Rating System

LEED BD+C: Core and Shell

Rating System Version

v2 - LEED 2.0

Inquiry

At over 2 million GSF, Beijing Parkview Green (PVG) is one of China\'s largest sustainable architecture projects. PVG is made up of four buildings, including two 11-story and two 20-story towers (Blocks A-D) that house a retail area, offices and a six-star hotel - all of which are encased in a "Microclimatic Envelope" (ME) composed of glass and plastic (ETFE - ethylene-tetrafluoroethylene). As a separate, non-structurally tied edifice, we ask that the ME be treated as an example of an Energy Conservation Measure (ECM). The buildings in and of themselves are fully functional, independent entities, designed to meet or exceed ASHRAE 90.1-2004 standards. Each of the buildings\' exterior walls was designed as if it were to have no benefit from the ME. The ME\'s microclimate saves energy by reducing annual average temperature difference between the buildings\' average indoor temperature and the "outdoor" temperature represented by the atrium space. The ME also reduces excess solar heat gain. The atrium has been designed to allow for wider temperature fluctuations than in the individual buildings; it is passively ventilated and spot-heated or cooled as a process load. We are requesting confirmation that our modeling strategy of the ME, outlined below, conforms to the Appendix G modeling protocol as required by EA Prerequisite 2 and EA Credit 1: Baseline Building Model: The ME will not be included in modeling the four fully-conditioned buildings. Each will have the appropriate envelope properties and mechanical systems as required by ASHRAE 90.1-2004. The four buildings would be directly exposed to the Beijing weather file. Vertical glazing will be modeled as fixed and the building interiors will be 100% heated and cooled mechanically. Facade and plaza area lighting will be modeled as process loads in the baseline building, but not the supplemental spot cooling or heating equipment. Proposed Design Model: The ME will be modeled using the glass and ETFE wall and roofing properties as installed. The Beijing weather file will be applied as the exterior condition of the ME. Within the ME, the atrium will be modeled as an open area so that airflow can occur freely within the space. In EnergyPlus, virtual partitions will be created to represent the temperature gradient within the vertical space. Using this information in conjunction with a CFD model, we will be able to create an hourly schedule for when natural ventilation from atrium air can be used in the office spaces at each elevation to satisfy the cooling and heating loads. We will model the proposed building as a "hybrid system" where "cooling is provided by natural ventilation when conditions are acceptable and by the default mechanical cooling system (AHUs and chilled ceiling in this case) when natural ventilation is inadequate to provide thermal comfort." The envelope of four buildings will be modeled as the exterior of the conditioned space, which faces the "weather" inside the atrium. The presence of the exoskeleton will require the windows of Buildings A-D to be modeled as interior windows. EnergyPlus will allow the use of a full interior and exterior window option, which will allow for solar radiation penetration through both the exoskeleton glazing and the fenestration on Buildings A-D. Mechanical equipment and lighting within the four buildings will be modeled as built. Plug loads and equipment and lighting in the atrium area will be modeled as process loads: including supplemental spot cooling and heating units on the plaza level; facade, exoskeleton and area lighting, and vertical transportation loads.