Can I Use Fiberglass Insulation Around My Gas Fireplace?

Drafts

• There are several reasons why you might feel cold air coming from your gas fireplace. If you have a gap between the framing of your house and the chimney and vent flues, use 26-gauge sheet metal to close the gap. A damper that doesn’t fit properly, or one that’s missing, will also allow cold drafts. Repair the damper or install a new one. The most common reason why you might feel a draft comes from the gas line. Stuff fiberglass insulation into the hole where the gas line enters the house to prevent the entry of cold air.

Doghouse

• An uninsulated, or poorly insulated doghouse is another reason why you might feel a cold draft. The doghouse is an external structure that is built to house the fireplace. It allows you to install a gas fireplace into the wall of your house without having to give up living space. Sometimes the doghouse is also referred to as the chase area. When the doghouse isn’t insulated properly, chimneys are prone to downdrafting. Fiberglass can be used to insulate the doghouse, but this isn’t usually a job for homeowners. Consult a professional builder or installer.

Clearances

• When installing insulation, you need to adhere to building code requirements regarding clearances. Gas fireplaces can be vented to masonry chimneys or to metal chimneys and use either Class A or Class B vents. Most states have adopted the International Residential Code that requires Class A chimneys to have a 2- to 2 ½-inch clearance to combustibles and Class B chimneys to have a 1-inch clearance. Section R1001.11 of the IRC Code also states that, with the exception of providing fire blocking, you can’t fill the air space, which means no insulation can be installed there.

Zero-clearance

• Gas fireplaces are usually zero-clearance fireplaces, but that doesn’t mean they don’t need any clearance to combustibles. It just means they can be installed in tight places close to combustibles. Steel projections are welded onto the fireplace to ensure proper clearances, and these projections should never be hammered flat to fit the furnace into a smaller space.