Air Quality Even though condominiums built after 1990 are more air tight than older ones, occupants still need to ensure that they operate the air handling system for the health and safety of their families. Most likely, these condos may require a Reserve Fund Study or some form of legal inspection.

The Need For Ventilation

The air handling system in your condo removes stale air and brings in fresh air. The control of indoor air quality is very important. Consider how many times you have noticed air quality problems such as:

  • Excess humidity
  • Condensation on windows and in corners
  • Stale air
  • Lingering odours
  • Second hand smoke
  • Dry air

In the past, accidental air leakage ventilated our units. Air leaked in through the walls, around windows and doors. Our homes were drafty and wasted energy. Today’s condominium units are built to more energy- efficient standards with greater control over drafts and air leakage. The control of indoor air quality no longer occurs accidentally. Your ventilation system has been installed to give you control over the indoor air quality in your home.

When to Operate Your System

Proper ventilation is necessary. It allows you to control:

  • Indoor air quality
  • Excess humidity
  • Odours

Your natural and mechanical ventilation system can help properly ventilate your unit. Excess humidity is one of the most frequent air quality problems. High humidities  in the fall and winter can result in mold and mildew damage to  window frames  and interior finishes. Excess humidity is usually a good indicator of the need for ventilation. The ventilation system installed in your unit will allow you to maintain acceptable humidity levels. It is your responsibility to use the system properly to protect your unit. Failing to use it may void warranties on items such as windows and interior finishes!

Additional    causes    of    thermal    bridging are shearwalls, spandrel beams, parapet walls,window frames, missing insulation and precast concrete panel anchors.

New Construction

Air Quality

New concrete  and  related  materials  require a tremendous amount of water during their construction. Although much of this evaporates during the first month or so, the start of the heating season aids in driving off more moisture. Coupled with the new woodwork, and other materials, this moisture creates higher than normal humidities and new buildings, during the first winter, need extra heat and ventilation to allow them to dry out.

In the first few months of owing a new condominium unit, extra ventilation may be required to reduce the build-up of moisture from the construction of your condominium building.

Additionally, identical condominiums may not have the same condensation problems.  This will depend on the life style and activities of the household and although appearing identical, one unit may have a slightly lower air infiltration rate, or be affected differently by exterior environmental conditions that could influence the humidity level.

Indoor Air Quality Control

Ventilation has a significant role to play in indoor air quality control, however, using ventilation alone to address problems may result in inadequate control and excessive energy use. Ventilation is one aspect of a total strategy to  control  indoor  air  quality in your home. A complete approach to air quality control includes:

  1. Remove as many sources of pollution as possible.
  2. Control  problems  at  source  to  minimize ventilation requirements.
  3. Ventilate as needed to control the pollutants which can’t be avoided.

For instance, if excess humidity is the key pollutant, air quality problem:

  1. Remove Sources:
    1. avoid excessive number of plants
    2. b. avoid using a humidifier
  2. Control Problems at Source:
    1. use bathroom fans during showers and for a minimum of 15 minutes after
    2. use range hood during cooking and leave on for 15-30 minutes after
  3. Ventilate as Needed:
    1. if condensation on windows persists or if indoor air is musty and stale, increase ventilation system use
  4. consider continuous system operation
  5. open operable windows (in winter 10-15 minutes on average per day)

How Do I Control Excessive Humidity?

Air Quality Condensation will occur on a surface when the  temperature  of  the  surface  is  at,  or below, the dew point of the air as often occurs in summertime on the outside of a bottle taken out of a refrigerator or when a person breathes on a window.

In wintertime the air inside a building is generally humid and warmer than the air outside and this creates a  potential for condensation to occur on surfaces whose temperature is below the dew point. These surfaces may be associated with windows and the area of wall adjacent to the windows with locations concealed within the outside walls.

In the first case, the inconvenience to the occupant is immediate and occurs in the form of water and ice build-up on the cold surfaces and as run-off onto the surfaces below when the ice melts.

In the second case water accumulates inside the walls as ice which melts and runs back into the building during the next warm period.

Condensation on windows, or other surfaces, is only one of the problem caused by excessive levels of relative humidity. Excessive humidity can encourage mould to form on drywall, cupboards to smell musty, rooms to feel damp.

