Anyone who lives in a tight house needs a ventilation system. Unfortunately, most ventilation systems are expensive. If you decide to install a high-quality heat-recovery ventilator (HRV) or energy-recovery ventilator (ERV) with dedicated ductwork, your ventilation system might cost you between $6,000 and $8,000.
To address the demand for less expensive ventilation systems, one manufacturer of HRVs and ERVs, Zehnder, has just come out with a low-cost ($1,250) ERV that doesn’t need any ductwork. The ComfoAir 70 hangs on an exterior wall in your bedroom or living room. It’s installed like a space heater with through-the-wall venting: you drill an 11-inch-diameter hole through the wall, slide a cylindrical duct (split into two half-moon sections by a horizontal partition) through the wall, and hang the appliance on the indoor wall. (For a photo showing the partitioned duct, see Image #2, below.)
The appliance is designed to pull exhaust air from a grille on one side of the indoor unit and deliver filtered fresh air from a register on the other side of the unit. The ComfoAir 70 has four speed settings: 9 cfm, 15 cfm, 23 cfm, and 38 cfm. Power draw at high speed is 19 watts, while the heat-recovery efficiency at high speed is reportedly 72.9%.
The appliance doesn’t come with a plug; it requires a hard-wired 120-volt AC power supply. (The ComfoAir 70 is equipped with a transformer; its operating voltage is 24 volts DC.)
Like most ERVs, the ComfoAir requires regular maintenance (cleaning the heat-exchange core and changing the filters).
It shuts down when the weather turns cold
The ComfoAir 70 approach comes with a few compromises: it doesn’t work when temperatures drop below about 15°F; and the maximum air flow rate of 38 cfm is quite low. According to Zehnder, the appliance is suitable for apartments that measure 600 square feet or less. If…