michaelmurfy: HRV - don't go near them, they're expensive, pushy and actually not that good.
I had heard all the HRV pushy sales horror stories to. Which is why we went for DVS. My elderly in laws have HRV. Recently the red light came on the control panel. They rang HRV who told them it needs to be looked at urgently. Long story short it was just the filter. All in all HRV charged them over $300 for a filter change.
I got 2 filters for my DVS on trademe for $70. Fitted one in 10 mins.