Can You Burn A Fire with Fireplace Doors Closed?
Answer: Yes, you can burn a fire with the doors closed if you buy doors that are made for that purpose. Doing so can dramatically improve the efficiency of your fireplace and help your wood burn much longer. But not all glass doors can be burned closed. This article provides a definitive answer and explains why you find contradictory information about the topic online.
Fireplace Doors Closed
Shown Above: Design Specialties Legend Arch Fireplace Glass Door Burning a Fire With The Doors Closed. This is approved by the manufacturer.
This question has raised some controversy and you will find conflicting answers depending on where you land with your search on the topic. One answer that Google mistakenly promotes says this: "Closing your fireplace doors doesn't make your fire burn longer. Allowing your fireplace doors to remain open will promote better airflow. Oxygen is a key element in healthy-burning fires. If your fireplace doors are shut, oxygen cannot reach the flames". That's a very misleading statement because some doors are specifically designed with a draft assembly that feeds air to the fire when the doors are closed. More about this later.
The truth is, very few fireplace doors are designed to be burned with the doors closed, so most places that sell fireplace doors will say you cannot burn them with the doors closed. That is more of a brand specific statement than a rule of thumb. All of the fireplace doors sold at home centers like Home Depot and Lowe's must be burned with the doors open. Pleasant Hearth, a popular brand sold on Amazon is one of those brands. On the other hand, our main brand Design Specialties makes doors that CAN be burned with the doors closed. They even have a lifetime warranty on the glass.
One online retailer even goes so far as to use this video from Inside Edition that shows how "Kelly Ripa and Mark Consuelos ended their Saturday with a bang, as their fireplace exploded while the family was relaxing in front of the fire". Ironically, what shattered in the video is not a fireplace door at all, but a free standing glass screen meant for gas logs (more about that below).
When someone selling fireplace doors says you cannot burn a fire with glass doors closed they are likely telling you the truth about the doors they sell, but not about glass doors in general. So below are some of the differences between doors that can be burned closed and those that cannot.
The thickness of the glass makes a difference when it comes to the amount of heat it can handle without shattering. Cheaper doors have weaker glass that is 1/8" to 3/16" thick glass, so it will shatter from the heat. Design Specialties uses 1/4" thick fully tempered safety glass.
The size of each glass panel in a door should not be more than 4 square feet per pane. This combined with 1/4" thickness is an important in order for the glass to handle the heat with the doors closed. If you watched the video mentioned above, the glass screen that shattered was is a single pane of glass roughly 40 x 30, which is over 8 square feet. It's no surprise a piece of glass that large would explode when set right in front of a hot fire. A properly designed glass door would have had 4 panes of glass closer to 1.75 square feet each, which is about 4.5 times smaller than the glass that shattered in the video.
Design Specialties has the option of having a draft assembly at the bottom of the door. This can be opened or closed to allow fresh room air into the fire from the bottom, where it is most efficient. Not only does this give your fire the proper amount of oxygen for good combustion, it makes your fire burn much longer. It also allows the excess air from the draft created by the fire to help cool the glass to a moderate temperature relative to the fire.
Fireplace Doors Closed
Shown Above: Design Specialties Savannah Aluminum Glass Door in Rustic Black with Clear Glass Shown With Doors Closed While Fire is Burning. Notice the draft assembly at the bottom which allows plenty of air in to support the fire.
The 1/4" thick fully tempered safety glass used by Design Specialties can handle intermittent temperatures around 750 degrees and constant temperatures around 450 degrees. As long as the fire is at least 6" away from the glass (as recommended) and the draft assembly is used properly, the glass will stay safely well below these temperatures.
If you are completely paranoid about the glass breaking even with the above things in place, you can always use ceramic glass instead of tempered glass. However, ceramic glass comes with it's own issues. For starters, it is a $1200.00 upgrade. Even more, because it is so expensive, Design Specialties does not have a warranty on it, so you buy it at your own risk. With that said, we rarely ever sell a glass door with ceramic glass.
How the glass is held into the fireplace door frame is also very important. If you want a door that can be burned closed, it needs to be designed to allow the glass to expand. Doors not designed for closure might have the glass set directly in a metal frame. Doors that can be closed will usually have high temperature silicone around the glass or some other method to hold the glass snugly in place yet allow it to expand and contract.
Mesh Curtains or Gate Mesh
All Design Specialties doors have the option of having sliding mesh curtains or gate mesh backup doors behind the glass. These not only allow you to burn the fire with the doors open, but also absorb and reflect some of the heat and help protect the glass from popping embers.
Heat Resistant Finishes
Door manufacturers that do not allow you to burn with the doors closed may use less expensive finishes on their door frames. If you close the doors, the heat builds up and can cause the finish to burn or discolor regardless of what happens to the glass. Design Specialties assumes you will burn a fire with the door closed, so the finishes they apply are much more costly, but can handle the heat. Their most popular powder coat finishes are actually baked on at very high temperatures, so they know they can withstand the heat.
Obviously glass can break, so it is important to know what precautions to take to prevent that from happening. It's pretty simple: If you build a reasonable fire and keep it least 6" away from the glass, you should never have any issues closing the doors made by Design Specialties. If you want a raging fire, don't close the doors...as a matter of fact, fireplaces are not built to handle a raging fire, so if you really want a raging fire, you are better off doing that outside your home. If a log rolls off the grate and sits against the glass, it can cause it to break, so pay attention to your fire and you can keep the doors closed all you want.
Why burn a fire with the doors closed?
Fireplaces are notoriously inefficient because they suck warm air air up the chimney and replace it with cold air from outside your home through cracks in the doors and windows. As much as 90% of the air that goes into your fireplace has nothing to do with combustion, it is just pulled up the chimney because of the draft. This can cause a net heat loss in your home with the fire sucking in more cold air than it replaces with heat. When sitting in front of a fire, it is not unusual for your face may be warm while you feel cold draft on your neck as the fire draws cold air in from other rooms behind you. So essentially, you may warm one room while you cool off the rest of your house.
Burning a fire with the doors closed dramatically reduces the draft and creates a more efficient air to fuel mix. You will find that your fires burn longer and you still get warmth from the fire since radiant heat goes right through the glass. The glass doors do block the hot air from coming into the room, but for the most part, the air heated from a fire is going up the chimney and not into the room anyways. So although you may not feel as much direct heat to your face, the overall efficiency of the fireplace can be dramatically improved and your home may actually experience a net heat gain.
The bottom line is, if you are considering adding glass doors to your fireplace, be sure you check the owner's manual or consult with a professional to see if the model you are considering can be burned with the doors closed.