New construction SIPS house in Anchorage (area) Alaska. Radiant in floor fuel oil boiler. 1300 ft plus 600 ft loft. I have an HRV and bathroom exhaust fans. We had venting installed for a range hood but now that it's time to install the unit I am considering just installing it as a recirc unit. It is just my wife and I, only thing we use the stove for is heating up soup, eggs, etc. Anything like meat, bacon, fish, etc we do out on the grill year round. A) Easier install :-) B) I won't lose the cabinet above the micro to a duct C) I could close off the existing penetration for the exhaust vent. There is a window 4' from the stove if we ever did have a "smoke emergency". I'm thinking I could always change the configuration and reinstall if I change my mind down the road. I've gotten a lot of great feedback here so looking for more!

I would still vote for a vent to the outside. In a tight house, simmering a pot of soup on the stove, or making pasta, generates lots of moisture that you probably don't want in the house. On the other hand it sounds as if the rest or your air circulation system would eventually get rid of the moisture, so I guess it would depend on how much cooking you do.

-Rosalinda

Two other considerations are building code and the lifestyles of the people who have the house after you, both of which usually argue for a properly vented situation.

How happy would you be with a toilet that recirculated its contents rather than discharging it outside the home?

Range hoods are a necessary evil in that they are a big gaping hole to the outside and vent conditioned air out like a chimney. They are necessary in order to prevent the house from getting all smelly from cooking smells. Only alternative is to not cook smelly food and therefore not have to use it as often.

Some range hoods funnel insane amounts of air like 2,000 cfm+. That's the price some people want to pay for cooking fish and onions. Range hoods also trap a lot of the cooking greases and oil so they have to have their filters cleaned out.

I don't like them and code does not require them as long as you are NOT using a gas or propane cook top. If you have the latter, you are stuck installing one because gas & propane requires outside venting. I am 90% sure that I will NOT install one in my home as it does not have gas and I will be using an induction cook top. In addition we don't cook smelly food but those times that we do, I will have an HRV working with a kitchen intake but it will not be near the cook top so as to not get contaminated with grease or cooking oils. One can always open a window when cooking onions.

In tight homes one needs to be careful with a range hood in that you replenish all the air you are funneling out the roof. If you don't have the proper make-up air coming in, you can create a negative pressure within the home.

If someone were doing a lot of cooking, where the heat loss amounted to significant $, I'd look at providing an outside air source on each side of the stove.

I would definitely vent to the outside simply because if you don't you may end up with a lot of unwanted moisture in your house. This is also a problem if you live in a humid environment, having extra moisture around the house on top of being in a humid environment can end up causing problems down the road. Hope this helped and good luck.

Posted By haese56 on 14 Apr 2013 04:58 PM
New construction SIPS house in Anchorage (area) Alaska. Radiant in floor fuel oil boiler. 1300 ft plus 600 ft loft. I have an HRV and bathroom exhaust fans. We had venting installed for a range hood but now that it's time to install the unit I am considering just installing it as a recirc unit. It is just my wife and I, only thing we use the stove for is heating up soup, eggs, etc. Anything like meat, bacon, fish, etc we do out on the grill year round. A) Easier install :-) B) I won't lose the cabinet above the micro to a duct C) I could close off the existing penetration for the exhaust vent. There is a window 4' from the stove if we ever did have a "smoke emergency". I'm thinking I could always change the configuration and reinstall if I change my mind down the road. I've gotten a lot of great feedback here so looking for more!

haese56,
Have been in my SIP home for 12 years, kitchen hood is also unvented, there has never been an issue with moisture /humidity while cooking, boiling water, etc., I always monitor humidity and see no change while cooking anything

I have had several homes with unvented hoods. Never an issue. Our new construction will not have a vented hood, as we are using a induction as well. But we are in a dry climate.

If all you do is boil water, then a recirc is fine. More intense cooking tasks release fumes, particles and vapors best sent outdoors with proper attention paid to depressurization / makeup air.

I would never build a home nor have anything to do with the HVAC in a home without an appropriately sized rangehood venting outdoors....just my $0.02

Posted By engineer on 20 Oct 2013 09:33 AM
If all you do is boil water, then a recirc is fine. More intense cooking tasks release fumes, particles and vapors best sent outdoors with proper attention paid to depressurization / makeup air.

I would never build a home nor have anything to do with the HVAC in a home without an appropriately sized rangehood venting outdoors....just my $0.02

Range hoods are sort of a "necessary evil" in homes that have gas/propane cook tops and homes that people cook food like a restaurant would.

