-Too little or too much ventilation

-Insufficient ventilation results in excessive indoor humidity

-Uncontrolled ventilation can cause exhaust leaks within the house

-Energy efficient mechanical heat recovery ventilation system

-Provides continuous circulation of filtered outdoor air

-Saves energy through use of a heat recovery device

Here are the specifications for a properly installed HRV system:1. If the kitchen exhaust is located in a ceiling or

wall, it must be within 300 mm (12 in.) of the ceiling. The duct must be accessible for cleaning unless the intake is equipped with a grease filter.

2. Supplemental exhausts in the kitchens and bathrooms are not exhausted by the HRV but are controlled by a manual switch in the room being served.

3. Door under-cuts or transfer grilles allow air movement from supply-air grilles to exhaust grilles.

4. If a solid-fuel-fired appliance is present, the HRV must be installed to operate without depressurizing the house in any operating mode.

5. Supply-air ducts carrying untempered air through heated spaces must be insulated to at least RSI 0.5 (R-2.9).

6. Exhaust ducts in unheated spaces must be insulated to RSI 0.5 (R-2.8).

7. The HRV supplies outdoor air directly to: the principal living area each bedroom any floor without a bedroom

8. The HRV is operated by centrally located manual controls or by automatic controls.

http://oee.nrcan.gc.ca/english/index.cfm?attr=4