Stop Sending Heat Down the Drain: Heat Recovery & Thermal Storage for Ontario Buildings

Phase two of the phased roadmap (see the pillar post) is recovery — and it’s often the single highest-return move in the whole plan. Every path to decarbonization runs through building heat recovery: buildings constantly generate and then throw away heat, and capturing it means the electrified plant you install later has far less work to do.

Buildings Waste Heat in Three Big Ways

Effective building heat recovery targets the three places Ontario buildings lose usable heat:

• Down the drain: showers, laundry and kitchens send warm wastewater straight to the sewer. Wastewater energy transfer (WET) systems and sewage-source heat pumps extract that heat and redirect it to space heating or domestic hot water.

• Off the cooling plant: cooling produces heat. Waterside and condenser heat recovery captures the heat rejected by chillers and reuses it — often enough to offset separate heating equipment entirely.

• Out the exhaust: ventilation blows conditioned air outside year-round. Airside heat recovery (HRV/ERV on exhaust) reclaims that heat while keeping fresh-air rates intact.

  
  

Wastewater Heat Recovery: The Overlooked Goldmine

Wastewater is one of the most consistent, year-round heat sources a residential building has — people shower every day, in every season. Wastewater energy transfer is a proven form of building heat recovery that pairs a sewage/greywater heat exchanger with heat pumps to produce heating, cooling and domestic hot water. For multi-residential buildings with high hot-water demand, it can become a cornerstone of the decarbonization plan rather than a footnote.

Thermal Energy Networks: Sharing Heat Across a Building

The real power of building heat recovery shows up when you stop treating heating and cooling as separate systems. A low-temperature thermal energy network moves recovered heat from where it’s rejected (the cooling side, the drains) to where it’s needed (space heating, hot water) — simultaneously. Reconfiguring a building around a shared thermal loop is what turns isolated efficiency measures into a genuinely low-carbon system.

Thermal Storage: Save Heat for When You Need It

Recovered heat and building demand don’t always line up in time. Thermal storage — hot- or chilled-water tanks, or ice storage — banks recovered energy and shifts it to peak periods. In Ontario, where electricity pricing and peak-demand charges matter, thermal storage also shifts load off expensive peak hours, improving both the carbon and the cost case for building heat recovery.

Recover, Then Replace

With loads reduced (Blog) and waste heat recovered, the heat pumps you install in the final phase (Blog : Cold-Climate Heat Pumps) can be dramatically smaller. Mann Engineering designs and delivers building heat recovery systems — wastewater, waterside, airside and thermal storage — for multi-residential and commercial buildings across Ontario. Contact Mann Engineering for a free assessment of where your building is wasting heat today.