How To Use Dehumidifiers To Prevent Mould And Improve Air Quality
By: Brothers Equipment & Supply
Mould thrives when indoor relative humidity stays high, especially above about 60 per cent for extended periods.
Damp materials support bacterial activity and musty odours, and spores can spread through normal household air currents. Controlling humidity interrupts this cycle and protects finishes, furnishings, and stored belongings.
When mould and dust mites flourish, allergy and asthma symptoms often worsen.
Reducing humidity helps limit mould spore counts and dust mite populations, which can ease congestion and improve sleep quality. Better moisture control also reduces that persistent damp smell that lingers in closets and basements.
Aim for about 40 to 50 per cent indoors in most seasons. In winter, staying near the lower end helps limit window condensation, in summer, the upper end still feels comfortable while preventing mould growth.
A simple digital hygrometer makes it easy to confirm you are in the right range.
Basements, bathrooms, laundry areas, and crawlspaces experience the biggest moisture swings. Cooler surfaces in basements promote condensation as warm summer air infiltrates, bathrooms collect steam from showers, and laundry areas add moisture during washing and drying.
These spaces are prime candidates for targeted dehumidification.
Manufacturers rate units by litres per day, which indicates how much water they can remove under standard test conditions.
As a starting point, a small bedroom or home office may need a 10 to 12 litre per day unit, a damp main floor or finished basement often benefits from 20 to 30 litres per day, and very wet spaces or large open basements may require 35 litres per day or more. Match capacity to room size and moisture level, then confirm with real world readings.
Refrigerant models are common and efficient in warm conditions, desiccant models excel in cooler environments such as shoulder seasons or unheated areas.
If your basement routinely dips below about 15 °C, look for a unit with a reliable low temperature defrost system or consider a desiccant design for steady performance.
Modern portable units typically draw between 300 and 700 watts depending on capacity and fan speed. Energy efficient models remove more moisture per kilowatt hour and include auto stop, humidistat control, and variable fan settings.
In practice, running a right sized unit for fewer hours often costs less than running an undersized unit continuously.
Check published decibel ratings if you plan to run a unit near a bedroom, nursery, or living room. Many portable units operate in the mid 40s to mid 50s decibel range on low settings, which is similar to a quiet conversation.
Choose models with a sleep mode or two stage fan for flexible night time use.
Portable units are affordable and flexible, ideal for targeted problem rooms. Whole home dehumidifiers connect to existing ductwork, support larger capacities, and maintain consistent humidity across multiple rooms.
If your entire home feels sticky in summer, or if you already run the fan on your central system, a whole home unit can be a practical upgrade.
Place the unit near the centre of the space or where dampness concentrates, allow at least 15 to 30 centimetres of clearance around air inlets and outlets.
Keep interior doors open when you want to dry adjacent rooms, close them when you need to focus on a single damp area. Avoid pushing the unit tight against walls or furniture, restricted airflow lowers performance.
Buckets are convenient for occasional use, but they fill quickly in damp conditions. For continuous operation, use a gravity drain to a floor drain or utility sink.
Where gravity is not possible, a small condensate pump lifts water to an appropriate drain, which keeps the unit running without frequent emptying.
In summer, set the humidistat around 45 to 50 per cent to control stickiness and prevent mould. In winter, aim near 35 to 40 per cent in colder regions to reduce window condensation and frost.
In marine climates or during rainy stretches, you may need a slightly lower set point to keep materials dry.
Dehumidifiers control moisture, air purifiers capture particles, and ventilation exchanges stale indoor air with fresh outdoor air.
Use bathroom and kitchen fans during moisture producing activities, combine a dehumidifier with a high efficiency particulate air filter in problem areas, and consider a balanced ventilation system in tight homes to manage humidity and carbon dioxide.
A clogged filter restricts airflow and lowers water removal rates. Check the filter monthly during heavy use, clean or replace it as directed, and vacuum dust from the intake grille.
