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Ventilation is required in buildings or homes to maintain air quality. It basically involves removing stale or polluted air from the indoor space and replacing it with fresh outdoor air. Basic ventilation can be achieved by opening a window or door and by the use of an exhaust fan.

The required amount of ventilation is primarily based on the occupancy level. That relates to how many people, for what periods of time and what they are doing. Typically, 15-20 cubic feet per minute of ventilation per person is required. Ventilation must be balanced to eliminate excessively positive or negative pressure situations. The ventilation rate must also be properly controlled to minimize humidity problems. Over ventilating in cold weather reduces the humidity level and adds to your heating costs. Over ventilating in hot weather increases the humidity level and adds to your cooling costs.

Tradesman Mechanical can help you with problems or concerns with Ventilation for your Winnipeg home.

Air Make-up

When a large volume of air is removed from the building space and this air is not replaced at the same rate that it is expelled, the building will experience a negative pressure (the air pressure outside the building is greater than the air pressure inside the building).

Some of the most common indicators of a negative pressure problem include the suction pressure that makes exterior doors harder to open and door locks that will freeze, infiltration of outdoor air causing drafts around doors and windows and poor indoor air quality due to back drafting through natural draft appliances. These problems are more pronounced during the cold season when windows are kept closed, reducing any natural pressure-balancing effect.

A make-up air system replaces the air that is expelled by a building’s exhaust fans, maintaining the proper balance between inside and outside air pressures. Since Winnipeg winters are as cold as they are, an electric heat bank is also required to preheat the incoming air to a minimum of 50f.

Tradesman Heating and Cooling can help provide solutions to the negative air or backdrafting problem in your Winnipeg home.

HRV / ERV Units

Heat Recovery Ventilation (HRV) – The purpose of a HRV system is to exchange the air in your house with controlled regularity, thereby ensuring that the interior air is fresh and healthy for your family. It removes stale, polluted, humid air from the bathrooms and kitchen, directs it through the HRV unit and then exhausts this air outside.

The HRV unit simultaneously brings in an equal amount of fresh air from the outside to replace the exhausted air. As the cold and warm air streams through the core of the HRV, the outgoing household air gives off heat to preheat the incoming cold air. The fresh air will then pass from the HRV core into the return air duct of the furnace where it is filtered, heated or cooled to room temperature and distributed throughout the entire house by way of the furnace duct system. The furnace fan is electrically interconnected to run on low speed mode whenever the HRV is in operation to ensure proper air circulation.

Tradesman Heating and Cooling can assist you with HRV repairs and HRV installations for your Winnipeg home.

Tradesman Mechanical is a Board Member/Contractor with the local HRAC Winnipeg Chapter.

Exhaust Fans


Bathroom and kitchen exhaust fans are a good solution for removing stale, humid or contaminated air from your home. There are however some limitations to their use.  Newer style kitchen exhaust fans are available in sizes well over 300 cfm (cubic feet per minute). High capacity exhaust fans can create negative pressure and depressurization in your home and cause issues with the balance and comfort level in your home. Air make up equipment would then be required at a high expense to install, and also a high expense to operate.

Older exhaust fans can be repaired or replaced if they become noisy or faulty.

Central Exhaust


Central Exhaust System is similar to a ventilating or exhaust fan in that their primary purpose is to remove unwanted air from inside the home.  The difference is a central exhaust system draws the contaminated air from multiple locations in the home via one central exhaust fan rather than multiple fans throughout the home. This central fan is usually located in the mechanical room are for serviceability. Central exhaust systems can be controlled by a regular switch, a timer or a dehumidistat that measures indoor humidity levels to control the fan.

Central exhaust fans are required to be inter-connected with any air delivery system (usually a furnace) so that the incoming fresh air is delivered to all living areas of the home. That is why you may hear your furnace fan running between heating or cooling cycles.  An HRV will do the same job but with much greater efficiency and lower operating costs.

Tradesman Heating and Cooling can upgrade your Central Exhaust fan to an HRV in your Winnipeg home.


Ventilation FAQ

How do I control my HRV/ERV or Central Exhaust?

For extremely dry homes it may at times be necessary to switch the main control to the “off” position temporarily. First check if the control has been set to the lowest point to ventilate (summer position/ counter clockwise). If the humidity level is still too low (below 30%), place the selector switch to the ‘off ” position for a few days.

A barometer will properly display the true humidity in your home. One may be purchased at your local hardware store. The small bathroom timers will still be functional and provide you with high speed ventilation (20 minute intervals) as you require. Once the required humidity level is reached for 3 or more days, you may return the selector switch back for continuous minimum ventilation. Remember: clockwise for more ventilation and counter clockwise for less ventilation. Homes with wood flooring are at risk of drying out if a minimum of 30% humidity is not maintained. If your ventilation requirements are drying out your home beyond this minimum level, a power humidifier should be installed.

I am building a new home. Do I need to install an HRV?

There was a time when some municipalities would allow Central exhaust systems or even basic exhaust fans by themselves, but that is no longer the case. All new home and major home renovation projects now require HRV’s and an air delivery system.

What size of Kitchen exhaust can I safely install in my home?

It is best to know all of the variables when it comes to ventilation and air balance in a home, but typically 270 cfm is the cut off limit before having to introduce make-up air.

Why is there water leaking from my ceiling fan?

During cold weather or on windy days the roof vent flap can become jammed or frozen open. This could allow for rain or snow to enter the vent pipe and leak back down through the fan unit. This can usually be corrected by incorporating a trapped section into the vent pipe.

How do I size a bathroom fan?

The absolute minimum air exchange for a bathroom can be based on 1 CFM for every sq. ft.

EG: 10 x 6 bathroom = 60 sq. ft. floor area. Therefore a 60 cfm (cubic feet per minute) fan is required.


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