One of the most confusing, and changing, practices is how to exhaust a high-efficiency, direct vent furnace.
But, no matter the code, or general practices, I don't like this.
These are enclosed systems. One recent practice that I don't like is that they take indoor air. Always I would prefer to see outdoor air as they suck in a lot to make the system work. Why take in so much indoor air when it is not necessary?
But, the exhaust is what seems so confusing.
The tubing pointing down is drawing air in. The tubing pointing out is the furnace exhaust.
These are very efficient furnaces, re-burning the initial exhaust, so what blows out is very cool, about 105F.
I went to the manufacturer of this furnace to see what their installation instructions indicate.
The instructions have the normal stuff - don't exhaust within 4' of a door or window, not under a deck, not onto a sidewalk or patio, not onto vegetation, etc., - a lot of common sense stuff.
Lately I have been seeing these vents right beside or under doors and windows, and asked a County inspector about it and he shrugged his shoulders.
HENCE MY CONFUSION!
This exhaust contains carbon monoxide, and while it might be discharging into the outdoor air, it can still be drawn back into the house, especially if it blows under a door!
But the exhaust location in the photo really bothers me.
The manufacturer website says this: "6 feet from an inside corner formed by two exterior walls - 10 feet is the recommended distance."
Looking around the neighborhood, in this row of seven townhouses, 5 were vented exactly like this one. And three of those were already lived in, so the County had extended the final occupancy permit and approved it. Looking further there were many other townhouses so finished.
I don't like it because this is a small deck, 8'x10', and this discharge is just below face level if someone is sitting on a chair. When the exhaust is blowing, I tested, you could feel heat at the end corner of the deck, so this exhaust is framed and directed back toward the deck by the house next door.
Even if the code is interpreted to say this is alright, I find this installation unsafe. Often in the code it says any question should refer to the manufacturer's installation instructions. The installation instructions may say not to install this under a deck, but why is it safe to install it over a deck, and framed by an interior corner?
Sending this photo and my question to the County I got no answer. (Hint: I never do...)
My recommendation: something might be "approved" but that does not mean it is smart. And if in response to a question you are told, as were my clients, not to sit near a furnace exhaust when the unit is operating, well, THAT ANSWER IS SIMILARLY NOT SMART!
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia.
Office (703) 330-6388 Cell (703) 585-7560