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Clark
Basic Member
Posts:248
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| 27 Mar 2010 03:48 PM |
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Posted By cmkavala on 27 Mar 2010 02:44 PM
use a ductless kitchen hood..............problem solved
Problem not solved, Chris. An ultra-tightly built home should have proper range hood ventilation. You still haven't convinced me that a motor actuated damper in the hood vent pipe is not a workable solution to heat loss through the vent when the hood fan is off. I know that range hoods don't come with 6" duct connections, but depending on air flow requirements, duct length and routing one can reduce the duct to 6". My 36" FanTech hood liner's 8" outlet is reduced to a 6" round duct with an inline FanTech FX-6XL exhaust fan which vents to a roof cap (also 6") with a gravity backdraft damper. It's true that the motorized damper I referenced doesn't indicate use as a hood vent damper, but it doesn't forbid it either. And why should it? What reason would you suggest for disqualifying this damper in a hood vent installation? The motor is located outside the duct. Any grease build up inside the pipe would not affect the motor's operation. The only negative I can see is the $100 price tag. |
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cmkavala
Veteran Member
Posts:4327
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| 27 Mar 2010 04:28 PM |
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Clark;
I live in and ultra tight home, ductless range hood and an erv system. It works!
The motorized damper will prevent the air coming in, but it is not adviseable to reduce 7" exhaust ducts to nor increase 4" dryer vents to 6" , motorized equipment has specific duct sizing to properly work.
I can see grease build up occurring at the reducer, you will not find ANY code book that will allow what you are proposing.
You can use gasoline to start your charcoal too, but its not adviseable. Its all negative and a bad idea., But thats just my opinion, which are like elbows ........ we all got them.
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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Jelly
Veteran Member
Posts:1017
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| 28 Mar 2010 09:43 PM |
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How long of a vent line can you run to exhaust a kitchen hood to the outside? An HVAC guy told me I should run my range hood vent 20 feet along a joist, turn and go up into the attic, run it another 25 feet, then turn and go down into a drop ceiling over a bathroom, then out a wall. Surely this is too long without another fan along the route? |
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cmkavala
Veteran Member
Posts:4327
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| 29 Mar 2010 01:08 AM |
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Posted By Jelly on 28 Mar 2010 09:43 PM
How long of a vent line can you run to exhaust a kitchen hood to the outside? An HVAC guy told me I should run my range hood vent 20 feet along a joist, turn and go up into the attic, run it another 25 feet, then turn and go down into a drop ceiling over a bathroom, then out a wall. Surely this is too long without another fan along the route? too far! ................ 25 ft. with no bends , deduct 5 ft. for each 90 deg. turn I couldn't find your plans in my archive , resend to me & I wil try to find an alternate route |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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Eric Anderson
Basic Member
Posts:441
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| 29 Mar 2010 10:45 AM |
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the hood I use came with a 6" port. Many do. I would suggest that most people don't need a huge exaust unless you got suckered into buying a huge stove.
Ductless only works if you have an electric stove. I prefer gas and accept the compromises that come with it.
Eric |
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| Think Energy CT, LLC Comprehensive Home Performance Energy Auditing |
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dpilati
New Member
Posts:10
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| 31 Mar 2010 06:58 AM |
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I have the same problem as the OP except I'm pretty sure it is an 8 in duct out a wall. I was "suckered" into buying a large range by my chef wife. The wind does open it and I need to fix it. The motorized damper seems problematic - just the wiring alone gives me grief. Not to mention, the potential failure - right when a large gathering is occurring. Having a small motor exposed to the elements (or grease since you would have to have one or the other) doesn't seem very reliable.
Any options for a large duct? |
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Clark
Basic Member
Posts:248
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| 31 Mar 2010 09:19 AM |
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Posted By dpilati on 31 Mar 2010 06:58 AM
I have the same problem as the OP except I'm pretty sure it is an 8 in duct out a wall. I was "suckered" into buying a large range by my chef wife. The wind does open it and I need to fix it. The motorized damper seems problematic - just the wiring alone gives me grief. Not to mention, the potential failure - right when a large gathering is occurring. Having a small motor exposed to the elements (or grease since you would have to have one or the other) doesn't seem very reliable.
