I thought about going straight up with it, but I don't have a lot of room due to the angle of the ceiling. Plus, I am going to be using a canopy style hood, so the chase would have to be rather large to be in proportion with the hood, and I'm not sure how that would look. I did think about placing cabinets on top and then a chase above that, but again I am probably too close to the rafters in the attic due to the slope of the ceiling. Consequently, out the wall and into the garage attic seems to be the simplest way to go. Plus, that gets the inline fan away from the house and makes everything more accessible. I don't mind enclosing the vent in drywall to bring it up to code. While the vent needs to be in a soffit, what about the inline blower? It seems like the blower should be left out in the open, with the remainder of the duct enclosed? That said, I can see what you are saying about direct penetrations from the garage into the house are not permitted due to fire concerns. However, would a solid duct running from the kitchen into the garage attic and out the roof fall within that logic? There are no breaks in such a duct run, since the only openings are at the hood itself and wall/roof cap. So as long as the penetration where the duct goes from kitchen to garage is sealed with fire caulking around the duct, how is there an issue? Again, I don't mind enclosing the duct run in a chase if need be, but it seems like overkill....

I'd like to add my (civil) 2 cents: TexasCatherder has a good question, and there are many right answers here. - Do you "need" a kitchen range vent? Yes, in most jurisdictions using international building code, some kind of kitchen ventilation is required. If you don't want it, don't put it in. But it may haunt you upon inspection at resale of the home. - No, few jurisdictions require a big ole' "range hood" over the range. In my community, it just needs to be some kind of vent that can circulate the right number of CFMs for the space. For example, a friend recently renovated her kitchen; she didn't want a big hood over her range in the island; and according to code, she went with a small wall-vent on the other side of the room on an exterior wall. That's enough for the "needs" of code. - But yes, like many have noted, a range hood does a better job of capturing grease and moisture than a wall vent. I'll bet my friend's lovely white kitchen wall gets a grimy film around that wall vent in a year or so. - Besides grease and water vapor, yes, gas-fueled heat sources produce toxins. It's not enough to kill or annoy most people, but the cumulative effects of the toxins isn't good, and those who are sensitive to allergies may suffer, and it's generally not a good idea to burn stuff (including chicken or toast) without ventilation. - Ventilation is important for indoor air quality and the structural integrity of the home. One thing that we recently became aware of is the need for ventilation just to get rid of moisture. If you have a well-sealed and insulated home, every-day water vapor from cooking, cleaning, bathrooms, laundry, etc. can build up and not escape the house. It can cause condensation inside walls and windows, which can lead to mold, which is a major indoor air quality issue in our part of the country. Additionally, although it doesn't seem logical at first, it can lead to structural problems. Air in a home circulates from colder regions to warmer regions, and the moist air goes with it. There's a photo in a an old-house-renovation book we have that shows rotting roof rafters in an attic: Rotting not from a leaky roof, but because of long-term water standing in a basement and crawl-space! It was three floors away -- how could that be? Air circulation moves the moisture up. - Anyhow, it sounds like our dear OP TexasCatherder got the point that ventilation is important. So maybe we can help her now focus on where to put it? Rather than debating the pros and cons of ventilation, perhaps we could start a new thread to help her with layout? She's going to have a beautiful kitchen, and folks here are great at taking the cook's priorities and giving suggestions for layout to help reach those goals.

I live not too far from you but a bit farther north in Alberta. I have always had my hood vented outside and have never yet had a problem with crazy amounts of draft. It gets windy here, on occasion I might feel the suspicion of a draft, but nothing bad enough to cause that kind of freezing temperatures inside my house! And on occasion I can hear the louvers for my range and bathroom fans clanking when the winds are bad. At present my hood is vented directly through the rear. Since my hood is on an outside wall, the distance involved is really small. I don't typically have water on my stove overnight but that sounds like overkill to me. I keep my house at a toasty 19 degrees (Celcius, unfortunately I don't understand the Farenheit system at all, but it's a few degrees below room temperature) so water freezing on the stove should be pretty much impossible. I'm not an expert in the field so I don't have all the vocabulary but the wall louver on the outside of the wall is supposed to help prevent drafts. It's a little piece of metal that sits flush with the outside wall covering the duct opening, when the vent is on the air pressure forces it to open so the air can flow. There's a little plastic "roof" over it that attaches to the outside wall which prevents snow/rain from getting in. I'm sure there's an equivalent system to make venting through the roof just as worry free. If it were that bad none of us Canadians would ever be able to vent outside! HTH

building2017 wrote: ... - What are the silencers I have read about and how do they work/would they work here? These are like giant truck mufflers, except designed for various diameter ducts. They have low pressure loss (forget the value but it is a lot less than baffles). Fantech is the source. - Any benefit re:sound to using two smaller liners instead of one big one and only using one at a time when using only one side of stove? Or is this magnifying the cost for no good reason other than sound? (Because I'm assuming I'd then have two runs up and out and two things on the roof because they wouldn't combine to avoid a turn and to ensure proper function? If only one side were run at a time, then MUA costs could be lower, but where code requires MUA, I am willing to bet a donut that the AHJ will demand an MUA system that can handle both at once. In theory, the sound reduction will be only 3 dB less. Also, when using the central burners, you will still need both systems for capture and containment. Well, I guess three things on the roof then with the MUA. While commercial systems mostly use roof MUA entry, and I use roof MUA entry, the options for residences are wide open and may include side of house entry, or entry into a basement that has an air path access to the kitchen.