Q:  Why do the insides of the windows on my four-year-old home get wet whenever it’s cold? Our furnace has no humidifier and the dehumidifier we’ve been running doesn’t help.

A:  Wet windows in winter are a common problem in modern Canadian houses and it happens because indoor humidity levels are too high in relation to the insulation value of the glass. When windows get cold enough they cause indoor air to condense and form moisture droplets on the window panes.

HRV unit installed in home
HRV unit installed in home

As you’ve discovered, a dehumidifier offers no help because it can’t make indoor air dry enough. The only real source of relief involves bringing more outdoor air into your house, and you can do this in one of three ways.

You can open windows part way before they freeze shut, or you can operate bathroom exhaust fans and range hoods more frequently and longer. Both these options work, but they also mean you lose heat.

Another alternative is a heat recovery ventilator (HRV).  These devices bring plenty of fresh, dry outdoor air into your home, and they do it while saving most of the heat in the stale air before sending it outside. HRV’s are permanent devices that cost a couple of thousand dollars to buy and install, and they really do work. No matter how wet your windows are, they will be dry with a properly installed and operated HRV in your home.

Thinking of installing a Heat Recovery Ventilator in your home? Connect with Verified by eRenovate™ HVAC Contractors by using the eRenovate Post My Project tool or the eRenovate App.


Steve Maxwell is Canada’s Handiest Man. An award-winning home improvement authority and woodworking expert, he’s truly a treasure of home wisdom and the ultimate home GURU. Be sure to visit his site at SteveMaxwell.ca.


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