ERV and wood stove
We are building an approx. 2400 sqft house in south central Alaska. It will be heated by a large wood stove (with backup direct vent heaters that we hope to not rely on except when out of town). We are exploring an ERV and trying to figure out the ductwork placement. For orientation, the downstairs is open kitchen/ living area, a bathroom, mud room, and laundry room, and the upstairs is 3 bedrooms and one small bathroom with shower. Our concern is that we will be relying on convection primarily to heat the rooms upstairs. We plan on putting some vents in the floor of the bedrooms to encourage air circulation with the living area below for more even heating.
From what we have seen about ERVs, it’s recommended to vent out bathrooms, laundry, and the kitchen, and to vent in to the bedrooms. The questions is, how efficient is the heat retention of the ERV really? We have fears of pumping cold air into the bedrooms upstairs. On the other hand, maybe it will help if all the hot air is rising? It’s one of those things that will be evident with experience, but I’m hoping someone else has lived out this experience and can advise.
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Your situation is very similar to mine. I have an open concept first floor with a living room, kitchen, mudroom, laundry room and a second floor with 3 bedrooms a bathroom and another living room, 2000sft overall. Wood stove down stairs in the living room and a Panasonic intelliblance 100 cfm ERV with supply air coming into the 1st floor living room, all 3 bedrooms upstairs and the upstairs living room and exhausting from both bathrooms and the kitchen. When it is 10 degrees outside and 74 degrees down stairs my thermal imaging camera reads that the supply air from the ERV is about 68-70 degrees which is better than I ever expected. The upstairs temperatures in those conditions are typically about 71 degrees in the upstairs living room and 68-70 degrees in the bedrooms so the ERV doesn't have much impact on the temperature positively or negatively.
Your situation may very depending on your insulation and air sealing. I have 12" thick double stud walls with dense pack cellulose and 24 inches of cellulose in my attic so my house holds heat well, but regardless of the insulation I don't think it would change the efficiency of the ERV.
Josh,
It's always good to hear real world data to confirm what we had been expecting based on the specs. Thanks.
Lookup the Sensible Recovery Efficiency (SRE) of the ERV you are interested in. Zehnder is 85-93% depending on the model.
One option is to get a duct heater for your ERV fresh air supply. This would be installed in the supply duct after the ERV so it would normally only need to run a bit to take the edge off the slightly colder fresh air.
On some of them you can adjust the temperature so you can also get a bit of extra heat if needed to the rooms. Won't be much heat, but might be enough to take the edge off overnight temps.