Makeup Air System Supply Air Metallic Perforated Panel Figure 3: Solar wall preheats outside fresh air. Heat pumps at the CÉROM research center. team chose an oil boiler to handle residual heating needs in the greenhouses. The boiler only works for about 15% of the yearly number of heating hours. Thanks to this optimal combination of systems, it was possible to reduce the size of the geothermal exchanger to only 56% of the greenhouse peak loads, keeping costs to a minimum. By reducing the size of the heat pumps the design ensures that the equipment will work more hours at full capacity, maximizing heat pump efficiency. Risks The use of new equipment is always risky. Nonstandard equipment is more costly and usually means more time and care during the design phase. This inevitably increases a project’s complexity. However, thanks to energy simulation software, the design team was able to ensure the economic advantages of the innovative concept, reducing the risks of nonconventional installations. www.info.hotims.com/25207-10 August 2009 ASHRAE Journal 55