Rating System

LEED BD+C: New Construction, LEED BD+C: Schools

Rating System Version

v2 - LEED 2.2, v2 - Schools 2007

Inquiry

This CIR is similar to the published CIR 2/2/2007 with a response on 2/26/2007. We are requesting an interpretation relating to hospitals. Our project is a 12 story 480,000 sq. ft. hospital addition with fossil fuel heat. Table G3.1.1A indicates that the baseline system should be packaged VAV with reheat (System 7). ASHRAE 90.1-2004 G3.1.3.13 requires the minimum volume setpoints for VAV reheat boxes shall be 0.4 cfm/ft2 of floor area served. However in many spaces of the hospital the minimum flow rate as required by the AIA guidelines is higher than 0.4 cfm/ft2. Can the minimum turn down ratio be increase to match the minimum requirement of the AIA guideline for the each room where specific values are given, while using 0.4 cfm/ft2 of floor area served in areas where it does not apply? This question is not in regard to the pressurization exception as clearly described in G.3.1.1(c), where those spaces are to be modeled as constant volume system type 3. It is referring to rooms such as patient rooms which require a minimum airflow rate of 6 air changes per hour with no specific pressure relationship requirement, which with a 10 foot ceiling corresponds to a minimum flow rate of 1.0 cfm/ ft2. Without modeling the systems with the same code required minimum airflows, it would be an unrealistic comparison.