Early in the design process, Valley View School District 365U had discussions of HVAC system selections. While a choice for direct expansion roof top units is typical in our area and for the school district, knowing that they wanted to design a school that was environmentally friendly and energy efficient, enabled them to steer quickly away from that choice to a much more efficient variable air volume with reheat, water cooled chillers, and hot water boilers. In previous experience with LEED, we would compare the base compliant ASHRAE 90.1 system - a roof top unit, with our choice of compliant ASHRAE 90.1 HVAC systems. The way the LEED resource guide is written, referencing the use of the Energy Cost Budget, does not allow us to compare our very efficient VAV system to the direct expansion roof top units discussed early on. One of your previous rulings states, "the reference standard was changed to limit gaming and inflated claims of energy savings." We think that the choice our client made to invest premium dollars for a more efficient system early on to reap energy savings qualifies for credit recognition. Do you agree? Are we permitted to compare the energy benefits of a direct expansion roof top unit to the system of choice described above?
The use of the Energy Cost Budget accounting method allows the LEED process to be more consistent in comparing energy performance between projects. ASHRAE 90.1 is nationally recognized as the basic comparison standard for identifying building energy performance, and there are significant advantages to the LEED program to using this standard consistently. An exception to this protocol will not be allowed for your project, so you may not use packaged roof-top equipment for your baseline. However, LEED recognizes some of the limits of the ASHRAE baseline protocol, and has adopted one exception to ASHRAE standard that you may be able to use to capture more of the energy credits for your design. (See below) It is true that the ASHRAE methodology limits the recognition of some good design measures that improve building performance. Your decision to steer the client away from packaged roof-top equipment will save cost in the long run, and this represents a good design strategy for the client\'s interests. However, to achieve LEED points for optimizing energy efficiency, you must follow the procedures described in ASHRAE 90.1 for comparing the proposed and baseline buildings. There is one exception listed in the Reference Manual which will allow you to capture some additional credit for your mechanical design strategy. On page 126, the LEED Reference Guide lists an exception to the ASHRAE protocol which allows a project to use an air cooled chiller as a baseline for water-cooled chiller designs if chiller capacity is less than 150 tons. If applicable in your case, this exception may allow you to capture additional energy performance credits. Applicable Internationally.