All About Your Chimney Lining

Lining your Chimney

Why are so many people having their chimneys relined these days? As cold weather approaches and you fire up your heating system, wood stove or fireplace, are you thinking about the inside of your chimney system?  In a perfect world, the inside of a chimney is something you’d never have to think about. Unfortunately the world isn’t perfect and many masonry chimneys aren’t either! Let’s discuss what can go wrong inside of a chimney and how chimney liners figure into it.

A chimney’s purpose is to carry the flue gases out of the home, and it needs to do this without getting over-heated. The problems with the inside of chimneys falls into two general categories: the problems that cause flue gasses to back into a house (smoke or carbon monoxide) and the problems that can cause house fires.

Most masonry chimneys are lined with fireclay tiles. This material has been used for 100 years and was a huge improvement to unlined chimneys of the 1800’s and before. In fact they served well enough until the 1970’s. Here’s what happened.

As people became conscious of the cost of heating, they started to put glass doors on the front of their fireplaces. This changed the fuel-air ration that had existed for eons. Suddenly masonry fireplaces that had never had problems before got full of soot and creosote in a matter of months.

Fireplace inserts caused the same problems, only even more so. The stoves were engineered for flue openings of six or eight inches round but were venting into chimneys built for open fireplaces. And fuel-air ratio was now so low that many chimneys collected a thick, wet, gooey tar. In some cases, chimneys were catching on fire within weeks after the stoves were installed!

Obviously the same was true for freestanding woodstoves.

And what about central heat flues, that is gas and oil? Well, those appliances changed too: they became much more efficient. The problem there isn’t creosote, as these fuels burn much cleaner. But it takes a certain amount of heat loss in the chimney to take the fumes up the flue and it wasn’t there anymore.

Three bad things happened to the masonry chimneys:

1. More heat was delivered into the home and the flues didn’t have enough heat to carry the gasses up and out!
2. The water in the exhaust condensed in the flues (instead of in the atmosphere). The inside of gas heaters in particular got very wet. Very, very wet indeed: so wet that they could freeze in the winter and block up, or so wet the wall paper inside the house was peeling where the chimney passed by. So wet that the freezing and thawing deteriorated the outside bricks themselves!
3. And carbon monoxide levels in the houses skyrocketed! Tens of thousands of people a year are affected by CO poisoning and many don’t even realize it. They just don’t feel so great; lethargic or as if they have a cold. And of course there are even deaths… it’s a bad situation.
   • For reasons more technical than this article will cover, a properly sized liner will extend the appliance life and its heating efficiency. This is true for both central heaters or wood burning appliances.
   • For gas flues you can use aluminum but it often doesn’t have a very long life with modern appliances. The best material for lining a chimney, whether gas, oil or solid fuel, is stainless steel. #316 is a very good alloy for chimney lining and is readily available.
   • The liner must be properly sized to the appliance for it to work properly. Either too big or too small is not good enough. Don’t get this wrong.
   • There are three systems in your home that can kill you: electrical, plumbing and venting.  Unless you really know what you’re doing, unless you’re the kind of do-it-yourselfer who’d dig up his own sewerage system etc. don’t try to do it yourself. While anybody who can work with tools can theoretically do anything, there are enough things to go wrong with a venting system that this isn’t something you should tackle yourself. Hire a professional.

   Add to this that in most cases tile chimneys are not particularly well sealed in the first place, just because that’s the way they’re built. Also, many homes now operated under “negative pressure.” That means that our airtight windows and doors, our weather stripping, and our fans in the house all conspire to prevent good draft in chimneys. All of these factors combine to create the need for smaller, positively sealed venting systems.

   This is where chimney liners come in. The info above pretty well describes why you need a modern chimney liner. Lining your chimney with a good stainless steel liner will pay you and your family dividends both in dollars and in vastly increased safety.  Make it your next home improvement!