ASHRAE Journal - May 2012 - 52

2012 Technology Award Case Studies
consistent. Sensible and latent transfer occurs, which assists in was in force at the time, using whichever was more stringent. humidification and dehumidification, reducing cooling demand Thermal comfort is based on ASHRAE Standard 55-2004. and limiting added humidification. Energy recovery unit bypass The air-handling systems serving the classrooms, music arcontrols and ductwork allow outdoor air economizer use in the eas, and commons areas are designed for 100% outdoor air, swing seasons. through the dedicated outdoor air system (DOAS) in conjuncChilled water cooling via the air-handling units is limited to tion with the energy recovery units, economizer damper bythe office areas, computer labs, media center pass and VAV box controllers, so most rooms and the fitness/multipurpose areas. A highhave a traceable method of ensuring ventilaElectricity Natural Gas (kBtu/ft2·yr) (kBtu/ft2·yr) efficiency screw chiller was installed with a tion rates. 65.40 16°F (9°C) temperature drop, to reduce pipe 2005 – 06 12.62 Thermal displacement ventilation (TDV) and pump sizes compared with the typical de- 2006 – 07 11.19 was installed throughout the facility, with the 70.61 sign of 8°F to 10°F (4°C to 6°C) temperature 2007 – 08 11.01 exception of the existing gymnasium, kitchen, 35.80 drop. service/receiving and shop areas. The audi2008 – 09 11.12 38.56 The existing, preconstruction (2005–06) torium air-handling system is designed for 26.78 energy use intensity (EUI) was 78 kBtu/ft2·yr 2009 – 10 11.14 100% outdoor air and the space is supplied (839 kBtu/m2·yr) for the existing 95,000 ft2 Energy use pre/post-remodeling. with mushroom diffusers below the seating (8800 m2). The EUI post construction (2009– area. Air is returned high in the auditorium 10) was 38 kBtu/ft2·yr (409 kBtu/m2·yr) for 175,000 ft2 (16 and stage areas. The new gymnasium is supplied with displace258 m2). The building has earned an ENERGY STAR rating ment temperature, low velocity, air behind the bleacher seating of 96. and the stratified air is returned high in the structure. Prefilters and MERV-13 final filters are provided for all Indoor Air Quality air-handling systems to help prevent particulate distribution Indoor air ventilation was designed to Standard 62.1-2004 throughout the air-distribution system. Airflow measuring dewith addenda and/or the Commercial Wisconsin Code that vices are installed on all air-handling systems serving classrooms and the majority of the remaining air-handling systems. Individual VAV boxes are installed for each space, so control and monitoring of each space can be accessed easily. Carbon dioxide monitoring and control are incorporated into the return air from the gym, auditorium and commons/cafeteria for reset control upon high or low CO2 concentrations being detected. TDV is designed to supply lower velocity supply air at the occupant level compared to mixing systems. TDV is typically more comfortable for the occupants, although diffuser placement is critical to limit air draft issues. The ventilation effectiveness of thermal displacement ventilation is considered 1.2 at a minimum, meaning a minimum of 20% more ventilation air is getting to the occupants. Removal of pollutants and contaminated air is more effective with TDV due to the space stratification. This stratified air is exhausted directly out of the building in 100% outdoor air systems. The DOAS, in conjunction with the TDV, reduced the duct sizes in most rooms, allowing higher ceilings for the given wall height. This provides better daylighting and allows the indirect lighting system to function more effectively. Radiant floor heating is provided as the primary method of heating for the majority of the new spaces, providing better thermal comfort during the heating season. Excluding the new gymnasium and auditorium, the radiant floor is designed with a 20°F (11°C) temperature drop and underfloor insulation to provide quicker response time. Finned tube radiation is designed for existing spaces, the gyms, and the wrestling area for primary space heating. Space activity levels varied by space and are factored into the building load calculation, but are based on 2005 ASHRAE Handbook—Fundamentals, Chapter 30. Clothing Rvalues were not factored into the load calculations due to the wide range of seasonal temperatures.
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ASHRAE Journal

May 2012

ASHRAE Journal - May 2012

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