A chimney cover is a cap that is installed above the crown of a chimney. A chimney cover prevents water, ice and snow from entering a home through the opening at the top of the chimney. Chimney caps can also prevent birds and small animals from entering and settling into a chimney and sparks from being expelled, which can pose a fire hazard. In fact, in some areas that are prone to fire, spark arrestor chimney covers are required on all homes with a chimney.
A chimney is essentially a vertical passage that vents smoke and gas created through combustion to the outside of a building. Chimneys are often constructed of masonry products such as brick, stone or concrete or metal. While many people commonly associate chimneys with fireplaces, chimneys are also often connected to appliances such as wood-burning stoves or furnaces.
Most chimney covers are constructed from stainless steel, galvanized metal or copper. In its simplest form, a chimney cover essentially sits either over the flue or over the top of the chimney. The top part of the chimney cover is typically a solid sheet of metal that blocks the elements, while the sides consist of a metal screen that allow smoke and gas to exit.
Chimney covers are made for both masonry and metal chimneys. Many chimney professionals agree that metal chimneys require chimney caps. The design and make-up of a metal chimney virtually assures that water, snow and ice can flow directly into an uncovered chimney, possibly causing damage. In addition, some metal chimneys utilize a multi-layered design which can be vulnerable to water intrusion between the layers when uncovered, causing premature damage and failure of the chimney.
It should be noted that a chimney cap can alter the effectiveness of a masonry chimney. The cap can reduce the ability of the chimney to draw smoke and gases up and out of a building. However, many experts believe that selecting the right chimney cover for a specific chimney can reduce the potential disadvantages.
There are several categories of chimney covers to fit the different sizes, shapes and styles of chimneys. For chimneys with one flue, a cover that is installed over and attached directly to the flue may be used. Some single flue chimney covers are designed for installation inside a flue. These are commonly known as a sleeve-fit chimney cap.
For chimneys with multiple flues, a top mount chimney cover may be used. Instead of covering each individual flue, a top mount chimney cap covers the entire chimney. Top mount chimney covers are typically attached to the chimney or chimney crown directly.
Chimney covers not only protect a chimney and a building from the elements, but can also increase the effectiveness of a chimney and prevent energy loss through a chimney. Specially designed draft increaser chimney covers increase a chimney’s ability to create the draft necessary to thoroughly vent all smoke and gas created by a fire. Chimney dampers increase the energy efficiency of a chimney by reducing the amount of interior air that can escape through a chimney and reducing the amount of exterior air that could enter through a chimney.