Hello Mr Marantz :
We had a gas fireplace installed into an existing chase 3 years ago. The house itself is 15 years old. Last winter, the first really cold one since the fireplace installation, we noticed that it became quite cold around the fireplace when the heat was not on. This was especially true on the windier days. We have been trying to determine if this is normal, as has been suggested by several people. At the same time, it has been suggested there is insufficient insulation around the fireplace or that the chase is not properly sealed. I have tried to find someone who would look into this question for us, but all of the persons I contacted (fireplace installation, chimney contractors, construction contractors, mechanical engineers) said they were not skilled in this area. In fact, most of them suggested one of the other trades people who had already turned down the job. Can you suggest whether there is a problem and if there is, suggest who would be best to contact for fixing it.
Thank you very much for your time.
Modern fireplaces, both gas and wood burning, are often factory manufactured units that are both high quality and very safe when installed according to manufacturer’s specifications. These units are often referred to as “zero clearance” units due to their minimal requirements for clearance to combustibles upon installation. These units are engineered and designed to be installed in a chase that is not much larger than the fireplace itself. The problems you are experiencing may be due to improper installation or one of a couple of other possibilities. We will look at several of these issues.
The first potential problem with cold around the fireplace is air leakage into the home around the unit, itself. Insulation may be installed around the unit, dependent on the design, but often the interior of the chase may be left open to meet proper clearances. If this area is well sealed around the fireplace, at the exterior wall and foundation, air leakage should be minimal. If there are gaps, even small ones, in the exterior of the chase then cold air may leak into the house. I recommend a visual inspection of the exterior of the chase and underneath, if not sitting directly on the foundation, for gaps or openings that may allow cold air and wind infiltration. Many times the bottom of the chase may not be properly sealed or finished and cold air can easily leak in underneath the fireplace. When doing this inspection, you should also check for the presence of vents on the exterior of the chase, which may give a clue to the next potential cause of your situation.
Many newer units have integral combustion air intake openings, which are connected to vents on the exterior through insulated ducts hidden inside the chase. This allows the units to bring in fresh outside air for combustion rather than using pre-warmed house air. This feature makes the fireplace much more efficient in energy consumption. If you have a unit with a sealed front glass panel, then this is likely the case. This fresh air intake will not normally have a damper or mechanism for preventing cold air intrusion when not in use, so this may be the source of the cold you are feeling. If this is the situation in your home, it may be quite normal to feel the area near the fireplace cool.
In most manufactured units there is a space underneath the firebox, which will accommodate the gas valve, controls, fan and wiring. This space is also used to draw in house air, which will pass around the firebox by convection, or with the help of a fan, when the flame is on. This allows some warm house air to be heated and circulate around the room that the fireplace is in. This area may not be well sealed around the pipes and wires entering it and may be the source of the cold, when the fireplace is not in use. This will be compounded if there are any openings in the exterior of the chase.
The current situation you are in, with reluctant contractors, is likely because it might be very difficult to determine the source of the problem without destructive testing. What this normally entails is cutting holes in the chase to see what it going on inside. If there is a defect in installation, that may be the only way to fully discover it. Very few contractors want to start cutting holes in your home, especially if they are not sure they will find the source of the problem.
Your best bet is to call the contractor that originally installed the fireplace and an additional fireplace expert. If the original installer has no solution for your dilemma, then you could have your independent contractor contact the original installer to ask him about installation particulars. The impartial second contractor may be able to determine the defect, if there is indeed one, by evaluating the installation procedure of the original contractor. A fireplace installation contractor that has been in business installing gas units for many years should be able to help with your situation. If you can’t get anyone to evaluate the situation, you may be able to contact the WETT certification officials in your area for names. The Wood Energy Technology Transfer (WETT) certification is for wood burning fireplaces and appliances, but many of the same contractors that install gas-burning units are WETT certified. Information is available on their website at www.wettinc.ca.