The Panasonic FV-04VE1 is the benchmark I am competing with. These are commercially available via Amazon and other distributors. The Panasonic design is based on a "capillary core" heat exchanger. A 40CFM unit is just under $350 and consumes 23W. I believe the Panasonic makes use of BLDC motor drives for quiet, reliable operation - something I'd also like to incorporate, for filter blockage compensation/pressure changes. Accessories for the Panasonic, such as Y-fitting ducts to retrofit existing exhaust ports, could be used in my project. They combine incoming and outgoing air in a single duct in such an application - side benefit of being a counter-flow heat exchanger by coincidence. The Panasonic units are made for bath fan retrofit/new installs, as opposed to whole-house ERV's. Given the price, it might take a while to recoup costs, if ever... not that my R&D unit would be any cheaper!