There'e no other way to say it - this is deadly air in being drawn back into the house - in Northern Virginia?
Say it ain't so!
Well it is.
A high-efficiency condensing gas furnace is a wonderful and extremely efficient appliance. I wish my furnace was this efficient.
Most gas furnaces, like mine, have a flue which expel their exhaust through a metal flue extending through the attic and roof. I am losing huge amounts of heat through my roof! And my furnace is only capturing, and using, a percentage of the heat generated by the furnace to send through the house. For every dollar I am spending on natural gas I'm really only benefitting from a small percentage of every dollar toward heat.
The high-efficiency condensing furnace re-burns its exhaust so that what blows out is really very cool air, 105F or so. At the same time it is drawing in fresh air, so it is an enclosed system and burns none of the oxygen in the house.
The thermal image to the right shows the fresh, cooler air drawn in through the vertical purple tube on the left and the warmer air through the yellow tube on the right. This system is operating as intended.
The exhaust has lesser carbon monoxide than a regular furnace would exhaust through the roof, but still its exhaust is laden with CO.
The two tubes, intake and exhaust, should terminate on the same side of the house and near each other, not near a window or door, and should look something like the configuration on the left.
Notice that the exhausted, warmer air is sent up and away.
The fresh, cooler intake air is drawn in from below.
In this way the intake air and exhaust do not mix.
Seeing this the other day bothered me.
The longer tube is the exhaust for this condensing gas furnace.
The partially-hidden shorter one is the intake.
Do you see a problem with this too?
Steam was generated by the exhaust tube and you could actually see it being drawn back in through the intake tube.
It really is drawing in deadly air.
Now, surely, that dissipates throughout the air in the house.
But why introduce that back into the home?
I did not see a carbon monoxide detector anywhere. Certainly there should be a couple.
This furnace, and system, was installed in 1994. That's pretty early in the history of this furnace type. I have seen other systems installed in that time frame and do not remember seeing this before. I don't think it was common practice for the intake and exhaust to have this configuration.
But it is a very easy fix and I highly recommended the buyers do! Doing so would be a Best Practice!
My recommendation: safety first. Introducing carbon monoxide into the air can't be good. Is it enough to be dangerous? Who knows! Over time maybe. And some occupants of the house might be more susceptible to CO presence - like the elderly or very young. So why introduce it in any quantity?
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560