Heat Pumps Add Cooling for Toronto Community Housing Residents

With the introduction of heat pumps, thermal comfort improved significantly in the summer months. Reliance on active conditioning (such as window ACs and fans) and passive conditioning (window and door opening) was also reduced. The majority of the residents also found the systems easier to use over time.

The CC-ASHP only achieved 43% of their targeted savings. There are two reasons for this: the outdoor units are slightly oversized, resulting in shorter run cycles in the shoulder seasons. However, this oversizing was necessary due to the ASHPs carrying the full heating load in the winter without relying on back-up heating. In addition, the outdoor unit needed enough capacity to match the combined output of all indoor heat, at the time of installation the smallest indoor heads available had capacities of 8,100 BTU/h, which is much greater than the heating load of the individual bedrooms.

The original baseboards were left in place as a cost savings measure, as removing them can be costly and invasive for residents. In order to avoid the old and new systems working at once, the unused baseboards were turned off at the breaker. A recent site survey confirmed that more than 50% of breakers are currently turned on, and could be consuming energy. This may be a cause of diminished savings.

Air source DHW heat pumps represent real opportunity for savings 

Air source DHW heat pumps reduced electricity consumption for DHW heating by 56% across the monitored suites, which represents 53% of the target savings for this measure. One of the challenges with this technology is that as it draws heat from the surrounding air, so there needs to be room for ample air flow. This has an added benefit in the summer as it adds further cooling to the suite but is a detriment during the heating season. The system also needs access to a drain, which may not always be present in a retrofit scenario. Only a small handful of units on this site had conditions in which these units could be installed.

However, as DHW heating represents over a third of the total site electricity consumption, installing the air source DHW heat pumps still represents a significant opportunity for savings. In a retrofit scenario the location of the DHW closet is important. Because the system cools the air in the wintertime, this can lead to overcooling of adjacent spaces and create comfort issues. There is also some noise associated with heat pumps, which could be disruptive to some residents. Access to ample airflow should also be considered.

Low-flow toilet replacements continuously reach savings targets 

Toilet replacements exceeded the expected target of 14% savings and saved 33% water in the past year and achieved 228% of the intended savings. This success is likely due to the poorer than expected pre-retrofit condition of the toilet fixtures, which may have had significant leakage. We have found low-flow toilet replacements to be consistently successful across multiple projects.

Solutions 

One of the major challenges was that at the time of installation (2019), most of the heat pump products on the market involved indoor heads with a larger capacity than the project needed. Due to this, cycling is occurring more frequently than expected, reducing performance. There are currently far more options available on the market for smaller units.

Another limitation that came up in the project design phase was the thermostat logic for the LG units. With the thermostats available for this product at the time, it was possible to set an upper and lower temperature limit, which is important for curbing the rebound effect. However, the control logic available only allows for one upper and lower setpoint for all modes, rather than individual setpoints for each mode (particularly heating and cooling). This results in the need to set a rather large temperature band and reduces potential energy savings. Again, there are now more thermostat options available on the market with customized temperature limits.

Residents were largely satisfied with the project and 80% found the heat pumps very easy to use. Despite some challenges, 60% of residents gave their overall retrofit experience a rating of 8 and above out of 10. The benefits of thermal comfort improvements cannot be overlooked. In fact, 64% of residents felt that the heat pump was significantly better than their previous heating system.

“Staff that came in to complete the installation were very professional and pleasant. They took the time to speak with my husband and assure him that he would like the units. They were right.” – Walpole Resident