Why Does My Fireplace Have a Plug?


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Note: This article is about wood-burning fireplace plugs. If you’re looking for information on electric fireplaces or electric cords in your fireplace, you may want to start here or here.

Fireplaces can diminish your home’s efficiency by letting cold air in through the chimney during winter and drawing cool air out in the summer. Preventing chimney drafts helps you make the most out of your fireplace year-round and lower your energy costs. 

Plugs are used to eliminate fireplace drafts and make your home more energy-efficient. Smoke from a burning fire is drawn out of your home through an open chimney. When a fire isn’t going, plugs stop air from flowing through the chimney, keeping your home warmer in winter and cooler in summer.

This article will discuss how plugs are used to optimize comfort and efficiency in homes with fireplaces. I’ll explain a bit about how fireplaces create drafts when not in use and how different types of fireplace plugs work.

Why Plug a Fireplace?

A crackling wood fire in winter feels warm and cozy but, when the fire is out, your fireplace lets in winter drafts and summer heat, taxing your heating and cooling systems and raising your energy bills. 

Understanding some basic elements of wood-burning fireplaces and how they work illustrates how fireplace plugs help control home temperatures and energy costs. 

Fireplace Basics

The basic components of a fireplace system (for our purposes) are:

  • The firebox, which is the area where logs are burned, 
  • The flue (or vent pipe, if the chimney is prefabricated), which runs inside the chimney; and  
  • The chimney, which starts at the top of the firebox and extends above the roof. 

Also, many fireplaces have a damper, which is a metal plate directly above the firebox or at the roof that can be opened and closed to control air exchange between your home and the outdoors through the fireplace. However, some so-called “open” fireplaces do not have dampers; because these fireplaces remain open, indoor and outdoor air flows through them year-round. 

When a wood fire burns, it produces smoke and gases, such as carbon monoxide. Opening the damper (if you have one) before lighting the fire creates a draft up the chimney that draws the smoke and gases up through the flue and out of your home. When the fireplace is not in use, the damper should be closed to prevent drafts; however, many homeowners commonly forget to do so.

Even when the damper is closed, it does not create a very effective seal, which means that some energy continues to be lost through the chimney throughout the year. One study concluded that homes with fireplaces consume over 30% more heating energy than homes without fireplaces. Over time, even a well-sealed damper tends to wear down, meaning the amount of air that enters your home through the damper will increase over time. 

Cold in Winter, Hot in Summer

Whether you have an open fireplace or one with a damper, the upshot is that your heating system works harder in winter to combat drafts entering through the fireplace. The reverse happens in summer when your air conditioning system is running. Negative pressure in the chimney draws hot air down into your home, and your air conditioning system must do extra work to cool the warm air pulled in through the fireplace. 

When your heating and cooling systems have to work harder to maintain comfortable temperatures in your home, you pay more in energy costs.

How Does a Fireplace Plug Work?

Fireplace plugs are designed to solve the problem of energy loss through chimneys. They prevent air from entering or escaping through the chimney by blocking the opening above the firebox and below the damper when the fireplace isn’t in use. 

A fireplace plug can be temporary or permanent. Both types of plugs improve your home’s efficiency by decreasing chimney drafts, making it easier for your heating and cooling systems to maintain consistent temperatures throughout the seasons, and help you save money on energy bills.

If you have a temporary plug, you will need to remove it (and open the damper if you have one) before lighting a fire. A permanent plug is designed to take the fireplace out of service and likely will require some amount of renovation to return it to a functioning state. 

Temporary Fire Plugs – The Sheep in Your Chimney

Temporary fireplace plugs go by a host of names, including chimney sheep, chimney balloons, chimney pillows, and more generically, flue blockers and draft stoppers. They all work by covering the mouth of the chimney and are equally effective for fireplaces with and without dampers. A great feature of temporary fireplace plugs is that you can easily remove them when you want to light a fire and replace them when the fire goes out.

If you see a wooly pad plugging your chimney with a handle or two protruding down into the firebox, you have a chimney sheep. Here’s a link to some chimney sheep in different sizes and shapes on Amazon to see what they look like.

Chimney pillows and balloons are devices that are placed in the chimney and inflated through an air tube until they fill the opening. They are usually held in place with a handle or rod propped against the floor or wall of your firebox. Here are pictures of some chimney pillows made of urethane and plastic.

If there’s a filled garbage bag jammed into your chimney with a cord hanging down, it may be a DIY temporary flue blocker like this one described in the US Department of Energy’s tip sheet on sealing air leaks in your home.

Sheep and DIY plugs can be pulled out with a gentle tug, and chimney balloons and pillows can be deflated through the air hose and then easily removed. 

Permanent Fireplace Plugs

Unlike temporary fireplace plugs, permanent plugs are designed to take your fireplace out of commission. A permanently plugged fireplace is also called a decorative fireplace, and you should not start a fire in it.

How can you tell if your fireplace is permanently plugged? 

If you see foam or other material caulked or sealed around the chimney mouth, or bricks installed in the fireplace opening, likely, your chimney is permanently plugged. The chimney also may have been blocked, sealed, or had components removed at or from the roof. 

Bringing a permanently plugged fireplace back into service requires careful restoration, and how you go about it depends, in part, on how the fireplace was plugged, what condition the chimney is in, and whether it was used as a conduit for other household systems. 

Final Thoughts

Fireplace plugs optimize efficiency when a fireplace is not used by reducing energy costs and maximizing comfort inside the home. 

Before you light a fire in a temporarily plugged fireplace, make sure to remove the plug completely. It’s also a good idea to have your chimney inspected to be sure it is in good working order before using it. 

If your fireplace plug is permanent and you don’t anticipate wanting to use it to light a fire, leaving the plug in place will help your home run more efficiently. You can find several ideas on how to use a decorative fireplace here. To make a permanently plugged fireplace functional again, you will need to rehabilitate the fireplace and ensure that it can operate safely.

Chris Hewitt

Chris is a Texas-based freelance writer who loves the outdoors and working in his garage. When he's not enjoying the Texas sun, he can be found tinkering with all sorts of things in his workshop.

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