Exhaust Vent Pipes In Attic Should Be Insulated And Vented

It really is a design choice.

Exhaust vent pipes in attic should be insulated and vented.

Fiberglass insulation cannot just butt up to the vent pipe touching it. Intake vents located at the lowest part of the roof under the eaves allow cool air to enter the attic. Duct already wrapped in insulation at home centers. So the decision to vent an attic space is not dictated by building code.

Of course all penetrations where drainage or vent pipe goes through walls especially into attic should be sealed around the pipe to prevent infiltration. You should never exhaust the bathroom fan directly into the attic. If this pipe is not insulated the heat carried in the air transferred to the pipe will cause condensation and potentially cause water damage at your ceiling or in your attic. A cold duct allows condensation of moist indoor air leading to drips from the exhaust fan.

In our neck of the woods vermont it is required by code to protect the vent stack from freezing. Just as is the case with insulation in other parts of your home you should regularly inspect and maintain the insulation on your duct work. Ventilating attic spaces is often viewed as a technical requirement for steep slope roof assemblies as well as a building code requirement. No you cannot vent your bathroom exhaust fan into the attic.

Although this isn t always possible in attic crawl spaces you should always insulate the duct to prevent condensation problems. The reason exhaust pipes are insulated in unconditioned spaces your attic is because they carry warm and moist air from your home to outside. Our photo above shows a long routing of bath vent fan ducts across an attic floor to an exit at the building soffit or eaves and the condensation of moisture in such vent lines. The best exhaust fan venting is through smooth rigid ducts with taped joints and screwed to a special vent hood.

We insulate the bath vent ductwork to minimize the condensation that will otherwise occur as warm moist bathroom exhaust air passes through cool ductwork in the building attic or roof cavity. However since the 2009 edition of the irc attics can be designed to be either vented or unvented. Although fiberglass may not burn it can melt contribute to a fire and the speed at which it spreads. The solution properly insulate the vent ducts.

Horizontal runs are covered with insulation bats in the attic usually. Hot air exhaust vents located at the peak of the roof allow hot air to escape. Now that you have safely sealed the air leaks around the furnace exhaust you can work on insulating your attic space. Otherwise the exhaust duct gets too cold when it runs through the attic.

Insulating around a furnace exhaust pipe. Your attic is not a temperature controlled environment is never the same temperature as your living space and generally closer to the temperature outside.