Humidity and Mould

Mould growth often starts in the corners of rooms and is encouraged by poor air circulation causing pockets of stagnant air aided, sometimes, by the increased rate of heat loss which occurs on external corners.

There are many causes of mould but germination depends on damp conditions often caused by excessive humidity. Mould growth, usually grey- green, black or brown in colour, first appears as spots or patches and may spread to form a furry layer. On paint, it may show as a pink or purple discolouration.


Notwithstanding current emphasis  on energy conservation, it is still necessary that cold, outside air be allowed into your unit, replacing the heated indoor air. This must be done to help control the level of humidity, remove odours, and provide fresh air for the occupants. To restore the air-change balance, it may be necessary to open a window for a brief period each day.

Condensation on Windows

Perhaps the most common indicator  that the level or relative humidity is too high is condensation on the room-side surfaces of windows in winter. Not only does this reduce visibility through the window but can lead to severe damage to sills, surrounding walls and furnishings.

What can effect the performance of  a window?

The following may cause condensation to form on a window at lower relative humidity

Air Circulation – a window may be in a area in which there is poor circulation of warm air. This means that the temperature of the inside glass surface is colder than in other parts of the unit and this may cause condensation to form at humidity levels which are practical for the rest of the condominium.

Drapes – By drawing heavy drapes over a window, the possibility of condensation can be increased because the flow of warm air is restricted.

Interior Insulating Devices – Insulating blinds, shutters or similar devices, applied to the interior of windows, can contribute to condensation problems when moist indoor air is trapped between the device and the widow. The insulating properties of these devices cause the temperature of the glass surface to be lower than normal and the trapped air to condense into moisture.

Varying Humidity Levels – Remember that the humidity in some rooms, kitchens and bathrooms in particular, can be higher than in other areas thus encouraging condensation to form on windows.

Orientation – If windows are exposed to prevailing windows, then they will be slightly colder than the other windows in the building and may cause condensation to form at humidity levels which are practical for the rest of the building.

Air Handling System

The most common  system in multi-use construction consists of a simple exhaust system of the type installed in your condominium building in combination with the fan coil heating and cooling unit contained in each suite. Your air handling system is capable of either intermittent or continuous use:

Intermittent Use

Many condo owners use their air handling systems intermittently to avoid noise and/or energy costs. Although turning fans on and off may reduce energy costs, this will add to the wear and tear of switches and mechanical components. Such an approach will be less effective at minimizing pollutants and could increase the risk of moisture problems.

Humidity can often be controlled by operating fans during activities involving moisture generation (use range hood while cooking, use bathroom fans during showers, etc.). Bathroom fans are often linked to the light switch for use during and after showers.

Continuous Use

Condominium owners that leave the fan on their heating/cooling operating continuously generally find that:

-temperature throughout their unit is more constant

-mould and mildew growth is reduced as pockets of stale air are eliminated

-switches require less maintenance

-the continuous fan operation of the heating/ cooling unit in conjunction with the intermittent operation of bathroom and kitchen exhaust provides a more efficient evacuation of “polluted” air from the unit.


  • exhaust fans in bathrooms
  • exhaust kitchen fan with grease filter
  • switches
  • windows and exterior doors
  • suite entry door
  • corridor fresh air supply system
  • heating and cooling unit

Fan Coil Fresh Air

This supply relies on fresh make up air entering your unit from either:

  • the space or crackage around your suite entry door from the fresh air supplied under pressure to the buildings corridor
  • from opening windows or exterior doors of the suite.

Old Air

When this fresh (new air) is introduced into the suite, it pushes the old stale moist air out through either:

  • the running of the suite exhaust system consisting of the bathroom and kitchen exhaust fans
  • opening exterior doors or windows

Circulation of Air

Circulation of air in your suite is required to create an acceptable interior air quality for the comfort of the occupants and to ensure that air flows over the exterior wall surfaces to either keep them cool in summer or warm in winter. This is accomplished by ensuring that the fan on your heating/cooling unit is operating properly and that the filters are cleaned and replaced regularly. Continuous operation of the fan is recommended in winter as an effective means of reducing the risk of condensation by eliminating the development of pockets of stagnant air.

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