Why do I need a chimney cap?
It has been said a chimney without a cap is like a house without a roof. Imagine how much water would come into your home during a rainstorm if you had a hole in your roof twelve inches square. Chimney flues may be even larger than that, so where does all that water go? It runs down the chimney and seeps into the bricks and mortar, settling behind the firebricks in the fireplace. The inside of the chimney stays wet long after the rain stops. This moisture erodes the mortar joints weakens the brick. Add to this a freeze / thaw cycle during the cold months, and you have all the needed ingredients for a deterioration as the water mixes with creosote and mild acids are formed. Even chimneys that are used for wood stoves are in need of a cover.
Here are some reasons to have a chimney cap:
• Keep out rain,snow and sleet.
• Keep out animals and birds.
• keep out leaves,twigs and other debris which could lead to a blockage or chimney fire.
• keep sparks from leaving the chimney and igniting nearby combustibles.
• help eliminate wind induced down drafts.
WATER & YOUR MASONRY CHIMNEY
The chimney is one of the most taken-for-granted parts of a home. Typically it tends to receive neither the attention nor the concern usually accorded other household service systems. The fact that chimneys may do their job reasonably well, even when abused or neglected, contributes to this atmosphere of indifference.
Chimneys are far from the passive black holes that most people assume them to be. They perform several vital functions, and their simple appearance misrepresents their complex construction and performance requirements. A chimney deteriorated by constant exposure to the weather can be a potential safety hazard. Weather-damaged lining systems, flue obstructions and loose masonry materials all present a threat to residents. Regular chimney maintenance is essential to prevent damage, deterioration and future high-cost chimney repairs.
A masonry chimney is constructed of a variety of masonry and metal materials, including brick, mortar, concrete, concrete block, stone, flue tile, steel and cast iron. All masonry chimneys contain combinations of, or possibly all of, these materials, most of which are adversely affected by direct contact with water or water penetration.
All masonry chimney construction materials, except stone, will suffer accelerated deterioration as a result of prolonged contact with water. Masonry materials deteriorate quickly when exposed to the freeze/thaw process, in which moisture that has penetrated the materials periodically freezes and expands causing undue stress. Water in the chimney also causes rust in steel and cast iron, weakening or destroying the metal parts.
Note: While most stone is not affected by water penetration, large amounts of mortar are required to bond the stone together properly. Therefore, a stone chimney – just like a brick chimney – should be protected from the effects of water penetration.
Water penetration can cause interior and exterior damage to your home and masonry chimney including:
In addition, when water mixes with creosote in a wood burning chimney system, it will generate a highly disagreeable odor that can permeate a home.
Preventing Water Damage
Chimney caps, also called rain covers, are probably the most inexpensive preventive measure that a homeowner can employ to prevent water penetration and damage to the chimney. Chimney caps have long been recognized as an important chimney safety and damage prevention component. Underwriters Laboratories (UL) specifies that any chimney lining system that is to be listed to their test standard must include a chimney cap.
Chimneys have one or more large openings (flues) at the top that can collect rainwater and funnel it directly to the chimney interior. A commonly-sized flue has the potential to allow large amounts of rain or snow into the chimney during just one winter when freeze/thaw cycles are common.
Chimney caps also provide other benefits. A strong, well-designed cap will prevent birds and animals from entering and nesting in the chimney. Caps also function as spark arrestors, preventing sparks from landing on the roof or other nearby combustible material.
A chimney cap should be easily removable to facilitate inspection and cleaning. For a long and effective service lifetime, a cap should be constructed of sturdy, durable and corrosion resistant material. Caps may be designed to cover a single flue, multiple flues, a large portion of the chimney or the entire chimney top. A full coverage chimney cap usually represents a larger initial investment. However, it is probably the best investment for long-term protection because of its ability to protect the entire chimney crown.