I spoke too soon - the third option isn't an option. There's a staircase between the kitchen and the garage - we can't cut across that. Bummer...

If you are doing a massive remodel why isn't there an external wall available in the kitchen?

Get an HVAC contractor out there to look at your ducting issues. Having never really seen it snow (a few flakes once) I can't advise about the ducting, though I think you'll probably also need make-up air.

What I can tell you is that ventilation is even more important where you have a well insulated and sealed home, and aren't about to open a window during snowfall, rain, cold, humid heat, etc. There are a lot of places I'd skimp before that!

I have to agree with plllog. The last place I'd scrimp is with anything inside the wall. Even if you had to get a cheaper oven/fridge as a result, that can be redone a whole lot easier down the road than ripping out drywall/cabinets to get at poorly installed ducting.

laat2 - I guess I'm not sure why doing a massive remodel would necessitate an external wall in our kitchen. Our current kitchen is on the top story of a 4-level split. We're moving it downstairs, into a re-done main level that will put the kitchen in the center, essentially. It will be located as "east" as it can go on that level, but to the east of it will be the basement (a half-flight down) and a living room (a half-flight up). To the north is the garage. To the west is a family room. To the south is a long sunroom that spans the length of the family room, kitchen and basement/livingroom - i.e. runs the length of the house. Four-level splits are a monster to deal with, but essentially, the kitchen is the "heart" of that main floor, and thus has no external wall within 15' in any direction.

We're coming from a decade of cooking on an electric range with an OTR microwave that we really never turned on while cooking - we only use it when we roast our coffee beans. Venting has never been a priority - we never gave it any thought at all. I think I'm really only aware of it now because I read these forums. Otherwise, we probably would have stuck an undercabinet hood over the cooktop and never thought twice about it. Even in my childhood home, where we cooked daily with NG, the exhaust was only turned on if someone burned something in the oven.

We're reusing our current frig and dw...bought a double wall oven off Craigslist...so I don't even really have any other places to scrimp from. Most of our remodel cost is in true construction (framing, roofing, siding, concrete, windows) and very little in "allowances" such as appliances. Our flooring has been purchased - nowhere to scrimp there.

Can anyone tell me what the result will be if we do have to run the duct down the wall and out across the basement? The option that had the three 90-degree turns? I know it's not great - I just want to know how truly bad it is...will it cut the 650cfms down to about 200? 100? 50? Essentially nothing???

AP

Forget 3 90* bends.

Think about using a 3x10 duct up through the wall, then convert to round in the attic. Vent out the roof.

What type of roof do you have? Is it steeply pitched. I recently had to put in some vents for my bathroom exhausts. If you deal with a General Contractor they often will say "I don't want to put another hole in the roof." However I was having a roofing company that also did siding/gutters do some other work and they mentioned that the preferred putting the vents for the fans on the roof. Although having another opening in your roof to make sure it is flashed correctly is a risk, when it is done properly it should not be an issue.

I agree with the advice to get professional HVAC advice. My vent goes through the roof, and I'm in one of those inhospitable climates (we've had frost already!) with real winters. I've also got heated MUA for my system, and the whole works is not something I nor my GC could ever have concocted on our own.

If you can't afford to install sufficient venting on your desired cooktop, you may be better off getting a smaller one with less capacity.

The GC's concern about running the range hood vent straight up through the roof should be fully explained to your satisfaction. It may simply be a warranty issue regarding the roofing material used.

Given your description of your normal cooking activities, it may be that a range hood really isn't a priority at this time. If you think things could change later you could consider advance preparations now in the way of extra space in walls etc. There are also units like the Vent a Hood ARS and Premier which are high end recirculation units for an outside venting problem area like yours . Hopefully there will be more choice in the future. While not very powerful, such units have the advantage of not requiring expensive make up air/heat exchanger installations for areas with cold winters.

Good luck!

I have to agree that it would be better to spend more here and get it right and make it up with something else you can easily replace or update later. You may not have noticed the need for ventilation as much when the kitchen was at the upper level of your home, but with it in the center of your home, you are going to be much more likely to having fumes and odors travelling to and lingering in other parts of the house.

Best by Broan has a chart in their catalog that allows you to calculate the decrease in cfms -- of the additional amount needed for longer runs and various turns. Also keep in mind that each 90, especially if they take the duct lower, is a place for grease to build up and would need to have access for cleaning to avoid a fire hazard (and possibly a lingering odor) down the road. I don't know if it is available directly, but when I was looking, you could download the catalog in pdf form and then look towards the last pages. I think you will need more to make 3 90s work.

A GC who doesn't want to put a hole in the roof may just like to try avoiding it, but it may also be an indication that he's had problems with them -- which seems to me to be more about the quality of work and care taken with something that has to be done right to avoid leaks.