Online educational resource on achieving indoor environmental quality with radiant based HVAC systems
Not for profit educational resource on indoor environmental quality.
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Fundamentals of indoor environmental quality / thermal comfort and air quality solutions using radiant based HVAC


Despite having been around for over 30 years, HRVs/ERVs are still treated by many as if they just arrived on the continent. I'll be investing some resources into this page to give you a history of some of the earliest models to be marketed in North America dating back to the late 1970's. This page is still under construction so come back again as we'll be expanding the content into applications and best practices.

Figure 1. Without contradictory evidence, I'm suggesting this is the earliest known ERV (yes before the HRV!) to be sold in North America. Unit was imported from Germany or Austria with first U.S. patents filed in 1978 (see Figure 2) and in Canada (1982) marketed under the trade name of Fan-X (P.M. Wright of Montreal). We specified these and their commercial models up until the mid 1990's and then switched out spec to the heat pipe technology (see Figure 4 below).

Figure 2. Images of U.S. patent filing and description.

Figure 3. The Fan-X unit was later made available in a "through the wall" version preceding modern day products by several years.


Figure 4. Canadian made heat pipe heat recovery ventilator (made by Enviro Air later Fantech) with a round hydronic duct coil from the Netherlands. Photo is early to mid 90's. I always liked the heat pipe technology and specified it as frequently as clients would accept. The round coils were made by Spirotherm (yes the very same company known for its high performance air separator). Both the Fan-X and Enviro Air units used the Kanaflakt inline direct drive variable speed fan.

Figure 5. Plate type HRV serving a basement and clothes drying room (heated with radiant walls). Today our go to system is the same one we used back in the early 80's, radiant based HVAC using a dedicated outdoor air ventilation system typically using an HRV or ERV. It's an elegant system that has worked for us for over 30 years and will continue to work well into the future.


More to come...



  1. Johannes Kirchmeier 1978 U.S. patent filing.

  2. Healthy Heating Integrated Design Course



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