Clear airflow keeps coils efficient and avoids unnecessary energy use.
Frost on the evaporator coil reduces performance. Many units include auto defrost that pauses the compressor while the fan melts ice.
In cooler basements, select a model with a robust low temperature mode, and elevate the unit on a small platform to avoid contact with cold floors.
Rinse the bucket and drain hose regularly with warm water and mild detergent.
Periodic cleaning prevents biofilm, slime, and odour that can develop in stagnant water. If a hose outlet smells musty, flush it and let it dry fully before reconnecting.
Keep a simple hygrometer in each problem area and note readings morning and evening for a week. Effective dehumidification shows as a steady downward trend toward your set point.
You should also notice fewer window streaks, faster towel drying, and a fresher smell in storage areas.
Persistent high readings, visible damp patches, or returning mould suggest a hidden leak, poor exterior grading, or infiltration through foundation walls.
In those cases, correct the source of moisture, improve drainage, or consult a qualified contractor. Dehumidifiers are a control tool, they cannot fix structural water entry.
Q: What Size Dehumidifier Do I Need For A Basement
Measure the basement, note musty areas, and start with 20 to 30 litres per day for a typical finished space. If humidity remains above your target after continuous operation, step up a size or add a second unit for far corners.
Q: Is It Normal For A Dehumidifier To Warm The Room
Yes, the process moves heat from the air to the coils and then back to the room, so a slight temperature rise is common. This is usually mild and can be helpful in cool basements.
Q: What Humidity Setting Prevents Mould Most Effectively
Keeping indoor relative humidity around 40 to 50 per cent limits mould growth, dust mites, and odours while maintaining comfort. Adjust a bit lower in winter to reduce window condensation.
Q: Can I Run A Dehumidifier With Windows Open
Open windows bring in outdoor humidity and reduce effectiveness. For best results, keep windows closed while the unit runs, then ventilate briefly when outdoor air is drier than indoor air.
Q: How Often Should I Clean The Filter And Tank
Check monthly during peak seasons. Clean the filter and rinse the tank or hose to prevent dust buildup and biofilm. Heavy use or dusty environments may require more frequent attention.
Q: Do I Need A Hose Or Is The Bucket Fine
A bucket is fine for occasional operation. If the unit runs daily or the space is very damp, set up a gravity hose or a small pump so it can drain continuously without overflows.
Q: Will A Dehumidifier Remove Musty Odour Completely
It often removes most of the smell by drying materials and limiting microbial growth. If odour persists, look for hidden moisture in carpets, wall cavities, or stored items, and clean or discard affected materials.
Q: Can A Dehumidifier Help With Condensation On Windows
Yes, lowering indoor humidity reduces condensation on cool glass, especially in winter. Pair the unit with proper window coverings, sealed frames, and steady ventilation for the best results.
Q: Is A Whole Home Unit Better Than A Portable One
For isolated damp rooms, a portable unit is flexible and economical. If multiple floors feel humid or you want uniform control throughout the house, a whole home unit tied to ductwork provides consistent results.
Q: When Should I Call A Professional About Persistent Moisture
If humidity stays high despite a right sized unit, if you see repeated mould growth, or if you notice water stains and peeling paint, call a professional. You may have a building envelope issue, a plumbing leak, or exterior drainage problems that need correction.
Dehumidifiers are a practical way to prevent mould and improve air quality in Canadian homes. Choose the right capacity for each space, place the unit for good airflow, and drain it continuously so it can work without interruption.
Keep filters and buckets clean, monitor humidity with a simple hygrometer, and coordinate moisture control with ventilation and air filtration. If high readings persist, address the underlying moisture source so your dehumidifier can deliver clean, dry, and comfortable air year round.
If you have any questions about our article “How To Use Dehumidifiers To Prevent Mould And Improve Air Quality” or need dehumidifiers for water damage contact us at sales@brothers-equipment.com or chat with us on LiveChat or social media.
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