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How We Did It Volume 4 — Heating & Cooling Using Mother Earth


When you park your car (or bike) at the priMED Mosaic Center, you will be doing so on top of the 32 geo-thermal wells (boreholes) that reach 70m (230 ft.) below the north parking lot. A ground-source heat pump, located in the mechanical room, circulates a mixture of food grade antifreeze (20% propylene glycol) and water through the network of three-quarter inch vertical piping.

Simply put, when the building requires heat, the high pressure glycol mixture is pumped through the system to “soak up” available heating energy from the soil and then back into the building’s mechanical room to the heat pumps. Here, the fluid temperature is elevated to 93°C before it is circulated throughout the interior of the building to the individual VRV heating units by way of another refrigerant loop. In the warmer summer months, the system is reversed and energy is dissipated back into the ground. Acting as a giant battery, the soil beneath the Mosaic Centre stores rejected heat during the summer months for use in our frigid Edmonton winter.

Efficiency was the primary design focus when selecting the heating and cooling systems as the Living Building Challenge Net-Zero petal requires all of the Mosaic Centre’s energy to be produced on-site. All of the energy for the building is generated by solar photovoltaic modules. With a limited amount of roof area, and a limited budget, it was crucial that the quantity of modules was minimized. Heating directly with electricity is extremely inefficient in comparison to using the same amount of electricity to run the compressors in the geothermal heat pumps.

So, when you visit or work at the Mosaic Centre, you will experience a space that has been cooled or heated solely using the sun’s free radiation in combination with mother earth’s complimentary battery service.

Want to geek out and learn more?  Explore the world of geothermal energy.

Meet the engineer that crafted the Mosaic Centre’s geothermal system and increased the systems return on investment.

Why the Mosaic Centre is heated & cooled using geothermal energy:

  • The most efficient heating and cooling system commercially available: 360% in heating and 600% in cooling
  • Reduced energy consumption by over 50% compared to the next most efficient system
  • Reduced the amount of PV required by 40,000 Watts; a cost saving of over $80,000 with the geothermal system factored in
  • Reduced maintenance costs over the life of the system
  • Highly resilient with a life cycle of that exceeds 100 years and offering a reduced net present value of the system
  • No roof-mounted or outdoor equipment required, reducing roof costs and increasing available roof area for solar modules


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