Any options for a large duct? The motorized damper that I found for a 6" duct also comes in other sizes including 8". Certainly the motor must be protected from rain and snow, but freezing temperatures should not be a problem. For a vent duct through the wall, I imagine that the short duct length and/or accessibility would preclude using the in-line motorized damper solution. There might be a small wall-mount motorized damper that would work for you. In my situation, the duct and in-line fan are accessible in the attic. I plan to cut the duct, insert the damper, and wire it to the fan without difficulty.  |
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yuka-atatakai
New Member
Posts:12
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| 13 Apr 2010 06:10 AM |
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Don't you think that you have to account for all fans in the entire structure? We have kitchen exhaust fans here (Japan) that have make-up air attached as a separate duct--both exhaust and make-up are 6". you are then providing make-up at the point of exhaust. And actually venting smoke, odors, etc more efficiently. These units need a little better dampering --both ways. My first airtight, super-insulated house was built in the mid 1970's when it was really a new thing. The wood stove smoke would be drawn into the house if more than one, toilet exhaust fan was turned on. That was later resolved by tuning the intake and exhaust pipes on an early model recovery heat air exchanger along with being careful not to run all the fans at one time! I have found that creating a slight positive pressure inside a home is more comfortable. Where indoor air is forced outward rather than cold air sucked to the inside. That was also a forerunner to a mcmansion at around 5000sf. I do not know what building green really means. If you compare a home to something that is living and provide adequate light, clean-air, controlled temperatures, and humidity, and try to do it in a sensible way that that does not squander natural resources (either fuel) or materials. Then you are making a place that is healthy to live in. If you can do it economically and build for your needs rather than status then--you have a hit. If that is green--count me in as a new charter member.  |
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jonr
Senior Member
Posts:5341
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| 13 Apr 2010 09:33 PM |
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At least in the Winter, I prefer to avoid any positive pressure - I don't want to push warm humid air into the wall cavity where the moisture may condense out.
The equivalent leak area of a typical home is going to be greater than a HRV or passive damper. This means that a ventilation fan pulls most of the replacement air through your walls. In any case, a HRV at or connected to the point of ventilation would be more efficient.
On another subject, I suppose one could produce a HRV like device with a pressure sensor and controlled fans that would actively keep the interior pressure equal to the exterior pressure (or even an upper level pressure equal to a lower one). Ie, when running a ventilation fan elsewhere, the intake fan might be running at full and the output fan might not be running at all. Might be more comfortable or less damaging to walls. |
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yuka-atatakai
New Member
Posts:12
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| 14 Apr 2010 07:40 AM |
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Hello jonr,
You are assuming that vapor will condense in the wall cavity. This will not be the case if you build a structure with exterior insulation, ideally no insulation in the wall cavity at all. Also, no vapor barrier to the interior of the structure. A typical design would have something like Thermax (foil faced rigid) foam on the exterior --a thickness adequate for the region. All seams taped, caulked or sealed so to prevent any migration of vapor to the outside. The vapor within the structure will never reach its dew point--thus no condensation. And if you have leaks--like around windows, doors, etc--then the slight positive pressure will force the air outward. I mean slight. And if you have a properly designed fresh air system, you will be introducing dry exterior air to the structure and exhausting stale, vapor ladden air to the outside.
I have seen systems similar to this marketed here--maybe 15 years ago. But each room had a small orifice that opened to the cavity between the siding and the exterior drainage plane. We have been furring walls for some time now to allow for circulation behind siding. In any case, this cavity is buffered from the extreme outdoor temperatures and vents upward--into the vents surrounding the roof. There is a central plenum with a fan (reversible) to change the pressure in the house from positive to negative depending on the season. Doors are undercut or other sleeves are cut into rooms that need additional circulation. But this system is duct free and very simple. This worked 15 years ago when condensation was the big issue on relatively well insulated homes with insulated glass. The problem was solved as well as the problem with mold. The little orifice to the outside operated like the iris on a camera (old camera) which could be tuned to allow different flows for different rooms.
I still like intake air to kitchen exhaust and dislike ductless fans with a passion--just circulating the same old polluted air.
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jonr
Senior Member
Posts:5341
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| 14 Apr 2010 08:42 AM |
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I agree, that's why I wrote "may". Warm, moist air forced through the inevitable leaks in walls/ceilings/gaps to a cold surface will form condensation. The question is exactly where it will occur and how much damage it will do. I agree, not as bad if it happens in or around foam.
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Clark
Basic Member
Posts:248
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| 14 Apr 2010 08:45 AM |
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Yuka-atatakai, I agree that keeping the home at a slight positive internal pressure is safe for homes built without wall/ceiling cavities. Positive pressure would be difficult to maintain, however, without effective dampers on all outside vents (kitchen hood, dryer, etc.) Passive dampers, like those found on most range hood ducts are designed to open when the inside pressure is positive relative to the outside air. What kind of dampers are used in Japan, in homes such as you describe, to prevent air from escaping through a hood duct when the hood is not in use?
BTW, FanTech recommends that its HRV be balanced so that the volume of intake and exhaust air are equal. I assume that maintaining either a positive or negative air pressure differential encourages heat loss and lower overall energy efficiency of the house.
Clark |
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yuka-atatakai
New Member
Posts:12
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| 14 Apr 2010 09:28 AM |
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jonr, I have been accused of jumping to conclusions and p.off people because i do not listed..Sorry, at least we are in agreement.
clark, the first house that I described for the 1970's was build in northern minnesota where we experience winters of -40F occassionally dipping to -60F, really the icebox for the United States!
the second application--with wall vents and plenum was built in Aizu-Wakamatsu, Japan--cold, lots of snow...I do not know what they used for kitchen fans. (if you want to see where this is-- use google earth.
third--exterior insulation is my house. Much milder temperatures still we get snow---no special dampering but intake and exhaust air to the kitchen fan. We are required to have a certain amount of airchanges per hour by building code. The air changers only have fans--simple wall mount that intake and exhaust with the same duct. My bathroom fans have a damper that opens when the fan is turned on. No power/normal close position. This cuts all exhaust either way--manufactured by Mitsubishi company--very simple, very cheap.
