Sorry, to write in English. I have had Thermia Duo 12 for 2 months and can only recommend it. The only negative thing that comes into my mind is that the metal case of it is not very carefully designed and tends to resonate (=makes noise). I would install it into a separated room only. The case of Lämpöässa is from much thicker metal for instance. And one more thing - I would certainly buy it with the "soft-start" device.
Jaak