Hi all,

I’m planning on adding an ADU to our house and just trying to figure out the ventilation. The order of business is to build the ADU and then gut and renovate the house.

We will install an ERV but I’m wondering if I can put one unit in the ADU and then eventually duct it into the house when we renovate — with the proper sizing to handle both living spaces, I think something around 150cfm or 200cfm would work for around 3,000 sq ft, 4 occupants, 3 bathrooms.  

I had one company tell me there should be two separate ERVS so if someone is cooking something smelly on one side it won’t stink up the other side. (Maybe that’s legitimate but the plan would be for the separate range hood to vent whatever is cooking. And how much does the exhaust air mix with the intake air?) Just not sure if two units is the best approach or if they’re just trying to sell me two units.

Also, I’m tempted to install the ERV and ducting myself, and then find an HVAC contractor to commission it. Would a good HVAC contractor be able to commission any system or only products they’re familiar with? 

Thanks very much.

Shaun
CZ6, Quebec