Our mechanicals contractor started roughing in the duct work for the ventilation system last week. If you recall my earlier post, Mechanicals (ERV and ASHP), I tried to model all the ducting to anticipate the problem areas.

Our installer, Phil, has been installing ventilators and air-source heat pumps for quite some time, and he has brought a lot of experience to the table. This will be essential in some of the tricky spots. Out of the four areas I was originally worried about, only one has Phil mildly stumped; connecting the outside air ducts to the ERV.

Determining how to orient and position the ERV in the basement in order to minimize the number of twists and turns is a real challenge. I don’t think we’ll actually know the final configuration until the unit arrives in a few weeks.

I’ve also been a bit concerned about the number of T connections that Phil has been using. My research has led me to believe that these should be Y connections. T connections impede the flow of air. Phil assures me that this is not an issue considering the relatively low air pressure in the system. I remain skeptical, but relented as long as the required air flow at each register can be achieved.

Lessons learned: I should have located the ventilator somewhere on the first or second floors instead of the basement. This would have greatly simplified connecting to the outdoors, although it would have brought the unit closer to the living spaces and potentially caused a noise or vibration problem.

I also should have moved a few walls so that they did not sit directly on top of a truss. Trusses are wider (3.5”) than normal joists (1.5”). This makes it extremely difficult to get vents and plumbing stacks up through these walls without some gymnastics.

I’ll add more details when the ERV unit arrives onsite.