Is your house too dry in winter? Each winter I get emails from homeowners wondering how they can make their homes less dry and more comfortable, but the solution is more complicated than it appears.
Making your home less dry in winter comes down to adding more moisture to the air. This is simple to do with a humidifier. What’s not so obvious is the tug of war that exists between your quest for comfort and your home’s freedom from mould. And part of this conflict comes down to the insulation value of typical windows in Canada.
Houses get dry in winter because cold outdoor air drops tremendously in its relative humidity as it makes its way indoors and warms up. This is why old, leaky houses are the driest of all. Lots of fresh air coming inside through cracks and drafts means lots of dry air in the house. Homes built to modern standards shouldn’t have a draft problem, but then there’s another issue, common to double-pane windows in Canadian houses.
If you add enough moisture to the air in your home to be completely comfortable humidity-wise when its super cold outside, then you’re likely to have excess condensation developing on the inside of typical window glass. A little is harmless, but condensation that’s heavy enough to run down the glass will cause mould to develop along the bottom of windows in time.
This difference in what your body wants and what your house wants happens because the insulating value of typical double-pane glazings is low enough that the interior surfaces of window glass can get cold enough to trigger damaging condensation during extremes of cold weather if indoor humidity levels were to be comfortable for everyone. But if you allow your house to dry out enough to eliminate all excess window condensation, then you’ll probably feel at least somewhat too dry.
So, for most Canadians, feeling somewhat too dry is the price to pay for harmless levels of window condensation, but windows themselves are both a situation on their own and an indicator.
Most modern homes have a layer of plastic on the warm side of insulation, immediately under drywall, to prevent indoor air from making its way into wall cavities where it can cool, losing some of its ability to hold water. Without plastic in place, the same condensation would happen inside your walls that happens on interior window glass. But this plastic layer is not always perfectly sealed, so condensed moisture can theoretically develop inside wall cavities if indoor humidity is too high. The state of window condensation is an easily seen indicator of the state of condensation propensity at your place.
Intentional humidity control comes down to you as a homeowner monitoring and managing the situation by adding more humidity to the air as needed. You can accomplish this with a portable humidifier or the humidifier built into some furnaces. Furnace humidifiers can be tricky though, because they’re out of sight and out of mind in most homes. If your house has a crazy amount of window condensation and you can’t figure out why, it could be that the furnace humidifier is cranked up too high.
So, what’s the solution for all this conflict between the humidity level you want and what’s good for your house? Triple-pane windows offer glass with greater insulation values, so it pretty well eliminates the gap between your comfort and the integrity of your house for most people.
That’s an expensive solution to the problem of dry skin and nosebleeds, but one to keep in mind the next time your home needs new windows. Until then, adding as much moisture to the air with a humidifier without causing excess window condensation is about the best you can do.
