modeling results as explained in previous CIRs (1/20/02, 6/27/01).