Range hood - why it's needed ?
I'll be transitioning from electric cooktop to my first Gas range. I'll be going with Viking D3 30'' RDSCD230-5B and Viking 30'' pro hood VWH3010.
I'm wondering why exactly do you have to vent, do you have to vent every time you run your stove and how many cfm for a 30''.
On our electric top we don't usually need that much venting, I put our 600cfm on lowest setting when cooking and maybe a medium speed on smelly foods.
Gas cooking means you now have combustion gases every time you cook. Venting those helps maintain good indoor air quality. Secondly, capturing and venting grease laden vapors helps reduce sticky deposits on kitchen surfaces surrounding your stove. Furthermore, if you are sautéing or stir frying, being able to capture and remove smoke from hot oils or caramelized meats as well as cooking odors that otherwise would linger in the kitchen. Finally being able to vent off excess heat from your stove when it makes your kitchen thermally uncomfortable all make for good reasons to exhaust vent your stove.
I'm not a building code authority, but I'm thinking that for residential stoves (lower BTUs, thus lower combusted gases compared to commercial stoves), venting is not strictly required.
I do know that if you install a commercial stove into your kitchen, you WILL be required to install the vent (generally because of the higher BTUs, thus higher amount of combusted gases).
With that said, I don't think you have to run the vent every time you use the residential stove.
However, running it will help alleviate the problems mentioned above.
As a side, many home range hoods are not vented properly: they simply exhaust back into the kitchen through a cheapo filter.
Not necessarily. Code where I live says there needs to be a hood but does not specify anything beyond that. It's quite ridiculous.
Residential building code is wildly variable from place to place.
I have a 1500 cfm hood. Code here would have required a make up air unit with this--at great expense. When I got my CO on this house, it was with a $49 non-ducted, 30" recirculating "hood" installed over my 48" dual fuel range and 18", 130,000K btu wok burner. It went to the donate pile shortly there after and I got to work installing my 6' stainless behemoth. My make up air is cracking the slider. It's free.
There's also the issue of heat output from the range which a hood will deal with. Heck, when it's really hot here I use my hood to quickly exchange air and cool off the whole house in the evenings.
Regardless of code requirements, if you're cooking in a manner where you believe a high btu, pro-style range will improve something, then you unquestionably need a hood. OTOH, I know more than one perfectly adequate home cook who has never had or turned a the hood.
Building codes may dictate you have a hood with an exterior exhaust, just depends on the codes where you live. They can't make you turn it on. However, the fact that you're generating carbon dioxide and water vapor as you burn the natural gas (methane), should be incentive to vent your range. If you need to vent every time you cook depends a lot on what and how long you're cooking. Frying an egg, maybe not, but preparing a meal with some burners on relatively high heat for an extended period of time, most definately.
Ideally, for a 30" range you would want a 36" hood, the extra width makes it easier for the hood to capture the vapors. The easier the hood can capture the vapors the fewer cfm you need. The closer the hood is to the top of the pot or pan the easier it is to capture the vapors, and agian the fewer cfm you need. What you need in the way of cfm is determined in part by the capability of your range and in part by what and how you cook. If you're frying bacon, for example, you want enough cfm to pull the very fine grease particulates up and out. If you're frying an egg in a non-stick pan, then it really doesn't take much air movement to take care of the combustion by products and the egg doesn't generate any grease, so very little air velocity is needed.