Condo Air Exchanger and Central Air Conditioner Filters

A clogged filter in an air exchanger (HRV/ERV) or central air conditioner increases energy consumption, raises noise levels and reduces air quality. In a divided co-ownership, the question becomes more complicated: who pays, who maintains the equipment, and how often should filters be changed? Here is a practical guide for the board of directors and co-owners, with concrete guidelines you can apply today.

Why the air exchanger and central air conditioner filter matters

The filter captures dust, pollen and pet hair. When it becomes saturated, airflow drops, the fan has to work harder and comfort decreases. In a condo, this can result in noise, lingering odours and higher bills. A clean filter promotes effective air exchange, supports occupants’ health and extends the useful life of the equipment.

For forced-air systems (furnace/heat pump/central air conditioner), the filter protects the evaporator from becoming dirty and icing up. In an HRV/ERV, it prevents the exchanger from becoming clogged. In both cases, regular maintenance reduces service calls and prevents costly breakdowns.

Private portions and common portions: who is responsible?

The answer is found in the declaration of co-ownership and the building plans. As a general rule, routine maintenance of an appliance located in a private portion and serving that unit exclusively is the co-owner’s responsibility. When the equipment serves several units or is located in a common mechanical room, responsibility rests with the syndicate and is charged to the common expenses.

• Individual equipment inside the unit (e.g., an HRV in the condo ceiling, or a unit furnace/heat pump): the co-owner pays for the filter.
• Central building equipment (e.g., roof fans, a central HRV or an air-handling unit with filters in a mechanical room): the syndicate pays for the filters and maintenance through the common expenses.
• Mixed situations (e.g., fan-coil units by riser): the filter may be inside the unit, but the equipment as a whole belongs to the common system. The declaration of co-ownership or the by-laws of the immovable may specify how responsibilities are shared.

The Civil Code of Quebec requires the syndicate to ensure the preservation of the building and the maintenance of the common portions, and each co-owner to contribute to the common expenses (see, in particular, sections 1072 and 1064 of the C.C.Q.). Consult LégisQuébec for the wording of the legislation.

• C.C.Q. reference (section 1072): LégisQuébec – Civil Code of Quebec
• C.C.Q. reference (section 1064): LégisQuébec – Civil Code of Quebec

Access to units and enforcement

When a filter for private equipment affects safety or causes nuisances, the syndicate may require reasonable access to the unit to carry out or verify necessary work, in accordance with the C.C.Q. (which governs access rights) and the by-laws of the immovable. Establish a clear process: written notice, reasonable notice, proof of maintenance and a record kept on file.

Frequency, filter types and signs of wear

Frequency depends on usage, pets, nearby construction and the type of filter (disposable, washable, MERV). In the Montreal context, with heating and ventilation used for much of the year, these guidelines are useful:

• Unit HRV/ERV: rinse or vacuum the pre-filter every 1 to 3 months; carry out thorough cleaning of the exchanger according to the manufacturer’s instructions.
• Central air conditioner/heat pump with furnace: MERV 8 to 13 filter; replace every 2 to 3 months during the season of use, more often if there are pets.
• Building central system: follow the maintenance plan provided by the manufacturer and mechanical consultant; often monthly to quarterly.

Signs that action is needed include increased fan noise, persistent odours, dusty grilles, rooms that do not cool or heat properly, rising bills, or frost on the refrigerant line.

Practical guidelines table

Note: Always confirm the information against the declaration of co-ownership, technical data sheets and the building’s maintenance logbook.

Safe procedures and record-keeping in a condo

Simple maintenance quickly becomes complicated without documentation. The board of directors benefits from standardizing the process for private units and common equipment.

• Define the approved filters: size, type (disposable or washable) and MERV rating recommended by the engineer or manufacturer.
• Distribute a reminder sheet in the spring and fall explaining where the filter is located, how to install it in the correct airflow direction and where to dispose of the old one.
• Require proof: a photo of the new filter in place, the invoice or lot number, and the installation date. Place it in the unit’s file.
• Record every action in the maintenance logbook. For common portions, record the filters’ differential pressure (ΔP) and replacement dates.
• Have the policy adopted at the annual general meeting and record it in the minutes. Update the by-laws of the immovable as needed.

One syndicate we assist reduced its service calls by 30% by standardizing MERV ratings and keeping a photo record for each unit. A simple seasonal communication was enough to establish the habit.

To equip your board of directors, see our operations management support service and our packages.

Noise, odours and condensation: when to call a professional

A new filter does not solve everything. Abnormal noises, vibrations, burning smells, condensation on ducts or persistent frost on refrigerant lines indicate a more serious problem (motor, wheel, condensate drain or obstruction in the ducts). In these cases, use a contractor holding the appropriate RBQ licence.

• To verify a contractor’s licence: RBQ.
• For good co-ownership practices: RGCQ.

The board of directors should keep work orders, invoices, photos and recommendations on file. These documents make budget planning easier and support the contingency fund through the maintenance logbook, by allowing for replacement at the end of the equipment’s useful life.

Central air conditioner and air exchanger: essential coordination

In a forced-air condo, the return-air filter protects both the heating and cooling systems. If the board of directors or co-owner increases the MERV rating, check the fan’s capacity to avoid an excessive loss of airflow. A rating that is too high can overload the motor and cause the evaporator to ice up, especially during hot and humid periods.

For common systems, coordinate the filter replacement schedule with seasonal maintenance visits (spring cooling start-up and the fall changeover to heating). Measuring differential pressure before and after replacement is a good practice.

Communication and document compliance

• Declaration of co-ownership and by-laws of the immovable: clearly specify responsibility for filter maintenance and the syndicate’s access to units for verification.
• Notice to co-owners: send a standardized reminder twice a year with instructions specific to the building and a link to the technical data sheet.
• Annual general meeting minutes: record resolutions adopting the maintenance policy and schedules.
• Unit file: organize maintenance records, which are particularly useful during a sale and when providing a certificate to a broker or notary. The OACIQ emphasizes the importance of complete disclosures in a transaction; make sure maintenance documents are accessible.

In addition, regularly consult the official texts of the Civil Code of Quebec on LégisQuébec to ensure that your practices remain compliant.

For more day-to-day management advice, browse our blog.

FAQ

• How often should a washable HRV filter be changed? Generally every 1 to 3 months, after vacuuming and rinsing, followed by complete drying. Follow the manufacturer’s manual and consider the unit’s environment.
• Can the board of directors require a co-owner to change their filter? If there is a risk to the building or nuisances are being caused, the by-laws may provide for this obligation and a right of reasonable access. Everything must comply with the declaration of co-ownership and the C.C.Q. (see the general principles governing the preservation of the building).
• Which MERV rating should you choose? In a residential condo, MERV 8 to 11 is often suitable. Above that, confirm the fan’s capacity and the airflow required by the equipment. Always follow the manufacturer’s or an engineer’s recommendations.
• Who pays for damage caused by a neglected filter? Depending on the circumstances, responsibility may fall on the negligent co-owner. Refer to the declaration of co-ownership, the by-laws of the immovable and, if necessary, the C.C.Q. and your insurer.

This article provides general information and does not constitute legal advice. For your situation, consult a lawyer or notary.

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