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Choosing a range hood?

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  • Apr 17th, 2015 8:56 pm
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Sr. Member
Nov 26, 2013
512 posts
39 upvotes

Choosing a range hood?

I currently have a ductless range hood which is useless and I would like to install a roof vented range hood because my range is on an inside wall. My biggest concern is I want to make sure to get a big enough range hood because right now as soon as you cook anything with spices the house smells and it seems like all the clothes in the entrance closet absorbs the smell, so my coat smells like curry chicken and I hate it. If my house is heated with an electric furnace and I have an electric range hood and no natural gas or combustion of any kind, can backdraft still be an issue if I buy a range hood that is too big? I just have an average 30" range I am not sure of the BTU, what size would be good to make sure it gets the jobs done?
11 replies
Deal Guru
May 1, 2012
10538 posts
11427 upvotes
Toronto
I am guessing this is a big job as you need to install a duct to your roof.

I am not sure what you mean with BTUs or what you mean with natural gas. The range hood works in CFM, the higher this number the better it will pull air out of the house. There is more to it than that, but generally speaking, if you have a sufficiently large duct, you can get a high CFM range hood.

If Curry smell is the main problem, I can tell you right now that there is no range hood large enough (residential) to annihilate the curry smell. If you do a lot of asian cooking, go with a high CFM Sakura... like the Sakura B52.
Sr. Member
Nov 26, 2013
512 posts
39 upvotes
Anikiri wrote: I am guessing this is a big job as you need to install a duct to your roof.

I am not sure what you mean with BTUs or what you mean with natural gas. The range hood works in CFM, the higher this number the better it will pull air out of the house. There is more to it than that, but generally speaking, if you have a sufficiently large duct, you can get a high CFM range hood.

If Curry smell is the main problem, I can tell you right now that there is no range hood large enough (residential) to annihilate the curry smell. If you do a lot of asian cooking, go with a high CFM Sakura... like the Sakura B52.
Well usually you size your range hood with the amount of btu's your gas stove can produce but my range is electric and there is a formula to convert watts to BTU but I am not sure how many watts my range is.
http://www.wikihow.com/Calculate-CFM-for-Range-Hoods

From what I have gathered so far once you get into the 400-1200 CFM range, if your only sucking out the air you are creating negative pressure inside the home, without the use of make-up air the air being sucked out is not replaced by outside fresh air. Where this becomes a problem(I think) is when you have combustion applicances(furnace,fire place, water heater) that use a chimney to exhaust the fumes, well the negative pressure inside the house can suck the fumes of these appliances back inside the home and this is called backdraft. This is a major issue because now you have carbon monoxide inside the home. When you use make up air, the make up air damper(installed in furnace return duct) is triggered as soon as you turn on the range hood so as long as it sucking air out, fresh air is coming into the home so there is never negative pressure that causes backdraft. Since I don't have make up air I was wondering if I could make a mistake and buy too big of a range hood in terms of CFM's?
Deal Addict
Jan 6, 2015
2860 posts
784 upvotes
Toronto, ON
I just got a Bosch 30" range hood. 600CFM over a gas range. Also it's 8" duct so supposedly the bigger the duct, the more air it extracts.
Sr. Member
Nov 26, 2013
512 posts
39 upvotes
Should I just insulate the part of the duct that goes through the attic? The part that is in the kitchen doesn't need to be insulated?
Deal Fanatic
Nov 2, 2005
5355 posts
2721 upvotes
WFH
No, in your case you can't go too big but if your home can't supply enough air for it to run at it's rated capacity you're wasting money buying a larger capacity unit in the first place.

The vent only needs to be insulated when it's outside the heated space.
Newbie
Jan 28, 2015
75 posts
20 upvotes
Concord, ON
Be prepared for ice dams on your roof as the escaping heat melts snow and refreezes regardless of the size. This is my experience. I have max 350 CFM which is plenty. The more CFM the more heat will escape from your electrically heated house. Ouch!
Deal Fanatic
Nov 2, 2005
5355 posts
2721 upvotes
WFH
MellowLite wrote: Be prepared for ice dams on your roof as the escaping heat melts snow and refreezes regardless of the size. This is my experience. I have max 350 CFM which is plenty. The more CFM the more heat will escape from your electrically heated house. Ouch!
That sounds like a bad installation. Adequate insulation on the pipe as it passes through the attic space will not only prevent ice buildup in the vent but also help prevent heat heat buildup in the attic space which may result in the ice dams you descibe.

Of course in a climate like we have it is preferable to vent through the wall if possible.
Newbie
Jan 28, 2015
75 posts
20 upvotes
Concord, ON
dirtmover wrote: That sounds like a bad installation. Adequate insulation on the pipe as it passes through the attic space will not only prevent ice buildup in the vent but also help prevent heat heat buildup in the attic space which may result in the ice dams you descibe.

Of course in a climate like we have it is preferable to vent through the wall if possible.
Hard to follow your logic. Heat melts snow. Insulating means more heat transfer to the outside, melting more snow.
Venting in the attic is insulated to code (R-12) to prevent condensation. Nothing wrong with the installation. Works fine. Ice dams have happened only 3 times in past 19 years. Proper ice shield is installed.
Deal Addict
May 10, 2011
1482 posts
540 upvotes
Ottawa
MellowLite wrote: Hard to follow your logic. Heat melts snow. Insulating means more heat transfer to the outside, melting more snow.
Venting in the attic is insulated to code (R-12) to prevent condensation. Nothing wrong with the installation. Works fine. Ice dams have happened only 3 times in past 19 years. Proper ice shield is installed.
I think he meant that because heat only goes up so if all the heat is escaping from the vent pipe then it won't cause the snow (which is lower than the top of the pipe) to melt.

*Usually* an ice dam happens when heat is escaping from the pipe into the attic instead of going up the vent, either because of poor insulation or a leak.
Deal Fanatic
Nov 2, 2005
5355 posts
2721 upvotes
WFH
csi123 wrote: I think he meant that because heat only goes up so if all the heat is escaping from the vent pipe then it won't cause the snow (which is lower than the top of the pipe) to melt.

*Usually* an ice dam happens when heat is escaping from the pipe into the attic instead of going up the vent, either because of poor insulation or a leak.
Exactly, but I now realise that MellowLite is probably referring to thaw/freeze on the roof around the vent itself. This is exactly why wall venting is preferred in our climate.

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