Last week, I talked about how heating oil and natural gas compare from several different standpoints. We get a lot of interest from homeowners who would like to convert their Boston residential heating equipment from heating oil to natural gas. While there are many benefits of making such a conversion, there’s one consideration that many homeowners overlook – until they’re confronted with a major repair to their chimneys!

We tend to take a chimney for granted. Chimneys are generally built at the same time the house is, and in very old homes, the chimney may have been used to service three or four different kinds of heating technologies. The purpose of the chimney is to give certain products of combustion, which are toxic, a safe exit from the home.

Over time, the chimney deteriorates. The outside of the chimney is exposed to weather, including cold air, water, snow and ice. The inside of the chimney is repeatedly heated and cooled, which causes problems with temperature-related expansion and contraction. Add on top of that potential hazards from wind and storm debris, and repairs that may not have used the proper mortar, and you have a repair in the making.
But these hazards don’t take into account what happens inside the chimney day-in and day-out. The inside lining of the structure, which is traditionally made of terra cotta tile – can be damaged by water, sulfur and household solvents. These chemicals, along with water, break down the surface of the chimney lining. This damage occurs whether you use oil or gas as a heating fuel. Once the surface is damaged, the chimney lining deteriorates and small pieces of debris begin to accumulate at the base of the chimney. Advanced deterioration of the lining can cause the chimney to admit soot and toxic gases into the living space of the home.

Conventional chimney maintenance requires regular inspection and cleaning. Periodically, the outer mortar must be repaired, too. Ultimately, the chimney must be relined when the deterioration to the inside lining becomes significant. As you may have guessed, relining a chimney isn’t cheap! It’s also one of those repairs that can’t be put off, and since it has to be done right, it is best done by someone who lines chimneys for a living.

It sounds like there are no alternatives to relining the chimney, but that’s not true! An exhaust process known as direct venting can come to the rescue when heating equipment is replaced. Direct venting is a technique used with high-efficiency gas heating equipment to conduct toxic gases directly out of the home and without using the chimney. Furnaces, boilers, water heaters and gas fireplaces can all be direct-vented. Fresh air intake and exhaust ports are installed and connected to the natural gas appliance. The appliance then vents the toxic products of combustion directly to the outside of the home, instead of using the chimney.

Direct venting requires the creation of a couple of small holes in an exterior wall of the home. The intake and exhaust ports use these holes to make a direct connection between the gas-burning equipment and the outside environment. In most cases, polyvinyl chloride (PVC) pipe is used for these ports because it’s inexpensive and easy to replace. Some homeowners prefer to use stainless steel exhaust ports to avoid potential problems with PVC outgassing – the subject of an upcoming post.

If direct vent equipment is used exclusively in a home, there’s no need for a chimney, and the existing chimney can be sealed. You’ll still want to have the chimney inspected periodically for exterior damage and mortar deterioration. (After all, a chimney is literally a “ton of bricks” standing inside your home!) Direct venting, when done in conjunction with heating equipment replacement, can save you money in the long run by eliminating the need for annual chimney inspections and expensive relining or repairs.

For more information about oil-to-gas conversions in Boston, or direct venting heating equipment contact us at (617) 362-0377 for a consultation.

DIY Air Conditioning, DIY Blog, DIY Heating

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