Are 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
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 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.
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.
Fighting the fear
Condensation is the most frequent concern that comes up about radiant cooling. Radiant cooling technology utilization is not as high as it should be worldwide because designers don’t trust that they can avoid condensation. I’m not sure why this is, especially for the fact-driven engineering community. Code-adhering, ASHRAE Standard 62.1 and 55-compliant buildings provide the indoor environmental quality boundaries for radiant cooling to shine. Sometimes engineers can still have emotional responses to the topic of radiant cooling. The radiant cooling conversation seasoned designers have is similar to this off-topic conversation:
Engineer: “I’m afraid I’m going to drop my phone in a lake.”
Cooling designer: “Are you standing next to a lake?”
Cooling designer: “Put up a barricade 10 feet from the lakeshore, so you can’t get too close to it and put your phone in your pocket, so it is secured.”
Engineer: “Okay, but what if I drop my phone in the lake?”
Cooling designer: “You would have to climb over that barricade and also pull your phone out of your pocket to have a chance of dropping the phone in the lake, so just don’t break those two rules and you will be fine.”
Unless you plan on engineering a leaky building that ignores ASHRAE Standards 62.1 and 55, you shouldn’t worry about radiant cooling condensation. If you are designing with people in mind, you have established the proper comfort and ventilation barricades so you don’t have to worry about radiant cooling condensation
Radiant cooling in action (in Canada)
If you still need convincing about radiant cooling, the best way to demonstrate the technology is to see it in action.
JSF High School in Brampton, Ont., was the first secondary school to receive a Canadian Green Building Council LEED Silver certification in Ontario. The school provides a comfortable environment for students by maximizing daylighting, incorporating a green roof and utilizing radiant heating and cooling. Classrooms, offices, the cafeteria and the gymnasium all tap into the radiant system, which shows that this isn’t only a technology for glass atriums (one of the most common uses of radiant cooling).
The Sheridan College Davis Campus Skilled Trades Centre, also in Brampton, was built to be a living laboratory for tradespeople-in-training. An integral part of this design is allowing students to work with and learn about the on-site mechanical equipment. The building uses a tri-generation system for chilled and hot water, as well as electrical generation. Additionally, the high ceilings in the training areas are a perfect match for radiant floors, because the occupants stand on the heated and cooled floors without having to include overhead space heaters above specific work stations. This project obtained a LEED Gold certification.
YWCA Toronto Elm Centre incorporates a thermal activated building system (TABS) that heats and cools a 17-storey residential tower and adjacent towers. To maximize usable floor space for residents, the design team chose radiant heating and cooling. The uninsulated TABS panels are a concrete slab with embedded PEX piping that acts as the floor and ceiling for the multi-storey project. These bi-directional radiant surfaces can allow designers to provide high ceilings for residents, potentially reduce ventilation clutter and also double the radiant surface area per unit, which allows for entering water temperature adjustments that increase energy efficiency. Additionally, the mechanical equipment can be located in the hallway, so maintenance staff don’t have to enter the 302 units to change filters and service equipment. Included in the energy plant design is a 3 million BTUH capacity vertical geoexchange well on site.
Earth Rangers Centre in Woodbridge, Ont., was originally designed to be a veterinary hospital but is now used to showcase sustainable technology while teaching visiting students about conservation. This building was certified as LEED Gold for New Construction, as well as LEED Platinum for Existing Buildings. A combination geoexchange, radiant heating and radiant cooling system has helped this site achieve 42 per cent better energy efficiency than was expected from its original plans. The centre is a showcase of modern, sustainable design that is available for tours if you want to see it firsthand.
By: Max Rohr