Chimney how does it work

There are various parameters that experts are familiar with which dictate the ideal height of a chimney. For example, the chimney stack on top of the roof must extend at least 3 feet above the point where it penetrates the roof. The flue is the liner inside the chimney that protects combustible parts of the home from the hot temperatures and toxic fumes inside it when fires are burning.

The width of the flue must be a certain ratio to the size of the fireplace opening. A flue that is too big will pull too much air out of the home, causing a loss of heat. When the flue is blocked, the obstruction interferes with the draft, resulting in a smoky, backdrafting appliance. Trained, certified chimney sweeps know what to look for, as far as the causes of potential chimney damage and a poor draft.

In West Hartford, CT, Northeastern Chimney is the place to call if you want knowledgeable chimney technicians to evaluate the condition of your chimney and provide expert repairs. Contact the professionals at Northeastern Chimney today by calling We Have Chimney Leaks! All Articles April Showers Bring…. Larger flues create stronger drafts, generally speaking, but in any case, eliminating creosote deposits and other clogs ultimately safeguards against chimney problems. Mandatory in some states, flue liners enhance the safety and performance level of chimneys in a couple of ways.

One, they prevent the overheating of combustibles adjacent to the chimney. Two, they make the chimney more resistant to the corrosion typically brought about by byproducts of burning wood. Without regular cleaning, a highly flammable substance known as creosote may build up within the flue, making the chimney vulnerable to high-heat fires. Though prefabricated chimneys are built to withstand very high temperatures, they can be so damaged by chimney fires that replacement becomes necessary.

Stainless steel liners can be installed in masonry chimneys when they are built or to correct internal damage in an existing chimney. Existing masonry chimneys should be inspected by a qualified chimney sweep before a wood-burning appliance is connected. Because a conventional masonry chimney has no insulation and functions as a heat sink that soaks up flue gas heat, it is advisable to install a stainless steel chimney liner before using it to vent a wood heating appliance.

If you have a masonry chimney that you want checked, hire a qualified chimney sweep to inspect it. If you see any deterioration of the bricks or mortar joints near the top of the chimney, or if there are dark stains on the brick work, you should have the chimney inspected immediately. Masonry chimneys that have been damaged by old age or a chimney fire, or are too large for the appliance you want to connect can be relined with a certified stainless steel liner.

These liners can be of either rigid or flex design. When wood is burned slowly to make a smoky fire, the smoke can condense on the cool inner surface of the chimney producing creosote deposits. Creosote is a highly-flammable material. If it ignites at the base of the chimney, it can produce a raging fire that travels up the chimney causing extremely high temperatures as it spreads.

The high temperature can damage the clay liners in a masonry chimney or the metal liner in a factory-built chimney. Chimney fires are the result of poor appliance firing technique combined with a lack of proper chimney maintenance. When wood-burning appliances are operated properly using the techniques outlined later in this booklet, some creosote may still be deposited, but it will be of a less combustible type. Instead of the black, tarry type of creosote that results from smoldering fires, the creosote that results from proper firing is soft, flaky and dark brown in colour.

Chimney fires can be prevented. Chimneys should be checked for creosote deposits regularly until you know how quickly it builds up in your chimney.

Conventional wood stoves can produce creosote quickly because they are unable to burn the wood as completely as the advanced designs.

In severe cases, enough creosote to sustain a damaging chimney fire can be deposited in only a few days. The newer, low-emission wood stoves burn the wood so completely that, when they are operated properly, their chimneys normally need cleaning only once each year. Never assume that the chimney is clean. Check it regularly to be certain, especially during the spring and fall seasons. If you do have a chimney fire, have the chimney inspected and repaired if necessary before using the system.

Thank you. View All. How Chimneys Work. Two factors affect the amount of draft produced by a chimney. If a home is sealed too tightly, or if too much air is being vented out, then negative air pressure is realized. If you find yourself wondering whether or not your chimney is working at all, an air pressure issue could be to blame. William B. Hussel, president of The Chimney Doctors , offers an easy way to test for sufficient airflow in your home using an open door or window and your fireplace.

Refer to the graphic below to see exactly how a chimney works:. An appropriately-sized flue should be one inch wide for every 10 square inches of fireplace opening. This ratio enables air to travel at the perfect velocity through the flue. If the flue is too big for the fireplace, too much air will exit the chimney and you will lose heat.

If the flue is too small, then air cannot exit the chimney fast enough and you may find yourself in a smoke-filled room. According to Woodheat. Extending the height of your chimney serves two main purposes:. Finally, to create a sufficient draft, your chimney must be free from obstructions and damage.