I recently moved into a home that is 25 years old. All of my previous homes were newish and had HRVs. Proper ventilation and indoor air quality are important to me, so I am going over retrofitting options. Based on my research, I’m learning towards an ERV for its ability to run all year round (I live in zone 7 with cold dry winters and hot humid summers).

Anyway, my question pertains to ducting. The easier solution would be to tie into my AHU, but I’ve read (mostly on GBA) that this is not an efficient method. I’m thinking of installing dedicated ducting to the ERV. Based on accessibility, I could add exhausts from all 3 bedrooms, but I can only access one common area to supply the fresh air. My question is: does my indoor exhaust and supply ducting need to be made equal? Do they need to have a 1:1 ratio, or  can I have 3 exhausts and 1 supply? I could potentially increase the diameter of the supply.