Throughout the last week I have been plugging away at the duct work for the HRV (Heat recovery ventilator). For those who don’t know, a HRV is a ventilation device that passes stale exhaust air from the house by fresh exterior air thus exchanging the heat from the exhaust to the fresh air. Best practices call for exhaust registers to be in the bathrooms and kitchen, while supply registers to be in the living spaces and bedrooms. When installing the exterior vent shrouds, one should place them at least 6′ apart so the two air flows don’t mix. Also, the shrouds should be on the same side of the house to avoid differential between air pressures.

For the ducts I have been running 6″ round main lines with 4″ round branches. For an HRV we are using a Venmar EKO 1.5 which runs on a very efficient 24 watt ECM motor while transferring 80% of the outgoing heat to the incoming air. In order to boost its efficiency I located the unit on the south side of the house where the exterior air will be warmer. The downside of this is that the HRV is in the master bedroom closet taking up most of the space.

HRV installation

The installation for the Venmar EKO 1.5 calls for it to be hung from joists by chains that have springs on them to mitigate the amount of noise it transmits. On the left side of the picture you can see insulated flex duct. The ducts that go to and from the HRV and the exterior need to be insulated to prevent condensation on them. One thing I didn’t like about the EKO 1.5 is that all four ports are on the top. Most HRV’s have two ports on opposite sides. Having all the ports on the top means they get in each others way. Also, if you are like me, and decide to install the unit on a second floor, you are guaranteed to have to make U-turns in the duct work. Whenever one is trying to move air (or any fluid) through a pipe one tries to avoid sharp bends that restrict flow and can increase noise.

HRV installation

Venmar EKO 1.5 HRV heat recovery ventilator installed

Our Venmar EKO 1.5 HRV heat recovery ventilator installed.

HRV condensate line run into toilet

The HRV produces condensation, which ordinarily is run into a bucket, to the outdoors, or into a drain line. A bucket is work, outdoors meant another penetration in our envelope, and my plumber didn’t think the inspector would allow it to go into the drain. Creativity won out–we ran it into the toilet! A 5/8″ diamond hole saw cut right through the ceramic.


Photos by Hannah


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