Decarbonizing Multi-Unit Residential Buildings: Insights from Minto's First Decarbonization Hackathons

LIVE Minto | 4 MIN READ | 2023-07-26

Over the past 18 months, there has been an increased focus on deep retrofits and decarbonization. Most events on the topic, however, have been focused on one sector – building owners, consultants, or contractors — with very few bringing together multiple groups across different areas to exchange ideas and experiences.

To help bridge this gap and foster collaboration, Minto hosted two decarbonization “hackathon” events in May 2023; one in Ottawa and one in Toronto. These events brought together a diverse range of participants, including consultants, contractors, vendors, and building owners, to tackle the challenge of retrofitting a multi-unit residential building (MURB) suite heating system. Most suites that currently heat via perimeter radiators use high-temperature hot water (180F), however, low-carbon heating systems generally produce low-temperature hot water (140F or less). Therefore as part of a whole building decarbonization project, the suite heating system must be modified in addition to the heating plant.

Participants from Ottawa’s Decarbonization Hackathon event.

Minto’s Castlehill building was selected as the example property for these events, and all hackathon participants were sent an information package which included the building’s mechanical system and drawings.

Each group included a mix of engineering consultants, contractors, building owners, and equipment suppliers. The goal for each participant was to provide input based on their role’s perspective, such as technical knowledge, installation considerations and logistics, site operation, availability, and capacity/limitations of equipment.

Participants from Toronto’s Decarbonization Hackathon event.

Each team presented one or two final solutions which were then discussed and evaluated by the entire group. The results are as follows.

Key Takeaways

There is no “one size fits all” solution. Building owners and managers must consider the life span of existing equipment and infrastructure, as well as other building objectives when selecting the right solution for each building.

Solution #1

Summary: Replace existing wall fin with small horizontal fan coil units (FCU) — (Jaga or similar).

Advantages:

• Uses existing hot water riser infrastructure. 
• Doesn’t require an upgrade to suite electrical system (fan electrical load is extremely low).
• FCUs can be installed on suite turnover to minimize the impact on residents.
• FCUs can use high-temperature water until the central heating plant has been switched to a low-temperature plant.
• FCUs can provide heating and cooling. An additional condensate riser needs to be added for units to provide full cooling capacity, but units could temper air initially (must stay above dew point to prevent condensate from forming).

Disadvantages:

• Doesn’t address indoor air quality, however stand-alone energy recovery ventilator (ERV) could be installed in the suite.
• Cooling at the perimeter and low level is not ideal from a comfort perspective, and could be considered lower quality than a traditional FCU or in-suite heat pump.
• Doesn’t allow for submetering. Energy costs would still be in the common area.

Estimated cost per suite: $16,000 per suite, additional $3,000 for stand-alone ERV.

Opportunities:

• Manufacturers to develop a horizontal FCU with an integrated ERV.

Solution #2

Summary: 2/4 pipe vertical FCU or heat pump, option for integrated ERV.

Advantages:

• Allows for simultaneous heating and cooling within the building (except for 2-pipe FCU).
• Allows for phased installation. Each riser can be brought online while the rest of the building operates via existing baseboard heaters.
• Heat pumps (HP) would allow for some of the energy cost to be transferred to the suite level (submetered).
• Better thermal comfort than horizontal FCU.
• Integrated ERV would improve indoor air quality.
• Specific to Castleview property – a central heat pump loop could also serve pool heating system.

Disadvantages:

• Requires a new set of risers (this could be neutral or an advantage if the existing risers are at the end of their life span and need to be replaced). 
• Would reduce useable floor space within the suite.
• Would probably require an upgraded suite electricity panel (additional capacity), but the heat pump option would reduce the electrical load of the central plant. 
• Could be implemented on suite turnover but may require work in the occupied suite to complete a full riser.
• Heat pump option would increase in-suite maintenance scope.

Estimated cost per suite: $24,000 - $30,000 per suite, depending on FCU vs HP, ERV or not

Opportunities: None identified in the hackathon.

Solution #3

Summary: Similar to Solution #2, however, run the new risers on the building exterior to horizontal (ceiling) FCU or heat pumps in the suites (option for integrated ERV).

Advantages:

• Allows for simultaneous heating and cooling within the building (except for 2-pipe FCU).
• Riser work can be completed independent of in-suite scope, reducing the impact on residents. In-suite work could be completed on suite turn-over.
• Heat pumps would allow for some of the energy cost to be transferred to the suite level (submetered).
• Units installed in the ceiling (above the washroom, closet, etc.) would not affect useable floor space within the suite.
• Better thermal comfort than horizontal (baseboard) FCU.
• Integrated ERV would improve indoor air quality.
• Specific to the Castleview property – a central heat pump loop could also serve pool heating system.

Disadvantages:

• Risers would need to be very well insulated (possibly part of the building over-cladding project), even if glycol is used there is an operational risk with having risers on the exterior of the building.
• Would probably require an upgraded suite electricity panel (additional capacity), but the heat pump option would reduce the electrical load of the central plant.
• Heat pump option would increase the in-suite maintenance scope.

Estimated cost per suite: Unknown

Opportunities: None identified in the hackathon

Other Considerations and Next Steps