Residential building code question - venting a gas cooktop (Austin: appliances, home builder)

[ChuckMc]

Does anyone know the building code for venting a gas cooktop? Does it have to be vented and if so, does the vent hood have to be within a certain distance of the cooktop? (This is for new construction.)

[escanlan]

Originally Posted by ChuckMc

Does anyone know the building code for venting a gas cooktop? Does it have to be vented and if so, does the vent hood have to be within a certain distance of the cooktop? (This is for new construction.)

There are actually multiple considerations for any requirement to even have a range hood on a gas cooktop. We will stay simple though and expect the other more in depth requirements are not an issue. With that approach the requirement to even have a range hood is made by the local Authority Having Jurisdiction (AHJ) which is the local Building Inspections Department. Also to be considered is if the cooktop manufacturer has placed a requirement on having a range hood although the AHJ can supercede that requirement as well (should not but they do).

If a range hood is required there are two sets of requirements. Since we do not know what version of the building codes your construction is under I'll provide the 2009 International Residential Code (IRC) requirements.

M1503.1 General. Range hoods shall discharge to the outdoors
through a single-wall duct. The duct serving the hood
shall have a smooth interior surface, shall be air tight and shall
be equipped with a backdraft damper. Ducts serving range
hoods shall not terminate in an attic or crawl space or areas
inside the building.
Exception: Where installed in accordance with the manufacturer’s
installation instructions, and where mechanical or
natural ventilation is otherwise provided, listed and labeled
ductless range hoods shall not be required to discharge to
the outdoors.

What this basically means is if the cooktop is in an unventilated area then a range hood, if installed, would be required to be ducted to the outdoors. The key here is "or natural ventilation" which is as simple as a window nearby.

As for the height requirement above the cooktop the IRC states the following.

SECTION G2447 (623)
COOKING APPLIANCES
G2447.1 (623.1) Cooking appliances. Cooking appliances
that are designed for permanent installation, including ranges,
ovens, stoves, broilers, grills, fryers, griddles, hot plates and
barbecues, shall be tested in accordance with ANSI Z21.1 or
ANSI Z21.58 and shall be installed in accordance with the
manufacturer’s installation instructions.

G2447.5 (623.7) Vertical clearance above cooking top.
Household cooking appliances shall have a vertical clearance
above the cooking top of not less than 30 inches (760 mm) to
combustible material and metal cabinets. A minimum clearance
of 24 inches (610 mm) is permitted where one of the following
is installed:
1. The underside of the combustible material or metal cabinet
above the cooking top is protected with not less than
1/4 inch (6 mm) thick insulating millboard covered with
sheet metal not less than 0.0122 inch (0.3 mm) thick.
2. A metal ventilating hood constructed of sheet metal not
less than 0.0122 inch (0.3 mm) thick is installed above
the cooking top with a clearance of not less than 1/4 inch
(6 mm) between the hood and the underside of the combustible
material or metal cabinet. The hood shall have a
width not less than the width of the appliance and shall
be centered over the appliance.
3. A listed cooking appliance or microwave oven is
installed over a listed cooking appliance and in compliance
with the terms of the manufacturer’s installation
instructions for the upper appliance.

Of importance here is that the manufacturer's requirements for the range hood, or integral range hood in a microwave, should be checked to see what they require. Again the AHJ can change this even though they should not.

Can you provide more details about the situation?

[ChuckMc]

Thanks for the reply and the information. It sounds like:
1. No vent hood is required if there is a window near by (which there is)
2. If I decide to install a vent hood, it must vent directly to the outside using the confirming materials/standards you detailed aboved (which it would)
3. There is no maximum required distance the vent must be from the cooktop (there is a minimum allowable distance, but no maximum)

More details about the specific situation:
I'm building a new house in Austin Texas using a local subdivision home builder. There will be a gas cooktop in the kitchen. The builder claims that code requires a vent hood be installed and that it must be positioned no more than x ft above the cooktop. We don't want the vent hood, but instead want a down draft vent or a vent insert that would be concealed near the ceiling about 6ft above the cooktop. It would be vented to the outside. There are several windows about 7ft away. I don't see where in the code it says we can't place the venting up at the ceiling or that the venting must be placed with x ft of the cooktop.

