An HRV does require 2 additional ducts installed on top of what you have. It also requires maintenance.
In our area I've seen a few freeze up due to condensing moisture meeting the current type of weather we are seeing now -20
It might be worth having a thermoelec or similar pre heater installed upstream of the HRV in the intake, which will pre heat the air to prevent freezing.
I am having an issue with my water heater. I have to kick the ice out of the intake on a daily basis in order to have hot water. I bought the house a little over a year ago, and the builder told me that kicking the ice out daily is "preventative maintenance". Personally I think that's a load of poop, ad I've owned other houses and have never had this issue. Would love some advice on this issue!! Thanks!!