What is a chimney plug?

Author: Lilliana Wehner  |  Last update: Tuesday, June 16, 2026

It's called the Fireplace Plug. You can kind of think of it as a plastic inflatable pillow for your chimney. Now, to install it, all you do is partially inflate it with that breathing tube and then slip it up in the top of the fire box. Now I'll just finish inflating this.

Should I plug my chimney?

Sealing a Chimney Causes More Problems Than it Solves.

Sealing off a fireplace and chimney always collects water inside the flue. Plain and simple, DO NOT seal off a chimney or fireplace because you will get a flue full of condensation problems!

How to plug a chimney when not in use?

What most people seem to do in this situation is install a chimney plug or balloon. The balloon is inserted into your chimney and then you blow it up until it fits snugly in the space thereby blocking the air flow. Chimney balloons with good reviews run up to $70 each on Amazon. Here's what one looks like:

How to stop chimney backdraft?

Try opening a window near the fireplace to increase airflow into the home before opening the fireplace door. The area will be exposed to more air, allowing for less to be immediately taken through the chimney. Also, consider using a fan or turning on exhaust fans to troubleshoot this problem.

How do you stop drafts from coming through your chimney?

You could go for an inflatable draught excluder, which will fit snugly inside your chimney. Just make sure that it has a small vent, so air can pass through. Or you might prefer a draught excluder made for the specific size of your chimney.

Flueblocker Chimney Plug | Energy Saving Product Guide

What causes a chimney to backdraft?

If there is an obstruction in the venting that interrupts the airflow, negative pressure builds in the flue, causing a backdraft forcing the smoke and fumes back down into the living space. Negative pressure can occur when there is a flue obstruction or insufficient air is being drawn into the fireplace.

Is it OK to block an unused chimney?

As one of the biggest causes of a draughty home, it can make sense to block a chimney opening, especially for larger unused fireplaces. Fixing a draughty chimney not only makes your home more comfortable, it helps to lower energy costs too.

How to plug a chimney hole?

Cut a piece of sheet metal in a rectangular shape slightly narrower than the hole diameter and a few inches taller than the hole. Put a long skinny bolt in the center to use as a handle. Insert the metal and move it until it is flush against the back blocking the hole.

Why do old houses have chimneys but no fireplace?

Chimneys and fireplaces were typical in house buildings before the 1900s because the fire was the primary method to heat homes. Once alternative fuels came into vogue, such as gas and electricity, people no longer relied on their fireplaces and either left them as-is for decoration or sealed them up.

How do I know if my chimney needs repointing?

The key signs that a chimney needs repointing include:
  • Discoloured and decayed mortar joints.
  • Flaking mortar.
  • Cracked chimney crown.
  • Spalling brickwork.
  • The last repointing was 30+ years ago.

Are ductless chimneys good or bad?

Conclusion. When it comes to choosing between duct and ductless chimneys, the decision depends on your kitchen setup and cooking habits. If performance and long-term savings matter, go for a ducted chimney. If convenience and ease of installation are your priorities, a ductless chimney is a good bet.

What happens if chimney is blocked?

Dangers of a blocked chimney

Carbon Monoxide Poisoning is also a real danger when blockages prevent harmful gases and toxic fumes from exiting the chimney as they should. When the smoke has nowhere else to go, back puffing occurs. This is when smoke comes back into the home instead of going out of the chimney.

Do chimneys bring in cold air?

Both masonry and zero-clearance fireplaces can bring cold air into a home that is too air-tight and doesn't allow sufficient air flow up the chimney. Compounding the problem is any appliances that push air out of the house such as kitchen vents and other fans.

How do you check if a chimney is working?

Create a small fire using tinder or paper at the fireplace. If the chimney flue is open, smoke will come out of the chimney with no issues. However, if the flue isn't open, the smoke won't go through a closed flue and up the chimney. Instead, it'll force its way into your home, filling the room with smoke.

How to block a chimney hole?

Chimney sealing options
  1. Chimney Cowl. A chimney cowl often resembles a hood and is placed over the chimney hole. ...
  2. Chimney Balloon. A balloon can also be used to seal off the chimney. ...
  3. Chimney Cover Clamp. ...
  4. Damper Clamp. ...
  5. The Permanent Chimney Cover. ...
  6. Metal Mesh Coverage.

What is the hole under the fireplace for?

Ash Clean-Out Door

A closable, non-combustible metal opening, below the fireplace to allow access to the ash pit. The door is often called the “ash dump”and is used to clean out the ashes from the fireplace.

How do you cap a chimney hole?

Slide the cap over the flue or insert into flue depending on design of cap. Leave at least 6 inches of space between top of cap and flue edge. The cap should come with self-tapping screws. Insert screws into holes on cap and tighten with screwdriver.

Do unused chimneys need to be vented?

Yes, chimneys need to breathe, even if they won't be used anymore. The vast majority of problems with chimneys are related to moisture, and that's the issue as regards ventilation. If there is no air flow in the chimney, moisture gets trapped and deterioration of the chimney structure will be accelerated.

How much heat is lost up a chimney?

In fact, you can lose 10 to 20 percent of the warm air from your home through your chimney's damper. Suddenly, your fireplace is increasing, rather than decreasing, your home's heating bills!

How much does it cost to block off a chimney?

Chimney removal costs

A cowl can be used to cap off the chimney, which will allow air to flow in and prevent any moisture from building up. This costs roughly £150. If you want to remove the chimney breast (the part of the chimney in the room) and have the space made up, this can cost between £1,750 - £3,250.

How do I stop cold air from coming through my chimney?

Damper. The fireplace damper is your first line of defense against cold air infiltrating your home when a fire isn't burning. Dampers should close tightly and block all the air above them. If your damper is warped, rusted or otherwise damaged, cold air in the upper flue is going to get past it.

Why does smoke coming out of a chimney always rise up?

Smoke is hotter than air. So, it is also lighter than air. That is why smoke always moves up.

Does weather affect chimney draft?

Masonry chimneys are constructed with porous materials, and the cold and wet winter weather can accelerate its normal deterioration. The cold outside air can also affect the air pressure inside the home and the chimney draft, which can cause a dangerous backdraft.

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