[austin-steve]

Originally Posted by ChuckMc

...
More details about the specific situation:
I'm building a new house in Austin Texas using a local subdivision home builder. There will be a gas cooktop in the kitchen. The builder claims that code requires a vent hood be installed and that it must be positioned no more than x ft above the cooktop. We don't want the vent hood, but instead want a down draft vent or a vent insert that would be concealed near the ceiling about 6ft above the cooktop. It would be vented to the outside. There are several windows about 7ft away. I don't see where in the code it says we can't place the venting up at the ceiling or that the venting must be placed with x ft of the cooktop.

Downdraft venting usually has to go through the slab and/or walls. So it's something that needs to be baked into the construction plans as it's not always easy to retrofit.

6 ft seems too high to be effective. Think about resale value to. The more you depart from "normal and expected" the more concerns you'll raise during your future buyer's inspection.

Inspectors flag retro-installed "microwave/hoods" that are not high enough above the cooking surface all the time, so the minimum distance is a known factor. I don't recall ever encountering a "too far up" hood though. It seems the distance could be mitigated by sucking power, for lack of a better term, but that would also increase noise.

I'd say, unless you have some specific reason to depart from the norm, or plan to stay in the home forever, stay within what's normal and expected for homes in your neighborhood. Many sellers eventually regret not doing so and don't understand why buyers don't appreciate their design choices. We see this a lot, and many more strikeouts than homeruns.

Steve

[10scoachrick]

In the house we're about to leave, we have a killer vent hood that is just low enough for me (5'11") to hit my head on when leaning over an interesting dish being prepared. Not sure why it wasn't installed just a couple of inches higher; but when cooking something particularly smokey/steamy, it's quite possible for some of the smoke to billow 'sideways' before it gets sucked into the hood. This hood is likely in the top tier of the non-commercial fans CFM rating, but still allows a fair bit of smoke to escape. In other words, the higher the hood, the less effective, as one would expect.

The time this is most noticeable is when searing meat or salmon on top of the cooktop before finishing in the oven...can be pretty smokey stuff!!!(But worth it...most times!!! Yum-Oh !!! )

[escanlan]

Originally Posted by ChuckMc

Thanks for the reply and the information. It sounds like:
1. No vent hood is required if there is a window near by (which there is)

One would be required if the AHJ dictates it or the manufacturer of the cooktop dictates it.

2. If I decide to install a vent hood, it must vent directly to the outside using the confirming materials/standards you detailed aboved (which it would)

If a vent hood is installed as noted above it would be required to vent to the outside if there were no other natural ventilation, if the home were of unusually tight construction (this is outside of the simple description/conditions as noted above), if the AHJ required it, or if the cooktop manufacturer required it for some reason. In the average home the recirculating range hood arrangements are considered acceptable.

3. There is no maximum required distance the vent must be from the cooktop (there is a minimum allowable distance, but no maximum)

The maximum distance is dictated by the range hood manufacturer. As pointed out above having the hood to high renders it potentially ineffective.

More details about the specific situation:
I'm building a new house in Austin Texas using a local subdivision home builder. There will be a gas cooktop in the kitchen. The builder claims that code requires a vent hood be installed and that it must be positioned no more than x ft above the cooktop. We don't want the vent hood, but instead want a down draft vent or a vent insert that would be concealed near the ceiling about 6ft above the cooktop. It would be vented to the outside. There are several windows about 7ft away. I don't see where in the code it says we can't place the venting up at the ceiling or that the venting must be placed with x ft of the cooktop.

I've placed some additional comments above in blue italic.

Depending on the location of the cooktop there are options other than an overhead range hood. If the cooktop is in an island the choices are limited to the downdraft which as Austin Steve points out is part of the original build plans. It can be added after the foundation pour but not easy by a long shot and certainly not by the builder or anyone that values their 10 year home warranty. The only other option on the island cooktop is a retractable vent hood that does come down for cooking and up when not in use. I have seen these but they are typically very high end and very expensive for a worthwhile unit. They are more commercial grade than anything else. If the cooktop is located on the outer wall you can again use the retractable hood or vent directly through the outer wall, below the cooktop, using another style range hood you can find on high end Viking equipment, as well as others. This hood retracts into the rear of the cooktop surface (below it), at the back wall, when not in use.

I have seen range hoods higher up than normal with high CFM (speed) fans to draw the discharged products upward. They also sound like an F16 taking off when you turn them on!

Is there another reason why a range hood is not appealing to you?