When contemplating the repair of a chimney, there are, unfortunately, many considerations which do not become apparent until after the work has been completed and the contractor is long gone. This frequently occurs as the result of misleading or misinformed analysis of the damaged chimney. It is all too true that when repairs are being discussed, one concern, regretfully, attracts more attention than others: price.
The question that is often overlook and only considered after the job is completed and the contractor departed is the fitness of the repair to work properly with the original appliance such as a fireplace or furnace. The time to ask questions about the fitness of the repair is before work begins.
This decrease in flue diameter size happens with regularity when a stainless steel liner, for example, is improperly installed for the original appliance. Remember, when a stainless steel sleve is inserted into an existing liner, the diameter of the flue is instantly decreased. Is this a real fix to the problem or just a cover-up? This is what happens when price is the primary concern.
To make matters worse, when a chimney liner is installed, it is required by Underwriters Laboratory (UL) to be insulated on the outside of the liner. The National Fire Protection Association standard 211 (NFPA 211) also requires all liners to be insulated around the outside. Firstly, insulating the liner prevents heat transfer – the number one cause of structural fires - to the outer walls of the chimney. Additionally, insulating the liner contains the flue temperature within the liner thus producing a hotter flue temperature which naturally increases the draft of the venting system.
It is a sad fact that most steel liners that we have seen installed have had no insulation. This will leave both the homeowner and the insurance company with a false sense of security. Oh, insulating half-way around the liner is not the answer!
You are only as safe as the weak points of the system!