HRV condensation in ducts in Greater Vancouver

Finding water or damp spots in the ducting connected to your HRV is a common Greater Vancouver problem, especially in winter. An HRV moves cold outdoor air and warm, moist indoor air through ducts, and where those temperatures meet uninsulated metal, condensation forms. Here is why it happens and how to stop water from collecting in your HRV ducts.

Why HRV Ducts Sweat

An HRV is a passive ventilation device that runs two air streams: cold fresh air coming in from outside and warm, humid stale air going out. When a duct carrying cold air passes through a warmer space, or a duct carrying warm moist air runs through a cold space, the surface can drop below the dew point and water condenses on it — exactly the same way a cold drink sweats in summer. In our damp coastal winters, the temperature swings make this especially common.

The usual culprits are insufficient insulation on the cold-air ducts, high indoor humidity, ducting running through unheated attics or crawlspaces, and a core or unit that is not draining or balanced correctly.

• Uninsulated or poorly insulated fresh-air and exhaust ducts
• High indoor humidity feeding moisture into the airstream
• Ducting routed through cold attics or crawlspaces
• A vapour barrier or insulation wrap that has come loose
• The HRV core or drain not handling condensate properly

Safe Checks You Can Do

You can safely inspect accessible HRV ducting for sweating, drips, or staining, and check whether the insulation wrap on the cold ducts is intact and sealed. Confirm the exterior hoods are clear so the system is moving air freely, and look at whether your indoor humidity is running high — lowering it with proper ventilation often reduces condensation. Most HRVs have a condensate drain; make sure it is not blocked.

Wipe up standing water so it does not damage materials, and note where the moisture appears, which helps a technician find the cold-spot causing it.

When to Bring in a Technician

If insulation is missing or damaged, if the core or drain is involved, or if condensation keeps returning after you have addressed humidity, a technician should inspect the installation. They can add or repair duct insulation, confirm the unit is balanced and draining, and correct routing problems. HeatLand can resolve HRV duct condensation and protect your home from moisture damage. Improvements to ventilation may qualify for CleanBC or FortisBC rebates, which a technician can help you look into.

Frequently Asked Questions

Why is there water in my HRV ducts in winter?

Cold outdoor air in the ducts can cool the metal below the dew point, so indoor humidity condenses on it. Uninsulated ducts and high indoor humidity make it worse during our damp winters.

Can I fix HRV duct condensation myself?

You can lower indoor humidity, clear the exterior hoods, and check that the condensate drain is open. Repairing or adding duct insulation and balancing the unit are best left to a technician.

Is condensation in HRV ducts harmful?

Ongoing condensation can lead to dripping, staining, and eventually mould or material damage, so it is worth correcting both for your home and for the HRV's performance.

Will lowering my indoor humidity stop the sweating?

It often helps, because less moisture in the air means less to condense. If the ducts are also poorly insulated, both the humidity and the insulation need to be addressed.

HeatLand Heating & Cooling is a licensed and insured, TSBC-certified HVAC company serving homeowners across Greater Vancouver. Our technicians diagnose the real fault, explain your options in plain language, and complete the work safely and to code.

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