Hi experts,

We’re adding insulation and air sealing our 1980s 3 bedroom, two-story house (2000 sqft) with basement in Michigan (zone 5).  We already have bath fans and kitchen exhaust in place. After pouring over previous discussions, I’m still a little lost on how to move forward on choosing an ERV system.  Would you please lend some advice on what you would choose?

Option 1. Add an ERV to the 2009 gas 3-stage, high-efficiency furnace (through the cold air return) and use our somewhat poorly designed (unbalanced?) ducts. Pros- we already have the ductwork in place, lots of good ERVs to choose from, and this is what our HVAC person is most familiar with. Cons- the energy penalty from running the furnace fan on the last non-electric utility in the house.  Also- would you expect poorer IAQ because of the immediate dilution of fresh air at the furnace?

Option 2. Ductless HRVs (Lunos) in each of 3 upstairs bedrooms, in main floor living room and office, and the basement tv room for a total of 6 devices. Pros- minimal disruption with install because we’re already working on the wall assemblies, fresh air gets to each bedroom and key areas, it accommodates a MERV 13 filter if we have trouble with wildfire smoke again, and it’s pretty well balanced. Cons- expensive (but maybe cheaper than running ERV dedicated ductwork in a remodel), concerns for noise when fans switches directions when trying to sleep, commitment to one brand if anything goes wrong. 

Option 3a- put in a stand alone ERV system in the basement or ground floor (between living room and office) and run a more limited dedicated duct system.  Would likely have supply ducts in 3 upstairs bedrooms, return in stairway and main bath; supply in living room, return in office; supply in basement tv room, return in rarely used guest bedroom. Pros- having a separate system without the need to run the main HVAC in the shoulder seasons, easily accessible central location for indoor/outdoor maintenance, most critical areas are ducted. Cons- Much more complicated/expensive to install, some ducts would be long and run through the (insulated, air sealed) attic, outdoor supply and exhaust could be separated 10’ vertically but could only be offset by a few feet (could the exhaust go under a deck?)

Option 3b- same as above but run shorter and more limited ducts.  Supply to upstairs master bedroom, and in furthest bedroom(?); supply to living room, return in office; supply in basement tv room, return in guest bedroom.

So I think my questions are- how “bad” is it to add an ERV to the furnace?  Is it better to have some fresh air ducted to many places (losing some CFM in ductwork) or lots of fresh air ducted to a few places (because air will disperse on its own)? Is Lunos the most efficient, quietest, simplest system if you can overlook it’s upfront cost?  Is it better to have the shortest system with fewer supplies and returns because the HRV fans are sized to distribute air throughout the space? 

Thanks in advance,
Elizabeth