Range hood ductwork through crawl space?
Anon Username
6 years ago
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writersblock (9b/10a)
6 years agolast modified: 6 years agoAnglophilia
6 years agoRelated Discussions
Range hood exhaust: straight up 2 floors and through roof OK?
Comments (5)Assuming that you build a system capable of 1000 to 2000 ft/min air velocity up the stack, there should be minimal condensation. Certainly grease particles and steam won't slow down and reverse direction. Residences tend not to condense much grease anyway because they are not cooking greasy foods for hours as a restaurant might be. Also, even with a cold attic, the stack will warm up once the blower has run for a bit. Establish an air flow rate (CFM) to achieve an actual 90 CFM per square foot of hood entry aperture, then size the stack diameter to achieve a velocity in the range noted in the paragraph above. Keep in mind that the blower rating must be higher than the CFM calculated on the basis of the sentence above to counteract pressure losses in the air flow circuit. (The air flow circuit may be considered to start at the cooking zone, pass through the hood baffles, continue out of the hood into the stack, go up the stack, flow past the roof blower or cap to the outside, and thence return from the outside back into the kitchen via one or many make-up air paths. No matter where one starts, it is the sum of the pressure losses in this circuit that determines how much lower the blower flow rate is relative to its rating. The relationship is given by the blower's fan curve; see Broan example below.) I would also plan on a damper at the hood and one at the roof. Most down-slope roof blower housings include dampers. Use of a roof blower allows use of a silencer in the attic to reduce noise, depending on space. This may also apply to using an in-line blower with a silencer. In this latter case, it may be necessary to jog the duct to have enough room for both in the attic. With respect to directional changes in the duct, the dominant causes of pressure loss are not jogs in the duct, particularly if they are 45-degrees or less, but rather the MUA path and the hood baffles. So it is not particularly inefficient to angle the duct in the attic to mate to the faux chimney placed where it best meets whatever considerations apply. kas...See Morehow to vent a range hood around AC ductwork
Comments (9)We need a lot more information, I think. Ideally, I would suggest, rip out your central AC system and replace it with a minisplit heatpump. Takes up less space, much more responsive, much more energy efficient, and neatly solves your problem. Unfortunately, it does incur a big upfront cost. So, this might not be what you want to do. The next question is, what is above your kitchen? Can you vent to the roof? If so, you might be able to have an S-shaped section of vent pipe that navigates past your AC ducts. Or you might be able to push your AC ducts into the ceiling joists above, and then there are all sorts of other ways to either route the vent to the side of the house or past the AC duct. If you can run the AC duct in the ceiling, that would also allow you to move it away from the wall. Of course, a bigger soffit would do the same job, but I can't tell whether that would look OK. It might also be possible to place the stove somewhere else. Or, if you are really desperate, you could get a VentAHood recirculation system. It's not as good as a properly venting hood. But of all the recirculating hoods, this is the only one that actually does work, as it has extensive filtering built-in. There are so many possibilities. But it is really hard to tell without seeing more details and without knowing your budget....See MoreRange Hood Ductwork - Flex or Metal?
Comments (8)All of this is backwards! To determine requirements, one starts with the cooktop size and based on cooking plume expansion determines the hood entry aperture (capture area) size. From this the flow rate (CFM) is determined, and thence the duct diameter. Also, based on the flow rate and local ordinances, personal preferences, house architecture, and exterior environment, one establishes the requirements for the make-up air system. When requirements are established the hunt for systems or components of systems can proceed. Details of the requirements process can be found in many "hood" and "MUA" threads on this forum. Absorbing the first dozen or so pages of Greenheck's commercial perspective on this topic may be helpful. See: http://www.greenheck.com/media/pdf/otherinfo/KVSApplDesign_catalog.pdf...See MoreDoable?--build soffit in adjoining room to hide range hood ductwork
Comments (20)julieste --- Adding to what kaseki said, the hood & soffit idea will be fine. I say this having had to do something similar in my 110 y.o. house. I do a lot of cooking. The set-up looks acceptable and works well enough. Of course, my "good-enough" solution was not the best possible venting set-up I could have had. Some here would say (and do say) that the "merely good" is the enemy of "the best" and only the most optimal will do. Others of us will say that, If you have the the time, interest and budget for "the best possible," have at it. For me, the best possible venting solution would have required reconstructing the back end of my old house. "Good enough" was what I had the time, interest and money for. I'll offer a couple of ideas you could consider in designing your project. One is to consider transitioning the ducting (at the kitchen-den wall) to run across the den ceiling in 3"x10" rectangular ducting. That could make for a shallower, less obtrusive-looking soffit. A second idea to consider might be recessing some shallow LED "can" lights in the soffit as that end of your den looks rather dim in the photo above (although that might be an artifact of the photo.) Maybe hang a couple more paintings at that end of the room. That could make a functional necessity look like an aesthetic design choice. Of course, some find recessed lighting and soffits to be aesthetically abhorrent. YMMV. An alternative to the soffit-and-vent design might be one of the Vent--a-Hood ARS units. (ARS stands for "air recovery system.") These seem to be one recirculating hood system that actually works reasonably well. These are expensive but might be less expensive that the cost of the soffited vent system you are considering. If interested, check out the thread "Vent-A-Hood Ductless ARS RANGE hood Update" which started here a decade ago and was still getting posts a month or so ago....See MoreNothing Left to Say
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