Effluent expands as it rises, so the 27-inch hood will have a better chance of capturing it. Larger hoods also allow some increase in their mounting height for taller cooks. (But keep in mind that to look over the range one has to bend, thereby reducing one's distance from the floor.) Position and type of hood lighting is also relevant, as a hot lamp just above one's head can be annoying. Larger hoods require more air flow in proportion to their aperture area (or at least in proportion to the area where the baffles are, depending on interior design details. And the make-up air has to support this flow. A roof fan or attic in-line fan will reduce local noise, and if space and resources permit, an in-line sound reducer/muffler/silencer will also help. One can converse in my kitchen next to my Wolf Pro Island hood with its 1500 cfm - rated roof fan at full power. I do have a Fantech silencer and have much of the ducting wrapped with vibration dampening sheets. Ultimately it is a trade in cost and appearance versus effectiveness and noise that each person has to make accounting for any limiting architectural factors. kas

No grill. kas has a 36-inch induction cook-top next to a Cooktek 3500W induction wok hob. The Wolf Pro Island hood was the largest standard size that I found in 2007 and that looked ok. A Wolf supplied, Broan manufactured nominal 1500 cfm roof fan is used along with a Fantech sound suppressor and 10-inch ducting. The hood internal aperture in the width direction is 61 inches while the distance between the farthest apart hob centers is 44 inches. The hood overlap on the left of the cooking zone of the wok is adequate, as is the overlap with the largest pan that should be used on the r.h. induction hob. The hood is 34 inches above the cooking surfaces. I like where Trevor is going with his modified hood design, both in size and lamp placement. With the Wolf, there is a lamp that is right over my head when wokking, leading to having to wear a hat or change to an LED lamp. And of course, larger is better for island hoods. Even if 31 inches of depth might not be needed at the low end of the range of hood placement (30 inches above the cooking surface), higher placement can provide headroom for taller cooks and/or less visual intrusion into sight-lines. What one can get away with in that respect will depend on cross drafts as well as the effluent expansion angle of the worst case relevant cooking. (Expansion angles may be found in the second article referenced in my first clipping.) kas

The chimney type hoods are often designed for form-over-function installations and don't have as many deeper options. Also, most of the ranges that really call for that kind of depth are the professional style ones where people often install a pro style hood to complement them. So that's the style most of the 27" deep hoods are available in. That said, some of the high end/custom hood manufacturers should be able to set you up with what you're looking for. One example is Modern-Aire. Their PS-20 pyramid hood shows as being available in 27" depth. I believe there is significant lead time when you order from them though. http://www.modernaire.com/modernaire/PS-20.html

Ideally, for several reasons, the house interior should be kept at the same pressure as the house exterior. However, it is usually sufficient for the house interior to operate a bit lower in pressure than the exterior, depending on the state of combustion appliances in the house. Combustion appliances taking in household air can be back-drafted with lowered house pressure -- sometimes as small as a fraction of an inch of water column -- thereby introducing carbon monoxide into the house. This is bad. Without such appliances, or with them having their own MUA, or being in a room sealed from the kitchen, replacement air wise, lower household pressures can be safe. But this is still a slight drop in pressure, because hood blowers typically gag when the pressure loss is higher than 2 inches of water column pressure, sometimes even less. (Sea level is about 407 inches of w.c.) And one doesn't want to depend on wall infiltration for MUA. It is insufficient and dusty. So, no combustion appliance risk, use a duct, filter, and heater if necessary (and damper). Pressure loss vs. design needs to be compared to the hood blower fan curve to see what penalty is being created in available full power air flow rate (CFM). If there is combustion appliance risk, then use a power-controlled blower in the path along with the other listed items. See Fantech, or Accurex, or maybe even Broan for an MUA package example. MUA should get into the kitchen via a diffuser that directs the MUA such that turbulence is not created at the cooking zone because turbulence will interfere with plume capture and containment. The reference to hot air is not clear; are you in the tropics? A review of MUA related threads in this forum may add insight.