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Indoor Air Quality · Humidity ControlWhole-Home Dehumidifier Installation
Whole-home dehumidifier installation puts a ducted unit beside the furnace that dries the whole house on its own humidity control, instead of asking the air conditioner to do a job it was never designed for. Installed, a ducted unit runs $1,500–$3,000.
An air conditioner only removes moisture while it is actively cooling. On a muggy 21°C day in late May or early September — the shoulder weeks when the lake is warm and the air off it is heavy — the thermostat is satisfied within minutes and the compressor stops, so nothing is pulling water out of the air for the rest of the day. That is why a house can sit at 65% relative humidity downstairs while the AC appears to be working perfectly. Our answer on why a house stays humid with the AC running walks through the same problem from the cooling side.
Below-grade space is where it shows up first. The 1950s and 1960s bungalows through Aldershot and Roseland sit on concrete block foundations that wick ground moisture straight through the wall, and the basements were finished decades later without a vapour barrier behind the studs. On the Escarpment side of town in Tyandaga, lots that slope toward the house push the same problem harder. A portable unit in the corner will move a few litres a day and then stop when the bucket fills, which is not a strategy for eight weeks of humid weather.
The install itself is straightforward and the details are what make it work: the unit ties into the return plenum, or gets a dedicated supply and return pair for the lower level so the basement is dried without over-drying the bedrooms; it drains by gravity to the floor drain, or to a condensate pump if there is no drain nearby; and it needs its own circuit rather than sharing the furnace's. Sizing comes from the pints-per-day rating measured against the floor area and how partitioned the basement is — an open rec room and a warren of small finished rooms behave very differently.
We will also tell you when the answer is not a dehumidifier. Leaking return ducts in a damp basement pull that air into the whole house, a badly oversized air conditioner short-cycles and never dries anything, and downspouts dumping against the foundation beat any equipment. If a repair or a tune-up fixes it, that is the cheaper recommendation. For everything else, our indoor air quality services cover the full range and you can book a humidity assessment any time.
A whole-home dehumidifier is the right fix when
- The basement smells musty by June even though the air conditioner runs all summer
- A hygrometer reads above 60% relative humidity on the lower level in July and August
- Condensation forms on cold-water pipes, the toilet tank or the ductwork downstairs
- You are emptying one or two portable units every day and still losing ground
- The AC satisfies the thermostat in a few minutes on mild, sticky days and shuts off before it dries anything
How it works
We take relative humidity readings on each level, check the AC's runtime and airflow, and look at the drain, the sump and where water is getting in.
Unit set and ducted, gravity drain or condensate pump run, dedicated circuit pulled, and the control mounted where it reads the space rather than the supply air.
We set it around 45–50% for summer, show you the filter interval, and explain why it gets shut down and drained before winter.
Brands: We install ducted dehumidifiers that pair with any furnace or air handler, and service the units already installed in finished basements across Halton and Hamilton.
Common questions
Isn't that what my air conditioner already does?
Only while it runs. Cooling and dehumidifying are the same process on a central AC, so once the thermostat is satisfied the drying stops. A dedicated unit runs on humidity rather than temperature, which is exactly what you need in the shoulder seasons and in a cool basement.
Where does the water go?
To a floor drain by gravity where there is one, or to a condensate pump that lifts it to a laundry tub or a drain line. There is no bucket and nothing to empty.
What humidity should I aim for?
Roughly 45–50% in summer. Winter is a completely different target — too much moisture then shows up as condensation on the windows, which our note on ideal indoor humidity in an Ontario winter explains.
I waterproofed the basement. Do I still need one?
Often, yes. Waterproofing stops liquid water; it does not stop humid summer air from condensing on cool block and concrete. If the readings stay above 60% after the work, the moisture is coming in through the air, not the wall.
Can this be done in a condo with a fan coil?
Not the ducted version — there is no plenum to tie into and no drain to use. In-suite humidity is handled differently, and our condo HVAC page covers what actually works in a fan coil suite.