High Performing Buildings - Winter 2008 - (Page 45)

screen area and the television monitors without blocking views and without the need for operable clerestory window shading devices. South-Facing Roof Monitors Daylighting in the gymnasium, multipurpose and dining areas of the schools is provided by south-facing roof monitors with translucent fabric bafﬂes in the light wells. These features eliminate potential direct beam radiation, reduce glare, and effectively diffuse light throughout the spaces. Clear double glazing maximizes visible light transmittance and minimizes glass-to-ﬂoor ratio. Optimally sized overhangs above the monitor windows protect the spaces from direct light during peak cooling periods. The monitor approach was used because of the large room dimensions and/or because the ceiling cavity is the thickness of the rooﬁng system. Therefore, the reﬂective losses associated with deep ceiling cavities were eliminated. Indirect ﬂuorescent lighting, compatible with daylighting, is installed throughout both schools. The lighting is dimmable and controlled by an occupancy sensor and a photocell sensor that work in conjunction with the natural daylight to minimize the need for artiﬁcial light. In spaces only used during the day, such as classrooms, where 60 footcandles is desired, one-sixth of the initial light ﬁxture cost was saved since daylighting provides at least 10 footcandles even on the cloudiest day. design approach that addresses the roof assembly, indirect lighting, and underﬂoor air-distribution system cut the installed tonnage at Northern Guilford by 75 tons and at Reedy Fork by 60 tons. Through daylighting simulations and DOE-2 analysis, it is predicted that daylighting will reduce the lighting energy by 49% at Reedy Fork and 50% at Northern Guilford. Because many of the school spaces are used well beyond typical school hours, the savings are greater and the return on investment is almost immediate. Results At both Northern Guilford Middle and Reedy Fork Elementary, daylight is the primary source of light within all educational and administrative spaces during two-thirds of the school day. The daylighting strategies produce half the amount of heat as ﬂuorescent ﬁxtures providing the same amount of lighting. Daylighting’s positive impact on cooling loads and the integrated LESSONS LEARNED In developing the daylighting strategy for Northern Guilford and Reedy Fork, the design team drew upon past experiences to avoid downfalls and maximize benefits. Human Factors To prevent teachers and students from overriding the controls and turning on the lights, the norm needed to be superior lighting from daylighting. The goal was to achieve in excess of 50 footcandles from daylighting for two-thirds of the school day. The design team did not count on view glass. Because low windows serve as good display areas, they were not considered for good daylighting. Technical Issues The design team focused primarily on south-facing glass. Passive heating benefits are important and south glazing requires 25% less glass area to achieve the same annual contribution as north-facing glazing. They also considered the limitations of interior lightshelves. Typical interior lightshelves are flat and solid. Since south-facing windows are difficult to control in terms of glare, the blinds on these windows are typically closed, resulting in darkness right under the lightshelf. Control Strategies Indirect lighting created a lighting scheme that is visually consistent with daylighting. The design team found that indirect lighting, if not using daylighting, is useful in halls in place of lay-in fixtures which produce a glare and make the space seem brighter than the classrooms. South-facing roof monitor with baffles in Northern Guilford’s gymnasium. Winter 2008 HIGH PERFORMING BUILDINGS 45

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

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