ID#2627 made on
SSc7.2 - Heat island effect - roof
LEED BD+C: New Construction, LEED BD+C: Core and Shell
At over 2 million GSF, Beijing Parkview Green (PVG) is one of China's largest sustainable architecture projects. PVG is comprised of four buildings, including two 11-story and two 20-story towers that...
At over 2 million GSF, Beijing Parkview Green (PVG) is one of China's largest sustainable architecture projects. PVG is comprised of four buildings, including two 11-story and two 20-story towers that house retail area, offices and a six-star hotel - all of which are enclosed in a pyramid-shaped "Microclimatic Envelope" (ME) comprised of glass and plastic (ETFE - ethylene-tetrafluoroethylene). The glass forms the vertical portions of the ME, while the horizontal sloping elements are constructed of ETFE. As a separate, non-structurally tied edifice, the ME operates in concert with the buildings at the site, providing benefits in energy conservation, solar reflectance, and stormwater management, while providing insulation value to the structures within. If you think of a glass covering on a cake stand, you have a pretty good idea of the nature of the ME. Although the ME is not a "roof" in the traditional sense, we are seeking an interpretation that it be considered one in the context of this credit. The ETFE portion of the envelope contains an interstitial layer of ETFE that is coated with a series of silver dots to achieve a high albedo, rendering the ECM more effective at rejecting unwanted heat, while providing near natural lighting levels to the environment below. Thus, we propose to use the reflectance and emissivity characteristics of the ETFE envelope as the project "roof" element that affects the project's urban heat island effect in lieu of the roof structures on each of the four buildings enclosed by the ME. We believe this makes the most sense, as it is the first physical element that sunlight encounters and will be the physical element that radiates heat (or not) into the ambient environment.
The project is seeking clarification as to which layer of roofing in their double skin envelope should meet the credit requirements for Sustainable Sites credit 7.2. For the purposes of this credit, the roof surface required to meet the credit requirements is the roof that would contribute towards the heat island effect. For this project, the outer most roof surface of the enclosed space would be the roof that would be required to meet the credit requirements. Any roofs that may be inside the enclosed space are considered to be interior building elements, and do not have a significant contribution to the heat island effect. The project should note - although skylights may be excluded from the calculation, a skylight is defined to be a transparent or translucent opening in an otherwise opaque roof. For projects where the primary roof surface is transparent or translucent, such as the plastic roof in this project, it is required to meet the minimum solar reflectance requirements of the credit for achievement. Applicable Internationally; China.
Related Addenda (Corrections & Interpretations)