great question, there are multiple levels to this, as HERs Raters we are only concerned with Exhaust flow, kWh usage and the sensible recovery. But as the "energy professional" our clients expect more. balancing these units is not difficult if the HVAC contractor installed them correctly. Irus style damper 18 inches of hard pipe can make your life significantly better. But every manufacturer is different, so taking an easy example, an ERV with 4 test ports on the front cover. the port diagonal from each other are the channels, each channel should be the same pressure. using a dg700 set to pr/pr and inches of water with hoses in the top two ports, will give you an idea of how balanced it is. using the iris dampers, you can open or close each side of channel A or B to balance out the flow pressures. second is to verify the flow. this can be done from there outside of the home if the intake damper can be reached safely using a typical flow hood or from the inside with a powered flow hood. if the ERV?HRV is tied to the HVAC duct system then i suggest using a pitot tube, this is way we need the 18" rigid pipe. directions on how to use the pitot tube will be in the box. fairly simple. also be sure the ERV?HRV is pressure pitched to the fan meter of the Furnace or air handler. the fan of the balanced unit is not designed to work with large HVAC ducting. the furnace fan added the needed velocity to move the air out into the conditions space. if this remains concussing, reach out to your provider, and thru them find a mentoring Rater that has experience testing and verifying these balanced systems. or if your in or near Mass, call me. 508-833-3100 another option is Jack Shafter - his is the HE territory manager for Broan/nutone, 617-571-9927. Broan is releasing a new line of AI balanced system that self balance. these are very cool and no brainer at the price point.