Home heating and hot water savings from midrise apartment retrofit

As these technologies were new to our climate zone, and the application of installing the ASHPs through an existing through-wall air conditioning sleeve was also new, there were a number of challenges in the process. As such, we are looking towards the second year’s heating season for improved savings results. 

The ASHP measure achieved 26% of its target energy savings. The Innova units are retrofitted through an existing AC sleeve, rather than through the wall itself, an installation scenario that was new for the installer. One challenge was the the need to insulate the cavity of the AC sleeve. When the original insulation proved insufficient, we had to re-insulate about 32% of suites in February 2022. 

A few issues with freezing in the condensate drainpipe caused water to back up. The drainpipe was installed at the installer-recommended angle of three degrees, however, in other cold climate areas the drainpipe is usually installed at a 30-degree angle, which increases drainage and prevents ice backup. Because of the original wall condition and electrical conduit running unseen through the walls, it was not possible to re-drill and re-angle the drainpipes. Instead, we added a heat trace line to all units in April 2022. The heat trace draws a small amount of power whenever the Innova is on, and the heat output is dictated by the outdoor temperature. 

Individual unit monitoring shows ASHP outperforms the original system. 

In many cases the original baseboard heaters had to be turned on in suites for extended periods of time while we took corrective action to address these challenges. Toronto and Region Conservation Authority’s (TRCA) Sustainable Technologies Evaluation Program (STEP) team monitored two sample suites to determine the co-efficient of performance (COP) of the combined ASHP and existing baseboards as a system, and both units revealed a COP of 1.4. Although the first-year savings are lower than expected, the COP of the system remains above that of the pre-retrofit system, and we have already seen increases in subsequent months.  

GAHP systems can benefit from continuous commissioning. 

The Vicot GAHP was unable to achieve its target gas savings in the monitored period. STEP provided in-depth analysis of the Vicot GAHP from January to June 2023. They determined that the GAHP provided approximately one third of the heating for DHW during the monitoring period, with the boiler providing the remaining two thirds. The GAHP started off providing approximately 55% of the heating load at the beginning of the monitoring period but this reduced to 30% by the end of the monitored period. This was correlated with a decreasing trend for overall DHW consumption from winter to summer, and also with a decline in the GAHP efficiency. The total GAHP efficiency for the monitoring period was 113%, but on a daily basis it ranged from more than 140% to as low as 80%. The total system efficiency was calculated at 90%, but on a daily basis it varied from 80% to 110%. The investigation led us to believe that frequent cycling was responsible for the reduced performance. Potential solutions to this issue are described in the Recommendations section below. 

Resident satisfaction with the retrofit process was lower than anticipated, with 14% of residents rating the process an 8 or above out of 10. Resident feedback demonstrated frustration with the multiple suite entries required to troubleshoot issues.

There was a slight increase in residents who described feeling “too cold” in the winter. A few residents remarked that the introduction of blowing air into their living space was uncomfortable. Perceptions of temperature can be influenced by the feeling of moving air, so it can often take time to adjust when moving from radiant heating to a heat pump system. Moreover, residents may now be experiencing comfort issues related to poorly insulated and leaky windows, a problem that was previously masked by the perimeter heating.

Opt-in cooling for a fee impacted resident satisfaction with thermal comfort.

There was a slight improvement in thermal comfort in the summer months, with fewer residents feeling “too warm.” Daily use of passive conditioning such as opening windows or balcony doors also decreased. It’s important to note that cooling was not enabled for all residents, and instead was enabled for a fee. Just under half of the residents have chosen to opt in. This decreased resident satisfaction as they had previously had access to the AC sleeve and were able to provide their own (albeit inefficient) cooling. Potential thermal comfort improvements are higher than reflected.

Utilizing the wall sleeve was important as it removed the need to add additional penetrations through the envelope. Allowing residents to use the system in both heating and cooling modes can improve their thermal comfort and overall satisfaction.

For further monitoring data, download Vicot Gas Absorption Heat Pump Analysis by Erik Janssen, Research Scientist, Sustainable Technologies Evaluation Program (STEP) of Toronto and Region Conservation Authority (TRCA).