Insulation Around Flue Pipe

You worry for good reason.

Insulation around flue pipe.

I have a fireplace insert in my basement. I don t know about a dryer vent but for most heaters and woodstoves it is not allowed. Air traveling over the surface of the flue pipe may be required to keep it safe and cool. Available in 24 lengths.

The gas furnace was in a garage and the flue pipe went up through the above attic. As such it can be used to insulate a chimney. Unless the manufacturer says you can pack insulation around the pipe don t. The opening around a furnace or water heater flue or chimney can be a major source of warm air moving in the attic.

Fiberglass insulation is naturally fire resistant. You should never have insulation in contact with a wood stove flue pipe. I was thinking of doing some better framing around it and maybe use rigid foam insulation but i read that building code requires a 2 gap around. Cut enough aluminum flashing from the roll to wrap around the vent pipe with an extra 6 inches to spare.

The pipe comes out of the wall into the garage and up to the roof. Rigid insulation increases the outside diameter of the liner pipe by 1 75. Because the pipe gets hot building codes usually require 1 inch of clearance from metal flues 2 inches from masonry chimneys to any combustible material including insulation. Always use fire resistant caulking.

I have added a picture. Compress the insulation around the rigid liner by hand until the two edges snap and lock together. At least you can keep air from flowing around the pipe. Probably a less heat loss than a window.

Now you must form an insulation dam to prevent insulation from contacting the flue pipe. This makes it an ideal insulation material for use in areas that experience high temperatures. In this case the b vent was also dented on the side so i know the airspace around the double wall pipe was compromised. It is often installed in gaps around the chimney and flue to prevent airflow that can siphon the heat away from the interior of the building.

I wouldn t worry much about not having a square foot of insulation here and there. I am reinsulating this wall and i need some advise on how to insulate this. Remove the insulation between the joists where the flue is located to clear an area about 18 inches away from the flue on each side. Apply a thick bead of high temperature caulk the flue on one side.

Do not use spray foam for any of the joints near a vent pipe. It had about a 5 rise from the furnace to the charred area in the attic.