Thread: powered vent needed?

Hello,

I inspected a 1947 built home today. There is a vent (no fan motor at all) above the gas range. Is there a requirement for a fan to be incorporated in the vent?

Thanks!
Dave

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Dave
Although I am not in your area, but I have to ask, was the kitchen new/renovated or circa 1947?

Exhaust fan over a gas range is only required in residential if the gas range manufacturer's installation instructions state it is.

Typically, that is only the high end (high Btu) "professional" gas ranges.

The home has been a little remodeled. Granite counter tops, new cabinets, new appliances. I thought there was a requirement to remove grease out of the air - just wasn't sure if that meant a powered unit, or just a hole in the ceiling, duct to the roof - like this house has.
Thanks for the inputs. I appreciate it.

If there s a window in the kitchen that opens then no cook top venting is needed for a house of this age

Originally Posted by frazier jeffery

If there s a window in the kitchen that opens then no cook top venting is needed for a house of this age

To my knowledge, operable windows were not required in any of the national model code in kitchens, nor was a range hood or ventilation for the kitchen or cooking unit (range, cooktop, etc, whether gas or electric) for residential dwelling units - unless required by the cooking units installation instructions.

Not in the past and not at the present either, not in the model codes - it may have been a requirement in local codes, but one would need to check that in their local codes (places like Chicago, LA, NYC would be the most likely local codes which may have/have had such a requirement, unlikely for smaller places).

Now if ... if the range hood which is installed (by choice) is ducted (which means to the exterior) then minimum cfm exhaust requirements are in the code for that exhaust fan, 100 cfm intermittent or 25 cfm continuous.

If the cooking unit installation instructions require a range hood and exhaust fan the range hood needs to be physically sized and cfm sized as stated/shown in the installation instructions.

A vent with no fan is a dumb hole in the wall. The air does not know which way to go under what circumstances. Therefore, it is purely at the mercy of the pressure regimes. If there is negative pressure in the Combustion Appliance Zone WRT(with respect to) the outdoors, air will infiltrate. If the situation reverses, then it will exfiltrate or exhaust passively.

There is no direct code requirement in the gas code to vent a gas range or oven unless as Jerry points out the appliance mfr. requires it. Still, such vents are not required to be interlocked to the gas control and thus manually operated. If the vent exhausts >450 cfm, it would require a powered makeup air system. That means even if it exhausted that much passively without a blower (ain't gonna happen unless that vent is about 16" ID)

You can legally use a recirculating hood if you prefer. Yes, its stupid as it just pumps aerosolized fat and particulates into the home. Note that those microwave oven/ hoods typically have a snap disc such that if the ambient temp. rises too high, the exhaust fan will actuate automatically. This happens when it is mounted too low over an oven such as at my in-laws. They light a burner and the vent turns on by itself in a few minutes. They think it is possessed. I tried to tell them it was too low but she is the smartest woman on the planet who obviously holds degrees in everything so I let her think its a loose wire...