Just launched: Carbon Emissions Inventory 2024

Performance Monitoring of Large Central Air-to-Water Heat Pumps in a Multi-Unit Residential Building

66 Walpole Ave, Toronto

Type

Town house complex, owned by Toronto Community Housing Corporation

Old System

Electric baseboard radiators, electric hot water tank, 7.6 LPF toilets

New System

LG multi-split cold climate air source heat pumps, Rheem Air Source domestic hot water heat pumps, and low flow toilet retrofit.

Partners

Toronto Community Housing Corp. | Ecosystem

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Project Details

66 Walpole Ave, Toronto: Town house complex, owned by Toronto Community Housing Corporation

Old System: Electric baseboard radiators, electric hot water tank, 7.6 LPF toilets

New System: LG multi-split cold climate air source heat pumps, Rheem Air Source domestic hot water heat pumps, and low flow toilet retrofit.

Partners: Toronto Community Housing Corp. | Ecosystem


October 2025. TAF commissioned Sustainable Technologies Evaluation Program (STEP) to provide operational analysis and optimization of an air-to-water heat pump retrofit.

Key Findings

  • The heat pumps fully met the cooling demand and supplied approximately 70% of the hydronic space heating load, reducing natural gas and carbon emissions by 21,000 m³/year and 30 t CO2e/year, respectively.
  • Low-GWP refrigerants are essential, as are safeguards to limit refrigerant loss, preventative maintenance, and contractor training.
  • The retrofit resulted in a slight increase in utility costs, largely due to the removal of the carbon price. Heat pump operation can be optimized around time-of-use electricity rates to mitigate this increase.


Recommendations

  • Create a mock installation to test new technologies.

    Understanding sequencing and interaction of trades, and troubleshooting issues without disrupting residents prior to a full building rollout improves results and resident satisfaction.

  • Enable cooling

    to increase resident comfort and satisfaction, reduce peak demand, and protect against health impacts of extreme heat.

  • Lengthen cycle times and reduce return temperatures to allow GAHP to reach maximal steady-state efficiency.

    Increase the deadband of the GAHP controller to keep it on for longer periods, installing the heat exchanger in a counterflow configuration to promote better heat transfer (and likely reduce the temperatures in the GAHP glycol loop). And, add more intelligent control to the recirculation loop such that it is not unnecessarily mixing hot water with the cold city water prior to the GAHP heat exchanger.

22%

reduction in greenhouse gas emissions

$5k

annual savings on energy bills

100%

tenant satisfaction with thermal comfort

17%

reduction in electricity demand

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