Chimney Cap Installation
Seven Oaks SC

A top-sealing damper is a cap and a damper in one. A spring-loaded plate sits on top of the flue under the cap and is opened or closed by a cable that runs down to the firebox. When it is closed, it seals the flue at the top, so rain, animals and outside air stay out even when the fireplace is not in use.

Homeowners ask about one for three reasons: the old throat damper above the firebox no longer closes, they feel cold or hot air coming down the chimney, or they want to stop the smell of soot on humid days. A standard screened cap does none of those things; it covers the flue but leaves it open.

A damper cap is only for a fireplace flue. It does not go on a gas furnace or water heater vent, which needs a listed vent cap under 2021 IRC Chapter 24, Fuel Gas. On a gas log fireplace, a damper has to stay open or be blocked open according to the appliance rules, so we look at your setup before recommending one.

A clamp-on cap grips the outside of a clay flue tile. A top-sealing damper usually mounts on the top of the tile with a seal and is held by the cap or a frame. Either way the tile has to be sound. A cracked or loose tile is repaired or the plan changes before anything is mounted.

The cap's screen has to leave enough room for smoke. The 2021 International Residential Code model text in 2021 IRC Chapter 10, Chimneys and Fireplaces describes a spark arrestor screen with an open area at least four times the flue outlet and mesh openings between three-eighths and one-half inch, removable for cleaning. That last point matters with a damper cap too, because the sweep needs to get past it.

In Seven Oaks the biggest cost difference is between a standard screened cap and a top-sealing damper cap, which has more parts and a cable that runs to the firebox. The flue size, the condition of the clay tile, and the material also change the quote. If the tile is cracked or loose, that has to be addressed before anything is mounted. We quote after measuring.