How Cold Weather Affects Your Chimney

According to the Farmer’s Almanac, we can expect that this winter will be cold and snowy here in Colorado. A cold winter means high heating costs. Keeping your wood pile stocked and stoking up a fire in the hearth on chilly nights can help you cut down on heating costs. Chimney problems can throw a wrench in your budget.

Before the temperatures drop dramatically, it’s smart to prepare your chimney for the winter and learn what problems to look out for.

Even though chimneys are built to withstand extreme temperatures, they are still affected by the cold. There are two main ways that cold affects chimneys:

• Breaking Down Bricks and Mortar

Bricks and mortar act like sponges; easily absorbing moisture. In the winter, when the temperatures drop, the moisture inside the masonry expands as the water freezes. When the temperature warms up, it contracts as it thaws. This process breaks down the bricks and mortar causing it to crack and chip. The more this happens, the weaker the masonry becomes.

The freezing and thawing process can cause serious and expensive damage. It can also create pathways for carbon monoxide and fire to enter your home increasing the danger of using your fireplace.

Treating the outside of your chimney with waterproof sealant is the best way to protect your chimney from the freezing and thawing cycle.

• Producing the Stack Effect

The “stack effect” is the name of an air pressure problem that can occur during the winter when the air in your home is significantly warmer than the air outside. You might remember learning in school that hot air rises. This is what causes the stack effect.

All the hot, heated air in your home moves upward, increasing the air pressure upstairs and seriously reducing the air pressure downstairs. When this happens, it reverses the airflow in your home. It can suck cold air down the chimney.

Unpleasant blasts of cold air aren’t the only downfalls of the stack effect. This air pressure problem can also make it more risky to light a fire in your fireplace. When airflow is reversed by the stack effect, carbon monoxide and smoke from the fire may be pushed down the chimney into your home instead of venting outside.

If this happens in your home, cracking open a window can help improve the airflow. Heating up the chimney before lighting a fire can also help. The simplest way to do this is to create a torch out of rolled up newspaper, light it and hold it up in the chimney. You’ll know it is working when you notice the smoke is going straight up. If these solutions do not work, you should contact a chimney expert. It is risky to use your fireplace when it isn’t venting correctly. If your carbon monoxide alarm goes off, you should open all of the nearby window, put out the fire and go outside. Even short exposure to carbon monoxide can damage your health.

The health of your chimney can impact the health of your home. Make sure your chimney is safe to use this winter by preparing it for the freeze-thaw cycle and making sure not to use your fireplace if the airflow if reversed. If problems arise, call on a CSIA-certified chimney professional.