Why Do Some Homes Consume More With a Heat Pump? The Hidden Impact of Air Leaks

A high-performance heat pump… but energy bills are still too high?

At AirGreen, we are often called by clients in Montréal, Laval or Longueuil who wonder why their central heat pump uses more energy than expected. They invested in high-efficiency equipment, sometimes eligible for LogisVert grants, but their electricity bills are not going down. On the surface, everything seems to work. Yet one essential factor is often overlooked: air leaks in the building envelope or the ductwork.

Understanding how air leaks interact with your heat pump

Unlike a wall-mounted air conditioner installed in a sealed room, a central heat pump relies on a properly sealed ductwork system and a well-insulated building envelope to deliver optimal performance. When there are air leaks, whether in the attic, around window joints, baseboards, or in poorly sealed metal ducts, the system is forced to run longer—especially during extreme cold on the North Shore or heatwaves on the South Shore.

Real case study: HVAC installation in Laval in a 1988 home

During a service call in Laval, we encountered a typical situation. The homeowner had a 36,000 BTU Lennox central heat pump, installed by another contractor a year earlier. Despite boasting solid SEER and HSPF ratings on paper, the electricity consumption remained abnormally high.

We performed a blower door test in partnership with an energy advisor, which revealed an uncontrolled air exchange rate due to leaks in a poorly insulated attic and flexible basement ducts. The result: heated air was escaping, and the system was compensating with extended cycles. After sealing the leaks using polyurethane foam and professionally sealing the HVAC ducts, monthly consumption dropped by 27%.

Common causes of excessive consumption with a heat pump

• Unsealed ductwork: often found in homes built before 2000 in Montréal, leading to heat or cooling losses.

• Leaks in the ceiling or attic: warm air naturally rises and escapes through poorly insulated spaces.

• Unsealed doors and windows: outside air infiltrates and throws off the HVAC system’s balance.

• Improperly calibrated or poorly placed thermostats: causing excessive cycles that wear down the compressor.

Warning signs your home is inefficient despite a good heat pump

• Rooms that stay cold even when the unit is running

• Large temperature differences between floors

• System turning on and off frequently (short cycling)

• Audible airflow sounds behind walls or floors

Good equipment isn’t enough: the importance of a full home assessment

At AirGreen, we emphasize a holistic approach to energy efficiency. Installing a high-efficiency central heat pump like the Fujitsu KZAH R-32 or the Bosch BIVA IDS Premium R-454B doesn’t automatically guarantee savings. These systems are designed for well-sealed homes. That’s why before each project, we assess:

• The condition of existing ductwork (sealing, insulation)

• The layout of supply and return vents

• The home's orientation and high-loss zones

• Eligibility for grants when duct sealing or window caulking is added

Available grants for improving your building envelope

In many boroughs of Montréal as well as in Longueuil and the South Shore, you can access additional grants for insulation work, air sealing, or optimizing ductwork. When paired with a new HVAC installation, your total subsidy amount can sometimes exceed $5,000.

AirGreen’s expert advice to avoid overconsumption

• Have your HVAC ductwork inspected with every heat pump installation.

• Choose a contractor who offers a basic thermal assessment before installing.

• Request bundled solutions: equipment + sealing + grille adjustments.

• Install a smart thermostat compatible with your central unit.

• Opt for Inverter technology heat pumps, especially in windy areas like Sainte-Julie or Beaconsfield.

Conclusion: A high-efficiency system needs a high-performance home

A central heat pump, no matter how advanced, cannot compensate for major structural inefficiencies. Thermal comfort, energy consumption, and system longevity all depend heavily on the effectiveness of your air distribution network and the building envelope. At AirGreen, we are committed not just to helping you choose the right product, but to ensuring complete optimization of your comfort and energy efficiency.

We operate throughout Montréal, Laval, Longueuil, the North Shore, and the South Shore, and our expertise is based on hundreds of real-world central heat pump installations, each with durable solutions tailored to residential or commercial configurations.