ASHRAE 62.2-2007 was required in the Florida Building Code in 2007. This basically says that a multifamily building 4 to 6 stories must have a certain amount of outside air introduced into EACH unit, that having enough OA in hallways and common areas isn't enough. LEED also requires meeting 62.2-2007 as a prerequisite. The latest FBC (2010) does NOT require multifamily midrise to meet 62.2-2007 as it brings in too much humidity and negates the point of optimal indoor air quality. The new code has reduced the amount of OA required per unit. Unfortunately, LEED is still requiring us to meet 62.2-2007, which leaves us two options: 1) design and install a humidity override system for each unit which is incredibly cost-prohibitive or 2) (and I personally know of projects where this has been done) just meet 62.2-2007 and keep costs down by not addressing the extreme humidity, which leads to extreme mold problems after occupancy. If we were to execute either of these choices, we would, in my opinion, not comply with the intent of the credit, which is to provide optimal indoor air quality in each unit WITHOUT a drastic cost differential. People always complain about how expensive LEED is and this is one of those instances that supports their claims. What can we do?
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Samantha Harrell
LEED Project Reviewer certificate holder115 thumbs up
April 6, 2012 - 7:41 am
Hi Andrea,
There's an article from Building Science related to this topic titled "BSD-107: Understanding Ventilation in Hot-Humid Climates". The article concludes that "In order to provide controlled ventilation in new houses constructed in hot humid climates without creating latent load problems it is necessary to take the following measures: Install tight ductwork and air handlers, balance interior air flows, size equipment correctly, provide supplemental dehumidification." So you're right that dehumidification is necessary, but at least you'll get credit for it under EQc3. EPA's Indoor airPLUS construction specifications also require that whole house mechanical ventilation system & controls are installed to deliver the prescribed outdoor air ventilation rate (ASHRAE 62.2 section 4), including ventilation restrictions in ASHRAE 62.2 section 4.5 (e.g., not greater than 7.5 cfm/100 s.f. in “Warm-Humid” climates as defined by IECC Figure 301.1), but this path also requires dehumidification.