Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.1

Inquiry

Our project is a science and classroom building of approximately 115,000 sq. ft. on a state university campus. For mechanically ventilated spaces, we understand that there are two possible compliance methods. We have questions about both methods. Using the first compliance method outlined in the May 2003, Version 2.1 Reference Guide, page 253, we understand that we can meet the requirements of this credit by demonstrating that the ventilation systems in the building will provide an air change effectiveness greater than or equal to 0.9 as determined by ASHRAE 129-1997. However, ASHRAE 129-1997 is primarily a laboratory test standard, and it "places strict limitations on the characteristics of spaces that can be tested with this method" in field tests (see the last paragraph in the Forward on page 1 of ASHRAE 129-1997). In fact, the limitations outlined in Article 4.3 on page 2 of ASHRAE 129-1997 are virtually impossible to achieve in field test conditions. Therefore, we do not understand how this standard is to be applied in meeting the intent of this credit. Using the second compliance method outlined in the May 2003, Version 2.1 Reference Guide, page 253, we understand that we can meet the requirements of this credit by complying with the recommended design approaches in ASHRAE 2001 Fundamentals Handbook Chapter 32. According to the Reference Guide, required documentation includes our certification that the design complies with these ASHRAE recommendations, as well as providing a "table summarizing the air change effectiveness achieved for each zone (must be 0.9 or greater)." Upon examination of the Letter Template, the declaration for this compliance approach does not appear to require a table summarizing air change effectiveness, but it does appear to require that "ADPI calculations be completed for each major space." We are not clear on the level of performance required to meet the intent of this credit. In the context of the compliance method where ASHRAE 2001 Fundamentals Handbook recommendations are to be followed, there is no method in Chapter 32 for quantifying "air change effectiveness." With respect to ADPI calculations, ASHRAE recommends that ADPI be maximized for each zone, but there is no reference to a minimum ADPI performance threshold (ADPI is a number between 0 and 100) in either the ASHRAE Handbook or the LEED Reference Guide. Also, ADPI values for perforated and louvered ceiling diffusers (the most commonly applied products) are not documented above room loads of 51 BTU/hr/ft2. As our building is a teaching lab, some spaces have loads that exceed this value. Please clarify how ASHRAE 129-1997 or ADPI are to be used to meet the intent of this credit, whether there is a minimum ADPI that must be achieved in each zone including rooms with loads in excess of 51 BTU/hr/ ft2, and what documentation of ADPI and/or air change effectiveness must be provided with the Letter Template declaration. Thank you.