SYSTEM DESIGN
Radiant cooling,
a Canadian tradition
A
re radiant cooling systems a good fit in Canadian markets? If comfort and energy efficiency are design goals, radiant is a great way to go, regardless of the location, unless you are building on the edge of the Arctic Circle and have no need for additional cooling, that is. There is no secret design trick to making a radiant cooling system work well. If you design with people in mind and adhere to existing comfort, ventilation and building envelope standards for new construction, you are set to add radiant cooling.
or unpredictable relative humidity levels in a building designed to Standard 62.1. By providing the prescribed amount of air changes, maintaining a relative humidity setpoint and delivering appropriate IAQ for occupants, you set yourself up nicely for radiant. For radiant cooling hybrid systems, a dedicated outdoor air system (DOAS) is typically used in conjunction with the embedded PEX piping. The radiant system is good at addressing sensible cooling loads and the DOAS system addresses the latent loads. These systems pair together well, because the DOAS keeps the IAQ in an optimal range for radiant to cool surfaces, without hitting dew point. No radiant specific rulebook here either.
Designed to exceed Commercial, new construction projects tend to be the best fit for radiant cooling, and that’s for a few reasons. A tight building envelope is a key prerequisite to be able to maintain infiltration and latent cooling loads. There are no radiant-specific considerations here. A well-sealed structure helps keep you away from wild humidity swings inside a structure, but commercial buildings generally have the HVAC controls systems needed to monitor temperature and humidity levels in each radiant room and will likely incorporate vestibules and other safeguards to mitigate infiltration. The next consideration is ventilation compliance with ASHRAE Standard 62.1 – Ventilation for Acceptable Indoor Air Quality. You won’t see elevated
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The third component that sets up radiant cooling for success is ASHRAE Standard 55, Thermal Environmental Conditions for Human Occupancy. This standard limits the temperature to which designers should actively cool a surface. For comfort reasons alone, it would be a bad idea to cool a floor in an office space to 5°C. You would feel like you had rink-side seats at a hockey arena and would be uncomfortable working on a computer all day in an office. In this scenario, the surface temperature in the room would be below the recommendations of ASHRAE 55. By keeping surfaces above 19°C, while maintaining relative humidity levels, you stay away from the dew point danger zone. You won’t sweat the slab if you play by these established rules.
