What happens if you leave fireplace damper open?

Author: Dewitt Brekke  |  Last update: Monday, November 24, 2025

Many people are under the impression that opening the damper helps cool the house, because warm air rises and will travel up the true. This is simply not true. Leaving your damper open will actually allow hot outside air to draft in, negating the effects of your air conditioning system.

Is it okay to leave the fireplace damper open?

OPEN OR CLOSED? The damper should be kept closed when there is no fire or coals burning. Warm air from your home will not be lost up the chimney when the fireplace is not being used. Fully open the damper before your start a fire and keep it fully open until all embers and coals have burned out.

How do you put out a fire in a fireplace before bed?

  • 1. Fill a plastic spray bottle with water. Use a medium-size spray bottle as opposed to a cup or bucket to prevent splashing or excessive steam.
  • 2. Spread the firewood and embers in the fireplace with a fire poker.
  • 3. Spray the fire with water using the spray bottle.

What happens if you forget to close the flue?

If the flue is left open after the fire goes out, all the heat generated will escape. Closing the flue will keep the heat inside; you must be careful not to close it too quickly, otherwise you may trap smoke and carbon monoxide in your home. It's best to keep the flue closed when the fireplace is not in use.

Does a fire burn hotter with the damper open or closed?

To create fires that produce more heat, open the damper as wide as possible when lighting a fire. A wide-open damper will increase the amount of air reaching the fire and improve combustion. As a result, the fire will burn hotter.

What happens if the damper is left open on a gas fireplace?

Does closing the damper make the fire last longer?

However, partially closing the damper will reduce the oxygen level in the chimney. This will reduce the burn rate resulting in a longer fire. It will also create a downdraft that will force the heated air back into the fireplace, thus increasing its efficiency.

How to maximize heat from a fireplace?

Evenly distributing small pieces of wood throughout the fireplace will increase air circulation and speed up the burning of the wood. This creates a sustainable fire, but the wood burns faster. Placing large logs closer to the fireplace will keep the fire burning longer between refills, maximizing heat output per log.

How much heat is lost through an open flue?

What's more, between 80 and 90 percent of the heat produced by wood burned in an open fireplace is lost up the chimney. This means that for every $100 you spend on firewood, you get only $10 to $20 worth of heat. The rest goes up the chimney.

What is the difference between a fireplace damper and flue?

The damper and flue are two different parts, but they are related and involved in the same function. The flue is the inside tunnel of your chimney that brings gases from your fireplace out of your home, while the damper closes or opens the access to the flue.

Will leaving the flue open make the house cold?

When you keep your chimney flue open though, you're allowing the hot air to travel into your home. If you're running the AC while the flue is open, then you're forcing your AC to work even harder to keep your home cool.

Is it okay to go to bed with embers in the fireplace?

Leaving embers in the fireplace overnight is not safe. It presents a fire hazard as embers can reignite and cause fires if left unattended. Always extinguish embers completely before going to bed to prevent potential fire risks.

Can you leave a fire burning overnight in fireplace?

In conclusion, we do not recommend leaving a fireplace burning overnight. Wood stoves or fireplaces are safe, as long as safety measures are followed. Leaving a fireplace or stove burning overnight translates into being left on unattended, a practice that is not recommended when we have a fire appliance at home.

How long do ashes stay hot?

Many people do not realize the length of time required for ashes to cool enough for disposal. Even after several days, a pile of ashes can hold enough heat to reignite and start a fire. Four days, or 96 hours, is the minimum recommended cooling period for ashes.

Should damper be fully closed?

The damper to your fireplace must be completely open when a fire is burning. If you close the damper even slightly, you risk allowing smoke and other dangerous contaminants from the combustion process into the house. And remember, the most dangerous by-product of combustion is carbon monoxide.

How long does it take for embers to go out?

How long do embers stay hot? Embers can remain hot for several hours depending on factors like size, type of fuel, and surrounding conditions.

How long does it take for a fire damper to close?

Actuator operated fire dampers are equipped as standard with a thermoelectric fuse, that activates the closing of the damper after the reaching or exceeding the ambient temperature of 72 °C. The actuator power circuit is interrupted and its spring closes the damper blade within 20 seconds.

How much does it cost to replace a fireplace damper?

In general, homeowners can expect to pay between $150 and $500 for a standard chimney damper replacement. One of the most significant factors that affect the cost of chimney damper replacement is the type of damper.

How to know if a damper is open?

For a damper at the top of the chimney, you'll have a chain that controls the device. If you can pull on the chain before it jumps back up, the damper is open. You can also start a small fire as a test. With a top-sealing damper, the smoke will have to move up the flue, so give it enough time to do that.

Can I use my fireplace without a damper?

Whether your fireplace is gas or wood-burning, if it was built with a pre-fabricated insert, then it almost certainly has a damper. And while older wood-burning fireplaces can function safely without a damper (gas fireplaces cannot), a chimney without a damper is just a gaping hole in the roof of your house.

Do fireplaces make a house colder?

In fact, it can be so inefficient that in some cases it actually makes your house colder. Inefficiency is not their only drawback. In addition to the risk of setting the house on fire, the smoke that ends up inside your home can contain harmful chemicals, which is a problem in tightly sealed modern homes.

How do you prevent heat loss in a fireplace?

Keep the fireplace damper closed unless you have a fire burning. It can be easy to forget to close it when the fire has burned out, but keeping the damper open can cause drafts and heat loss in the rest of the house. But be careful, it can also be easy to remember to open it when you start a fire.

Does a fireplace draw heat out of a house?

Wood-burning fireplaces are only able to create a very small amount of heat to begin with, so it's no surprise that they're actually the least efficient type of fireplace when it comes to producing heat. They're also very good at working against themselves by pulling heat right out of your home.

Why can't I feel the heat from my fireplace?

Issues may arise from a variety of factors: creosote build up or other blockages in the chimney flue, insufficient ventilation, or negative air pressure within the home. These factors impact not only the heat of your fires, but also the safe usage of your fireplace system.

Does a fireback really work?

Firebacks also deflect radiated heat back into your home. Instead of contacting the brick firebox and traveling up the chimney flue, heat that touches the fireback makes its way out of the firebox and into the house rather than up the flue.

Should I close the glass doors on my fireplace?

Keeping fireplace doors open results in a more lively fire but can lead to heat loss and safety concerns. Closing fireplace doors improves efficiency, enhances safety, and directs heat into the room. Oxygen is vital for a healthy fire, and closed doors draw air from outside to maintain an efficient burn.

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