Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.2, v2 - LEED 2.1, v2 - LEED 2.0

Inquiry

This is a LEED NC v2.1 higher education, 240,000-sf student union building located in Washington State. We have provided Radiant Panels to service the heating and cooling loads of general office space. The radiant panels rely on a secondary water loop that supplies either hot or chilled water depending on the demand of the system. Outside air is being provided through operable windows or a dedicated 100% outside air handling unit. After doing some research on several energy modeling programs, we have not been able to find one that can model this approach. Instead, we used a four pipe fan coil unit and zeroed out the fan energy to try and mimic the water loads, but take away the fan motor loads. When we compare the proposed case with the base case for ASHRAE 90.1-1999, the proposed case in the energy model will call for a four pipe fan coil unit (system type 7), which in turn will designate the base case to be a four pipe fan coil system as well. It is our opinion that the base case does not need to be this. For a conventional office space in Washington, the industry standard is to provide a standard rooftop VAV unit and provide each zone with a fan powered terminal with reheat. Also, by using the Budget System Type flow chart in ASHRAE Standard 90.1-1999 and inserting data specific to our project (e.g. water cooled, fossil fuel heating, and non-residential space), we get System Type 2, which is a standard VAV with reheat system. Given this approach, can we use the standard VAV system as a base case for the radiant panels since we are not really using Fan Coils in this system?