Thanks for the feedback. I meant the approach of David L. Meinert, btw, not the `make' article.
do you people know these HRV's, might be inspiring...
http://www.homeventilation.co.uk/retroVent.php
comes at a 400 something GBP price tag, but I find it hard to believe the efficiency of 80-90% given the small surface.
This one, I'm extremely fond of, and there's lots of positive talk on it on German fora
http://www.oekoluefter.de/bilder.htm
http://www.oekoluefter.de/video.htm
It's by a tiny manufacturer. but it's a beautiful thing with magnetic bearings etc.
I had to mess up the urls, hope that works