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I live on the east coast of Canada, where we get cold winters, and warm summers. Humidity swings are common in all seasons. The house was built in the 1990s, is heated with electric baseboard heat, and cooled with air conditioners in the summer.

We have an older-style "air exchanger" unit (in a cold/unheated basement room) which I have been very hesitant to use in the hot summers and cold winters.

I read this about air exchangers (emphasis mine):

Air exchangers work by circulating stale indoor air out of your home and circulating in fresh air from outside. Exchangers use one fan and vent system to blow indoor air outside, while another sucks fresh air in.

In my mind, I see that as follows:

In winter:

  • blowing my very expensive heated air from inside to the outside
  • sucking very cold winter air into a once-warm room that cost me a fortune to heat in the first place

In summer:

  • just the opposite of above

Am I correct in this line of thinking?

Will it cost more to heat and cool my house if I run the air exchanger?

**What, if any, long-term issues with the house would I be causing if I don't run it?

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    Think most air exchangers also have a heat recovery system. They will warm up cold winter air coming in with the heat going out. Do not think it is a one to one idea, but you do not get -20C air blowing into the house. At least that was the idea back in the 80s with the R2000 builds.
    – crip659
    Dec 23, 2022 at 14:39
  • I don't think mine has any heating elements, though I could be wrong. It's weird but I can't seem to locate much info online about them (in general on on my unit specifically). I'll add a few pics to the question.
    – GWR
    Dec 23, 2022 at 14:45
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    They do not have heating elements. What they do is pass the air back and forth in kind of a maze/loops so the temperatures can equalize without mixing.
    – crip659
    Dec 23, 2022 at 15:15
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    Note that the top line of the label says "Lifebreath Heat Recovery Ventilators", so it seems a safe bet that this is indeed a heat recovery ventilator as explained in P2000's answer below.
    – Mark
    Dec 23, 2022 at 18:54

2 Answers 2

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Exchanging Air

If you wish to provide fresh air into your home, you need a separate ventilation system for that. You can theoretically leave a door open, or run a fan like a bathroom fan or hood fan to circulate air, but these will cost a lot in lost cooling in the summer and lost heating in the winter.

Heating & cooling systems generally have a fresh air intake that is connected to the ductwork before the furnace or A/C. This intake is just a passage without any means for heat exchange. It's simple but not energy efficient.

Energy efficiency for fresh air intake can be provided by a ERV or HRV.

Through these, fresh outside air that is drawn in is cooled or heated using the "coolness" (in summer, with A/C) or "heat" (in winter) of air that is sent out. You need power to run the fans in it, but the cooling or heating comes for free.

ERV : heat and moisture exchange

An "Energy Recovery Ventilator" will exchange inside air for outside air, replacing the stale air with (hopefully) more fresh outside air, and it will exchange the moisture.

Not only is the incoming air heated by the outgoing air, also inside moisture is exchanged to humidify the incoming cold and dry but fresh winter air.

In hot and humid climates, an ERV is used to keep out humidity.

HRV

If humidity is not a concern you can use an HRV (Heat Recovery Ventilator), which is practically the same but without the moisture exchange. This is suitable for the heating season in cold climates, whereby inside humidity is controlled by a separate humidifier.

Have a look:

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Stale inside air goes out and better outside air is pulled in.

Heat Exchanger

That cubic-shaped block in the middle brings the two flows of close to each other, flowing over aluminium plates, to allow the temperature to equalize through the metal: the fresh outside air is cooled a bit by the air sent out, so that the air conditioner does not have to cool it as much as when your draw-in hot air from the outside.

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Further reading in ERV vs HRV:

https://www.ecohome.net/guides/2276/choosing-between-an-hrv-and-an-erv/

Image credits:

https://www.pinterest.ca/pin/469781804853382012/

https://www.pvhvac.com/blog/erv-or-ventilating-dehumidifier-which-is-better-for-georgia-homes

https://www.engineeredair.com/index.php/our_products/category/energy-recovery-and-iaq-products

https://www.brighthubengineering.com/hvac/55429-how-to-install-window-air-conditioner/

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Your machine is a HRV, so utilize it with impunity

By the labeling, your "air exchanger" is actually a Heat Recovery Ventilator, or HRV. This machine not only brings fresh air in and sends stale air out, it runs the two through a heat exchanger that preconditions the fresh air to be closer to the indoor air temperature. As a result, you can run your ventilation system without having to worry about running up your energy bill.

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    Well, near impunity. The heat recapture isn't perfect. But it's enough to limit losses, probably to less than a less-well-airsealed house would lose to air exchange via leakage.
    – keshlam
    Dec 24, 2022 at 6:00
  • @keshlam yeah, it's not perfect, but it's close enough that Allison Bailes uses the word "impunity" for it, and they know more about this stuff than I do for sure! Dec 24, 2022 at 6:13
  • Good enough. I would really like to find a small unit that could hold up to workshop use, to evacuate solvent fumes from my basement while tolerating possible sawdust. (The rest of the house is undoubtedly getting more than enough airflow just because it isn't built to modern hypertight standards.)
    – keshlam
    Dec 24, 2022 at 6:24
  • In theory this answer makes sense, but placing my hand over the air output in any given room in the house tells me the air being pumped from the machine into the rooms is quite a bit colder than the heated air in the room.
    – GWR
    Jan 4, 2023 at 23:03

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