Temperature imbalances in multi-residential buildings are a common issue in Ontario, often referred to as the “hot hallway” problem. Residents may encounter hot, humid air in corridors, even when their own units are adequately cooled. Lobbies can become greenhouses. This isn’t just a comfort issue; it is an operational failure. Ironically, the ventilation systems intended to maintain air quality and safety can exacerbate the problem.
The source of the heat: the makeup air paradox
Many multi-residential buildings rely on rooftop makeup-air units (MAUs). These units are mandated by building codes to draw fresh outside air into the building to pressurize corridors and prevent odours from migrating between suites.
Traditionally, these units were only designed for heating. They perform effectively during -20 C winter conditions, but on a summer day that exceeds 30 C, MAUs continue to pull in hot, humid outside air and pump it directly into corridors. The ventilation system is effectively heating the common areas in the summer.
Rooftop heat pumps
Replacing single-function MAUs with modern rooftop heat pumps addresses both heating and cooling needs. A heat pump is a high-efficiency, two-way energy device. In winter, it pulls heat from the outside air to warm the building. In summer, it reverses the process, removing heat and humidity from the incoming air before it enters hallways. This approach maintains code-compliant ventilation while improving thermal comfort year-round.
Considerations for conversion
Upgrading common area ventilation to a heat pump system can provide multiple operational benefits:
- Solves the comfort complaint: It immediately eliminates the “hot hallway” phenomenon. Common areas finally match the comfort quality of the suites.
- Operational savings: Heat pumps move heat rather than creating it by burning gas. Modern units can operate at 300 to 400 per cent efficiency, significantly lowering operational costs compared to gas-fired equipment.
- Decarbonization and value: Replacing gas-burning equipment with electric heat pumps aligns with net-zero goals, improves the building’s ESG profile, increases asset value, and often qualifies for significant government incentives.
For decades, common area cooling was treated as a luxury. With today’s rising summer temperatures and energy concerns, it is a necessity. Upgrading from a heating-only ventilator to an all-in-one heat pump is a strategic
Investment that provides year-round thermal regulation and operational efficiency. Evaluating existing rooftop systems can help building operators determine whether a heat pump conversion is appropriate for their facilities.
V. Platek, P.Eng, is a president of Platek Engineers Inc. He can be contacted at (905) 290-2625.
