Mechanical pressure imbalances can lead to all kinds of moisture problems and also produce very poor comfort zones in your home. 

Testing can determine 
  • if there is enough heat being provided
  • If it is properly distributed
  • If the heat loss calculation is accurate
  • If you are pressurizing a zone or the entire building
  • What needs to be done to bring the pressures into balance and increase the comfort.

Principal Exhaust Fan Pressure Testing 
-using the blower door manometer

The principal exhaust fan is the way to get fresh air when the furnace is not running. It is also a way to reduce excessive interior positive pressures in many cases.

A properly balanced Principal exhaust fan is required by the Alberta Building Code 
Sealed Combustion Furnace Pressure Testing 
-using the blower door manometer

Older homes used a "B" vent or chimney to exhaust hot air for heating the house. This created a slight negative pressure that "sucked" air in through openings, penetrations, potlights, etc. This provided drying and reduced air leakage into walls and attic spaces.. 

Sealed combustion furnaces (High Efficiency) only have a fresh air intake into the return air system. The combustion is sealed and has no effect on the air pressures. Since the furnace brings fresh air in, but has nothing discharging air, it creates a slight positive pressure. Sometimes the pressures can be excessive leading to problems. This can push humid air into the exterior walls and attic spaces.

Watch the video below to see.
Average pressures created in new homes is 3 Pascal’s as an average. In some cases tested homes were as high as 21 Pascal’s and the air forced into walls and attic spaces is tremendous. 

The higher pressures mean the more "perfect" the interior air barrier (poly) must be.
If the Principal exhaust fan has been balanced to the intake, the pressures will be balanced when the ventilation fan is running.

This fan is not automatically run when the furnace is running nad must be manually turned on by the occupants 
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