Earth Rangers Wildlife Centre - Case Study of Concrete Use for Energy Efficiency

摘要

The Earth Rangers Wildlife Centre is a 5000 sq m structural concrete building under construction at the Kortright Centre for Conservation north of Toronto and scheduled to open late 2003. The building has several outstanding features - it is the largest facility in Canada dedicated to the treatment and rehabilitation of wild animals; it is the most energy efficient education and health care facility in Canada; and the use of concrete makes a significant contribution to its excellent energy performance. All floors and roofs in a 2-storey structure are structural concrete slabs, all of which have embedded polyethylene tubing providing 100% of the space cooling and heating. The floors and exposed concrete ceilings act as the heating and cooling elements of the mechanical system - there is no forced air heating or cooling and no perimeter radiation. In addition, the 3500 m~3 of concrete act as cool thermal storage during the cooling season, significantly reducing the peak afternoon cooling load, and allowing the cooling system to pre-cool the building at night for use the following day. Thermally activated slabs for cooling are new to North America ; this is the largest known application in a humid climate in North America and the first installation in sloped cathedral roof slabs. Special coordination was required with the installation of reinforcing steel, electrical conduit, and mechanical slab penetrations. 15 km of tubing was installed and slabs poured at -10 to -25 deg C ambient air temperature in Jan-Mar 2003. The building is ventilated with 100% outside air and at a high rate as required by a health care facility. Normally, heating and cooling this outside air would constitute the single largest HVAC energy load. At the Wildlife Centre, 9400 L/s (20,000 cfm) of ventilation air is brought into the building through a grid of 9 buried 900 mm dia precast concrete pipes, connecting to a double foundation wall, which acts as the outside air plenum for the air handling units. The walls of the buried pipes and the foundation act as a large ground-to-air heat exchanger, pre-warming the outside air in winter and pre-cooling it in summer. At design heating and cooling conditions, this ground heat exchanger reduces the HVAC load by 30 kW and tempers the air by 3 degrees C. Concrete was chosen for the piping material because of its demonstrated success in several European installations in resisting mold growth in the buried ducts. Ground duct performance was modelled with FRAME, a finite element analysis heat transfer program developed by Enermodal. The building energy performance was modelled both with Carrier Hourly Analysis Program and with Natural Resources Canada's "EE4" program, used for all buildings applying to NRCAN's Commercial Building Incentive Program. The Wildlife Centre is predicted to use 65% less energy than a reference building designed to Canada's Model National Energy Code for Buildings. Application will be made to the US Green Building Council for LEED certification. The use of concrete in the radiant slabs and the ground heat exchanger ventilation tunnels will contribute several points to the LEED rating.