You do not say anything about the specs of the hood you are getting or the configuration of the venting up to that 10-foot horizontal run. Without knowing any more, my initial reaction is that your architect is looking at what is adequate and workable versus your builder being focused on a most optimal configuration. It is the difference between the "best possible" and "good enough."

Assuming your architect is proposing something like a short vertical stack up through a cabinet with a 90° bend that sends the ducting ten feet to an exterior wall across the top of the cabinets, I think you'll be fine with your ten foot horizontal run.

I've had that kind of set-up for a decade, except that my horizontal run is closer to six feet rather than ten like yours will be. I've also got a couple of bends in the ducting (for navigating the structure of this old house and its cabinets. (Obviously, not new construction. Still, I'm getting adequate ventilation from the stove and my hood provides pretty good grease separation. Seems like I have to empty the hood's grease traps frequently. The one time I had to get into the ducting a couple of years ago, I found relatively little grease build up. I knew (and know) that my configuration is not the absolute ideal possible configuration for venting efficiency but it has been a sufficient one for my kitchen.

I agree with Jwvideo's first paragraph.

I'd go for best possible since this is a new build. That would be straight up.

A roof exhaust might be less noisy on the ground outside than a side exhaust, all else being equal. Also, side exhausts have to avoid being near windows or exhausting onto a deck. In general, though, I think the best approach depends on many details we don't know.

We were faced with the same dilemma when doing our kitchen remodel and had planned on going out the side of the house, up until the last minute. I chickened out because I was worried about the performance of the unit. So I bit the bullet and we ran it straight up to the roof. We lost a little space in the master bedroom but overall I am happy with the performance and noise level of this solution.

I appreciate the insight and knowledge from you all. It's given me a lot to think about, and I am leaning towards modifying the upstairs design so we can run vent up to the roof.

dan- I agree I need to give more info, sorry, we are still in design stage and I have not chosen a range yet. I am planning on a gas range.

dan- In regards to vent duct size- is this not a case of bigger is "always" better? So in some instances 10inch would actually be less appropriate?

Also- my interpretation of the plans indicate that the vent would indeed be terminating near/above(?) a window. That's a big concern correct?

Whatever you vent is going to be where the vent lets out. Therefore, the moisture and smells are all going out that hole. My house was built without any duct at all (along with some other weirdnesses). I was lucky that I could vent onto a side yard where the services and meters are. It is also the only outdoors path into the back yard. When the hood is on, you walk through a miasma of housebreath. The vent points down, which is the right thing so that you're not hit in the face with it.

Not something you want on a patio or other place you're trying to enjoy, nor by a window through which it's going to come right back into the house. I don't know if it can also leave fog or even particulates on the window glass. Hopefully the filters and gravity would take care of the latter, but Kas is the physics expert, not me.

Keep in mind that architects often aren't concerned with function. Wright's roofs leak because of poor functional design in his high art design. Meier designed the Getty Center with way too few restrooms, and by the time they figured it out, it would have cost too much to fix, so they finished building then remodeled. Architects are artists first and foremost, and mostly want to do what looks good, which is why they often go for what will minimally work, but looks cool, rather than using maximal function as a constraint and working that into the design (which is what Deusenberg was famous for--engineering first and a gorgeous coach on top of it).

"Housebreath" That cracked me up! And yes you do have a very good point about design over true function and practicality.

Duct size should be such that at the actual flow rate (not the blower rated flow rate) the velocity in the duct ranges between 1000 and 2000 ft/min.

Definitely tape. Insulation will help, particularly if you run the blower for a few minutes to warm the metal ducts before generating a lot of steam that needs to be expelled. Also, with cold ducts the lower end of the flow velocity range (1000 ft/min) is better than the higher end in order to minimize impingement grease collection.

Although potentially interfering with attic space, the duct run should have had some slope on its way to the roof, and the duct sections should be oriented so that the higher duct pieces fit INTO the next lower duct pieces.

I'm referring to the velocity of the air (ft./min.) in the duct when the blower is on HIGH setting. This is the actual flow rate of the blower (CFM) constrained by all of the pressure losses, divided by the area of the duct (sq. ft.).