[Daox]

I was reading on the Canadian Passive House Institute website and found this:

Although heat recovery ventilation units (HRVs) were pioneered in Canada and the US, over the past decade European manufacturers have taken HRV performance levels well beyond anything achieved in the NorthAmerican market, and have re-designed heat exchanger cores completely. Passive House-compliant units are certified by the Passivhaus Institut, which in 1996 developed a more stringent HRV testing protocol to that used in North America. As a result, the best European HRVs achieve over 92% heat exchange, as measured from the inflow and outflow air streams.

Due to the much smaller size of their heat exchanger cores and lower insulation and air sealing levels, most Canadian or US models likely do not exceed 50% efficiency under the same measurement criteria.



Passive House-compliant Heat Recovery Ventilator (HRV)



The best-performing European HRVs are significantly larger in size than conventional North American models, and all incorporate 'counter-flow' heat exchange cores, developed specifically for Passive Houses, which provide much greater heat transfer area and therefore improved performance over the 'cross-flow' cores used here in Canada

Sounds like the US/CAD models are just too small! 92% is amazing. The ones I was looking at the other day you were lucky to see much more than 60%! Sounds like a bigger DIY option would be far superior.