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nunya
LXI 483
MVM
join:2000-12-23
O Fallon, MO
·Charter

nunya to Lurch77

MVM

to Lurch77

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

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.

ArgMeMatey
join:2001-08-09
Milwaukee, WI

ArgMeMatey

Member

said by nunya:

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.

We have an old leaky house. I had an energy audit with a blower door test, and was given an ordinal list of improvements to reduce outside air infiltration. We did the top items on the list: Insulating all outside walls, weatherstripping doors better, sealing unused windows. Other items on the list were rebuilding windows to eliminate window weights, and then insulate those cavities, insulating basement walls. The ERV didn't even make the list. So in a loose house, your money is better spent on other stuff.

I also draw air with the bath and range vents, but I am not worried about backdrafting because I have a direct vent water heater and 90+ furnace drawing outside combustion air. Only the gas dryer draws combustion air from inside.

So anyway, after the insulation and weatherstripping, the auditor re-did the blower door test, showed me the reduced infiltration, and gave me my rebate certificate. With that, the state program paid for most of the audit and paid me for part of the improvement cost.

Lurch77
Premium Member
join:2001-11-22
Green Bay, WI

Lurch77 to nunya

Premium Member

to nunya
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.

JustBurnt
@rr.com

JustBurnt to nunya

Anon

to nunya
said by nunya:

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

Can't leave out Roofers