kitchen vent make-up air advice needed please (cross post)
threeapples
11 years ago
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andi_k
11 years agolast modified: 9 years agoathensmomof3
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Make-up Air - Please explain what I need to tell my contractors
Comments (6)See Martin Holladay's article. If you don't get makeup air from a dedicated intake, it will be drawn through all the air leaks in your home and possibly even backdrafting CO from the furnace and water heater if these are not closed units. Though I know you're looking for a cheap answer, I'd suggest finding a more educated HVAC designer with commercial experience to be safe. However, if you don't run the exhaust all out all the time there may be no need for makeup air. We had a 700 cfm unit that was only run full throttle when my spouse cooked fish and offal. I just cracked open a patio door and all was OK....See MoreKitchen hood make-up air advice needed
Comments (1)Writing in generalities, one approach is to provide MUA to the furnaces so they don't get back drafted from negative house pressure. In some cases this can be done by tailor made or factory made hardware directly to the furnaces. In other cases the furnace room would be sealed from having an air path to the kitchen. If possible, which depends on heating type, this would address the safety issue. The VAH flow rate then would be determined by how negative the house pressure got with whatever leakage the house and air conditioning has. A kitchen MUA could then be added if necessary to get good hood flow. You may want to condition this air. This is the bigger bucks part of the problem. Either furnace hot water has to be diverted to a heat exchanger in the air path (if the heating is hydronic), or electric resistance coils used in the airflow. Adding another furnace for the occasions of high vent flow is overkill because, unlike a restaurant, the periods of high flow would be a small part of a day. The kitchen MUA has another issue -- normally one wants to filter out critters and bugs and even dust from the air duct, and this causes a pressure drop. In such a case the MUA will not be making up as much air as desired unless a blower is added to the MUA path. Now there has to be a scheme for controlling the blower. However, if not conditioning or filtering the air is acceptable, then a large duct to a diffuser with a damper controlled by detecting hood air flow is a simple, low-cost solution. Broan makes a unit for this, or DIY using one of many Honeywell motor controlled dampers is an option. I suggest reading or at least skimming the literature linked at my "my clipings" page. In particular, Greenheck covers the topic well, albeit from a commercial point of view. But the commercial POV is the one that led to the Pro-style ranges and counterpart ventilation systems we are addressing with MUA. Last, while I think HVAC solutions other than another furnace are options, the more DIY one gets solving MUA the more one is trading one's time versus paying for a slightly more expensive turn-key system. But at the 10K price point, even with a hands-off goal, I would look for other bids/approaches including HVAC companies concentrating on restaurant HVAC systems. kas...See MorePlease advise - Make-up Air system
Comments (2)The Broan makeup air damper for kitchen ventilation was the first residential application on the market. I think they deserve some credit for offering this design while others were silent. I've read the easiest passive make up air approach is a run of tubing in the basement through the crawl space to the outside, with an appropriate critter cage attached. I've had to read the below Broan MUA spec sheet a couple of times or more. Newer models may be available. Looks like you best come up with a installation guide for the Ventahood you choose. It will address a lot of the questions you ask. So you're going to run the ventilation ducts up to your attic and then out exteriorly to a cap? Your HVAC contractor should definitely be in on that. Good luck. Kitchen range ventilation is tough on the mind and budget for many of us. Here is a link that might be useful: Broan MUA damper This post was edited by SparklingWater on Mon, Feb 18, 13 at 21:47...See MoreRange hood and make up air advice
Comments (1)A bathroom fan duct may be only 4- or 6-inches in diameter, whereas a kitchen hood duct for a system that works for your size hood needs to be at least 8 inches for good flow. The bathroom duct may be aluminum or PVC, the hood duct must be steel. I doubt that combining the two functions into a single duct would even pass code requirements. Venting to a patio strikes me as moving the odor outside to the one location you don't want it. Search this forum for make-up air related topics to begin. It is possible to get away with a controlled damper "hole in the wall" under some conditions. We can discuss your questions further once you have some basic understanding. Grease and water vapor laden cooking effluent plumes, whether odoriferous or bland, have to be captured and contained by the ventilation system. I recommend a flow rate of 90 CFM per square foot of hood aperture. For any reasonable duct length, hood filter restriction, and imperfect MUA, assume that the blower's rated CFM has to be 1.5 x higher. This subject is also treated here extensively. Kitchen renovation is a really big project with many conflicting demands. It requires a lot of research to match one's goals with the available space and funding. Do not scrimp on the research. Layout, appliances, cabinets, plumbing, power, lights, .... the list is very long and may lead to recursive design as more is discovered about all the interacting subjects. Try to avoid a divorce. :) Good luck! kas...See MoreUser
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