High Performing Buildings - Winter 2008 - (Page 52)

well as heating in some cases. When comparing fan power to pump power, pumps can use as little as 10% of the equivalent energy consumption of fans. Thus, to minimize fan energy, both ground and second ﬂoor slabs were selected to have PEX tubing embedded within, turning them into radiant emitters used for space heating and sensible cooling. The slabs are exposed with minimal ﬁnish to better operate as a low-temperature radiant system and to combine well with the ground-coupled heat pumps temperature range (able to easily supply hot water up to about 100°F) (Figure 1). Cooling slabs only require water in the range of 60°F during the cooling season. This is roughly the same temDAY L I G H T I N G The last typical main use of energy in commercial building is due to artificial lighting. The daylighting potential for the second floor retail area was carefully studied. A roof monitor and two sets of clerestory windows allow daylight to the second floor while minimizing glare. Furthermore, sensors shut down the general artificial lighting when indoor lighting exceeds a set minimum. It was estimated that daylighting will meet about half of the yearly operating lighting load and allow substantial energy savings (Figure 4). perature that can be obtained from a geoexchanger when not using heat pumps during the ﬁrst few months after the heating season, known as geothermal-free cooling. As long as the ground is cool enough, a separate pumping system, parallel to the heat pumps, supplies the slabs with cool water directly drawn from the geoexchange system, further reducing heat pump use and energy consumption. Building Envelope Finally, the building envelope was evaluated regarding the potential energy savings from various R-values for the walls (wood I beam frames with blown in cellulose insulation), roofs (both insulated steel and wood About half of the yearly operating hours are naturally lighted, allowing substantial energy savings. deck), and windows (low-e double glazing). The ﬁnal values speciﬁed are R-35 for the walls and R-40 for the roof, twice the MNECB required values of approximately R-17 and R-20, respectively. The windows have an installed winter U-factor of 0.3 with various shading coefﬁcients adapted to each facing. Cost Effectiveness In retail store settings, artificial lighting is important to attract customer attention to the displayed goods. The building uses artificial lighting for this purpose; however, a variation of lighting intensity reduces installed lighting power density. The circulation aisles have the lowest intensity, the racking has a medium intensity, and the wall displays have the highest intensity with accent lighting. Combined with efficient fixtures, the installed lighting power is 58.5 kW (1.3 W/ft2). This is lower than the MNECB building requirement for retail areas (2.5 W/ft2) or Standard 90.1-2004 (1.5 W/ft2). Figure 4 Daylighting for the second floor retail area. The use of many standard off-theshelf or prefabricated components minimized work performed on site. A careful balance between ﬁrst costs and operation costs was reached with a slight oversizing of the water and air-distribution systems, reducing required pumping and fan energy. By using liquid (water-propylene glycol) instead of air as the energy transport media, the need for large ductwork was limited to ventilation needs only, ensuring energy savings over the life of the building. Ductwork was also minimized by reusing the hybrid system as a distribution system for the DOAS. Another cost-effective component, slab thermal inertia used as a storage device combined with predictive logic prevented installation of unneeded heat pumps and shaved peak electrical demand. The additional costs for the mechanical equipment were estimated at $475,400 in 2003 52 HIGH PERFORMING BUILDINGS Winter 2008

Table of Contents Feed for the Digital Edition of High Performing Buildings - Winter 2008

High Performance Buildings - Winter 2008 Passing On the Gift: Heifer International Headquarters Head of the Class: University of Florida’s Rinker Hall How Far Can You Go? Pearl River Tower The Proof Is Performance: How Does 4 Times Square Measure Up? Lighting the Way: Two Guilford County Schools Montreal’s Retail Example: Mountain Equipment Co-op® (MEC)

High Performing Buildings - Winter 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.