How do I reduce the whistling noise my HRV makes when the wind picks up during Ottawa winters?

Wind-induced HRV whistling is one of the most common winter noise complaints in Ottawa homes, and it happens because strong winds create pressure differentials across your exterior intake and exhaust hoods that force air through the unit at irregular velocities, causing turbulence and resonance in the ductwork. When Ottawa gets those brutal northwest winds off the Ottawa River at 40 to 60 km/h during January and February, even a well-installed HRV can start to whistle. The good news is that this is almost always fixable.The first thing to check is your exterior hoods. Standard builder-grade hoods with flat damper flaps are notorious for whistling in wind. Upgrading to a wind-resistant hood designed for high-wind applications — such as a Broan or Venmar wind hood with baffled internals — costs $80 to $150 per hood and can eliminate the problem entirely. You have two hoods (intake and exhaust), and both should be upgraded. While you are at the hoods, check that the damper flaps move freely and are not stuck partially open, which creates a reed effect that amplifies whistling. In Ottawa, ice buildup on damper flaps is common when temperatures stay below -15°C for extended periods — the condensation from warm exhaust air freezes the flap in a partially open position.Ductwork and Damper SolutionsIf new hoods do not solve the problem, the whistling is likely occurring inside the ductwork. The most common cause is undersized duct runs — when builders use 5-inch duct for an HRV that requires 6-inch, air velocity increases and whistling becomes much more likely at high wind speeds. Correcting undersized duct is a more involved fix at $500 to $1,200 depending on accessibility, but it permanently solves the problem. Another frequent culprit is flex duct with sharp bends. Flex duct should never be bent at more than a 45-degree angle, and sharp 90-degree turns create turbulence that whistles. Replacing sharp-bent flex duct with rigid metal duct and proper elbows costs $300 to $800 for a typical HRV installation.Installing an inline duct silencer on the intake side — the side most affected by wind — is an effective and relatively affordable fix at $150 to $300 for the silencer plus $100 to $200 for installation. A 6-inch silencer that is 24 to 36 inches long, lined with acoustic mineral wool, can reduce wind-driven noise by 15 to 25 dB without significantly affecting airflow. Make sure any silencer used in the cold-air intake path is rated for Ottawa's temperature extremes, as some acoustic liners can absorb moisture and degrade in freezing conditions.One often-overlooked solution is adjusting the HRV's balancing dampers. Every HRV has internal or external balancing dampers that set the ratio of supply to exhaust airflow. If these are set so that the unit runs with a slight positive or negative pressure imbalance, wind gusts can push the system past a resonance point and trigger whistling. Having an HVAC technician rebalance the HRV with a flow hood — typically a $150 to $250 service call — can reduce wind sensitivity significantly. If you have been chasing this problem through multiple Ottawa winters without success, a soundproofing or HVAC professional with specific HRV experience can diagnose the exact resonance point — the Ottawa Contractor Directory at justynrookcontracting.com/directory is a useful resource for finding specialists in your area.Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:Reno's by Daniel FrauwallnerJC CarpentryDreamwood Construction & RenovationsEastern Residential SolutionEasySave PaintingView all contractors →