Here's what I did: I have a 27x27 garage the extra room on the sides is great for storage. You need to have the electrical spec'ed out - as it will come into the garage through the slab. Also do you want a three way switch from the house to the garage? I would run 2 - 20 amp circuits, be sure to have at least two outlets on each wall, and an outlet on each side of the door. For lighting, 4 high output 48" fluorescent fixtures (two tubes each). I also have exterior lights on each side of the door, on a photocell. I'm in Minnesota - the garage is insulated / sheet rocked / and heated with a gas unit heater. If you plan to heat the garage - you will need insulated garage doors, and double glazed windows. Having it sheet rocked and painted is really nice. With a new slab - when it's cured - I would give it two coats of non-slip epoxy. Cleans up really nice with a hose / powerwasher. I have some of this - it's really nice: Gladiator Storage

I built my custom home and design it as well. It was my first and I was very green. My advise is make sure you know what you want and what you are willing to pay for. Learn who your builder is and do not trust too much when they start tell you what you (should) want. I learned the hard way and two months into the build project I had to practically live at the construction site. The builder did not like it much but it was my house and not his so I did not care. We budded heads when he kept defaulting to "his standards". He was good for the big strokes but when it came down to the details he failed. Pick out as many items as you can upfront so you can get a very good idea of cost. We went $50k over budget and that was because the builder's defaulting to "his standards" at the budget discussion table that I was not aware of until we were into the build project. I initially took his advise on some designing, I wish I didn't. When I became the wiser I starting taking things back in my own hands. And I am speaking of selections like cabinetry, windows, flooring tile, countertops doors, decking materials and much more finishes. I had a budget I wasn't suppose to go over and he, the builder, did not make it clear as to what we were going to get within that budget. I do not regret that I went over. And I tell you if I had another $50k laying around I would have used it up.

Third, people who build truly custom homes are taking a huge financial risk and usually do not make money in the short run or the long run. They usually lose money, but they tend to live in a home that is well suited to their lives for a long time. This. I'm in a market that is booming with new construction, and the reality is, some of these homes will be valued hundreds of thousands less than the build cost when it comes time to sell. Anyone who thinks building a new home is a wise financial investment should research their own markets to analyze their risk. Very informative post, @homechef59 ! Thank you!

For capture, the hood entry aperture (with preferably some reservoir volume below the baffles -- likely more important than extreme overlap depending on hood air velocity) needs to overlap the plume width at the height of the entry aperture. There are three effects to be considered: (a) plume expansion from the pan base, (b) laminar or turbulent cross drafts from air conditioning, MUA, and people moving about, and (c) the degree to which the rising plumes are constrained by a back wall, side cabinets and/or hood skirts, and the air flow along the counter itself. (Some commercial gear stands alone without counter effects.) Ex mente computational fluid dynamics is difficult, so one must use some judgment here. Try to picture the air as a fluid that is moving and may be disturbed in ways that are very location dependent, then decide where to stop in the battle between perfect and good enough. While what @M wrote provides many insights, let me add a few. The higher velocity components of the plumes are generally contained within a 10-degree half angle cone, so this determines the hood size for undisturbed air given a burner layout and variety of pan sizes that might be used. There is some margin for air pulled across the hood aperture edge features that 'kind-a' makes up for the sloppiness of treating the exterior hood size as the hood aperture. Given a counter and side cabinets for wall hoods, hood height of 30 - 36 inches, then a 3-inch overlap from the cooktop edge (generally wider than the pan edge) will be adequate for the 10-degree expansion given the flow field under the hood near the edges. (Note commercial griddles, for example, extend all the way to the appliance edge.) But wait, there's more. Do we have a calm kitchen, or people moving about? Is this an island hood? Are people milling about on the side opposite the cook? How is MUA introduced to the kitchen? MUA will cause a draft of sorts that at best can be made fairly laminar, but will still be a plume bias, particularly for a island hood. And if the MUA is turbulent it can mess up the plume sufficiently to interfere with capture. Commercial hoods are typically set at 7 ft above the floor, or 4 ft above normal residential counter height. At this height I would go wider than the nominal 3 inches each side, not only for the increased expansion size at that height, but also for the increased cross-draft sensitivity. (Note 4 ft x tan10deg = 8.5 inches (from the pan base edge). It may be of value to read the long thread related to @opaone's commercial hood installation: https://www.houzz.com/discussions/5745986/commercial-range-hood-install#n=69 for sizing and other parameters he has chosen. As another reference, I have the largest Wolf Pro Island hood over a 36-inch induction cooktop and a Cooktek induction wok hob. The prevailing wind from the down-hall MUA diffuser and a nearby wall mounted split a/c head is from the cooktop toward the induction wok. This hood has a 61 x 27 aperture and is sufficient for all cooktop cooking, and for all wok cooking so long as the a/c is not aimed across the island. Otherwise the wok might spill a bit past the hood edge. Air flow appears to be (haven't made enough measurements to average it out) at least 100 ft/min into the hood (times 10 sq. ft. aperture area = 1000 CFM). Induction plumes are typically lower in energy than gas cooking plumes due to the lack of combustion products, but the hot oil/grease plume velocities will be similar.