Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.1

Inquiry

Credit intent is to provide for effective delivery and mixing of fresh air to support safety, comfort and well-being of building occupants. This project is a small (9000+ SF) school for the deaf with a small student body and a low student to teacher ratio. The school is located on an island and a considerable distance from traffic, manufacturing facilities and other sources of outdoor air pollution. Ventilation effectivenes has been accomplished with the use of Halton dispersion diffusers (displacement ventilation) mounted low to the floor. Ventilation air is introduced at the breathing level rather than discharging at the ceiling. Return air is taken at the ceiling on the opposite side of the room from the diffuser in order to promote effective cross ventilation. According to the mechanical engineer: "Airflow calculations for ventilation effectiveness with displacement diffusers are difficult as design coefficients vary with each diffuser and space conditions. However Mr. Andrew Livchak of Halton Industries states, "Interpretation IC 62-2001-31 to the ANSI/ASHRAE Standard 62-2001 recognizes that ventilation effectiveness of DV systems can be greater than i (maximum value for mixing ventilation systems)". This is also stated in ASHRAE 129-1997, Appendix B." During occupied non-cooling periods ventilation is 100% outside air at a rate of not less than 20 cfm per occupant. Although this approach results in fewer air changes per hour it assures the introduction of pure clean air at the breathing level while eliminating the mixing of return air and fresh air and reduces fan power. During occupied cooling periods the central air handling units increases speed to provide the amount of air required for air conditioning while maintaining an outdoor ventilation rate of not less than 20 cfm per occupant. Does this strategy in this project meet the intent of this credit?