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Oconto, WI
reply to nunya

Re: External air supply for an 80% AFUE furnace?

said by nunya:

They learned all their evil conniving tactics from electricians and plumbers.

I am curious about the subject though. Would an ERV make any difference in an old drafty house. E.G., would the "least path of resistance" rule apply to air as well?

In my house I have the furnace, water heater, bath vents, and dryer. I'm sure they are pumping copious amounts of air out of the house, which means air is coming in from somewhere anyway.

An HRV/ERV takes in approximately the same amount of air as it exhausts. On the better units you can adjust the intake to exhaust ratio. But overall you are not bringing in a substantial amount of extra air for combustion. And the more you bring in compared to exhausting, you are lowering the ERVs efficiency anyway. It's bringing in more cold air compared to less warm air exhausting. So there is far less heat transfer to condition that incoming air.

For example, lets say your ERV brings in 100cfm. It is exchanging that air by also exhausting about 100cfm. This is what they do, create air changes per hour for better air quality. But your standard efficiency furnace is still consuming combustion air and pumping it out the stack. So where is that combustion air coming from? It's not from the ERV, as it is already pumping out what it brings in. Combustion air comes from same places it has always come from. Leaking windows, uninsulated walls, doors, vents, etc.