"Have you thought of changing the wall studs to 2x6" rather than 2x4"?" I don't wish to destroy the wall on the far side. I have a large map wallpapered to the other side. I could build out with a false wall for some additional distance, but I don't see that as necessary since I can do at least 3-1/2"x14" (almost equivalent to a 8" round duct). Plus, I found a standard "Straight Register Boot" to transition to 8" diameter. I believe 3-1/2x14" equates to about .05 friction loss for five feet). I just don't know what 2200-2500 FPM will equate to in sound level at the hood. I foresee cutting a 4x15 opening (or bigger), at the back of the hood. I am re-reading rjpjnk's post and I remind you I only have five straight feet till it feeds straight into the fan venturi. I found this is an engineering handbook: Duct velocity should be between 1500 and 4000 FPM  Hood velocities (not less than 50 FPM over face area between hood and cooking surface)  Wall Type - 80 CFM/ft2  Island Type - 125 CFM/ft2  Extend hood beyond cook surface 0.4 x distance between hood and cooking surface Filters  Select ï¬lter velocity between 100 - 400 FPM  Determine number of ï¬lters required from a manufacturerÂs data (usually 2 CFM exhaust for each sq. in. of ï¬lter area maximum)  Install filters at 45 - 60°to horizontal, never horizontal Using this as a guide I think an average 400 CFM for general-purpose venting @ 1500 FPM means that I am well covered with a variable speed 1000 CFM external fan and 8" duct area. I'm guessing that at 1500 FPM it will be pretty quiet. The old Vent-a-Hood units are supposed to deliver 300 CFM each and I usually only use one. They are super noisy at near my ear level and 18 inches away. The air passes through a 3-1/2" x 4-1/2" rectangular opening! That's small and seems to equate to almost 3000 FPM! I guess it's no wonder they're so noisy... Am I missing anything? Bad calculations or asumptions?

Okay Amy, from a woman's standpoint who doesn't understand the intricacies of this important task, I hired experts as it seems you will too. So, if you are trying to get a general idea of how it happens, I can tell you. We just had something similar done 3 weeks ago. But on a MUCH smaller scale, I might add. I had a load bearing wall between the kitchen and DR that we wanted to make more open. It supports at least half of our house. We went from a 36" open doorway to approx 80" open. The GC took measurements and found out the size of the header beam that the load required, structurally. When the time came, the carpenters opened up the walls and ceiling, moved the electrical out of the way and installed two temporary walls on each side of the existing ceiling/walls against the attic joists (we have a single story ranch so this might be different for you)Once everything was in place and the load could be essentially transferred to the temp suppports, they sawed thru the existing beams and installed the new longer heavier beam. I ended up with a new 12" deep header where I used to have two walls and an open doorway. It was either that or go into the attic and cut the joists to install a steel beam to carry the load if I wanted a flat ceiling. I opted for the less scary (to me) and more cost effective header :) Also, I googled 'removing a load bearing wall' and watched a few YouTube videos ahead of time so I could kind of understand the process. HTH!

Benjamin, I would think that an experienced builder could look at it and tell you what needs to be done right off the bat, without going to the expense of hiring an engineer. There's nothing wrong with getting a quote and then deciding to do all or part of the work yourself. The reason I asked if the original builder put up the wall, is that the work looks kind of amateurish to me. Why go to the trouble of building a wall, using that much wood and not finishing it, when a simple beam with support posts would have been much easier to do. What is on the floor over that wall? Maybe a previous owner was trying to correct a problem or trying to put in additional support for something heavy (like a waterbed). If the wall is a true bearing wall, I would think that it's also supporting another bearing wall on top of it. I'm having a bearing wall taken down on my first floor and wanted to move one of the supports for the beam that the builder is putting in. My builder told me that the support had to be there because it would sit over a support in the basement and it's important to transmit the load from above all the way to the ground.

The roof framing is unlikely to span from the center pole to the outer deck posts; that would require unnecssarily large and expensive roof beams. You can be pretty sure the walls are load bearing if they're supported on foundation walls. Rearranging the walls will also change the lateral bracing of the house. I would try to find the original drawings at the local building department and see if the original structural engineer is still available.