ERV recap

After expending some brain power to conceive the layout of our ventilation system, after finally having the exhaust in place and after endless duct sealing, the ERV is finally up and running.

How does it perform?

I read a lot about how an ERV ventilation system works and performs, and I was familiar with the technical accounts and with various testimonials. But I have to admit that it still did not prepare me for the real experience.

We finished the ERV installation in early March, when we still had very crisp and cold mornings.

On such a morning, when it was close to freezing outside, I went right up to the ERV, placed one hand on the still un-insulated air-intake elbow, and the other hand on the on the fresh air supply into the building.

To my big surprise, the air-intake elbow was close to freezing while the fresh air supply into the building was at about room temperature. I shouldn’t have been surprised because I should have known that this thing – the ERV – is a very effective heat exchanger.

Getting a physical sense of the temperature difference, which demonstrates the effectiveness of the unit, caught me a little off guard. Seeing this gadget at work is quite an experience!


After some experimenting, we figured that it is best if we run the ERV on the low setting for most of the day, but use the timer or booster switch in the bathroom when we take showers.


Because I have not yet insulated and subsequently waterproofed the outside of our foundation wall, there is still a lot of moisture migrating into the living space through the exposed limestone wall.

And that was the idea: let the moisture escape to the inside (i.e., let the foundation wall dry out) and remove that moisture through the ventilation system.

Once the foundation wall is insulated, there will be a whole lot less moisture migrating into the living space. At that point, the ERV may only need to run in booster mode for a couple of times a day, usually when the bathroom gets used.

What are the take-aways…

… from the whole installation process?

I need to get the duct work installed way earlier in the process.

For the 1st and 2nd floor, I should install the duct work along with or right after any framing work. It is relatively easy to route plumbing and electrical around the duct work.

It is not easy to route duct work around electrical and plumbing lines. Plus, the more routing around I do with the ducts (the more bends and elbows I have), the more friction there is that lessens the efficiency at which I can deliver and distribute fresh air.

About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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