Chimney is one of the last technical and architectural details that we pay attention to when building or buying a house, and that is a big mistake. A chimney can cause so many problems and troubles that it must be given special attention.

When building a house, the final quality of all elements, including the chimney, depends mostly on the quality of subcontractors. If you want to know how to check the quality of contractor click here.

Now, let’s look at the things you need to know about chimneys as a homeowner:

Sizing

Determine the correct height and diameter of the chimney in accordance with the factory specifications of the stove you use.

Proper sizing of chimneys is a key factor that should ensure proper, healthy, safe and efficient operation of the entire heating system. Read more about it here.

Inspection

At the absolute least, the chimney should be inspected before the heating season begins. The chimney should be swept to remove soot and tar and to verify that there are no blockages such as dislodged masonry or bird’s nests. A smoke test should then be performed to see whether there is any substantial flaw that could allow combustion products to leak through the chimney walls. The structural stability of the chimney should also be evaluated, as well as its wind and water tightness.
Read more about this here.

Materials

Chimneys and flues are available in a variety of materials, including stainless steel, concrete, travertine, clay, ceramic, and plastic. Masonry chimneys are constructed of concrete, travertine, clay, or ceramic. Plastic flues are only permitted in low temperature condensing applications.

Check the specification of stainless steel chimney systems and flexible liners because only a few are particularly designed for use with gas powered appliances. Chimney systems with liners made of clay and pumice are ideal for wood, multi-fuel, oil, and gas. Concrete gas flue blocks, as the name implies, are only to be used with gas effect fires and must not be utilized with wood-burning fireplaces.

Concrete gas flue blocks, as the name implies, should only be used with gas effect burners and not with wood or solid fuel fires. There are also factory-made pumice and ceramic chimney systems available.

Although they can be retrofitted, pumice and ceramic chimney systems are more commonly found in new homes since they require a foundation and their building process is best suited to a bricklayer’s skill set.

Working principles

• The difference in air pressure between the appliance and the top of the chimney. (created by the height of the chimney)
• The difference in temperature between the appliance’s exhaust gas and the outside temperature
• The route of the chimney. (the straighter the better).

Pots and Terminals

It is critical to ensure that the chosen pot or terminal does not obstruct the exit of combustion products. The area of the outflow must be at least equal to the area of the flue. If the terminal has a hood, the output should be double the size of the flue. For wood burning and multi-fuel appliances, an open terminal is usually suggested.

Rain caps or anti-downdraught terminals, on the other hand, may be used. Rain caps and anti-downdraught terminals are offered in two configurations: with and without anti-bird mesh. When using a mesh terminal, there is a potential of soot buildup, so regular cleaning is essential to avoid blockage.

Insolation

One of the keys to a well performing chimney is consistent insulation along the complete length of the flue. Otherwise, there is a danger of excessive cooling of the smoke at the exit of the chimney, which reduces the flow.

Bends

Bends in the chimney should be avoided because a straight vertical chimney works better. If bends are necessary, no more than four must be included along the length of the chimney. The bend’s angle from the vertical should be no more than 45°, with the exception that 90° factory-made bends or tees may be classified as equal to two 45° bends. It is critical that cleaning is simple at any change of direction in the flue.

Cleaning

Burning fires leads to the accumulation of soot and creosote in a chimney, a flammable, sticky substance that can cause chimney fires. So it has to be removed! Hiring a professional chimney sweep is always the best option but it can get expensive. So if you want to save some money, consider picking up a few tools from the hardware store and cleaning your chimney yourself.

• Measure your chimney flue
  If you’re guessing, it’s better to overestimate because the chimney brush must reach the entire length of the chimney!
• Buy a hardware
  You need a chimney brush, either wire or plastic, chimney brush extension pipes (alternatively, you could buy a weighted rope designed to be used with the chimney brush, or a rope pulley system), a smaller stiff wire brush, a plastic tarp or drop cloth for protecting inside of your house, a ladder tall enough to reach your roof (if you plan to clean your chimney from the top down) and a broom and dustpan.
• Wear old clothes
  Also cover your hair, wear work gloves and put on a dust mask and goggles.
• Prepare your house for the cleaning
  Cover furniture with light fabric and roll back your expensive rugs.
• Remove the damper
  Detach it from the chimney and set it aside on the drop cloth, so it won’t obstruct the chimney brush as you proceed with cleaning the chimney.
• Scrub along the entire length of the flue with the brush
  There are three methods to do this: from top to bottom, from bottom to top
  and a pulley system with a partner.
• Clean the bottom of the chimney
  Use the small wire brush to clean the bottom of the flue that you may have missed with the brush.
• Clean the flue’s entrance
  At the very bottom of the chimney, often located in the basement, you should find a small door going into the area under the flue. The creosote and soot will be collected there. Since creosote is a flammable substance, it should not be thrown in the trash.

Alarms

It is recommended that all wood burning and multi-fuel appliances should have a carbon monoxide alarm fitted within the same room as the appliance. An alarm is important because carbon monoxide is a dangerous, odorless and invisible gas.

At the end, we would like to point out some Dos and Don’ts when it comes to chimneys

Do ensure that the flue pipe connection from the appliance rises vertically for at least 600 mm before any change of direction is contemplated. The reason for this is that the flue draught is crucial nearer the appliance because of the higher flue gas temperature. Any horizontal or angled runs at the bottom of the flue will create severe restriction to flue gas movement and affect appliance operation.

Do ensure that the effective height of any chimney with bends (vertical distance between appliance and terminal) is at least twice the horizontal distance between the appliance and terminal.

Do try to position the chimney inside the building to avoid excessive cooling and risk of condensation.

Don’t clean a flue using just chemical chimney cleaners or vacuum cleaning, because it cannot be an alternative for correct chimney cleaning, mechanical with brush and rods. (Some chemical cleaners can invalidate manufactures warranties)

Don’t use any single wall flue system as a chimney.

Don’t allow clothes, furnishings or any combustible materials to come into contact with the surface of any flue pipe or prefabricated metal chimney.