“The little metal cap on the top of my chimney blew off in the wind. Is that a problem?” The staff of the Newton Falls Public Library understands not wanting to climb up on the roof of a house during this cold winter weather. Knowing nothing about the subject, we first looked at Heating, Ventilating, and Air Conditioning Library by James E. Brumbaugh. The chimney cap (or capping) described in the volume was built of masonry [p.127], and was not what the patron needed. On p.136 there was a drawing of a stove with an exterior pipe and a ‘shanty cap’ on top. The staff continued the investigation using both terms.
FireplaceMall.com has instructions for How to Install Your Chimney Cap. As well as detailed installation directions for different styles of caps, the author of the article states “chimney cap . . . keep the rain from damaging your chimney flue and to keep squirrels, raccoons, and bats from taking up residence.” www.TheChimneySweep.ca included additional reasons for why your chimney needs a cap. Besides the previously mentioned critters, this site also lists “birds, small boys and other would-be thieves.” This website gives very detailed reasons for the importance of the cap, including: “rain coming down an open flue . . . causing unpleasant odors and deterioration of flue walls. It can run down . . . where it causes rust damage . . . Rain plus coal soot forms sulfuric acid, which is particularly destructive . . . An Ohio sweep removed a dozen dead birds from a blocked gas flue one cold winter's night. . . Hordes of bats flew down the chimney of one house, driving the family out. The homeowner and his neighbors killed 195 bats inside the house. . . The remains of a man missing for seven years were found when his house and chimney were torn down by a wrecking crew.” The site recommends having a professional do the installation.
The library’s patron felt that these were certainly valid reasons for having the cap replaced as soon as possible.