I have installed few Zehnder systems and I am not sure if my rep is giving me the info I need or the info that helps me buy more foam piping from him. The large ducting (7" Comfopipe) coming off the unit at the 4 ports for supply (fresh and to house), exhaust to exterior and from interior). Which are most critical to be insulated piping. If my supply from the ERV is running through a conditioned space, would a sheet metal duct without insulation gain condensation? Would the exhaust from my interior space require insulation? Since the comfotube is not insulated it seems like the additional cost for 39" runs at $77 is not the best cost option.
There are a lot of situations where I have extended internal runs from the ERV to the silencers/manifolds in order to keep my Comfotube runs under the recommended 35'. In a current install I have about 25' horizontal to a 12' vertical of 2 runs of Comfotube. That is not cheap and if I can do these types of runs in sheet metal with sealed seams and no insulation, there is a big cost savings to my client.
The supply and exhaust from the exterior I am more comfortable using the Comfopipe to ensure I don't get condensation.