Page 318 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

280 Cha pte r S i x

FIGURE 6.7.1 Trane CDQ (Cool, Dry, Quiet) is a dessicant wheel which is placed in series with the
cooling coil and can help provide dry air to a space for better humidity control. (Photograph
Courtesy Trane.)

Intent
Provide a comfortable thermal environment that supports the productivity and well-being
of building occupants.
Requirements
Design HVAC systems and the building envelope to meet the requirements of ASHRAE
Standard 55-2004, Thermal Environmental Conditions for Human Occupancy with errata
but without addenda. Demonstrate design compliance in accordance with the Section 6.1.1
Documentation. Project teams can choose to use the addenda to ASHRAE 55-2004, but only
if applied consistently over all the credits applied for the LEED 2009.
Potential Technologies and Strategies
Establish comfort criteria per ASHRAE Standard 55-2004 that support the desired quality
and occupant satisfaction with building performance. Design building envelope and
systems with the capability to deliver performance to the comfort criteria under expected
environmental and use conditions. Evaluate air temperature, radiant temperature, air
speed, and relative humidity in an integrated fashion and coordinate these criteria with
IEQ Prerequisite 1, IEQ Credit 1, and IEQ Credit 2.

Calculations and Considerations (LEED 2009)
Thermal comfort controls usually refer to some form of conditioning and are for both
heating and cooling. This conditioning can be active (mechanical HVAC systems) or
passive (natural ventilation) or a combination of both (mixed-mode conditioning).
Levels of comfort are different for active and passive systems, and ASHRAE Standard
55-2004 separately addresses these two. For the mechanical systems, there is a predicted
mean vote (PMV) comfort model which deals with both a thermal balance and a thermal
comfort. PMV is based on a thermal sensation scale that ranges from cold (−3) to hot
(+3) for low airspeeds (<40 ft/min). Section 5.3 of the standard covers naturally
ventilated spaces and criteria vary with mean monthly outdoor temperatures.