Stop Heat Going Up the Chimney: Modern Damper Choices and Safe Practices

Damper condition affects comfort and energy use. Old throat dampers can leak; top-sealing dampers and inflatable flue seals provide better airtightness and weather protection. Always open the damper before lighting, close it only after the chimney cools, use glass doors per manufacturer instructions, and get annual chimney inspections. Maintain smoke and CO detectors and consult a professional for installation.

Why your fireplace damper matters

A working damper keeps warm house air from escaping up the chimney when the fire is out and helps control airflow while a fire burns. Old metal throat dampers can warp or leak, letting cold air, rain and pests into your home. Sealing the flue properly reduces drafts and lowers heating losses.

Common damper types today

Throat (traditional) dampers

These are mounted just above the firebox. When new and well-sealed, they work fine, but age and heat can deform the metal. Inspect and replace worn gaskets to restore a seal.

Top-sealing (top-mount) dampers

Top-sealing dampers sit at the top of the chimney and form an airtight seal at the flue opening. Because they seal against the chimney itself and use modern gaskets, they resist warping and block weather and animals more effectively than old throat dampers.

Inflatable flue seals and flue pillows

Inflatable devices (often called flue pillows or chimney balloons) are inserted into the flue when the fireplace is not in use to block drafts. They are a low-cost, removable option for stopping heat loss when there is no fire.

Practical tips to keep heat in

• Always be sure the damper is fully open before lighting a fire and fully closed once the chimney has cooled and the fire is out. Never close the damper on a burning or smoldering fire.

• Consider a top-sealing damper or a well-fitting throat gasket to improve airtightness over a leaky metal damper.

• Use tight-fitting fireplace glass doors when recommended by the appliance manufacturer. When closed, they reduce warm-air loss; when burning, follow the manufacturer's guidance for door position to maintain safe draft.

• For short-term, low-cost sealing, an inflatable flue pillow or removable foam gasket provides an effective barrier when the fireplace is unused.

Have a qualified chimney sweep inspect and clean the chimney and damper at least once a year. Creosote buildup, damaged flue liners, and stuck dampers are safety hazards and can increase heat loss. Keep working smoke and carbon monoxide detectors on every floor. If you're unsure about installation or compatibility with your fireplace, hire a professional chimney technician.