Hello all. I had an energy audit since my last post. Turns out I don't need whole house ventilation since I get about double the air changes I should (haha...old houses). One of the recommendations was to replace our Weil Mclain boiler (which I believe is about 20-25 years old) with a wall hung Navien Combi. I don't know anything about these systems but did read that it was important that the unit be rated as a real boiler and not just a heat exchanger. Could anyone tell me whether the Navien is a good unit or if there is a better one I should be considering? We have hot water radiators. Thanks.