Planning to install an ERV (Energy Recovery Unit) and have been advised that a concentric vent is easier to install and the risk of short circuiting output and input is negligible. My feeling is if I am willing to invest to install an ERV, it might as well be done optimally. Is it significantly better to install two vents, one input, one output, and space them appropriately (say 6”), or is a concentric vent “good enough”?
I feel the air in my house is rather stale.
Thank you!
Firstly, I agree the the incidence of recirculation is likely negligible, assuming you terminate in an open area. Combustion appliances use concentrics by the millions without problems. If you jam it in a corner you could have problems, of course.
Then, a 6" spacing doesn't do anything that a concentric termination doesn't already do. You'd need to space them apart several feet or more to (almost) completely eliminate recirculation concerns.
Finally, a small amount of recirculation is not dangerous. It merely reduces overall efficiency slightly. Whether that minimal concern is worth the hassle of running separate ducts is up to you and local conditions.
Disclosure: I'm not an HVAC tech, nor am I certified in any way to give advice. My knowledge is based on long experience and association with experts.