Two weeks ago, the owner of a triplex on the Plateau called us because his three tenants were complained of shortness of breath stuffy and with windows that leaked in the winter.
His building? A classic 1960s Montreal building with outdoor spiral staircases and no ventilation maintenance for at least a decade.
When we inspected the system, we found clogged ducts, mold in the return air ducts, and a pressure imbalance that was drawing cold air in through the cracks.
In Montreal, about 60% of the units are in multi-unit buildings—duplexes, triplexes, and quadruplexes. Most have outdoor staircases, architectural styles that often date back several decades, and ventilation systems that work… let’s say, only halfway.
That’s why ventilation maintenance in these buildings isn’t just a matter of comfort. It’s a matter of health, costs, and responsibility.
Why Outdoor Stairwells Pose Unique Ventilation Challenges
Montreal apartment buildings with outdoor staircases are an iconic design. But when it comes to ventilation, they’re far from ideal.
The Effect of Outdoor Stairs on Natural Draft
In a traditional house with an interior staircase, warm air rises naturally and creates what is known as the «chimney effect»—a natural draft that helps circulate the air.
With outdoor staircases, this effect is significantly reduced. Each unit becomes a closed box with little vertical airflow.
The result? Moisture builds up, especially in the winter when we heat our homes and ventilate less.
According to BC Housing and the INSPQ, buildings without effective natural draft require mechanical ventilation to compensate. Otherwise, problems with humidity and indoor air quality are virtually guaranteed.
During the Quebec winter, when windows are kept closed for months on end, ventilation becomes even more critical.
Shared Ducts and Pressure Imbalance
In many apartment complexes built before 1980, the ventilation ducts are interconnected between the units.
This creates strange pressure shifts. A tenant who turns on their range hood can draw in air—and odors — the apartment downstairs.
Contaminants also spread: smoke, allergens, cooking particles, and excessive moisture. If one unit has a problem, the others suffer the consequences.
You see this all the time in the apartment complexes in the Plateau, Rosemont, and Villeray. These systems were designed in the 1960s and 1970s and were never intended to meet modern air quality standards.
The Consequences of Poor Ventilation Maintenance in a Montreal Apartment Complex
Neglecting ventilation isn't just unpleasant. It has real, measurable consequences.
Humidity, Condensation, and Mold in Winter
Montreal winters are tough on poorly maintained ventilation systems.
You're heating the house while it's -20°C outside. The humidity in the kitchen, in the bathroom, The air needed for breathing and daily activities has nowhere to go if the ventilation system isn't working properly.
This moisture condenses on cold surfaces—windows, exterior walls, and corners of rooms. And mold begins to grow.
According to BustMold, buildings with poor ventilation have a 40% higher risk of mold compared to those with adequate ventilation.
In neighborhoods like Hochelaga or the Plateau, we regularly respond to calls at apartment buildings where tenants discover mold behind furniture or in closets.
Hidden Costs on Energy Bills
A clogged or poorly balanced ventilation system forces your heating system to work harder.
Stale air doesn't circulate well, rooms heat up unevenly, and you compensate by turning up the thermostat.
According to AirGreen, a poorly maintained ventilation system can result in energy losses of 200$ to 500$ per year in a multi-unit residential building.
It may seem abstract, but take a look at your Hydro-Québec bills for January and February. If they’ve gone up for no apparent reason, your ventilation system is probably to blame.
How often should the ventilation system in an apartment with an exterior staircase be maintained?
There's no one-size-fits-all answer, but there are guidelines based on the type of system you have.
Recommended Frequencies by System Type
- Natural ventilation (windows + ventilation grilles) Annual inspection of the grates to ensure they are clear. Cleaning of the exterior grates in the spring and fall.
- Mechanical ventilation (bathroom/kitchen exhaust fans) Clean the filters and fans every 6 months. Complete inspection of the system every 2–3 years.
- Heat Recovery Unit (HRV/ERV) Clean the filters every 3 months. Thoroughly clean the heat exchanger core once a year. Have a professional inspection performed every 2–3 years.
Central ventilation ducts should be inspected every 3 to 5 years and cleaned as needed, depending on their actual condition.
Difference Between a Renter and a Homeowner
In Quebec, it's clear: the maintenance of ventilation systems is the owner's responsibility under the Housing Code.
Tenants must use the property reasonably and report any problems, but they cannot be held responsible for preventive maintenance.
However, certain simple tasks—such as changing an accessible filter or cleaning a vent grille—can be shared if this is clearly stated in the lease.
In practice, it’s in your best interest as a property owner to handle this directly. You maintain quality, protect your investment, and avoid complaints.
Career Counseling vs. DIY Solutions: What Really Works
Many homeowners and renters try to manage ventilation on their own. It works… to a certain extent.
What House Cleaning Can't Solve
You can clean the visible grates, replace the accessible filters, and vacuum the air vents.
But here's what you can't do:
- Access the internal filters of the central systems
- Clean the biofilms that form inside the ducts
- Detect leaks, disconnections, or crushed pipes
- Balancing the pressure between the units
- Inspect the hidden parts of the system
Biofilms are particularly sneaky. They’re a layer of bacteria, mold, and organic matter that sticks to the inside walls of pipes. A household vacuum cleaner can’t remove them.
