Bathroom Fans with HRVs and ERVs

Bathroom exhaust fans may be used with heat recovery ventilators (HRVs) but may not work as well with ERVs (energy recovery ventilators). These devices try to recover humidity that a bathroom fan tries to eliminate. The “ASHRAE” standard clarifies the cross leakage allowed in specific energy recovery systems. ERVs can leak up to 10% of the outgoing and incoming air.

It may be ill-advised to rely only on HRVs or ERVs. It depends on a few factors:

• The permeability of the walls and ceilings

• The amount of thermal insulation in the building

• Climate zone

Depending on the relative locations of the exhaust and return ports, there may be cross-flow which pulls moisture into other rooms. There is a chance the bathroom may evacuate at a lower rate if there is bathroom ducting in the same place as the CFM unit.

The advantages of dedicated bathroom exhaust fans are:

• Quick removal of moisture and smells 
• Separate exhaust with no cross-flow to different areas 
• A decrease in ineffective defrost cycle time  
• The resulting decrease in duct condensation. 

For bathroom fans to be effective, they need to be controlled either by delayed-off timers or by delayed-off motion detectors, and they have to be used by occupants. The latter will start the fans when they are not required, and they have to be used by occupants. If you are going to use three-bath exhaust fans, it may be wise to drop the HRV and central ducting. Utilize the bath fans as exhaust-only ventilation by installing one or more in parallel with 24-hour programable timers. It can also shorten the duct runs and make the fans even more efficient. Depending on the seal of the house, you may need to install passive make-up air inlets. It works very well in superinsulated homes.

Always seek help from a professional electrician before attempting any work yourself. Contact Mike Fuller Electric in Ottawa today for your bathroom fan HRV or ERV inquires.

Tel: (613) 225-3249

Email: [email protected]