ID#1940 made on
EQp1 - Outdoor air introduction and exhaust systems
LEED O+M: Existing Buildings
Our building is a 36 floor, 750,000 gross square foot (GSF) high rise office building in a major metropolitan city. The building has four space types: 1) retail 2) lobby 3) commercial office, and 4) s...
Our building is a 36 floor, 750,000 gross square foot (GSF) high rise office building in a major metropolitan city. The building has four space types: 1) retail 2) lobby 3) commercial office, and 4) server room. The retail tenants are located on the ground floor and are served by dedicated HVAC systems. The commercial office spaces are located on floors 2 through 36 and are served by eight air handling units (AHUs) with VAV boxes and electric reheat. Each AHU serves one half of eight alternating floors. Example: AHU-1 serves the northeast half of odd numbered floors 3 through 17. The server rooms are located on floors 2 through 36 and are served by dedicated cooling systems. The server rooms combined comprise less than 0.5% of the total GSF of the site. Due to the amount of tenant improvement projects that have been completed since the building was constructed in the mid 1980s, a complete set of current mechanical and architectural drawings for the building are not available. It is also not possible to obtain a complete set of drawings for all spaces served by any one given AHU. However, the original mechanical infrastructure has remained unchanged. Given the large size of this building, the large number of tenants, and lack of complete documentation, we are proposing a sampling strategy to document that the building complies with EQ Prerequisite 1. Specific details are summarized below. Note that for the purposes of this CIR, "calculation" implies a calculation confirming ASHRAE 62.1-2004 ventilation rates was completed. Occupancy levels for each space will be based on ASHRAE 62.1 2004 guidelines. Calculation Approach: Retail: One calculation will be completed for each retail tenant space. Lobby: One calculation will be completed for the lobby area. Commercial office: Confirmation that each office space is served by a typical HVAC system will be completed through site surveys, customer interviews and review of available drawings. If unique spaces in terms of space use or HVAC system type are discovered a separate calculation will be completed for the space. Calculations will be performed on 10% of the typical office floor space to determine the average ventilation rate in terms of cfm/sf. The resulting ventilation rate per square foot will be applied to the remaining air handling units to determine if compliance with EQ Prerequisite 1 has been met. Example: For a 100,000 SF building, calculations on 10% of the space or 10,000 SF would be performed. Assuming, the calculated average ventilation rate was 0.19 cfm/SF and each air handler serves 30,000 SF, the ventilation air required at each AHU equates to: 0.19 cfm/sf x 30,000 sf = 5,700 ventilation cfm. Server rooms: Excluded from the scope of this credit because they are not regularly occupied spaces, and because they comprise less than 0.5% of the GSF. Submissions: The actual minimum ventilation rate for the each AHU will be measured and compared with the outdoor ventilation rates calculated above. Given that all AHU's use dedicated minimum outdoor air (OA) damper sections that operate at full open when the AHU is running, we propose measuring the actual OA CFM being introduced. In addition, documents will be submitted (i) ensuring that the building exhaust systems are working as designed, and (ii) shall include the results of a quarterly inspection of building OA & exhaust systems to confirm they are working as designed. Will this proposed strategy meet the requirements and intent of the pre-requisite? If not, please clarify how this proposal should be revised.
The proposed approach does not meet the requirements of this credit. It would not be acceptable to calculate the minimum ASHRAE 62.1-2004 ventilation rates based solely on cfm per square foot. The calculated Minimum Vbz calculation must account for both zone floor area and actual occupancy levels per space type in the overall breathing zone. ASHRAE 62.1-2004 requires that you meet the target minimum ventilation rate (CFM) based on space use, square footage, and occupancy within the space served by each air handler. For multi-zone air handling units (AHUs), the total AHU CFM requirement must be built up from the characteristics (space types) of each zone. Actual OA delivered must be reported for all AHUs serving the buildings. To demonstrate compliance with ASHRAE, OA delivery from each AHU serving occupied zones must be tested and reported. Where this is not feasible due to the physical constraints of the existing ventilation system, you must document that the system supplies at least 10 CFM/person for each of the applicable space types under each AHU and clearly illustrate the physical constraints. For more information, please see the LEED-EB V2.0 Reference Guide Second Edition October 2006 language detailing the calculation and documentation requirements for this prerequisite. ASHRAE 62.1-2004 requires the following formula to show that the delivered OA ventilation rate exceeds the minimum standard ventilation rate per breathing zone (Vbz): Minimum Vbz = (Rp
Related Addenda (Corrections & Interpretations)