I plan to install island range hood for my kitchen. Not sure what is the best way to duct out. Is ducting to the roof is the only way? I am choosing most likely cosmo 36", shall I choose size 8 ducting or 6?
There are 2 ways, roof or side wall vent-hood. You will probably prefer the sidewall vent hood with flap by looks of roof, roof is usually preferred but sidewall is allowed by code. Duct 8-6" is overkill and only required by compliance if a secondary suite (check your local code though), a 4" is more than adequate and what most are done in. Typically the space is used above cabinets and hole cut through the wall and vent hood installed, sealed. After that area with ducting is "bulk headed with drywall or matching wood too hide it all and look aesthetic. Essential!!-use a insulated line if going flex or insulate around the one you do use as condensation will occur. This is a big mistake amateurs make on roof vented ones..they run it straight up and then condensation in winter causes dripping to come down out of the vent grill, seen it dozens of times, I usually put a little bend in mine angles away from the actual range hood install. On the sidewall installs no need but insulation is crucial on any kitchen exhaust install and a good caulking seal where the hood vent sticks out. Note: I have seen total incompetent's put them in the soffit!- what you you think will happend in winnter?
Hi John, Thanks for your commend. So you mean if choose the sidewall way, the duct go up into the attic and down near the space above the cabinet, then go out from side wall? I thought the duct would be a metal duct not a flex soft one? Or the duct will be attacked to the ceiling?
You can just run it along top of cabinets, then pop out exterior wall at nearest point is easiest... you can buy insulated flexible 4"or 6" ducting at homedepot even.. it is not going to be a heated line so metal duct not needed. All original hone construction is done with metal ducts, they are original code and stronger can also be steam cleaned etc after.. but for remodels flex is nicer, is never going to be handled in the location and really who do you know ever had a residential line cleaned? it would take 30 years and major greasy cooking to clog a line., it's a simple job just labor intensive.. expect about 2 grand for total job, drywall up the bulkhead etc... other option is also run straight up from stove and into attic space and the roof vent is placed about 3 feet down from the ridge, do not place it down near eaves. Any line must be insulated to prevent aforementioned condensation and dripping issues. PS: duct sizing can be important in regards to range hood CFM! most standard Brian range hood are good with 4" but if you have one of those big commercial vents check the manufacturer's recommendations sometimes they do require up to 8 in it's all about adequate flow of air.
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