Stovetop Hood-Can I Retrofit a Vent?
We have been making numerous updates to the kitchen in our 1983 Connecticut colonial home. We are putting in stainless steel appliances and wanted to get a matching stainless steel hood. However, it seems the choices in hoods are very limited if they are not vented.
What are my options in retrofitting a vent for a hood? The new cooktop (gas Thermador 5-burner supplied by propane, 13,000 BTU model) is not close to any outside wall, but I could vent it through the 2×4 wall cavity behind the stovetop down to the basement and then snake a vent out to an outside wall (approximately 25 feet across the basement).
We already have a similar “basement-venting” arrangement (but with a full size round sheet metal vent) for a Jenn-Air grill.
Is this practical? Are there any special requirements necessary? Is there a fire hazard in having the vent go through such a narrow space? If so, how can I mitigate this and what is the code for such a thing?
Thank you.
Replies
Can be done!
First, buy a fan with a low sone rating so you'll use it and won't shut if off due to noise!! Just saw this in a new house inspection; in a raised voice so I could hear her, lady said "It's awful loud" 3.5 sones or lower.
General code rules are that all duct must be metal to contain any fire that may start. (grease/dust on duct surfaces)
A standard style hood will have a knockout at the back of the hood that is 3+1/4 X 10 or 12 inches. You can buy off-the-shelf rectangular snap together duct (called wall stack) and transition pieces (boots) that have those dimensions. The boots/wall stack will take you down to the basement joist space. Non standard looking, more expensive hoods may have some other required/supplied pieces before you get to the wall stack.
From the boot at the bottom of the wall stack to the exterior, you may need 6,7,8 diameter duct to keep the resistance down and keep the volume flow up for such a long duct run. The size will depend on the flow volume for the chosen hood.
Ducts should be sealed at all joints to get the air out of the house. The best is a water based fibrated "mastic" brush on sealant (looks like a bucket of caulking) applied over fiberglass tape wrapped around every joint. The stuff is cheap so don't scrimp. This should also prevent any grease/oil leakage at the joints.
If you live in a cold winter area, the last 3-5' of duct should be insulated and have a sealed vapour barrier covering the insulation (this can be bought by the foot). This will prevent condensation on the duct near the outside wall due to small damper leakage or cold inside the duct.
And of course- a good exterior hood.
I use to build commercial kitchens... vents that have airborne grease need to have as few bends as you can get... need to be 100% sealed... we had to weld every seam.... in your situation i can see grease lay'n in the bottom of your duct work...
pull'n air is always better than push'n it... so an outside fan is better than a fan in the hood
is there any way you can go up and out the roof? vs down & across... snake'n is a bad word for hood ducts....
ponytl:
I used to work in commercial air balancing for a while. I agree that the duct runs should be as short and straight as possible but this one may need a couple of 90 degree .
Restaurants/institutional kitchens have multiple deep fryers on 12-18 hours /day and produce a lot of crap that does get into ducts. A home range duct system wood take 20+ years to build up the grease of a commercial system so might not need the heavier welded ducting you speak of.
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i said we had to weld ours.... but his needed to be 100% sealed.... the word "snake'n" just doesn't go well with how to run range hood vents...
true home vents going up & out collect very little grease... but not so true when you lay em down....
would i do it if i had no other way... yes... and just make sure my insurance was paid up
p
In Southern California there is Vent A Hood, San Yang and Kolbe which do not have a grease filter. They centrifically seperate the grease from the air. I have seen cups of grease in Vent A Hoods that owners did not know they were to empty. In a lot of Chinese kitchens San Yang is popular.
Went to San Yang and Vent-a-Hood websites and saw very litlle technical (Sang Yang Pai seem to have copied Vent-a-Hood; not uncommon) or a lot of "smoke and mirrors" claims by Vent-a-Hood. They claim to have quiet hoods but give no test ratings (sones). The San Yang Pai ad says 5 sones and as such does not meet the building code in Canada (too loud).
After a bit more searching found this at the applianceadvisor website:
The Range Hood Industry: Time to Pump the CesspoolWe have noticed that in the range hood industry, the use of fictional, illusionary, or highly exaggerated performance specifications is growing with the rise of imports. Some brands are promising performances twice as high as seems possible. As consumers can't confirm performance, there is no penalty to the corrupt brands, and in fact corrupt practice, and deceitful marketing has been rewarded with both market share and distributor growth.To our knowledge, the Home Ventilating Institute (HVI) is the only organization with standardized range hood performance testing and certifications. In 2000 an ApplianceAdvisor editorial was instrumental in convincing the largest transgressor in coming over from the dark side and HVI certifying their product line in 2003. Now in 2005, the ApplianceAdvisor is here asking HVI to start a program to confirm by testing the promised performances of all other uncertified brands, and to release the results of this testing to the public, to smite the corrupt, and to reward the honest. To bring balance, and whole grain crunchy holistic stuff to this depraved and unscrupulous industry.I have a dream......smaller than most perhaps, but a dream nonetheless.UPDATE: July 17: The following brands are HVI certified for performance, meaning that these brands have a tested performance that matches their promised marketing performance. -Air King (undercabinet) -GE Profile -Universal Industries -Broan, Nutone, Best, Venmar -Fuji and Panasonic -Artech USA (certification nearing completion)