This CIR is in reference to ventilation design for a four-story, 238-unit residential building in Massachusetts. The building in question has approximately 30 distinct unit types-from studios to three-bedroom units. The focus of this CIR is on the LEED requirements for ventilation within the residential units. The proposed ventilation of the building uses a combination of mechanical and natural ventilation as described per the following: The total building conditioned area of the building is 263,256 square feet. Approximately 10 percent of the building area is common space; this public space is mechanically ventilated per the requirements of ASHRAE 62.1-2004. Public hallways are supplied with 100% outdoor air from constant volume roof top air handlers. Other common areas including Library, Exercise Room, Community Room, and Leasing Office spaces have individual air handling units. The Exercise Room, Community Room, and Leasing Office have outdoor air supply. The Library is naturally ventilated with all spaces less than 8 meters from operable windows. The outdoor air to the public spaces is filtered, heated and cooled as required to maintain the temperature at a preset level. The living units are comprised of various combinations of the following spaces: Kitchens, Unit Entryways, Unit Corridors, Dining Areas, Living Rooms, Dens, Bedrooms, Closets, Mechanical Rooms, and Bathrooms. Heating and cooling for the units is provided by a recirculating fan coil unit. Every unit Kitchen is equipped with an occupant-controlled (intermittent) 100 cubic feet per minute exhaust hood and every unit Bathroom has an occupant-controlled (intermittent) 60 cubic feet per minute exhaust fan; both of these are ducted directly to the exterior. Based on the EQ prerequisite 1 CIRs (Rulings dated 5/15/2007 and 9/24/2007) the "calculations to demonstrate compliance with ASHRAE Standard 62.1-2004 for mechanically ventilated spaces in residential projects, will include showing air changes per hour and/or cfm per person outdoor air ventilation rates (for living areas), and cfm exhaust (for bathrooms and kitchens), according to the requirements of Appendix E." As per the requirements of ASHRAE 62.1-2004, Appendix E, Table E-2, the "living areas" volume is defined as all area within the conditioned space. Many of the residential units utilize an open plan that joins Living Room, Dining Area, Kitchen, Unit Corridor, and Unit Entryway into a single conditioned volume. In some instances a small portion of the living area volume is greater than the 8 meter distance from window wall to be considered naturally ventilated; this area is associated with the functions of Kitchen, Unit Entryway and Corridor use. Question 1a: As per ASHRAE 62.1-2004, Appendix E, Table E-2, Outdoor Air Requirements for Ventilation of Residential Facilities, Footnote C; the ventilation requirements for Kitchens and Bathrooms may utilize supply air from adjacent living areas to compensate for exhaust air. Please confirm that no direct outdoor air supply is required for Kitchens and Bathrooms. Question 1b: For living units with the Kitchen entirely within the 8 meter distance from window wall-and meeting the requirements of natural ventilation as defined in ASHRAE 62.1-2004-is a kitchen exhaust required? Question 2a: What, if any, outdoor air supply is required for Unit Entryways and Unit Corridors? Can the entry and corridor spaces be excluded from being considered "occupiable spaces" since there are not large enough to be furnished with desks, chairs, etc. and are only occupied for short periods of time? Question 2b: If outdoor ventilation air is required to the Unit Entryway, but not the Kitchen-in instances where the Unit Entryway and Kitchen are greater than 8 meters from the window wall and the Unit Entryway is substantially open to the Kitchen-can we consider the Unit Entryway to be a part of the Kitchen and thus the requirements of ASHRAE 62.1-2004 are met through the inclusion of the required exhaust fan? Question 2c: If the option described in Question 2b is not acceptable, then is mechanical ventilation required for the Unit Entryway? If so, what is the calculation method for this outdoor air supply? Can we deduct the volume that is within 8 meters of the window wall as naturally ventilated area and only provide ventilation air for the remainder of the Unit Entryway volume that is beyond 8 meters? Question 2d: Based on the acceptable ventilation calculation method defined in the response to Question 2c, can the ventilation air be transferred from the positively pressurized public hallway that receives 100 percent outdoor air? Question 3: For residential units with Dens, internal rooms designated for home office use, mechanical ventilation will be provided per the requirements of ASHRAE 62.1-2004. The outdoor air in these spaces is ducted directly to the Dens from the same equipment that supplies the public hallway air distribution system. Please confirm that this is acceptable. Question 4: For every unit type that has a Bedroom, the entire floor area of these rooms is within 25 feet of a window wall with an operable window opening dimension greater than 4 percent of the floor area of the spaces it serves. Based on these data we believe that these rooms are in compliance with the LEED requirements for natural ventilation, please confirm. Question 5: Where mechanical ventilation is required for outdoor air supply, will the following system be in compliance? Adding an appropriately sized fresh air intake supply to the current re-circulating fan coil unit where the fan coil unit is designed to be resident-controlled, using a thermostat that includes settings for (1) automatic operation based on actual temperature in the space versus the resident-controlled set point, In "automatic mode" the fan will start as soon as the thermostat calls for cooling or heating. Since the fan operation will be intermittent, outside air supply to the unit will also be intermittent. (2) fan-only operation In "fan only mode" outside air supply and re-circulation will be continuous. Hot water coils or DX system will be activated only when the thermostat detects that space temperature drop below or rises above the thermostat setting. (3) an off-position. In addition, a resident controlled damper on the outdoor air intake will be provided. This damper is provided to allow for occupant control over potential drafts from outside air intake, to control over additional utility cost associated conditioning outdoor air, and to prevent the coil from freezing when the system is in the off position as outside air penetrates the system. Question 6: The ASHRAE 62.1-2004 standard does not seem to address outdoor air ventilation supply requirements for public stair towers (including egress stairs). Please confirm that there are no supply air requirements for stairs as per LEED EQ prerequisite 1.
The applicant submitted a multi-question CIR requesting clarification on a number of items that relate to EQ Prerequisite 1, Minimum IAQ Performance, and ASHRAE Standard 62.1-2004. Please note that the intent of a CIR is to provide clarifications about the LEED Rating System credit requirements as they pertain to a specific project scenario, rather than provide interpretations of the referenced standard. To request interpretations for approved ASHRAE Standards the applicant must request those through ASHRAE at http://www.ashrae.org/publications/detail/14778. Also please note that, as some of the questions in this CIR border on design assistance, this ruling will only address questions that are within the purview of the USGBC to respond to. Answer 1a: Correct, as long as the total ACH for all living areas within the Unit (including Kitchen and Bathrooms) meets the requirements of table E-2 and section 5.8. Answer 1b: Yes, a direct exhaust is required to satisfy section 5.8. Answer 2a: No. Unit Entryways and Unit Corridors need to meet the ACH requirements of table E-1 at 0.35 ACH. Answer 2b: See response to 2a Answer 2c: See response to 2a Answer 2d: See response to 2a. The transfer air from a pressurized public hallway is not intended to meet OA requirements, rather only odor and smoke control. Answer 3: Yes, this approach is acceptable as long as it meets all the required City/ County/ State /Federal Fire Life Safety Rules. Answer 4: This approach may be acceptable as long as the applicant can demonstrate compliance with section 5.1 of ASHRAE 62.1-2004. Answer 5: No, the proposed system is not acceptable. The units need to be provided with 0.35 ACH continuously, if they are mechanically ventilated. Answer 6: Outdoor air ventilation supply requirements for public stair towers (including egress stairs) are typically governed by City/ County/ State /Federal Fire Life Safety Rules and do not fall under the purview of ASHRAE 62.1-2004.
Related Addenda (Corrections & Interpretations)