Mechanical systems affect the house-as-a-system by causing pressurization or depressurization in a house while operating. By mechanically moving air and water around a house you effectively move moisture, heat and sound as well. Exhausting air may create a back drafting situation for spill susceptible appliances as well.

Mechanical system components include:

• Ventilation System
• Heating System
• Cooling System
• Domestic Hot Water System

Ventilation System

Ventilation systems are used to move air around the home, exhausting moist, stale indoor air and replacing it with fresh outdoor air. They are used for the following reasons:

• Exhaust excess moisture and contaminants
• Provide fresh air to dilute indoor pollutants
• Required by Building Codes in new construction
• It is necessary and it works!

All new homes now require a ventilation system as per the Building Code. It needs to be properly sized and installed. In Canada the most common type of system installed is a Heat Recovery Ventilator (HRV), which use a core to pre-heat the outside air coming into the home by using heat from the outgoing stale air.

Requirements for ventilation systems:

• Mechanical ventilation equipment must be provided in new construction and some large renovations
• Ventilation systems must be capable of operating on a continuous basis
• The ability to exhaust from each bathroom and the kitchen must be provided
• Ventilation system controls must be provided to allow for both continuous operating levels and higher peak exhaust rates
• Where the operation of exhaust equipment can induce significant negative pressures, the ability to provide fresh make-up air to the house must be in place

If you are insulating during/after a ventilation system is installed make sure to:

• Seal all ductwork penetrations in the exterior walls
• Seal all ductwork coming from the top floor ceiling or attic if the system is installed there

Close attention must be given to all penetrations from the exterior walls/attic as they effect air tightness greatly. Continuity of the air barrier must also be maintained in order for the house to perform as expected.