QUESTION: What is the reasoning behind the caps on the top of brick chimneys? I understand that some caps control wind, but are there other purposes for them?
ANSWER: As you suspected, chimney caps can play a role in wind deflection. They do this by blocking direct wind access to the chimney and prevent smoke from being blown back down your chimney into your home. This is referred to as back drafting.
These caps are designed to keep out the rain, snow and debris. Some caps have screens in their design. These screens or spark arresters keep burning material from escaping the chimney onto the roof. The screens also keep out animals and smaller debris.
Who needs chimney caps? Well--from the safety standpoint--caps with spark arresters are a smart investment for everyone. If you have back-drafting problems, then a cap would also be a logical purchase.
All new chimney construction uses caps, but a cap may not be absolutely necessary for your chimney. You should weigh the benefits against the costs and decide for yourself.
Cap design: If you are unsure if you have a cap, take a look outside. On masonry chimneys a heavy flat plate of steel, stone, or concrete is often used for a cap and more stylish ceramic caps are also available.
These chimney caps potentially make chimney cleaning difficult. A large selection of light metal chimney caps fabricated from galvanized or stainless steel are available for masonry chimneys. These are readily attached or removed for cleaning.
Remember that creosote constantly accumulates in your chimney and needs to be periodically cleaned out. Chimneys with more than one-quarter inch buildup of creosote should be cleaned.
If you are thinking of cleaning it yourself, make sure you understand all parts and necessary tools to do the job. If you are unsure of the chimney’s state and especially if your chimney is 30 years old--invest a little bit of money to have the chimney professionally inspected.
Older chimneys may need a cleaning and possible repairs. In time, mortar cracks and crumbles, leading to possible chimney and house fires. Contact a certified chimney sweep. They’ll give you a full report on the chimney’s condition and explain any needed cleaning or repairs.
Produced by the Energy Extension Service, a division of the Washington State Energy Office.