How to Eliminate Wet Winter Windows

Increased Ventilation is the Only Cure

window condensation due to ventilation problems

Friends of mine from the city came up to their 700 sq. ft. lakeside cottage last week, and they enjoyed a nice, cozy stay in the building I designed for them 5 years ago. It’s made of structural insulated panels (SIPs), so it’s very easy to heat. Part of this is because SIPs create such an airtight structure,  but this does present one drawback.

Heat Recovery Ventilator (HRV)

Even though no one has ever lived in this cottage during winter, I knew for sure that window condensation was going to be a problem for them. That’s why I included convenient connections for a heat recovery ventilator (HRV) when I drew up my plans, though the HRV isn’t installed yet. Sure enough, a couple of days into my friends’ stay, I got word that water was running down the inside of the glass panes and pooling down below. They’d tried a dehumidifier before talking to me, but I knew that wouldn’t work and it didn’t. Dehumidifiers can’t lower indoor humidity enough to prevent condensation on most windows.

Ventilation is Key

My suggested solution was to open an upstairs window an inch or so, then run the downstairs bathroom exhaust fan for a while. That did work, and once the windows were clear, they stayed that way without running the fan. One way or another, homes need ventilation. An HRV provides fresh outdoor air while reclaiming most of the heat from the stale indoor air before shooting it outside. But if you’d rather not spend the $2500 necessary to install and HRV, then an open window and exhaust fan does wonders.

Posted on January 15th, 2011


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