The short answer
Check the Damper Seal
The damper is the metal plate inside the flue that blocks airflow when closed. Over time, it can warp, rust, or collect soot, leaving gaps that let cold air pour into your living room. Open the damper and inspect the edges for daylight or feel for drafts with your hand.
If the seal looks worn, a local chimney professional can replace the damper or add a new gasket. For a quick fix, you can temporarily stuff a rolled-up towel or a chimney balloon above the damper, but remove it before lighting a fire. A tight seal stops most cold air and also keeps warm air from escaping.
If you notice water stains or a musty smell near the fireplace, moisture may be entering through the chimney. That dampness can lead to wood damage and mold in the walls, so address it early.
- Inspect the damper for gaps or rust
- Close the damper when the fireplace is unused
- Use a chimney balloon for a temporary seal
- Replace a worn damper or gasket
- Look for water stains or musty odors
- Keep the flue dry to avoid moisture issues
Install a Chimney Cap
A chimney cap sits on top of the flue and blocks rain, snow, and animals while still letting smoke escape. Without a cap, cold air can drop straight down the chimney, and in wet winters, rain can soak the flue liner. That moisture can freeze and crack masonry over time.
Installing a stainless steel cap is a straightforward job for a roofer or a chimney professional. It also prevents birds and leaves from blocking the flue, which reduces draft and keeps cold air out. A cap with a damper on top, called a top-sealing damper, gives you an even tighter seal at the top of the chimney.
If water has already gotten into your walls or ceiling, you may need to dry the area and repair any damage. Check for peeling paint or soft drywall near the fireplace.
Add a Glass Door
Glass fireplace doors create a barrier between the room and the firebox, cutting down on cold air that sneaks past the damper. They also improve energy efficiency and reduce drafts when the fireplace is not in use. Look for doors with a tight-fitting frame and tempered glass.
Installation is usually simple, but you need to measure the opening accurately. A local pro can fit the doors and make sure they seal properly. Keep the glass clean so you can see the fire, and close the doors whenever the fireplace is idle.
If you have a wood-burning fireplace, always open the damper before lighting a fire, even with glass doors. This prevents smoke from backing up into the room.
Seal Gaps Around the Firebox
Cold air can also enter through gaps between the firebox, the surrounding brick, and the wall framing. Use a high-temperature silicone caulk to seal these cracks, but only when the fireplace is completely cool. This stops drafts without affecting the fire's ventilation.
Check the area around the fireplace mantel and the hearth for any openings. If you see light coming through, seal it. For larger gaps, a chimney professional can apply refractory mortar. This also helps keep warm air from leaking out, reducing your heating costs.
If you suspect water has damaged the wall or floor around the fireplace, a water damage inspection can identify hidden moisture. Address any leaks before sealing, as trapping moisture can cause mold.
Use a Fireplace Plug
A fireplace plug is an inflatable or foam insert that you place inside the flue below the damper. It creates a tight seal that blocks cold air and prevents heat loss. It is easy to remove when you want to use the fireplace, making it a flexible option for seasonal use.
Measure your flue size before buying a plug, as they come in different dimensions. Follow the manufacturer's instructions to install it securely. Always remove the plug before lighting a fire, as it can melt or block smoke.
For a more permanent solution, consider a top-sealing damper, which replaces the old damper and seals at the top of the chimney. This reduces cold air and also keeps rain and debris out.
Talk to someone now
Phones are answered 24/7 for Redmond and nearby communities.
Call Now (425) 407-5186Frequently asked questions
Why does cold air come down my chimney even with the damper closed?
The damper may not seal completely due to rust, warping, or soot buildup. Cold air can also enter through gaps around the firebox or if the chimney lacks a cap. Inspect the damper for gaps and consider a chimney cap or top-sealing damper to improve the seal.
Is it safe to use a chimney balloon to block cold air?
Yes, but only when the fireplace is not in use. A chimney balloon is an inflatable plug that seals the flue. Always remove it before lighting a fire, as it can melt or block smoke. Check the balloon regularly for leaks and follow the manufacturer's instructions.
Can cold air from the fireplace cause water damage?
Cold air itself does not cause water damage, but a damp chimney can. In wet climates, rain can enter an uncapped flue, soaking the masonry and leading to leaks in the walls or ceiling. If you see water stains or musty odors, address the moisture quickly to prevent mold.