The Benefits of a Certified Professional Interview
An INVC- or NADCA-certified technician uses specialized equipment that you don't have at home.
Camera inspection to see exactly what's happening inside the ducts, even in hidden sections.
Industrial vacuum cleaner with HEPA filtration that creates negative pressure—all the dirt is sucked out directly without being released into the air in your home.
Mechanical brushing and pneumatic whips to dislodge stuck-on deposits.
Balancing the system to ensure that each unit receives the correct airflow.
At Vortex Air, we follow these protocols for every service call. We show you the before-and-after results with photos or videos.
Have your plex ventilation system inspected—no obligation — A free inspection will tell you exactly where you stand.
Regulations and Standards Applicable to Montreal Plexes
Residential ventilation in Quebec is regulated, but not always as strictly as one might think.
What the RBQ Requires (and Does Not Yet Require)
Since 2012, mechanical ventilation has been required in all new residential buildings in Quebec.
What about existing buildings? It’s not retroactive. You’re not required to install a mechanical system in an old apartment building that’s never had one.
However, you have a general obligation to provide safe and sanitary housing. If a tenant can prove that poor ventilation is affecting their health, you could face problems with the Housing Board.
Installed ventilation systems must comply with the Quebec Building Code. If you are renovating or adding a system, the work must be performed by a contractor with an RBQ license.
What's Changing with the 2026 Terms of Office
The City of Montreal and the provincial government are working on new standards to improve indoor air quality.
It is expected that requirements for smart ventilation systems with humidity and CO2 sensors will be mandated in new construction and major renovations.
For owners of multi-unit buildings, this means that if you plan to do major renovations in the coming years, you'll likely need to upgrade your ventilation system.
It's better to plan ahead now than to be caught off guard.
Actual Ventilation Maintenance Costs in a Condo Complex in Montreal
Let's talk about money. It's always better to know what you're getting into.
Average Costs per Building and per Housing Unit
For a complete maintenance service of a ventilation system in a typical apartment complex—including inspection, duct cleaning, and balancing—expect to pay between 5,00$ and 1,500$ for the entire building.
Per unit, this amounts to approximately 1,50$ to 3,00$, depending on the system's complexity and the condition of the ducts.
If your ducts haven't been cleaned in 20 years, the cost will likely be at the high end of the range because the job takes longer.
Basic routine maintenance—cleaning the filters, visual inspection, flow rate tests—can cost as little as 200$ to 400$ per year if you have it done annually.
Why Preventive Maintenance Costs Less Than Repairs
Here's the reality: a neglected system will eventually break down.
A fan motor that's clogged with dirt and runs for too long will burn out. It costs 500$ to 1,200$ to replace, plus installation.
Clogged ducts that cause smoke to back up can damage your heating system. Repairs can cost thousands of dollars.
A dryer fire caused by a lint-clogged vent? The damage can run into the tens of thousands of dollars, not to mention the safety risks.
Preventive maintenance costs only a fraction of those amounts. The return on investment is clear.
For shared dryer vents in apartment buildings, annual cleaning is really all about fire prevention. It's worth every dollar.
Common Myths About Ventilation in Apartments with External Staircases
Let's separate fact from fiction. There's a lot of misinformation out there.
«Opening the windows is enough in winter»
This is the most widespread myth.
Yes, opening the windows lets fresh air in. But in winter, when it’s -15°C, you’ll lose all your heat, freeze your pipes, and create uncomfortable drafts.
On top of that, the freezing outside air comes in so quickly that the moisture inside doesn't have time to escape effectively. You're freezing for no reason.
A controlled mechanical ventilation system does the job without wasting heat or causing discomfort.
«Closing the vents reduces costs»
Closing the vents in «unused» rooms is a bad idea.
It throws the whole system out of balance. The pressure changes, air doesn't circulate properly, and your furnace or turn on the air conditioner to compensate.
The result? You end up using more energy, not less. And you create areas of stagnant air where moisture and contaminants accumulate.
Ventilation systems are designed to operate with all vents open. Please follow this instruction.
«Old Plex buildings breathe naturally»
We often hear people say, «Old buildings breathe through their cracks, so there’s no need for ventilation.»
It’s true that older Plex buildings aren’t as airtight as modern ones. But «breathing through the cracks» isn’t the same as controlled ventilation.
You have no control over where air enters and exits. In the winter, cold air comes in from below and makes the floors freezing. In the summer, hot, humid air seeps in everywhere.
This «natural ventilation» wastes energy and creates uncomfortable conditions. Proper mechanical ventilation works better—and costs less.
How to Tell When a Maintenance Issue Is Urgent in Your Apartment Complex
Some signs are obvious. Others are less so.
Visible signs
Excessive condensation on your windows even when the humidity level is reasonable? Your ventilation system isn't working properly.
Do you see mold around ventilation vents, in the corners of rooms, or on windowsills? That’s a red flag.
Is dust building up quickly around the air vents or coming out of them when the system starts up? The ducts are probably very dirty.
