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GAHPs: Technology Assessment and Field Test Findings

GAHPs: Technology Assessment and Field Test Findings

GAHP technology offers significant performance improvements when compared to conventional gas-fired heating equipment. Based on this pilot installation, GAHPs can generate significant carbon and operating cost reductions when installed in the appropriate context.

These are some of the conclusions reached by The Atmospheric Fund (TAF), which invests in urban solutions in the Greater Toronto and Hamilton Area (GTHA) to reduce carbon emissions and air pollution. 

But what did TAF do to reach these conclusions?

Let's go deeper in TAF project...

The challenge

Multi-residential buildings represent the backbone of the housing stock in the Greater Toronto and Hamilton Area (GTHA). While these buildings are a critical asset to the region, many of them are also in serious need of reinvestment and renewal. Deep energy retrofits can renew the housing stock while also achieving a wide range of benefits – reducing operating costs, improving indoor environmental quality and resident comfort, and creating local jobs.

Key figures

41% of households in the GTHA are in multi-residential buildings.
64% of existing multi-residential buildings were constructed before 1990.
46% private rental, 37 per cent condominiums, 18 per cent social housing.
Multi-residential buildings account for 5.1 million tonnes of carbon emissions, equivalent to a quarter of regional building emissions.

The solution

The Atmospheric Fund (TAF) launched the TowerWise program in 2007 to accelerate deep energy and emission retrofits across the multi-residential building sector. Working with building owners, utilities, governments, and other key stakeholders, we set to work identifying and overcoming the many barriers to deep decarbonization in the sector.
One key barrier is that the technical and economic feasibility of deep retrofits has not been adequately demonstrated. So they partnered with affordable housing providers to design, construct and finance major retrofits in 10 buildings housing over 1,700 low-income families. Building upgrades included new condensing boilers, gas absorption heat pumps, heat recovery ventilation, LED lighting, smart thermostats, and many more. They continue to document the effects of these upgrades through real-time monitoring of whole building performance as well as research-grade instrumentation of key equipment and systems.

As one of few such demonstration programs in Canada, TowerWise retrofits showed that 20-30 per cent energy and carbon savings are not only achievable but highly profitable. The lessons learned and data collected have been used by provincial and federal partners to support the development of new programs and equipment regulations.

From TAF website


Not all heat pumps are electric. Back in 2016, TAF installed two gas heat pumps in a large residential complex, one of the first large-scale field pilots in a cold climate. Our new report charts their progress and reveals some exciting results and lessons.


Why not all electric? In fact, while electric heat pumps in Ontario are certainly lower carbon and most efficient, gas absorption heat pumps (GAHPs) enable buildings to consume natural gas more efficiently, and are a key priority for reducing carbon emissions. For building owners who don’t want to switch from gas to electric-heating, GAHPs offer an affordable and efficient alternative.

We installed two such heat pumps in a Toronto social housing building built in 1972, containing about 400 residential units. Our goals were to monitor the system and determine whether actual performance would measure up to expected performance, and whether this technology would be appropriate for future projects in cold climates across North America.

Field monitoring over last winter revealed that theheat pumps achieved 114% efficiency. During extreme cold weather (down to -13°C) the heat pumps continued to save natural gas and emissions compared to a modern condensing boiler. Over the past summer, as the exterior temperatures warmed up, performance increased to a maximum of 125% efficiency, in line with manufacturer performance curves.

Overall, these units are expected to save nearly 5400 m3 of natural gas and over 10 tonnes of carbon emissions annually compared to a 90% efficient condensing boiler (that’s equivalent to driving a gas combustion automobile around the Earth’s circumference!) Our findings have shown that GAHPs are significantly more efficient than conventional gas-fired heating equipment and can reduce emissions and gas consumption, while avoiding switching to a higher cost fuel. We also found that domestic hot water applications are ideal for this technology due to the relatively low water system temperatures required. This enables the heat pumps to operate at their most efficient levels.