Radiant Heating & Cooling
Manitoba Hydro’s dominant source of heating and cooling is through exposed radiant concrete ceiling slabs. Warmed water is pumped through flexible plastic pipes embedded in the concrete floor slab, which heats the building by thermal radiation (infrared radiation moving from a warm object to a cooler object) . This type of heating provides good thermal comfort because it addresses the fact that thermal radiation between occupants and surrounding surfaces is as influential in thermal comfort as air temperature (for this reason evaluated comfort is often based on "operative temperature," which falls about halfway between air temperature and the average surface temperature in a space). The slab heating and cooling system also provides comfort without excessive air motion, whereas typical systems heat by blowing large amounts of warmed air, making spaces drafty and noisy. Inevitably the slab heating also warms the surrounding air to a small degree, but as the closest air is stratified exhaust air its affect is negligible to the overall comfort of the building occupants.
One way that radiant heating saves energy is by relieving fans of the burden of delivering heat. A second is linked to radiant heat exchange: a radiant system can provide excellent comfort conditions mostly by warmed surfaces, allowing air temperature to drop 1-2°C, which also raises the relative humidity. Thus, less energy is needed for fresh air heating and humidification. A third advantage, in the case of slab heating, is that the temperature of the water for heating can be very low (~28°C) compared to that of a radiator or air heating coil (~60°C). This is because a very large area (the entire underside of the slab) serves to heat the space. A low heating temperature, in turn, allows for the efficient use of Condensing Boilers or natural heating sources such as Geothermal Wells and ground source heat exchange/storage.
Most of 360 Portage’s radiant heating and cooling slabs are located in the office space but there are additional loops that have been installed to add or subtract heat energy from the buildings buffer zones such as South Atrium or the East/West Double Facades. For example, additional heating may be extracted for Geothermal Storage in the summer by running colder water into the South Atrium’s exposed floor slab. In winter this additional heat can be used to maintain minimum temperatures (5-6°C) in the double facades, providing an excellent buffer between the office space and the -35°C outside air temperature.
Related Performance Goals:
Energy Performance-Sustainable Design
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