How to close an unused chimney

Home> Home Improvement> How to Seal an Unused Fireplace and Save Money on Heating Bills

If you have one or more brick fireplaces in your home, you can save a lot of money on your heating bills by sealing them when they are not in use. This article explains why fireplaces are so inefficient, how much money could go into your chimney, and a variety of methods of waterproofing your fireplace.

Masonry chimneys are notoriously inefficient

As radiant heat from the fire pours into your room, there is a feeling of warmth, warmed air, pollutants and gases from the burning fire rising up the chimney and into the atmosphere. The air from your room, already heated at some cost, is lost in the chimney in the chimney. While the fire is burning, heated room air continues to be drawn into the chimney.

When you go to bed at night, if there are any embers left over from the fire, leave the hatch open. This protects you from deadly carbon monoxide, but also allows more heated air to escape into the chimney.

If you forget to close the fireplace when you are not using the fireplace, the loss of heated air will continue. One study estimates that up to 80% of American households accidentally open their smoke flaps after the fire dies down.

Even when the damper is closed, exhaust flaps are inefficient

Even when the chimney flap is closed, there are air leaks at the edges of the flap. Another study estimated that the effective leakage area of ​​closed dampers averaged about 30 square inches - which is a 5.5 '× 5.5' square opening the size that allows for a continuous flow of heated air to the outside.

During the heating season, when the smoke flap is closed, part of your valuable warm, heated air escapes the chimney. The reason for this is the 'chimney' or 'stack' effect. Warm air in your home rises and draws cold air through cracks around windows, doors, vents, and other places. This creates a slight difference in air pressure between the higher and lower zones in your home. There is a 'neutral' pressure zone between the upper and lower pressure zones.

Your fireplace works the same way. The pressure is higher near the top of the chimney, lower near the bottom, and in between is the 'neutral' zone. If your chimney is higher than the top of your house (as it should be) the 'neutral zone' will be higher than the 'neutral zone' in your house. This difference causes an upward draft in the chimney and sucks in warm room air at the edges of the closed smoke flap.

According to the US Department of Energy, sealing and caulking chimneys can reduce air leaks by up to 14% and save up to $ 275 a year for a typical homeowner. If you seal more than one fireplace, you can save even more.

You can find more information about this in a Whitepaper by Mark Tyrol, PE, White Paper - Seal Chimney Seals with Weather Strip to Save Energy .

Conditioned air also escapes your fireplace

Now think about the cooling season. It's hot outside and you turn on your air conditioning. They closed all the windows and doors to make the system work better and save energy.

But there are still air leaks around ducts and cracks around windows. Together with the internal pressure differences, this means that your valuable cooled air escapes at the edges of your smoke flap.

How To Seal You Masonry Chimney

There are a few products you can buy that are specifically designed as fireplace seals. You can (1) buy a device that suits your needs and install it yourself. Or you can (2) make one yourself.

- 1. Buy a chimney sealer

Here are three types of woodburning stoves you can buy on Amazon:

  • (a) a balloon-shaped Balloon, which is available in different sizes, depending on the size of the smoke gas,
  • (b) a rectangular balloon pressing against the damper, and
  • (c) a decorative cover over the chimney opening

Vein Chimney balloon is an inflatable balloon seal. It should be installed directly above the damper or in the bottom of the smoke outlet.

The one shown here is 12 'x 12' and fits many chimney drafts. It is also available in many sizes to fit any type of fireplace opening.

Chimney Balloon 12 'x 12' Inflatable Blocker (Medium Chimney Pillow Get it now

- (b) Another Battic Doors Chimney Draft Stopper, the Large fireplace plug, is a rectangular 38 'x 16' inflatable pillow that is pressed against the damper with an adjustable height post to keep the pillow firmly pressed.

It fits almost every brick fireplace,

Chimney draft stopper (large plug - suitable for most masonry chimneys with flaps up to 38x16 ') Buy Now

- 2. Make your own fireplace damper sealer

If you don't want to buy an inflatable pillow, you can do it yourself.

Look into the opening of the fireplace and note the shape of the opening just below the damper. Your damper seal will be installed there. Measure each side of the opening just below the damper gasket and transfer the measurements to a sample printed on cardboard. Cut out the pattern and lay it down to see if it fits. Make adjustments to your measurements to keep them snug.

  • Foam insulation board. Transfer the final pattern to a piece of foam sheet and cut it out. Press the foam gasket tightly under the damper. You can use steel isolation springs to hold them in place.
  • Plywood and insulating foam gasket . Transfer the pattern to a piece of plywood and cut it out. Lay the foam pipe insulation over the edges of the plywood. The pipe insulation presses against the brick and ensures a good seal. You can also glue rigid foam insulation to the plywood for even more insulation.

- 3. Decorative cover over the chimney opening

If you have a metal chimney screen, however, you can attach a cover that fits with magnets that attach the cover to the metal screen. This one from Amazon offers a fireproof (not fireproof) Pavenex fabric cover .

If you don't have a metal screen, you'll have to improvise.

Or go to Beverly Fireplace Fashion for a bespoke fashion cover for every fireplace type.

Medium Pavenex Fireplace Blanket Stops Heat Loss Overnight, Buy In Black

Cautionary note. . .

Whether you are using a balloon seal or a rigid seal, be careful not to start accidental fires in the closed fireplace. I think it's a good idea to put a little label on the chimney that it's sealed.