Chimneys have been around for a long time.
Their purpose has changed somewhat over the years, first being used for fireplaces and stoves and later for boilers and furnaces.
Many early chimneys were made of mud and sticks. Not many of those buildings are around to look at, for obvious reasons.
A little while ago, I had a house in Bangor that had an ancient behemoth boiler that was converted from coal to oil. The flue pipe (the pipe that ties the boiler to the chimney) was 10 inches in diameter. That was a big flue pipe. It had to be. The house used 3,000 gallons of oil to keep the place at 61 degrees Fahrenheit.
As you might imagine, we insulated the place and replaced the boiler with a much smaller new boiler with a correspondingly smaller flue pipe.
Everything was fine for about a year until someone pointed out that the chimney was starting to show some signs of deterioration at its highest point. The mortar was discoloring.
In my earnest attempts to save energy, which cut the heating bill by more than half while making the house comfortable, the chimney was getting cold. Since the chimney was more than 40 feet tall and had spent most of its past 100 years in the wonderful warmth of excessive fuel consumption, the 5 feet that were up in the air on the top of the house never, ever froze. That is until Mr. Energy Efficiency showed up.
And I am not alone. As we all make these old arks tight and more efficient, we use less fuel. All those wonderful, glorious old chimneys have a problem with this.
It is not the end of the world if the chimney is cold, but the cold chimney condenses all the stuff that we vent in it from burning our fuel of choice.
For years, we have known about creosote from wood burning. We (or most of us) know that chimneys for wood burning stoves and boilers have to be lined properly to minimize the effects of creosote formation and the possibility of chimney fires.
A cooler chimney has a similar effect with oil and gas. When we burn gas, which is a relatively clean-burning fuel, there is a tremendous amount of water that is in the exhaust gas. If the chimney is cool enough or is used intermittently as in a well insulated building, ice can actually form in the chimney. Ice can also block a chimney and allow carbon monoxide to enter the home. This is a killer since it is an odorless gas. Wood and oil fuels also exhaust carbon monoxide, but they are smelly enough for us to usually recognize a problem with improper venting.
Oil can also form ice in a chimney flue. There can also be the formation of acids in a cool chimney. If acid forms in any condensed flue gas, it can attack the mortar in an unlined chimney. That was the discoloration I saw on my chimney.
Fortunately, there are some simple, although expensive, solutions.
First, all chimneys need to be lined. The liner can be a traditional clay tile liner or a stainless steel liner. Stainless steel liners can be insulated with high temperature ceramic fiber insulation, which helps the steel warm up quickly.
There also are some flowable cementatious liners that can be installed into older chimneys. Unfortunately, there are a lot of older homes that do not have lined chimneys. Current code mandates that whenever you install a new heating appliance into an existing chimney, the chimney must be lined. This is a good thing, although it will set you back at least $1,000.
A second alternative is a power-vented or direct-vented appliance. These will vent oil or gas combustion byproducts through an approved side wall venting system that will replace a conventional chimney. They are usually less expensive than a chimney and are convenient.
The downside to a sidewall-vented device is that if there is a malfunction, such as a dirty oil burner nozzle, you will be washing off a big black smudge mark from the side of your house and probably will be re-painting.
This all is a big hassle, but it’s an inevitable issue as we make the transition from homes that gulp fuel to those that sip it.
Questions for Tom Gocze should be mailed to The Home Page, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. A library of reference material and a home-project blog are at www.bangordailynews.com/thehomepage.html.