The Purpose and Function of a Chimney Cap

When you look at the top of your chimney, you may notice a flue pipe in the center of the chimney. It’s where the smoke and fumes are expelled while the roaring fire in the fireplace is keeping your home toasty. However, just as smoke and fumes exit the flue, water, snow, and other debris can also get inside and cause costly damage to the chimney. Installing a chimney cap can protect your flue and chimney, but not all chimney caps are the same. Here’s what homeowners need to know when buying or replacing a chimney cap.

Inhibits moisture intrusion

Moisture that gets in the chimney can have a devastating impact accelerating its deterioration resulting in costly damages to the masonry, flue liner, and other components. It can also affect its structural integrity causing it to lean or even collapse. A chimney cap is a device designed to push moisture away from the chimney keeping the flue dry when it’s raining or snowing.

Prevents flue obstructions

The top of the chimney is often the highest point of your home, and without a chimney cap, leaves from nearby trees and other debris can blow in from the wind. It can also be an inviting place for small birds, raccoons, squirrels, and other small animals seeking shelter from predators. These uninvited guests and foreign objects can obstruct the flue opening blocking the venting of smoke and fumes when you’re using the fireplace. With nowhere else to go, dangerous toxic fumes can be pushed back into your living space, increasing the risk of carbon monoxide poisoning.

Reduces downdrafts

Would you heat your house with the windows wide open? That’s the effect of an uncapped chimney. On those windy wintry days, a burst of strong winds can cause a sudden chilly downdraft that cools down the flue making your fireplace less efficient. If the winds are strong enough, it can even blow smoke, soot, and ash into your living space. Installing a full-width chimney cap that covers the entire flue and chimney crown will minimize downdrafts.

Guards against roof fires

The temperature inside a wood-burning fireplace can reach over 1100°F. The high heat combined with combustion gases can cause hot embers to splinter and fly out the flue and onto the roof, potentially igniting a fire. When purchasing a chimney cap, ensure that it contains a spark arrestor. It will stop any hot embers in the flue from sparking a fire.

Full-Width Chimney Cap

There are essentially two types of chimney caps: a flue top chimney cap and an outside mount chimney cap. Since a flue top cap just covers the flue opening, an outside mount cap is a better option. An outside mount chimney cap covers the entire width of your chimney, including the chimney crown, which is a common source for water leaks. Not only is it more aesthetically pleasing, but it also protects the cement crown reducing the risk of water damage.