Fireplace Glass Doors

Does A Wood Burning Fireplace Need Glass Doors?

In Wood Burning Fireplaces by James O'KellyLeave a Comment

Many traditional wood burning fireplaces can be found with or without doors on the front of the fireplace opening.

I have two open wood burning fireplaces in my home, and neither of them have glass doors. I’ve recently been looking into whether a fireplace needs doors, and so does a wood burning fireplace need glass doors?

Many wood burning fireplaces can work effectively without glass doors. Studies have shown that glass doors on a fireplace can significantly reduce the heat radiated out into the room from a fire, but also providing heat savings for a home when the fireplace isn’t in use.

I’ve discussed in more detail below whether a wood burning fireplace needs glass doors, whether they help, and the other purposes of having glass doors on a fireplace.

Do You Need Glass Doors For A Fireplaces?

Up to 80% of the heat generated by a fire in a wood burning fireplace can be lost up the chimney, rather than being used to heat a room.

Appliances such as wood burning stoves help to solve this problem by providing a sealed environment for the wood to burn, and helping to increase efficiencies up to 80%, rather than the 20% efficiency typically seen for wood burning fireplaces.

Depending on the size, layout and the design of the both the fireplace and chimney, glass doors may or may not have a positive impact on heat output during a fire.

A wood burning fireplace typically provides more heat to anything near the fire, but can suck vast amounts of air from all rooms in a home up the chimney. As a result, this may cause a net loss of heat in a home.

Having glass doors on a fireplace can help reduce the amount of air being lost up a chimney when closed, assuming that the doors incorporate closeable air vents on the surround, and therefore helping to prevent warm air from leaving a home.

On the other hand, glass fireplace doors may inhibit the airflow to a fire to such a point that the fire keeps going out. A poorly burning fire also produces more smoke, which in turn can significantly increase the build up of creosote in the chimney and requires it to be swept more often.

Glass doors can also blacken over time and reduce visibility to the fire.

We have wood burning fireplaces located in our living room and kitchen, and neither of the fireplaces have doors on them. We also don’t believe that the fireplaces have ever had doors on them. Although our fireplaces don’t have glass doors, we’ve never had any problems when having a fire in them.

Do Glass Fireplace Doors Help?

Depending on the circumstances, glass fireplace doors may or may not help to produce more heat from a wood burning fireplace, and so do glass doors make a fireplace more efficient?

Glass fireplace doors can be more helpful in older properties where there are likely to be more drafts. In an older house with more drafts, warm air can be lost up the chimney and replaced by colder air from the outside, therefore effectively making the house colder by having a fire. In such situations, glass fireplace doors can help prevent a loss of warm air from the house both when having a fire and when the fireplace isn’t in use.

On the other hand, studies have shown that glass doors on a fireplace can also reduce the amount of heat that is radiated from the fire into the room.

A study by Warren, D. J. titled ‘Energy Efficient Masonry Fireplace. Design and Performance Evaluation’ concluded that:

‘Glass doors were found to reduce the amount of sensible heat lost in the flue gases but at the same time they drastically reduced the radiant energy emitted by the fireplace.’

Warren, D.J.

Another study by the Georgia Institute of Technology found that during a project titled ‘Circulating Fireplace Combustion Efficiency Studies’:

‘The loss of radiation heat transfer to the room when the glass doors on the fireplace are closed is significant and the overall efficiency is reduced.’

Georgia Institute of Technology

Furthermore, an article published by Osborne and Hansen titled ‘Improving Fireplace Efficiency’, states that:

‘Glass doors do substantially reduce amount of heat radiated from the fire into the living room.

The greatest heat savings with glass enclosures occurs as the closed doors reduce heat loss up the chimney when fireplace is not in use.’

Osborne & Hansen

It can therefore be seen that while glass fireplace doors can help prevent loss of warm air from a home when the fireplace isn’t in use, they can also reduce the amount of heat radiated into a room during a fire.

As every fireplace and chimney combination is different, glass doors may need to be fitted to a specific wood burning fireplace before tests can be done to see whether or not they help reduce heat loss up a chimney, or improve heat output into a room.

What Is the Purpose Of Glass Doors On A Fireplace?

Why do fireplaces have glass doors? The benefits of having glass doors on a wood burning fireplace include:

  • Prevent warm air from the room from being sucked up the chimney.
  • Provide a finished look to the fireplace.
  • Help keep the heat in the house when the fireplace isn’t in use.
  • Help prevent heat loss when a damper can’t be closed for a prolonged period of time after a fire due to ongoing gas emissions from the embers.
  • Help hide the mess within the fireplace after a fire.
  • Provide a great view of the fire behind closed doors.
  • Help improve the safety of having a fire around small children and pets.
  • Prevent hot embers and ash from spitting out into the room.
  • Help the fireplace fit in with décor of the room.
  • Prevent pets from spreading ashes around the room.
  • Replaces the need for a fireplace screen.
  • Helps to lower heating costs.
  • Reduces any problems caused by downdrafts in high winds.
Fireplace Glass Door

Should Wood Burning Fireplace Glass Doors Be Open Or Closed?

It’s recommended that glass doors on a wood burning fireplace are left open during a fire.

Doors on a fireplace that use tempered glass are more susceptible to shatter due to high temperatures from a fire, and so it’s recommended to always keep fireplace doors open when having a fire.

The U.S. Fire Administration (USFA) states that:

‘If your fireplace has glass doors, leave them open while burning a fire.

If the doors are closed, air supply will be restricted, which causes creosote to build up in the chimney.’

U.S. Fire Administration (USFA)

Glass doors on a wood burning fireplace can be closed when the fire has subsided, and should be left closed at all times when the fireplace isn’t in use to prevent heat loss from a home.

Wood Burning Appliance Safety Tips by the City of Columbus states that:

‘Close glass doors when the fire is out to keep air from the chimney opening from getting into the room.’

City of Columbus

Do Fireplace Doors Save Energy?

Having doors on a wood burning fireplace can help save energy by preventing warm air from leaving a home, both during a fire and when the fireplace isn’t being used. Closed fireplace doors can also help prevent air conditional air from being lost from your home during summer months.

Studies have shown that leaving glass doors closed when the fireplace isn’t being used can provide the greatest heat savings. Fireplace dampers typically don’t fully seal, and so doors on a fireplace can help further reduce the loss of air up a chimney when used in conjunction with a damper.

Studies have also shown that glass doors on a wood burning fireplace can significantly reduce the amount of heat radiated into the room by a fire.

It can therefore be argued that glass fireplace doors are more advantageous when a fireplace isn’t being used to save energy, compared to when having a fire.

Do you have glass doors on your fireplace? Do they make a noticeable difference to your heat output during a fire, or help keep your home warm when the fireplace isn’t in use?

Let us know in the comments below.

Further Reading

A Complete Guide To Fireplace Doors

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