Most people notice humidity before they ever think about it. In January it shows up as static shocks off the light switch, a dry throat in the morning and gaps opening between hardwood boards. In July it is the clammy feeling in the family room even though the air conditioner is running, or the musty smell when you go down to the basement. Both have the same root: the amount of moisture in the air, and how your house and its heating and cooling system handle it.
This guide walks through what is happening in each season, how to tell whether your house is too dry or too damp, and what tends to help in the different kinds of Waterdown houses.
Why does the house get so dry in winter?
Cold air cannot hold much water. When outdoor air at the kind of temperatures we get here leaks into the house or is brought in by a ventilator, and the furnace warms it up, that same small amount of moisture is spread through much warmer air. The result feels dry.
The heating season here is long. At the Hamilton RBG climate station near Waterdown, the normal daily average temperature is -4.7 °C in January and -3.9 °C in February, so the furnace is warming outside air for months on end. The colder it gets outside, the drier the house tends to feel.
How can I tell if my house is too dry or too damp?
Your windows are the most honest gauge you have. A small hygrometer from a hardware store helps too, but watch the glass first.
Signs the air is too dry:
- Static shocks, dry skin, cracked lips and itchy eyes
- Wood floors, trim and doors shrinking or creaking more than usual
- Plants and furniture drying out
Signs the air is too damp:
- Water running down the inside of the windows, or frost on the inside of the glass on cold mornings
- Dark spots or mould in the corners of closets and on outside walls
- A musty smell in the basement, or sweating cold-water pipes in summer
One point that surprises people: the right winter humidity level goes down as it gets colder outside. A level that feels comfortable in November can fog every window in a February cold snap. If you see condensation forming, turn the humidifier down rather than wiping and waiting.
What about newer houses in Waterdown South and Waterdown Bay?
Houses built in the newer subdivisions are much tighter than older homes, and they come with a heat-recovery ventilator, or HRV. The HRV brings in fresh outdoor air and exhausts stale air, passing heat between the two streams so you are not throwing heat away.
That fresh air is also dry winter air. An HRV set to run hard all winter can leave a new house feeling as dry as an old one. On the other hand, an HRV that is turned off or clogged lets cooking, shower and breathing moisture build up, and the windows start to sweat.
What to check in a newer house:
- Is the HRV running at a sensible setting for the season, rather than on high all winter or switched off?
- When were the HRV filters and core last cleaned? Neglected filters choke the airflow.
- Is the HRV balanced, so it brings in about as much air as it sends out? An unbalanced unit is a common service call in these houses.
It is also normal for a brand-new house to feel damp in its first winter or two while the framing, drywall and concrete dry out. Running the HRV properly matters more than adding a humidifier during that time.
And in the post-war surveys like Glenlea, Buchan Court and Renwood Park?
Most of these houses have forced-air furnaces, which means a humidifier can be mounted right on the ductwork. There are three general kinds:
- A bypass humidifier, which uses the furnace's own airflow through a water pad. Simple and the least costly to buy and run.
- A fan-powered humidifier, which has its own fan, so it adds more moisture and does not depend on a bypass duct.
- A steam humidifier, which boils water electrically. It adds the most moisture and works even when the furnace is not heating, but it costs more to install and to run.
These houses are often on their original ductwork, which can be undersized for a modern furnace. That matters for humidity too: if there is not much room or airflow at the supply plenum, a bypass unit may struggle, and a technician should look at the duct layout before recommending one.
A humidistat with an outdoor temperature sensor is worth asking about. It lowers the humidity setting automatically as the weather gets colder, which saves you from fogged windows on the coldest nights.
What about the old houses in the Griffin Survey and the McMonnies and Stock Survey?
The pre-war houses in the old village were built long before anyone sealed a house tightly, and many still heat with hot-water radiators. They tend to be drafty, and drafty houses are dry in winter because so much cold outside air is coming in.
Without ductwork, a furnace-mounted humidifier is not an option. Room humidifiers in bedrooms and living areas are the practical answer, and sealing the worst drafts around windows, doors and the attic hatch will do more than any machine. Where a house does have converted ductwork from an old gravity furnace, it is worth checking the condition of that ductwork before adding a humidifier to it.
Why does the house feel clammy in summer even with the air on?
A central air conditioner cools the air and pulls moisture out of it at the same time. That moisture drips off the indoor coil and leaves through a condensate drain. For that to work well, the system has to run long enough on each cycle.
An air conditioner that is too large for the house cools it quickly, shuts off, and never runs long enough to dry the air. The result is a cool but sticky house. A system matched to the house removes more moisture. If you are planning air conditioning installation, ask how the system was sized for your house rather than copied from the old unit's label. Work is performed by 313A refrigeration and air conditioning mechanics.
Other summer moisture checks:
- Leave the furnace fan on auto rather than on, so water on the coil drains away instead of being blown back into the house.
- Make sure the condensate drain is clear. In newer houses a blocked drain can shut the system off or leak onto the floor.
- Turn the HRV down on muggy days so it is not bringing in more humid air than you need.
Do I need a dehumidifier in the basement?
Basements stay cool in summer, and warm, humid outdoor air that reaches them can condense on the floor, walls and cold pipes. Air conditioning often does little for a basement because few supply registers reach it.
A portable dehumidifier is the usual fix. Drain it to a floor drain with a hose rather than emptying a bucket, keep the filter clean, and keep it away from walls so air can circulate. For houses that fight basement damp every summer, a whole-house dehumidifier tied into the ductwork is another option, though it costs more up front. Before buying anything, check the outside: downspouts that dump next to the foundation and soil sloping toward the house cause a lot of basement damp.
Is there anything to keep an eye on for safety?
A furnace humidifier connects a water line to your heating system. If you ever see water dripping from the humidifier onto the furnace cabinet, shut off the small water valve that feeds it and have it looked at, since water and the furnace's electronics do not mix. Replace the pad or clean the scale each year, as a neglected humidifier can grow mould. And if you have a gas furnace, make sure your carbon monoxide alarms are working, whatever season it is.
What does it cost to sort out humidity?
The cost depends on the fix. Cleaning an HRV, changing a humidifier pad or rebalancing airflow is routine maintenance. Adding a bypass humidifier is a modest job, a steam unit or whole-house dehumidifier is a larger one, and resizing an air conditioner only makes sense when the old one is due for replacement anyway. Ask for a written price before any work starts.
If you want the humidifier, HRV and condensate drain checked as part of a seasonal visit, see furnace and AC maintenance.