I have come to the conclusion that building tight can be done---then you have to worry about getting fresh air back in.
I do not know who FanTech is---the first time that I saw this "green building talk forum" was about a week ago. It is getting habit forming...have to spend more time working and less time typing. But it is great to communicate with people who have interest in building issues. Especially those who speak "English"! I am surrounded by a population of " Japanese" customers who do not speak "English". I have been building for 40 years and still have not lost interest. If anyone does not understand my words it is because some of the thoughts are based on Finnish concepts, others have roots in Minnesota, yet more have developed in Japan... Sometimes my thoughts cannot be put into words because I am either uneducated or confused--sometimes both. Please feel free to straighten me out at any time--and do not take offense if what I say seems offensive. It is not.
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Bigrig
New Member
Posts:92
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| 14 Apr 2010 09:52 AM |
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Fantech is a manufacturer of fans (whole-house, inline, roof-mounted, etc.) and HRV/ERV units. Mostly residential and small commercial.
http://www.fantech.net/
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JR in WV
New Member
Posts:11
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| 16 Apr 2010 11:27 AM |
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I agree about ductless fans. All they do is provide additional white noise in the room, without any benefit as far as cleaner air is concerned. I have a large gas stove and need exhaust when frying especially. Our hood was built custom by the roofers, who have better sheet metal skills than other local trades. It has a large variable-speed exhaust fan on the roof directly above the stove. I can't imagine needing a maze like duct path for a rangehood exhaust, that seems like over-complicated (poor) design. No offense, I have my own problems to cope with!
Yuka-atatakai - Welcome to the forum, it is interesting if you like building things.
JR |
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yuka-atatakai
New Member
Posts:12
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| 16 Apr 2010 04:51 PM |
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Hello JR in WV!
Looks like you have a good solution for your situation. Your fan resembles commercial units at restaurants, I helped put one in once as a volunteer (member) at our local American Legion club, that one had a large make-up air furnace also attached and some motorized dampers. When you start one of those fans---they really move air!
And no offense taken-
My thoughts on any design is to use the simplest practical solution. Even very difficult things can be broken down into a set of simple problems with practical solutions.
For fans--shortest, straightest route is best--you solved that!
Yes, I like working with things. Something to keep my mind busy. Even working in unrelated trades, sharpens overall skills. I once took 8 years to totally restore a sports car to show stopping quality. Trouble with that was--once the restoration was complete, it was too nice to drive! Ending up selling it and moving on to other things. I heard that it later was sold at auction in Scottsdale for big bucks...but not by me. It was a phase to go through, lots of memories and a feeling of accomplishment. No big expenses if you use money otherwise spent on bad habits like smoking, drinking etc. Things like that build patience if you try to do things right. |
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mrwagner
New Member
Posts:3
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| 24 Jun 2010 06:01 PM |
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Hi all,
New to the forum, and have a related problem. We recently looked at a newly built home with a high end stove top and 700 cfm hood vent. When I later asked about where the hood was vented, the answer was "to the attic" from the listing agent. After further inquiry about this to the builder, we were told that the hood was vented to a "recirculating system" in the attic which filtered most of the grease and moisture out of the exhaust before release into the attic - this is supposedly technology so new that the manufacturer (Fujioh) has not info available on the website. That it could filter most of the moisture out seems unlikely to me, let alone how the grease collection is ultimately handled. Nevertheless, I would like to give the builder the benefit of the doubt, but it seems most of the details on this are second hand from the vendor rep to the builder, and I have no way of verifying the details.
Has anyone here heard of such a recent technology?
The builder has offered to vent out of the roof if this is a major issue for us, but I am kind of wondering why this was not done in the first place. The builder says this route was taken to avoid condensation/dripping back into kitchen that occurs with roof vented exhausts.
Thanks for your thoughts on this.
mrwagner |
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cmkavala
Veteran Member
Posts:4327
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| 24 Jun 2010 07:03 PM |
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mrwagner;
yes this is a major issue for you, make the builder vent to exterior the way it should of been done in the first place, any other explanation is simply BS! |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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Dana1
Senior Member
Posts:6991
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| 25 Jun 2010 10:21 AM |
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Venting even filtered kitchen exhaust into the attic doesn't meet code, and will very likely create mold conditions in the attic in many climates (even if it has a dessicant wheel or other dehumidifying technology. ) The condensation will now be happening in your attic instead of the duct- not a solution.
Side-venting kitchen or bathroom exhaust usually keeps condensation issues under control, but you have to place it carefully to avoid creating issues on the exterior. If it has to go through the roof, insulating the duct where it passes through the cold attic keeps it from condensing & dripping. (This isn't rocket science.) |
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cmkavala
Veteran Member
Posts:4327
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| 25 Jun 2010 07:51 PM |
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mrwagner;
Even though is a new home, You might consider hiring a home inspector, given the fact that the builder cut corners on the the hood exhaust. You may want to know if there are other items are substandard |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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