Posted by lascatx on Fri, Aug 7, 09 at 13:45 > Are you planning on using that cabinet for storage or just to hide the duct? No, the cabinet is mainly for hiding the duct; very little room left over in there for storage. Posted by lascatx on Fri, Aug 7, 09 at 13:45 > you can put up a panel matching the cabinet doors and add some trim -- molding to frame it, a medallion or whatever. We've been playing w/ this idea for the past couple of days. The problem is that there is already this type of decorative panel over the window which is to the left of the hood. On the right of the hood, there is another similar panel over the built-in fridge. So I think it looks really good now with the 15-in tall cabinets that the builder installed over the hood. I'm very worried that putting another panel in place of the cabinets would look like overkill in moldings. So I don't know what to do!!! PLEASE LET ME KNOW WHAT YOU THINK, LASCATX! By the way, the hidden duct is in the upper 11" of the 15"-tall cabinets. So if there were a way to "shorten" those upper cabinets by shaving off the bottom 4 inches, then I'd end up w/ the hood at 30" high. However, DOES ANYONE KNOW HOW HARD THIS WOULD BE TO MODIFY? Is it worth the extra 3" or 3.5" that I would gain? Is there a way to fashion 11 or 12" cabinet fronts (even false fronts would be ok) for the shortened cabinetry, so that it would still look like cabinets over the hood (and not like decorative-panel overkill that I was afraid of)?

I totally get the 24"-27" placement being too low for comfort, although at 5'2", not much hits me in the face. :) My last hood was at 24" and what I found most annoying was trying to get spaghetti out of a pot. I don't have the cooktop here, but the depth of the hood is 19" (including 3 1/2" of front controls). The front of the cooktop sits at about 22", so if I understand what I'm reading here, if I'm going to cook anything smelly I need to do it on the back burners, otherwise, I'm probably okay.

That is a popular idea, Walt, but I don't think it completely survives close scrutiny. If a blower could be turned on so that it changes from zero to full blade RPM in zero time (infinite torque applied), there would be a period of lower air flow rising to the steady-state value while the inertia of the household air was overcome by the pressure change at the hood and the pressure losses along the make-up air path reached their static value. This doesn't take very long. Because real blowers speed up over a period of a several seconds for the larger sizes, the flow pretty much keeps up with the static flow that would result at each blower RPM as the blower accelerates to its final RPM. When a burner or hob is turned on, the energy input to the pan raises the pan temperature similarly due to pan base (and perhaps food contents) thermal inertia. The pan only wins if the thermal time constant of the pan is shorter than the time constant to get the air moving in the make-up air path. I think you will find for most cooking examples that the air flow is stabilized before you can smoke the pan, even if it only contains a little butter, if the pan base is at all substantial, and one attempts to set the flame/hob power at a level appropriate for the cooking to be done. Conversely, one may see that really thin pan bases and/or long MUA paths can allow the pan smoke to get ahead of the airflow. Also, my argument above assumes that the hood blower is auto turned on to a level that the pan conditions will require. If the hood is turned on as a function of plume temperature read at the hood, air flow might well lag keeping up with the pan conditions. I fully agree with keeping the fan on for a while after cooking; not all of the plume will be captured during cooking unless the hood is very large and the cross drafts are negligible. So, for the alert cook, this auto blower operation is a frill. Conversely, for those who forget about turning the hood on until it is too late, it is a great help. kas

First is capture, and this requires plume overlap by the hood. Now it is true that plume divergences vary with different factors, but all need to be overlapped, and few hot grease plumes will stay inside the boundary of the cooktop width except those from the center hobs. Capture is not ameliorated by a lower BTU level at the cooktop surface. Second is containment. This performs the removal of the captured plumes from the hood entry volume and expels it outside. To avoid reflections on the sheet metal, or at least to contain reflections, a minimum velocity of hood air is needed to entrain the plume elements into the hood flow to get them through the baffles. This varies with the velocity of the plume components (which varies with the heat input to the pan and whether combustion heating is being used) as well as hood design. So the CFM required for, say, steak searing will be slightly less with induction than with gas, and it might be possible to get away with a nominal 60 CFM/sq. ft. of hood instead of 90 CFM/sq. ft. I would expect that this would still depend on just how hot the searing was, whether the flame was on maximum or we are mostly dealing with a very hot cast iron pan with lowered flame, and how well the hood entry volume (reservoir) was able to average the initial grease vapor transient from throwing the steak into the hot pan. Without computational fluid dynamics evaluation of a particular case, or schlieren photography of the physical hardware in action, the best I can do is generalize. I have 90 to 100 CFM/sq.ft. and can capture induction wok cooking and induction searing effectively, but the transients are somewhat modest, and my hood is very long with some advantage in reservoir volume. So I know it works for me. What I can't "know" is how every other hood would work for me or for any other cook. Hence, I'll stick with 90 CFM/sq.ft. as a recommendation, with a suspicion that for non-extravagant induction cooking, lower specific flow rates may prove sufficient. Budgets and space are in many cases limited, so avoid having a zero percent solution because the 100 percent solution is unaffordable or infeasible.