Is there rust or corrosion on the system's metal components? There's moisture where there shouldn't be any.
Invisible Signs (Air, Odors, Health)
Persistent odors—musty, stale, smoky—that keep coming back even after you clean? They’re probably coming from the vents.
Does the air feel heavy, stagnant, and hard to breathe? There isn't enough air circulation.
Are tenants experiencing new or worsening respiratory problems—such as allergies, asthma, or eye and throat irritation? If so, indoor air quality is likely compromised.
Are your heating bills going up for no apparent reason? An unbalanced ventilation system is forcing your heating system to work harder to compensate.
If you notice two or three of these signs at the same time, it's time to take action.
Why Choose Ventilation Vortex Air for Plex Maintenance in Montreal
Maintaining the ventilation system in a multi-unit apartment building is different from that of a single-family home. It requires local experience.
Local Expertise in Montreal Apartment Complexes
We’ve been working in Montreal’s office complexes for over 10 years. We’re familiar with the buildings in the Plateau, Rosemont, Villeray, and Hochelaga.
We know how the utility rooms from the 1960s and 1970s are built, where the ducts are hidden, and what problems tend to arise depending on the neighborhood.
This local expertise allows us to quickly assess the situation and propose solutions tailored to your type of building.
Our team of more than five certified technicians has seen hundreds of different setups. Nothing surprises us.
Transparent and Certified Methodology
We follow INVC standards for every job. We are also in the process of obtaining NADCA certification, which ranks us among the most reputable companies in the industry.
Our process is simple and clear:
- Free inspection — We’ll come check the condition of your system at no charge and with no obligation
- Honest Assessment — If your ducts are clean, we'll tell you. We don't sell unnecessary services.
- Detailed Proposal — You'll know exactly what's included and how much it costs before we get started
- Certified Work — We clean according to established protocols, using the appropriate equipment
- Final Check — We'll show you the results with photos or videos
Mohamed and Omar, our co-owners, personally oversee major projects. You'll be speaking with the actual decision-makers, not with an employee who has no authority.
Get a clear assessment, with no pressure — Contact us at 514-214-7492 or visit vortexair.ca.
FAQ – Ventilation Maintenance in Apartment Buildings with Exterior Staircases
Who is responsible for maintaining the ventilation system in a rental unit?
It's the owner's responsibility, period.
Maintaining ventilation systems is part of your obligation to provide safe and sanitary housing. You cannot pass this cost on to tenants.
Some landlords include clauses in the lease requiring tenants to replace accessible filters, but professional maintenance remains your responsibility.
Is mechanical ventilation required in an older apartment building?
No, not if the building was constructed before 2012.
However, if you’re doing major renovations or if a tenant proves that poor ventilation is affecting their health, you may be required to take action.
It’s better to install a proper system now than to wait for a formal notice from the Régie.
When is the best time of year to perform maintenance?
The best time to visit is in the spring or fall.
In the spring, you clean up the debris left over from winter before the warm season begins. In the fall, you prepare the system for the months when the windows will be closed.
Avoid performing maintenance in the middle of winter when the system is running at full capacity, or in the middle of summer if you have central air conditioning.
Do outdoor stairs contribute to indoor humidity?
Indirectly, yes.
Outdoor staircases reduce natural draft inside the building. This limits vertical air circulation and creates conditions in which moisture accumulates more easily.
The problem isn't the stairs themselves—it's the lack of compensatory airflow.
How long does a duct cleaning take?
For a typical duplex, between 3 and 5 hours. For a triplex, between 5 and 7 hours, depending on the complexity.
We can spread the work out over two days if that works better for your tenants. The important thing is to do the job right.
Does it really improve air quality?
Yes, in a measurable way.
Studies show that professional cleaning reduces airborne particles by 50 to 70%. Allergens, dust, mold spores—all of these are significantly reduced.
However, if the source of the contamination isn't addressed—active mold, water seepage, smoke—the problem will eventually return.
Are there any grants available in Quebec?
Currently, there are no specific grants for duct cleaning.
However, some energy-efficient renovation programs—such as Rénoclimat—include components designed to improve ventilation. You may be eligible if you install an HRV system or upgrade your mechanical ventilation.
Check with your local municipality and Hydro-Québec. Programs change regularly.
Conclusion — Strategic Maintenance for Healthier Housing
Montreal's apartment complexes with outdoor staircases are a unique part of the city's architectural heritage. But when it comes to ventilation, they require special attention.
The air we breathe in our homes directly affects our health, our comfort, and our wallets.
A well-maintained ventilation system protects your tenants, reduces your energy costs, and helps you avoid complaints and legal complications.
It's not an expense—it's an investment in the longevity of your building and in your tenants' satisfaction.
At Vortex Air, we’ve been helping Montreal homeowners and renters breathe easier for over 10 years. We understand the challenges because we work in these buildings every week.
If you're not sure what condition your ventilation system is in, we can give you a clear and honest answer after a free inspection.
Contact us at 514-214-7492—we're available 24/7—or visit vortexair.ca to schedule your inspection.
Because a healthy home starts with the air we breathe.
