Background 1: We are designing a mixed use hotel / apartment building in the Philadelphia area. We are investigating the ventilation strategy required to comply with LEED EQ p1 for the living areas in hotel / apartment units. We understand that the IMC 2003 is the applicable mechanical code. We are proposing the following ventilation strategy: natural ventilation through operable windows for hotel / apartment living areas and bedrooms with recirculating systems (PTAC units) for space conditioning; mechanical ventilation via exhaust fans and transfer air for bathrooms and kitchens in hotel / apartment units (see question 2); and central mechanical ventilating units serving corridor / core areas. Question 1: Under this strategy we believe that the living areas and bedrooms would qualify as "natural ventilation" not "mixed mode ventilation" since the PTAC units are recirculating only and do not draw any outside air. Both the International Mechanical Code and ASHRAE 61.1-2004 allow recirculation-only mechanical systems to be installed in spaces where ventilation is provided by natural means. Since the living areas will comply with the natural ventilation requirements, they would not require the mechanical introduction of outside air as is necessary for "mixed mode ventilation." The corridor / core areas would be classified as "mechanically ventilated." We would like verification that including PTAC units in a space with operable windows does not change its classification from "naturally ventilated" to "mixed mode." Background 2: ASHRAE 62.1-2004, Appendix E, indicates that ventilation in residential living areas "is normally satisfied by infiltration and natural ventilation." It also indicates that "the air exhausted from kitchens, baths, and toilet rooms may utilize air supplied through adjacent living areas to compensate for the air exhausted." Section 6.2.8 indicates that "exhaust makeup air may be any combination of supply air, recirculated air, or transfer air." Question 2: We are proposing that the makeup air for kitchen and bathroom exhaust be drawn from corridor ventilation by undercutting the doors to hotel / apartment units. The air would be transferred from the corridor through the living areas to the toilet and kitchen areas. In this scenario, we believe the living / bedroom areas would comply with natural ventilation requirements and be considered "naturally ventilated" while the corridors / kitchens / bathrooms would comply with mechanical ventilation requirements and be considered "mechanically ventilated." We wouldn\'t have any spaces that are considered "mixed mode ventilation." Is this classification accurate based on LEED guidelines? We would like verification that transferring air through a space with operable windows does not change its classification from "naturally ventilated" to "mixed mode." Background 3: ASHRAE 62.1-2004, Appendix E, indicates that ventilation in residential living areas "is normally satisfied by infiltration and natural ventilation." It also indicates that "the air exhausted from kitchens, baths, and toilet rooms may utilize air supplied through adjacent living areas to compensate for the air exhausted." Section 6.2.8 indicates that "exhaust makeup air may be any combination of outdoor air, recirculated air, or transfer air." Question 3: It appears that the applicable code (IMC 2003) and ASHRAE 62.1-2004 Appendix E and section 6.2.8 allow makeup air for toilet and kitchen exhaust to come from infiltration ("outdoor air"). Is this acceptable under LEED EQ p1?
The CIR has posed three follow on questions regarding residential compliance under the referenced ASHRAE standard. The first question asks if living spaces served by operable windows and recirculation only air conditioning units qualify as "naturally ventilated" under the referenced standard. If the living areas and bedroom spaces meet the requirements for location and size of openings for naturally ventilated spaces, outlined under section 5.1.1 of ASHRAE 62.1-2004, these spaces are considered naturally ventilated. The second question is asking whether naturally ventilated spaces with air transfer to mechanically ventilated spaces are considered mixed mode. These space will be considered natural ventilated, if they meet the criteria outlined in section 5.1 of ASHRAE 62.1-2004. While this approach may meet the credit intent, the design team should consider negative factors such as noise transfer and fire ratings. The best overall design approach will take into account these factors as well as climate and local codes for the sake of the building occupants. The third question is asking if infiltration as a source of makeup air for toilet and kitchen exhaust, acceptable under ASHRAE 62.1-2004 Appendix E, is acceptable under the requirements of EQp1. The EQp1 language asks project teams to choose the more stringent requirements of the local applicable code and ASHRAE 62.1-2004 Ventilation Rate Procedure. If ASHRAE 62.1-2004 Ventilation Rate Procedure is the more stringent of the two, then the project team can refer to Appendix E for Residential Facilities and Healthcare facilities. Appendix E is referred to in Note 6 of General Notes for Table 6-1, under section 6.2 Ventilation Rate Procedure in ASHRAE 61.1-2004 and allows projects to use air supplied through adjacent living areas to compensate for the air exhausted.