Thread: Vent clearances from window

What are the required clearances for this vent. It is serving a gas fired wall mounted direct vent unit located just inside.

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Hmm ... are you sure that is direct vent, i.e., the appliance is getting combustion air from outside the house?

If not it will need a 4' min. clearance from beneath and from the side of a window or house opening. NFPA 12.9.2

Originally Posted by Mike Lamb

Hmm ... are you sure that is direct vent, i.e., the appliance is getting combustion air from outside the house?

If not it will need a 4' min. clearance from beneath and from the side of a window or house opening. NFPA 12.9.2

Mike,

My error.

It is a natural draft vent. It get's it air from inside the house and there is no power to the unit.

- - - Updated - - -

I see these a lot.

I tell people that it is too close to the window as exhaust gases may enter the living space, but their answer is almost alwaysw the same: "DUH" hello mr. inspector. Do you really think the window will be open in mid-winter when they are using it??

They make a good point.

Originally Posted by Ken Amelin

Mike,

I tell people that it is too close to the window as exhaust gases may enter the living space, but their answer is almost alwaysw the same: "DUH" hello mr. inspector. Do you really think the window will be open in mid-winter when they are using it?? They make a good point.

It's a point but not a good one. Adults and children can open or crack a window in winter for any number of reasons and it doesn't have to be a good reason. A house can easily be under negative pressure and suck CO fumes right in from that vent. Report it as wrong and hopefully Mr. DUH won't be dead wrong.

12.9.2 A mechanical draft venting system of other than direct-vent type shall terminate at least 4 ft (1.2 m) below, 4 ft
(1.2 m) horizontally from, or 1 ft (300 mm) above any door, operable window, or gravity air inlet into any building. The
bottom of the vent terminal shall be located at least 12 in. (300 mm) above grade.

It's always good to report it, CYA!!

Since it is Natural Draft, not mechanical, the termination would have to be 5' above the connection to the appliance for proper draft, and 2' higher than any portion of a building within a horizontal distance of 10 feet. That would put it above the roof. This is my understanding of IFGC 503.5.4.

Originally Posted by Ken Amelin

I tell people that it is too close to the window as exhaust gases may enter the living space, but their answer is almost alwaysw the same: "DUH" hello mr. inspector. Do you really think the window will be open in mid-winter when they are using it?? They make a good point.

During extended power outages you hear stories of CO poisoning because people run a generator in the garage or basement. I think it's important to try and anticipate people's lack of common sense. Even when a vent is more than 4 feet under a window I make a comment about it. I could not care less about what some code or spec says.

Also, it's funny to see a masonry chimney right next to the wall vent. You'd think the vent could have been somehow tied into one of the chimney flues rather than the way the installer did it???

Guys, sorry to burst your bubbles but that has to be a direct vent. Not mechanical vent, not natural draft per se but a thermosyphoning direct vent. Natural vent cannot terminate out a sidewall. Look closely and you'll see a pipe inside of a pipe. That's a direct vent. DVs cannot share with a fireplace flue.


As always, locate the make and model and that will take you to the listed instructions which is where you get your clearances. Probably just fine where it is.

A typical distance for a direct vent unit is 12 " from an openable window, but don't quote me. I opened a manual for a Robur gas wall heater and got the typical 12". 30 cm in Canada.



A. clearance above grade, veranda, porch, deck,
or balcony (12 inches (30 cm) minimum)
(3)
B. clearance to window or door that may be
opened (12 inches (30 cm) minimum)
(3)
C. clearance to permanently closed window
(minimum 12 inches (30 cm) recommended to
prevent condensation on window)
D. vertical clearance to ventilated soffit located
above the terminal within a horizontal distance
of 2 feet (60 cm) from the center–line of the
terminal (18 inches (46 cm) minimum)
E. clearance to unventilated soffit (12 inches (30
cm) minimum clearance to vinyl soffit (36
inches (90 cm) minimum)

Originally Posted by John Kogel

A typical distance for a direct vent unit is 12 " from an openable window, but don't quote me. I opened a manual for a Robur gas wall heater and got the typical 12". 30 cm in Canada.



A. clearance above grade, veranda, porch, deck,
or balcony (12 inches (30 cm) minimum)
(3)
B. clearance to window or door that may be
opened (12 inches (30 cm) minimum)
(3)
C. clearance to permanently closed window
(minimum 12 inches (30 cm) recommended to
prevent condensation on window)
D. vertical clearance to ventilated soffit located
above the terminal within a horizontal distance
of 2 feet (60 cm) from the center–line of the
terminal (18 inches (46 cm) minimum)
E. clearance to unventilated soffit (12 inches (30
cm) minimum clearance to vinyl soffit (36
inches (90 cm) minimum)

Double 5 lap siding? 2" window sill? Anybody have a micrometer?

Originally Posted by Chris McIntyre

Double 5 lap siding? 2" window sill? Anybody have a micrometer?

And do you measure to the flange or to the inner surface of the exhaust vent?

Lot of good replies.

One additional thought, some of these devices are thermostatically operated, in which case the argument the window will be closed is a total fail unless the window automatically closes.

A window open that low in the building envelope is likely to see negative pressure to indoors due to the buildings stack pressure.