ASHRAE Journal - January 2010 - 27

This technology has been used mostly in Europe due to the stringent building codes that require fully daylit building interiors while maintaining good thermal performance of the building envelope. DSFs meet these criteria, work well with natural and hybrid ventilation designs and can minimize the excess heat gain in the summer via operable louvers. This technology is, in theory, superior to a conventional high performance building envelope. However, the limited design knowledge, the lack of analytical tools that can model the complex thermal behavior and an incomplete understanding of how the technology works is producing designs that exhibit mixed performance results.21,22 Two successful DSF designs include the Daimler Building in Berlin built in 1996 and the Deutsche Post in Bonn, Germany, built in 2003.4,23 The Daimler building is reported to use 30% less energy for space heating than a naturally ventilated German office building and exhibits a whole building energy intensity 24 kBtu/ft2·yr (271 MJ/m2·yr), which is a very low intensity considering that Berlin has similar heating degree-days as Chicago. From an electricity use standpoint, the low energy design could achieve potential savings as high as 59% using technologies and design approaches that include best-in-class fluorescent lighting design with a low LPD of 0.6 W/ft² (6.4 W/m²), daylighting controls, best-in-class cooling plants and alternate HVAC designs such as DOAS and chilled ceiling system. At the end-use level, cooling energy use of the low energy design is 40% lower thanks to the efficient lighting design and use of the latest generation of variable speed, frictionless, centrifugal chiller that can achieve an IPLV of 0.45 and a full load performance of 0.5 kW/ton (1.75 kW/kW). The plant size requirement based on the coincident peak cooling load predicted by the DOE 2.1E model is reduced from 160 tons to 120 tons (563 kW to 422 kW), a 25% reduction. The DOAS design can achieve fan power and energy savings of as much as 70% based on total airflows of 0.2 cfm/ft² (1 L/s·m²) compared to the reference design of 1 cfm/ft² (5 L/s·m²) since DOAS are designed to only deliver ventilation air.24,25 As shown in Table 5, total predicted energy savings relative to a Standard 90.1-2007 building are estimated to be approximately 54%. This value drops to ~46% for the entire building with the inclusion of plug loads. While this level of savings does not look impressive relative to industry goals, energy intensities below the predicted values of 30 kBtu/ft²·yr (349 MJ/m2·yr) are difficult to achieve. As an example, the best levels of energy performance from a sample of 120 LEED projects recently analyzed were in the range of 25 kBtu/ft²·yr (284 MJ/m2·yr) and examples of high performance designs exten- 135359_a01 Fallon 12/03/08 DB ` www.info.hotims.com/27101-141 January 2010 ASHRAE Journal
ASHRAE Journal - January 2010

Table of Contents for the Digital Edition of ASHRAE Journal - January 2010
