ASHRAE Journal - September 2011 - 50

(windows and skylights) have separate switching from the rest of the interior spaces allowing lighting to be controlled off when it is not needed. Outdoor lighting used high efficacy fixtures with low-cutoff, allowing the energy to be reduced by nearly 50% below the ASHRAE minimum levels. So far, the metered electricity (Figure 3) is in line or exceeds expectations, although the natural gas metered (Figure 4) consumption exceeds the simulated consumption. A search for reasons for the anomaly in December is still ongoing as the building continues to be monitored.

40,000 35,000 30,000 25,000 kWh 20,000 15,000 10,000 Simulated Proposed Design Metered Data

Indoor Air Quality ASHRAE Standard 62.1 and ASHRAE Stan5,000 dard 55 were considered essential in the design process. The design used Standard 62.1-2004’s 0 Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Ventilation Rate Procedure to determine the Metered data unavailable for July. outdoor ventilation rates of each air handler. The intent of Standard 62.1-2004 was more difficult Figure 3: Simulated vs. metered electricity consumption. to meet in heating mode, because of the heated 900 air being delivered at the floor and returned at the ceiling level where displacement is being used 800 and the use of 90°F (32°C) supply air from the Simulated Proposed Design overhead VAV system, respectively. 700 Metered Data Since the use of displacement ventilation was a key energy efficiency feature of the project, 600 it did not make economic sense to provide two 500 return paths (ceiling and floor) to increase the ventilation effectiveness of the system, and 400 super insulation of the windows and skylights was not cost effective to reduce the winter sup300 ply air temperature; CO2 sensors were added to the central air handlers to allow the outside air 200 dampers to turn down below the target calcu100 lated in the Ventilation Rate Procedure. In an effort to overcome the ventilation effectiveness 0 penalty, this proved to be a wise choice given the Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Metered data unavailable for September. variability in occupancy in the library and first costs, thereby saving energy despite the poor Figure 4: Simulated vs. metered natural gas consumption. wintertime ventilation effectiveness. One space where special attention was given to ventilation floor slabs, and depressing the mean radiant temperature effectiveness was the main reading room, where the displacehas been initially an untested experiment. To understand ment supply air temperature was not raised significantly in the the transient behavior of the concrete during the flush winter time, but instead the envelope loads were handled by cycle, the team looked for software that extended beyond a perimeter finned tube convector, allowing the supply air to DOE-2 or load calculators.* EnergyPlus has been develremain slightly cooler than the space temperature. oped with this transient behavior in mind. The design team The heating and cooling system was designed to maintain ultimately chose to use a similar well-validated tool with 75°F (24°C) in the summer and 70°F (21°C) in the winter a European background because of its calculation engine, time, consistent with common procedures for an air-condiuser interface, and ability to model PPD and PMV based tioned design and meeting the requirements of ASHRAE on Fanger’s comfort models. The simulations were used to Standard 55. Improving and extending the comfort range by test a variety of conditions, wall thicknesses, and nighttime night flushing the building to store “coolth” in the wall and flush control strategies
*DOE-2

is known as incapable of modeling radiant heat transfer between surfaces, and it is unable to always model thermal mass accurately without adjustments to the custom weighting factors. Other load calculators also tend to deemphasize the role of radiant heat exchange.

ASHRAE Journal

Therms

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September 2011

ASHRAE Journal - September 2011

Table of Contents for the Digital Edition of ASHRAE Journal - September 2011