Fireplace Glass Door Open or Closed

Can you burn a fire in your fireplace with the glass doors closed? The correct answer is: Yes, for some glass doors and no for others.

This article answers the question in detail and explains why there is so much conflicting information about this topic online.

Overview

Some glass doors are capable of being burned closed, while others are not. This depends on the way the door was constructed, the materials used and the manufacturer’s instructions or warranty. If you read editorial from a website or brand that sells doors that cannot be burned closed, you are obviously going to get contradictory information compared to a brand that can be. The lower end mass produced fireplace doors sold at Home Depot, Lowe's and brands like Pleasant Hearth commonly sold on Amazon, must be burned with the doors open. High end door manufacturers like the ones I sell have doors have some doors that are made specifically to be burned open or closed.

Instructions for Open Doors:

These are generalized instructions that apply to most of the doors that I sell. If you buy glass doors somewhere else, be sure to read the operating instructions and warranty before you make your purchase.

1. If the doors have a bottom draft, you can close the doors when starting a fire and open the bottom draft. This helps start the fire quickly and eliminates the smoke problems that normally occur due to low draft when starting a fire.
2. When the fire gets going well and a good draft is established, you must then open the doors and enjoy your fire. Make sure to add the optional mesh curtains or gate mesh backup door for this purpose when you buy your doors.
3. When the fire starts to die down, you can close the doors and close the bottom draft. Fireplaces tend to smoke the most during this period and closing the doors is a great benefit. It also allows you to leave the damper open and retire for the night without worrying about cold air coming into your home.

Additional Instructions for Closed Doors:

These instructions apply ONLY to glass doors specifically designed to be burned both open and closed. These types of doors may be made with tempered or ceramic glass and the functionality differs depending on which type of glass you choose.

Note: If this is a feature you desire, please let me know during our communications and I will specify doors with this capability.

1. Once the fire is established, keep the bottom damper open and continue burning the fire with the doors close or open, it is your choice.
2. If your doors are allowed to be burned closed and have tempered glass, be careful that the flames stay at least 8" away from the glass and maintain a reasonable fire (no burning Christmas trees or 2x4s).
3. If your doors are allowed to be burned closed and have ceramic glass, you can build a more robust fire and the flames can lick the glass occasionally, but be reasonable because even though the glass may be able to handle the heat, it is still possible to burn or discolor the finish on the door frame (Still, no burning Christmas trees or 2x4s).
4. Emergencies: An added benefit of having doors you can burn closed is the fact that you can close them and close the damper if you have to leave in an emergency, or simply want to go to bed or leave the room and extinguish the fire.

Burning with Doors Closed – Why do it?:

Fireplaces are hugely inefficient and can even operate at a negative efficiency. The heat from the fire creates a strong draft, sucking warm air from your room up the chimney. Less than 10% of that air has anything to do with combustion, it is just sucked out from the draft. This creates a vacuum and all of that air gets replaced by drawing cold air into your home from outside through cracks in windows and doors. You may only feel the heat of the fire if you are right in front of it, or if you are lucky, it may warm the room. But the rest of the house suffers from the cold air coming in, so the rooms further away from the fireplace will be colder when you build a fire. This can create a negative efficiency. Burning fires with the doors closed reduces the draft significantly, so although you get less heat in the room, the rest of your house does not suffer as much and you may get a net positive efficiency.

Only certain doors can be burned closed. Some with tempered glass and others require ceramic glass. Here is the difference between the two:

Tempered vs Ceramic Glass:

Tempered glass can handle sustained temperatures up to about 450F without breaking from heat. If you have doors with tempered glass that can be burned closed, the flames need to stay at least 8” away from the glass, otherwise it can shatter. Ceramic glass can handle temperatures up to about 1450F and can handle flames occasionally touching the glass. If you wish to burn fires with the doors closed, we highly recommend upgrading to ceramic glass, particularly if your fireplace is rather shallow and the grate is less than 8” from the front.

Tempered Glass Can Loose Its Temper!

Tempered glass is made by heating normal glass to roughly 1200F and cooling it rapidly. The rapid cooling changes the physical properties of the glass creating a state of high surface compression and edge tension, which gives it additional strength. Subsequent heating of the glass to high temperatures and allowing it to cool at a normal rate in a room can weaken the glass, or even cause the glass to "loose its temper". Burning a fire with the doors closed may not shatter the glass the first time, but it may be more prone to breakage the more it is done. For this reason, some glass door manufacturers will not allow you to burn fires with the doors closed at all, while others allow you to burned the doors closed, but tell you to build reasonable fires and keep the flames at least 8" from the glass. For safety and insurance purposes, it is best to follow the manufacturers recommendations.

Shop For: Fireplace Doors with Ceramic Glass Here!

Final Note:

All fireplace doors are required to at least have tempered glass, but not all of them are allowed to be burned closed. This depends on what the manufacturer allows in their warranty or operations manual. For example, all doors sold by Home Depot and Lowe’s and most doors sold on Amazon, must be burned with the doors open.