When to Close the Damper on My Fireplace?

What is a Fireplace Damper?

Chimney Sweep Masonry Diagram from Ash AwayA damper is a small mechanism that is built into your fireplace that is designed to seal up the chimney when the fireplace is not being used.  This is done to prevent warm, interior room air from being pulled into the firebox and up the chimney.  The damper is a door of sorts, that when closed, separates the firebox from the chimney.

If a damper is not opened when a fire is built, smoke will back up quickly and fill the room.  Guaranteed!  So, you always want to check to make sure the damper is fully open when a new fire is built.

Open or Closed?

The best way to check for an open damper is to simply look inside at the top of the firebox.  Do this before you get a fire going!  If it’s open, you will be able to see up the chimney.  If it’s offset you might not be able to see all the way up the chimney, but you will be able to see at least part way.  It should be quite obvious if it’s closed.  The chimney will not be visible.

Some dampers are cast iron and operate on a worm gear mechanism.  Some will pivot open and closed by moving a lever forward and backward.  And others might slide on a rod or bar.  Regardless of how they open and close, make sure the damper is fully open before you light the kindling and get a fire established.

A fireplace damper should always be kept open while the fire is burning.  Furthermore, keep the damper open until all the embers are done burning.  Smoke and dangerous carbon monoxide can enter the house. Once the ember bed is completely out, close the damper.  By doing so, the warm air from your living room is not lost by moving into the fireplace and then up and out the chimney.

Every year, WE LOVE FIRE experts get phone calls that go something like this: “Why does my living room cool off so fast and the furnace operates more when I get a fire going?  Shouldn’t the house stay warmer?  My family room feels drafty.”  Odds are, the answer to this question:  the fire and embers have gone out and the damper was left open.  By leaving the damper open, heat is being lost as warm air is being pulled through a hole in your living room (the chimney) all the way up and through the roof.

Pay close attention to the damper position, it’s very important.

Does My Fireplace Have to Have a Damper?

Some, but not all, zero clearance, factory-built fireplaces have dampers.  All masonry fireplaces should have a damper.

Generally speaking, if your fireplace is designed with gasketed, ceramic glass doors, it will not have a damper.  EPA certified fireplaces and stoves are designed with primary air controls that allow specific amounts of air into the firebox for efficient combustion.  In essence, the chimney is always “open” and cannot be closed off with a damper.  The gasketed doors are used to control the burn rate and prevent air leakage and smoke from entering the room.  Insulated or air-cooled chimneys are required with this type of equipment.

If you own an older stove or fireplace, perhaps one with bi-fold doors, there should be a damper that can be opened and closed.  These are not sealed up or gasketed units.  The air control over the burn rate is usually not too precise.  And, efficiencies are not rated, but are very low.

Air Control vs. Damper

Do not confuse the primary air control with the damper.  There are separate and distinct functions for both.  The primary air control will control the burn rate.  That is, how hot or lively the fire grows is determined by the air control.  The damper, again, opens and closes the chimney to create the draft that’s necessary for the smoke to be expelled out.

Dampers in free standing wood stove pipes or connector pipes is old, outdated technology.  They are not recommended with today’s equipment.  Manufacturers design stoves that are easy to operate.  Today, we control the amount of air into the stove, not the amount of air out by placing a restriction or damper in the connector pipe!

What Do I Do? Mine's Broken!

If the original damper for your fireplace is missing or beyond repair, your WE LOVE FIRE expert will likely recommend a lock top sealing damper.   Basically, this type of damper is a spring-loaded cap installed on the top of the chimney.  A cable is installed into the firebox.  When operated, the cable springs the cap up (or down) to open (or close) the chimney.  These are quite effective at thoroughly sealing up the flue and preventing the loss of warm air when the fireplace is not in use.  If yours needs replacing, this is a project that’s probably best left to the professionals.

Remember that your WE LOVE FIRE dealer is a terrific resource and we’re here to help in any way we can.

Below is a list of fireplace and grill stores that service Virginia (VA)

Mechanicsville, VA

Hearth & Home Shoppe
8151 Mechanicsville Tpk
Mechanicsville, VA 23111

Visit Store Page

Roanoke, VA

Dixie Building Products Inc.
3342 Melrose Ave NW
Roanoke, VA 24017

For more information, contact your local fireplace and grill store..

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