GBA - Why Range Hoods Don't Work

As per Martin Holladay, Building Science expert:

"Large kitchen exhaust fans -- whether range hood fans or downdraft units -- are incompatible with tight, energy-efficient homes. "

Personally I don't want a gas/propane range because of the harmful by-products it produces. You build a home to NOT off-gas with nasty chemicals but then stick in this gas cook top that produces carbon monoxide (CO), nitrogen dioxide (NO2), ultrafine and fine particles, formaldehyde, etc.

Then comes the energy penalty. You build a tight home so it doesn't leak air but then stick in a 1,000cfm range hood that can suction up your small pets and kids through the vacuum it creates. How much conditioned air are you dumping through that range chimney? Even with it off, it still leaks air as it's not 100% sealed when off. It's a huge energy hog.

Therein lies the dilemma. Either you cook using electric convection range tops and don't cook greasy, smelly food (which isn't good for your health anyway to be eating greasy foods) OR you get your 6-gas burner cook top and fire that 1,000cfm range hood while you cook your fried sausages.

By-the-way that 1,000 cfm range hood is removing about 3 tons of conditioned HVAC air from that home. Another factor is "backdrafting" which occurs from the range hood sucking out air and creating negative pressures within the home. Choice is yours.

Laboratory ventilation hoods work well and it wouldn't be hard to incorporate some of their design attributes into a range hood (side walls, glass panel, etc).

On the other hand, in many cases the number of hours where it is needed are low enough that it isn't worth worrying about. Always calculate the $.

Laboratory ventilation hoods simply exhaust toxic fumes to the outside with tremendously powerful draws. Clean benches or laminar flow hoods use HEPA filters to create a clean working environment inside the hood but don't do anything to remove toxic fumes from the room.

The best solution I found for a tight home and a "professional" kitchen with a large gas range was to use a Vent-A-Hood and provide local make-up air through an openable skylight. The Vent-A-Hood uses a bit less draw than most to accomplish the same thing. You don't have to run the hood at full output if you just want to remove some vapors or combustion products. Most hoods' full draw is designed to help control a serious cooktop fire or full range output. We very seldom run at full output.

There is not much use in trying to find a perfect solution to this long-standing problem.

To update this old thread range hoods are now required by code and they have to be ducted outside, even if there is no gas being used.
The best solution is to use a seperate make up air source, that has a solonoid actuated damper, tied to the range hood which also has one.
No to figure out a good place and routing for it.......

Posted By whirnot on 24 Apr 2014 12:42 PM
To update this old thread range hoods are now required by code and they have to be ducted outside, even if there is no gas being used.
The best solution is to use a seperate make up air source, that has a solonoid actuated damper, tied to the range hood which also has one.
No to figure out a good place and routing for it.......

Which code are you referring to?

In my county they are NOT required unless you have a gas cook top.

Oregon Mechanical code requires a hood. I guess I assumed it was derived from International code. Maybe not

If one must get a range hood vent, do they make ones that have damper doors to prevent cold air from coming in or conditioned interior air from funneling out like a chimney when the range hood is NOT in use?

I once again verified in my area that a range hood is NOT required with electric cook-tops. The code is specific to each area. I would check with local codes to make sure. Some will require it and some won't.

A blank assumption that vented range hoods are effective is a bad assumption. My experience with a vented range hood and gas stove and CO2 meter indicates that our vented range hood was very effective at removing fumes from the kitchen and house. With our range hood on and the gas stove on the normal combustion gas CO2 would continuously increase in the kitchen and the rest of the house until the stove was turned off. The CO2 level sometimes wouldn't come back down to normal levels until the following day even if the stove wasn't turned back on.
I completely agree with Lbear and cmkavala's comments.
I now live passive house with recirculating range vent with heavy duty carbon filter. We are all electric with induction cooktop and no longer have to worry about combustion gases in the house.
The presence of a vented range hood doesn't automatically mean it's very effective at removing combustion gases, toxic fumes or cooking smells.

Do you ever fry anything (even if just like eggs, pancakes, french toast, etc.) !? If possible I would always vent!!!  I can't stand the feeling of grease in the air.

For Nelson, what kind of hood do you have?  Ours is recirc and is definitely not effective. We are electric so combustion is a non issue.

Ros is right. Recirculating a range hood is a bad joke. The best you can hope for is to trap some grease.

If you could, more especially wit gas, you want to vent to the outdoors. Smell, humidity, heat, gas byproducts. You can forget to turn it on but you can't open a window for the same effect.

2000 cfm...in a residence? OK...