ERV exhaust in bedrooms
thanks to everyone that has helped with my questions in the past. My current confusion is around exhausting the bedrooms vs supplying them through the ERV. I realize there is an old article on this and a few QA posts, but I was not able to find an answer that really made it clear or people actually doing this. Has anyone ever done such a setup before? The original GBA article below introduces the idea, but no examples. A later QA post answer by Martin says this has been “debunked”. Malcom also posted to a recent post that this was false, but I’m having a lot of trouble with the math. Supposedly the reason it is debunked is that the flow rates are too low to affect temperatures in a measurable amount. So let’s setup a scenario:
1. Outdoor temp of 32F.
2. Indoor temp of 72F in greatroom.
3. Considering a bedroom with closed door.
4. 80% efficient ERV supply or exhaust at 20CFM continuous ventilation.
5. For 20CFM, ACH = CFM * 60 / volume. For a 10x10x10′ bedroom, this would be 1.2 air changes per hour.
In this scenario, if I were to supply the bedrooms with outdoor air, every ~45 minutes the room is being replaced with 64F air (72-(72-32)*.2). If I were to exhaust the bedroom, the air in the bedroom would be recirculated with 72F air every 45 minutes. That’s a temperature delta of 8F just from the ERV which seems huge. Also, why not exhaust the bedrooms? That should still help mitigate CO2 levels in the bedroom and in a way that should be warmer and less likely to blow on occupants. If the air you’re pulling in from the rest of the house is stale or smelly it seems like you have other issues that need to be resolved.
From the post https://www.greenbuildingadvisor.com/question/hrv-duct-set-up
Martin stated “The idea that unusually creative ways of ducting HRVs might help equalize indoor temperatures has been debunked, because HRV air flows are too low to move much heat around your house. For more information on this issue, see:
But none of the linked articles seem to debunk this from what I read, I may have missed something.
Original article: https://www.greenbuildingadvisor.com/article/a-new-way-to-duct-hrvs
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