At 0.39 ACH50, we need a good ventilation system. The FHB House will have a topflight system: a Zehnder ComfoAir 350 ERV. I’ve installed HRVs and ERVs in a number of new homes and large remodeling projects. In those cases we picked up the unit and then cobbled together the supply and exhaust ducting from steel round and oval duct and various fittings and registers. The ComfoAir is a complete system — the main unit, silencers, flexible supply/exhaust duct, register heads and a whole assortment of other pieces and parts.

I worked with Nick, Ryan, and Damian to install the ducts and registers. Rather than running a trunk and T-system with steel ductwork, the flexible ducts are all home runs from the register back to the manifolds. Each supply/exhaust register receives two 3-in. diameter flex duct. The two small-diameter ducts provide sufficient supply to each bedroom and living area, and exhaust from the bathrooms, kitchen area, and laundry.

And with their small diameter and flexibility, it was pretty easy to route the ducts through 2×4 walls and I-joists. The main challenge was pushing each duct with an O-ring into a receiver port on a register or manifold. Even after lubricating the O-ring with liquid soap, it often took two guys to wiggle, push, and pull the joints together.

While not all registers will require the full airflow provided by two ducts, we ran them anyway and capped some ducts off in the utility room. That way, when commissioning the system, if we indeed need more exhaust or supply to some rooms, we can connect the extra duct.

With so many ducts leading from the second floor rooms down to the basement, we had to sacrifice 9 in. of wall depth inside the pantry closet. Careful routing and duct arrangement kept the space loss to a minimum.