Should you keep your fireplace doors open or closed?
Fireplace doors should always be kept open while a fire is burning. Doors can only be closed if there is no fire burning.
3 Really Good Reasons to NOT Burn a Fire with Your Doors Closed
1) You will shatter your glass doors. Standard tempered glass is made to withstand temperature up to about 450 degrees. Typical fireplaces reach temperatures between 500 and 1200 degrees. Ceramic glass is designed to withstand temperatures up to about 1400 degrees.
2) It is not safe. Masonry fireplaces are all brick or stone which absorb and reflect the heat much better than metal prefab fireplaces. Additionally, prefab zero clearance fireplaces are surrounded by wood which can be a combustible fire hazard, therefore have specific regulations regarding the ventilation of fireplace doors.
3) You lose the fire’s heat. With the doors closed 99% of the heat of your fireplace with go directly up the chimney.
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Ceramic vs. Tempered Glass
99% of the time your fireplace doors should be OPEN when you are burning a fire. In the off chance you have: ceramic glass doors, a masonry fireplace, and do not care about any heat coming into your room – then it is OK to burn a fire with your glass doors closed.
Ceramic glass doors cost 3 to 4 times as much as standard tempered glass, but they are designed to withstand the high heat that fireplaces generate.
Tempered Glass on the other hand is not made to withstand high heat temperatures! This image shows what happens to tempered glass when it gets too hot.
Fireplace Door 101 (The Basics)
Fireplace doors were designed when fireplaces only burned wood and were used to heat a room. The problem is that no one wants to stay up to wait for the fire to burn down so you can close the damper and go to bed. If you close the damper too early you will wake up to the smell of a smokey room. If you go to bed and leave the damper open, it is just like leaving a window open, and lots of cold air would come into the room making your house freezing cold. If you stay up until the fire is totally out, you wake up dead tired.
You may be asking, “If I’m not supposed to burn a fire with the doors closed, why do I see so many pictures of it online?” The reason why is because fireplace door manufacturers photoshop fake fires behind the doors to make them more visually appealing. At Brick-Anew we recognize that these images can be confusing to customers and do our best to avoid using them whenever possible.
Frequently Asked Questions
Does closing the fireplace glass doors keep the fire burning longer?
No – Closing the doors is not going to allow the fire to burn longer because there is plenty of oxygen coming from the open chimney. Shutting the doors does impedes how much oxygen reaches the fire, but it will not increase the life of the fire. Better airflow is another benefit to leaving the doors open and the better the airflow the better the combustion, so your fire should burn hotter and generate more heat if the doors are being used as intended.
Does keeping fireplace glass doors closed heat the room radiantly (as opposed to directly)?
No – tempered glass is not meant to radiate heat. If you want a radiant heat source in your fireplace you need to investigate direct vent fireplaces. They were designed to heat a room radiantly. The have the fire behind a pane of ceramic glass mounted in a specially designed prefab fireplace. Standard bifold doors were not designed to do anything other than prevent cold drafts from coming into your room.
Remember: Fireplace glass doors were originally designed to prevent heat loss from inside your home when the fireplace was not in use. If you left your fireplace doors open while not burning a fire you would notice in just a few short hours a drastic temperature drop because all of the hot air would get sucked up the chimney allowing the cold air to come down the chimney and into your room. Shutting the doors when the fireplace isn’t in use prevents warm air from being sucked out of the room. Closed doors also prevent warm air from being pushed into the room. With the doors shut all that hot air goes right up the chimney.
Direct-vent fireplace with ceramic glass
What about Masonry Fireplaces?
This same question is often asked about masonry fireplaces with tempered glass doors, but the issue is still the same. Tempered glass doors were designed to be opened when the fire is burning, as tempered glass is not made to withstand the high heat of a full fire. The heat can still cause the glass to break, but you do not have the fire hazard you have with a prefab fireplace. Glass doors should only be shut when there are just a few embers burning at the end of the night, and you are ready to head to bed.