Skolink:timmmay: Heat Recovery Ventilation systems can stay on at night, because instead of just running a fan that pushes air out the cracks in your house it sucks clean air in from outside, heats it from the stale moist air it takes from the house, and so you get fresh, pre-warmed air. It's not perfect, there's some waste, but it's better than the alternative.
Just to clarify, Heat Recovery Ventillation should not be confused with the 'HRV' system which Marc Ellis markets, they are two different things. The Marc Ellis type system is what timmmay has installed, with no heat exchanger.
Correct. Heat Recovery Ventilation is a technique of ventilation that reuses existing heat, not a company. I had HRV the company over once to tell me about their products, and they were snake oil salesmen who either lied or exaggerated, and when I started asking tough questions just couldn't answer them.
The system I have in is from a different manufacturer, it was there when I bought the house. It's a little two outlet system, outputting into my hallway and into my kitchen. It's quite effective of bringing a little heat into the house on sunny days, and even on cloudy days the ceiling cavity is slightly warmer and drier than the house, so overall i'm pleased I have it.
If I were putting one in i'd get a much better heat recovery system, but total cost would be about $5K and cutting the holes in each room could reduce the effectiveness of the insulation further.