Choosing the Right Size Chimney Cap

The last thing to consider is the size of your chimney cap.

You will either need to take measurements of your chimney on the roof, or hire a contractor to do it for you. If you do it yourself, be sure to bring a pencil, paper and tape measure (or yardstick) with you and take very careful measurements. You should use a metal square to be certain that you are measuring using true 90 degree corners.

For flues that extend beyond the chimney crown more that an inch and are square or rectangular, be sure to measure both the length and width of the flue. Measure the outside diameter of a round clay flue.

When you have multiple flues, or a single flue that does not extend more than one inch above the crown, you will need to take measurements of all the areas you want your chimney cap to cover. It is best to start with the longest side and then move clockwise, being sure to measure each side of the flue or flues. Make sure you are using 90 degree corners and properly recording your measurements.

For top mount chimney caps you need to remember that you want at least five inches of clearance between the top of your chimney cap and the top of the flue. This measurement between the top of the chimney crown and five inches above the tallest flue is called the screen height.

You will now need to decide if you want a simple chimney cap, or a damper chimney cap combination. If you decide that you require a damper, we recommend that you purchase a Lyemance brand. A Lyemance can provide you will up to 90 percent energy savings when compared with other damper brands, and come with a chimney cap combination.