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HVAC Systems - Engineered Ventilation


There are 4 ventilation options in the HVAC systems section of Cool Calc. This section only pertains to mechanical ventilation. Intermittent bathroom fans or kitchen range hoods should not be included as sources of ventilation unless the bathroom fan is wired to be running 100% of the time.

Outside Air Dampers - Outside air dampers bring in fresh air with no attempt to temper the air as it is brought in. If the more air is brought in than exhausted, it will result in a positive pressure situation and infiltration would be reduced. 

Heat Recovery Units (HRV) - Heat Recovery ventilators utilize the heat of the exhaust air to warm up the fresh air in the winter time. The heating efficiency refers to how much heat is recovered from the exhaust air. Values typically range from 50-80%.

Energy Recovery Units (ERV) - One of the benefits of an ERV is that it transfers heat and moisture between incoming and outgoing airstreams. That means it takes much less energy to heat/cool the air you bring into the home. When "Energy Recovery Ventilator" is selected, you will be prompted to enter the "Latent Cooling Efficiency".

Efficiency  ratings for HRVs and ERVs can typically be obtained from the manufacturer's product data material.



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    Robert Stopielo

    why isn't kitchen and bathroom exhaust fans considered in manual j ? granted i know they arent being used 100% of the time but they suck out condition air and then pull in outside air through leakage .

  • Avatar
    Cool Calc Support

    This is what Section 24-6 (Local Exhaust Equipment) of the ACCA Manual J book states. "Homes are commonly equipped with kitchen and bathroom exhaust equipment. If this equipment is not part of an engineered ventilation system, the momentary ventilation load (increase in infiltration) is ignored, providing this equipment is used sparingly and intermittently."

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