The heating and cooling system in this building is a great example of the District’s commitment to recovering sustainable resources, since this building is actually heated and cooled by treated effluent.  With this feature, MMSD is the first building in Wisconsin using wastewater as a heating and cooling source. This innovation saves significantly on energy and costs, all with a resource that literally goes down the drain.                                                                                                                   



In designing the heating and cooling system, MMSD engineers had considered a traditional geothermal system, which uses the heat of the earth to regulate building temperature. However, the engineers realized that treated wastewater would be a perfect stand-in for geothermal. Treated wastewater reused at the treatment plant (called W4 water) has a temperature range very similar to geothermal (50-70 degrees), and the temperature of effluent is actually more consistent. As another bonus, most of the infrastructure was already in place on campus for this feature, and all that was necessary was adding the piping.

During operation, between 100 to 220 gallons of treated wastewater are flowing through the heating and cooling system every minute.




The W4 water is the heat source (or heat sink) for 26 heat pumps located throughout the building and for the heat pump in the buildings ventilation unit.  The heat pumps use a refrigerant and compressor to provide warm or cool air to the spaces.  When a space needs warm air, the heat pump increases the temperature of the refrigerant, which pulls heat from the W- water (decreasing its temperature). When a space needs cool air the heat pump decreases the temperature of the refrigerant, which rejects heat to the W4 water (increasing its temperature).

Air handling equipment in the main building and garage uses energy recovery technology, which preheats or precools ventilation air by pulling energy from the exhaust, which in turn reduces electricity consumption.