Is a heat recovery ventilator necessary for a well-insulated addition in Ottawa?

In a well-insulated, airtight addition, mechanical ventilation is not optional in practice. The Building Code sets mechanical ventilation requirements for houses, and your designer will confirm what your addition needs and whether the existing system covers it. Without good ventilation, moisture, cooking smells, emissions from new materials and stale air build up, and in a cold climate that moisture can lead to condensation, mould and damage inside walls.

A heat recovery ventilator (HRV) brings in fresh outdoor air and exhausts stale indoor air continuously, passing the two streams through a core so the outgoing air warms the incoming air. That means you get fresh air without throwing away as much of the heat you paid for, which matters through Ottawa winters that regularly reach well below -20°C.

Without a ventilation system, you face an uncomfortable choice in winter: keep windows closed and live with stale, humid air, or open them and lose heated air. An HRV removes that tradeoff, delivering tempered fresh air rather than outdoor air straight into the room.

There are two common ways to ventilate an addition. If your home already has an HRV, a contractor may be able to extend its ductwork to serve the addition, provided the existing unit has enough capacity and the duct route is practical. Otherwise, the addition can get its own unit. Ask for both options and a ventilation calculation that shows the airflow the addition needs.

Equipment choice matters in a cold climate. Ask how a unit handles frost on its core during long cold snaps, since cores can ice up and units use defrost strategies that briefly change how they operate. An energy recovery ventilator (ERV) is an alternative that also transfers some moisture, and some people prefer it in very dry winter homes. Your HVAC contractor can explain which suits your house.

Moisture control is the benefit people underestimate. Breathing, cooking, showering and laundry all add moisture to indoor air. In a tight addition without ventilation, that moisture condenses on the coldest surfaces, such as windows and the inside of exterior walls. An HRV steadily removes humid air and helps keep winter humidity in a comfortable range.

Installation details count. The intake and exhaust hoods need to be placed apart from each other and away from dryer vents, gas appliance exhausts and garage openings, and the ducts need to be insulated and sealed where they pass through unheated spaces. The unit needs balancing after installation so it moves the air it was designed to move. Ask whether balancing is included.

Ask your designer to confirm the ventilation requirement for your addition, then compare itemized quotes from HVAC contractors that state the airflow, the equipment, the duct work and the balancing.

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• 613Bins
• RenoMotion Inc.
• Denys Builds Designs Renovations
• Titley Construction
• Elie The Carpet Guy Inc.