Mario Kani, Sustainable EDGE, Toronto

For over a decade we have been using hydronic radiant heating and cooling in ceilings. The benefits of a fully hydronic house with moderate heating and cooling water temperatures and no recirculated forced air are many, including: 

  • Complements low energy envelopes which require lower heating and cooling capacities
  • Provides better comfort
  • Delivers healthy indoor air
  • Promotes minimum noise in living spaces
  • Requires minimal and smaller ductwork (ventilation only)
  • Results in lower distribution energy (by using a pump instead of a fan)
  • Increased flexibility for thermal supply source such as solar or geothermal energy

Locating the radiant cooling on the ceiling provides the maximum output for a specified design surface temperature. While we have designed several projects using concrete radiant ceilings, we have found that for wood construction, Warmboard is a natural match for ceiling installation, placed just behind the drywall. Warmboard is also an ideal candidate for radiant heating in the ceiling as well, able to provide either low- or high-intensity heating during winter months.

The principle of ceiling cooling is based on average surface temperatures between 60ºF to 70ºF over a large surface area, resulting in draft-free, low-intensity cooling. The cooling surface temperature needs to be high to avoid surface condensation. This system only does sensible cooling of the living space (i.e. no moisture removal) so that dehumidification needs to be done separately. For a successful ceiling cooling installation, the project’s attributes should be as follows: 

  • A high performance thermal envelope to minimize cooling loads through careful glazing selection and summer shading,
  • Significant envelope airtightness
  • 100% outdoor air ventilation without recirculation (also known as DOAS: dedicated outdoor air system )
  • Ventilation heat recovery (preferably an ERV)
  • Dehumidification of outdoor air with 45ºF to 50ºF chilled water (e.g. directly from ground water or via ground source heat pump) resulting in drier ventilation air than room air.

We look forward to using Warmboard–R, the thinner retrofit product in our next radiant ceiling project.