Home>Discussions>INSULATION & HVAC>Installing Range Vent and Bathroom Vents
5 posts / 0 new
Last post
maurices5000
Installing Range Vent and Bathroom Vents

I have a gas stove and I'm insalling a Range vent hood. The handiman who is installing the hood is adding a flexible vent through the roof. Is the roof the best or only exit for the range?

I read that is it best not to use flexible ventilation but to use metal. Does it really make a difference? Is there some other material that i can use that is in between.

I'm also venting my bathrooms. I'm thinking about venting them through the soffits. I hear that i should limit my roof penetrations. Except for the vent fan which pushes the air out, i don't see my moist air would run through the soffits since hot air naturally rises.

Thanks!

mike_g
Re: Installing Range Vent and Bathroom Vents

1)When running duct, use the staightest path possible as every bend adds static pressure, lowering the CFM (air movement). 2)you can use flexible metal duct. 3)Ducting out the eve is common, it vents fine because the air is being firced out, not relying on natural convection (when ducting a bath fan, insulated duct works best, because is does not allow the air to cool which allows the moisture to condense)

maurices5000
Re: Installing Range Vent and Bathroom Vents

Thanks Mike. the the roof the preferred exit for the stove vent?

Sombreuil_mongrel
Re: Installing Range Vent and Bathroom Vents

Hi,
Don't use flex for range vents; all of those ridges catch grease = fire hazard.
Use the recommended size ducting in galvanized. If you live in a cold clime, a thermal break at the outside wall is a good idea, it prevents the cold from conducting through the duct and minimizes a cold-plunge convection current. That's when a cold draft is emitted from your vent hood even though the outside damper appears closed.
Bath vent ducts can also benefit from a thermal break, or insulation. A hint if you don't have either- start the fan before the shower is running, so drier room air warms the metal, preventing most condensation. Having more CFM's is also helpful, as more air flow/turbulence removes some of the conditions needed for condensation.
S_M

canuk
Re: Installing Range Vent and Bathroom Vents
mike_g wrote:

1)When running duct, use the staightest path possible as every bend adds static pressure, lowering the CFM (air movement). 2)you can use flexible metal duct. 3)Ducting out the eve is common, it vents fine because the air is being firced out, not relying on natural convection (when ducting a bath fan, insulated duct works best, because is does not allow the air to cool which allows the moisture to condense)

I have to disagree with exhausting out the eves.
Regardless how much you might think the warm moist air is being exhausted out some of that moist air will end up in the attic through soffit vents ---- bad idea.

If you need to use the roof --- but --- you may have issues with moisture running back down --- if you can go out the gable end or a wall that would be best.
Besides , the more penetrations in the roof the more chance of leaks.

Sombreuil_mongrel wrote:

Hi,
Don't use flex for range vents; all of those ridges catch grease = fire hazard.
Use the recommended size ducting in galvanized. If you live in a cold clime, a thermal break at the outside wall is a good idea, it prevents the cold from conducting through the duct and minimizes a cold-plunge convection current. That's when a cold draft is emitted from your vent hood even though the outside damper appears closed.
Bath vent ducts can also benefit from a thermal break, or insulation. A hint if you don't have either- start the fan before the shower is running, so drier room air warms the metal, preventing most condensation. Having more CFM's is also helpful, as more air flow/turbulence removes some of the conditions needed for condensation.
S_M

I agree with not using the flex ( even if it's metal ) as any inspector around here would make you tear it out for the reasom S_M mentioned = fire hazard.

Use the galvinized rigid metal ducting and insulated for both the kitchen and bath fans.

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.