of an HRV’s heat-recovery feature. Even so, dust and pollen are filtered and ventilation is improved by installing one. 

The possible disadvantage of HRV units in off-grid homes is their electrical circuits and fan: the unit’s small-load blower and control circuits actually consume quite a bit of electrical energy. An HRV uses about 2,000 watt-hours in a 12-hour day, which is at least 50% of a winter day's off-grid energy production.

 Unfortunately there are only a handful of options available for off-grid use:

• Change the 120V fans to a lower-flow 15W computer-style fan which is more efficient. Lower-powered fans consume less HRV energy for a day’s operation, at around 300 watt-hours. You’ll need an electrical expert to handle this modification.
• Put in an air loop intake with a bathroom-style vent fan.
• Put in an air loop intake together with an indirect venting gas, pellet stove or wood fireplace. 

When you use the vent fan in the kitchen or bathroom or while working a wood stove, stale air is drawn outside. Thus, a partial vacuum is created that draws in dry, fresh, cold air which mixes with the room’s warmer air before moving out to the living room. The air intake is controlled even though it is not as efficient as through a HRV unit. Still, this is better than relying on air leakage to get fresh air (which causes uncomfortable drafts). With the intake damper adjusted, the humidity of the building is controlled via the entry of cold and dry winter air.

Any air circulation design should be discussed with building officials for approval before implementation. The officials need to be aware that one should not use an off-grid electrical system to power an HRV unit.