Class of Kitchen Over Range Exhaust Through Vented Attic?

cloudd

"Class" of Insulated flex 6" duct for my over range exhaust (standard 30" 5x burner gas stove) venting through attic to the roof.

I have noticed that my rigid duct that goes straight up from the kitchen into the attic and straight up through the roof to the exhaust vent is not insulated. My attic is not climate controlled. I believe that this should be insulated to avoid condensation that forms on the duct in the attic. I would like to fix this problem the proper way so that it is to code.

I would prefer to replace the attic section of the duct with a flexible 6" insulated duct pipe that would be about 5' in length. My 2nd option would be to insulate the already existing rigid 6" duct pipe.

What class of flexible insulated duct pipe would I require for this and do they make them in the required class?

If I was to wrap the exiting duct what is the correct type of insulation wrap that is required by code?

HomerJSmith

My 2nd option would be to insulate the already existing rigid 6" duct pipe

Yes, must be rigid. Wrap it with fibre insulation.

pecmsg

So why does it have to be insulated?

cloudd

HomerJSmith said:

My 2nd option would be to insulate the already existing rigid 6" duct pipe

Yes, must be rigid. Wrap it with fibre insulation.

This is in Canada. The temperature in this area can drop to -9C approx so condensation of the pipe in the attic (basically outside temperature) will happen.

Does the fiber wrap have to have a specific backing on it or no backing? if no backing won't the fiber wrap absorb the condensation/moisture out of the pipe?

What is an example of an expectable product that can be used?

pecmsg

Fiborglass insulation with a vapor barrier. 

mattmia2

Vapor barrier is on the outside(cold/attic side). looking at the model code it says that vents from range hoods need to be smooth so that essentially means it has to be rigid metal pipe. You want metal anyhow to reduce the chance of a fire on the range or in the pipe from spreading to the attic but it doesn't appear to be required in the model code.

PC7060

M1503.Range hoods shall discharge to the out- doors through a single-wall duct. The duct serving the hood shall have a smooth interior surface, shall be air tight and shall be equipped with a backdraft damper. Ducts serving range hoods shall not terminate in an attic or crawl space or areas inside the building.

Henry

cloudd said:

HomerJSmith said:

My 2nd option would be to insulate the already existing rigid 6" duct pipe

Yes, must be rigid. Wrap it with fibre insulation.

This is in Canada. The temperature in this area can drop to -9C approx so condensation of the pipe in the attic (basically outside temperature) will happen.

Does the fiber wrap have to have a specific backing on it or no backing? if no backing won't the fiber wrap absorb the condensation/moisture out of the pipe?

What is an example of an expectable product that can be used?

Canadian building code requires sealed rigid galvanized pipe. Depending on distance to an exterior outlet, insulation may or may not be required. You should check with provincial and local building codes. In my case, I have a Jenn air gas stove which vents directly through the outside wall. No insulation is required. I also have a 650 CFM range hood on the stove going through the outside wall. No insulation is required.