ASHRAE Journal - August 2012 - 53

2012 ASHRAE Technology Award Case Studies
NCMA was constructed in 1982 with a gross square footage of 171,870 divided among four levels. The facility includes offices, exhibit space and restaurant/catering operations. Open to the public Tuesday through Sunday and occupied seven days a week, the museum averages 25,000 visitors per month with a peak daily occupancy at approximately 2,500 visitors and 150 staff.

$90,000 Guarantee Period Begins 2/1/2007 $80,000 $70,000 $60,000 $50,000 $40,000 $30,000 $20,000

Existing Systems and Equipment

The existing system consisted of J – June $10,000 M – March S – September D – December four constant-volume, chilled-water $0 air-handling units (AHUs) with hot J S D M J S D M J S D M J S DM J S D M J S DM J S D M J S D M J S D M J S D | | | | | | | | | water reheat boxes, each including 02 03 04 05 06 07 08 09 10 11 a steam humidifier. A central utility Figure 1: Financial savings. (NCMA – Historical total monetary data [from monthly electric and natural gas bills].) plant that included two R-11 centrifugal chillers manufactured in 1979 and two constant speed blow-through the main air-handling units at a constant The savings opportunities were so cooling towers supplied chilled water, 52°F (11°C) dew point. Since the mu- great that the museum could afford hot water and steam. Serving the mu- seum’s temperature requirements are to completely retrofit the heating and seum humidifiers, steam-to-hot water 70°F (21°C) in all zones, this reduced cooling central plants, the direct digital heat exchangers and domestic hot water the number of humidifiers from 92 dis- control (DDC) system, the outside air system were two 600 hp (5886 kW) fire- tributed steam humidifiers down to one system and the air control system. The tube boilers operating at 110 psig (759 centralized cold-fog humidifier. This project also included lighting retrofits in kPa). The museum’s annual energy costs also eliminated the need for boiler sys- the non-exhibition areas and several wawere $6/ft2 ($64.58/m2) at approximate- tem steam for humidification. The ad- ter conservation measures. A 12 year, $5 ly 300 kBtu/ft2 (11 357 kJ/m2). dition of a single pretreated outside air million performance contract was cresystem eliminated the need for untreated ated to finance the project. The guaranGetting the Outside Air Right outside air mixing at each of the air-han- tee includes annual savings of more than Controlling the outside air was the dling units and virtually eliminated the first consideration. Raleigh, N.C., has need for individual zone reheat in the Building at a Glance a subtropical climate with winter lows summer months. The air-handling units averaging 35°F (2°C), and summer now mainly condition space-sensible highs averaging around 90°F (32°C). To heat only. North Carolina manage the amount of outside air enterMuseum of Art ing the facility, a dual-mode, dedicated Paying for the Improvements Location: Raleigh, N.C. outside air unit was installed to pretreat, One of the museum’s goals was to host measure and control the airflow and dew more high profile traveling exhibits. To Owner: State of North Carolina point of the outside air. The unit is set to meet the strict environmental requirePrincipal Use: Fine Arts Museum maintain the building at a slightly posi- ments that many traveling exhibitions tive pressure. During unoccupied hours, require, the museum needed to upgrade Includes: Offices and exhibit space the airflow is reduced to account for the the mechanical systems. Since the muEmployees/Occupants: 150 employreduction in exhaust air from the build- seum’s energy and operating costs were ees/25,000 visitors per year ing since a number of exhaust fans are relatively high, the recently enacted cycled off at the end of the day. North Carolina performance contracting Occupancy: 100% Using a single unit for all outside air legislation and process was used to fund Gross Square Footage: 171,870 pretreatment greatly simplified the mu- and deliver the project. Performance seum’s climate control system. Using contracting allowed government-owned Conditioned Space: 171,870 ft2 hot water pre-heat coils, chilled water facility operators to finance and pay for Substantial Completion/Occupancy: cooling coils and a high-pressure, high- renovations and improvements based on January 2007 purity, cold-fog humidification system, guaranteed future utility and operational the pretreated air is then distributed to savings.
August 2012 ASHRAE Journal 53

ASHRAE Journal - August 2012

Table of Contents for the Digital Edition of ASHRAE Journal - August 2012