Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.2

Inquiry

Question: We would like to confirm that our HVAC energy modeling strategy in our Vivarium areas is acceptable to USGBC. In particular we would like to confirm our baseline model and associated assumptions will be accepted. ASHRAE 90.1-2004 does not clearly address Vivarium requirements. We feel that laboratory references are the most applicable. One large difference between Laboratory and Vivarium design is that current industry standard for Vivarium design is constant volume air systems. This results in not being able to meet turn down requirements published in ASHRAE 90.1-2004. Project Description: Our project is a 217,900 square foot vivarium with integral boiler and chiller plant. The facility includes the following functions: Vivarium (approx. 55% of program area) Vivarium Support (approx. 15% of program area) Laboratory (approx. 10% of program area) Laboratory Support (approx. 5% of program area) Office (approx. 15% of program area) Mechanical / Electrical Rooms Mechanical Penthouse Baseline Model - Vivarium and Vivarium Support Air Side System Description: Air System - 100% outside air constant volume reheat system with 50% effective heat wheel.  A minimum of 15 ACH (air changes per hour) is utilized due to room occupancy and ammonia odors. 10 - 15 ACH is referenced by ASHRAE and the Guide for the Care and Use of Laboratory Animals. This air change rate is heavily influenced by animal density, animal size, species, type of bedding, and frequency of bedding change out. Our project has concluded that 15 ACH is the correct air change rate for our application during heavy room occupancy.  ASHRAE 90.1 - 2004, chapter 6.5.7.2 requires constant volume systems to have heat recovery with 50% effectiveness. This limits available technology to heat wheels. Heat wheels are known to pass ammonia odors. For this reason we do not feel it would be logical to model the heat wheel if it is not a realistic option for a baseline design. Can the submitted model be based on a 50% sensible effective run around glycol heat loop in lieu of a 50% effective heat wheel? Proposed Model - Vivarium and Vivarium Support Air Side System Description: Air System - 100% outside air variable volume reheat system with 50% effective sensible run around glycol heat loop.  Unoccupied: 4 ACH minimum with active control of airflow override due to high temperature, high CO2, and high ammonia levels. Temperature, CO2, and ammonia will be continuously monitored. Airflow will actively adjust based on contaminant concentration levels in each space. In this facility high room turn over will occur on a regular basis as studies start and finish. A significant amount of energy can be saved based on an unoccupied mode.  Occupied: 11 ACH - 15 ACH variable volume system. A significant amount of energy can be saved by reducing the airflow when space occupancy is low. In order to drop to 11 ACH we need to be assured that the environmental conditions in the room are acceptable. In this facility room occupant loading will be highly variable dependent on study. Some rooms will be very densely populated and others very lightly populated. We feel the best way to achieve an acceptable environmental condition is by monitoring environmental conditions (temperature, CO2, and ammonia) and actively modulating airflow between the minimum and maximum values to a desired set point.