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Interview with Aura Lee MacPherson

Aura Lee MacPherson on radiant wall heating.

Aura Lee MacPherson of MacPherson Engineering in Regina says they have been providing creative engineering solutions for radiant heating and cooling for all types of buildings for years through their Radiant Link system [], and have now engineered a simplified, economical system which uses the thermal mass of concrete basement walls.

1. What brought about your new idea?
We got a call from the Star Blanket Cree Nation in Saskatchewan which maintains 81 homes and was having mould problems in its basements. We found that many of the basements were energy inefficient and unhealthy to live in, and did not even remotely meet the ASHRAE 55 thermal comfort standard. We thought we could come up with an affordable solution that could be used on our housing stock across the country.

2. How does it work?
The current forced air system by itself was not working for all areas of the house. The basements were suitable only for storage and were prone to mould growth. We connected the existing high-efficiency furnace to an in-wall radiant heating system to raise the average wall surface temperature from 14°C to a constant 21°C, effectively using the thermal mass of the concrete. The relative humidity was measured at 14.3% with a dew point of 8°C after the system was installed, eliminating the formation of condensation and resultant mould on the previously cold surfaces.

3. Did you put together a team to help with the idea?
We reached out to Dr. Katherine Arbuthnott, Professor of Psychology at the University of Regina whose research indicated the level of comfort in a home has direct effect on the health and wellness of the occupants. We also consulted the Ministry of Education which has a lot of expertise in the in-floor heating and cooling of schools. And finally, we had generous industry partners: Uponor which donated its manifolds, PEX piping and expertise, the Prairie Co-op  Fort Qu’Appelle Home Centre which  supplied  Amvic’s  Ampex insulation panels, and the installer RS Plumbing & Heating.

4 What are the economics?
The average installed cost for a residential boiler used in a floor warming application is in the range of $21,000. The technology we used for this project cost about $8,500. It uses off-the-shelf products that are affordable and simple to operate and maintain. The system works for retrofits and new construction.

5. How do you see your solution being applied elsewhere?
Using thermal mass really appeals to the traditions of First Nations people who have very strong identity to Mother Earth. The passive effect of basement walls holding heat in the winter and storing coolness in the summer conforms with the principles of respect for the environment and protecting Mother Earth. This solution will work everywhere – in First Nations housing and in other regions, for retrofits and new construction.