Heat loss from gas fireplaces
Will installing a gas fire in an existing open fire prevent heat loss up the chimney? If not what would you recommend?
Answer from Green Energy Efficient Homes
If you install a gas fireplace insert in an existing fireplace this should reduce heat loss up the chimney. Most traditional wood-burning fireplaces have a baffle that you can open or close partway up the chimney, and people typically forget to close the baffle when no fire is burning; as a result, any heat from a furnace, electric, or solar heat source tends to get sucked up the chimney in cold weather due to the stack effect. Even if you remember to close the baffle it likely has a poor seal, as the baffle is usually made of metal, and over the years heat from the fire can warp it to the point where it doesn't shut all the way or leaves gaps around the edges. And when you do burn a fire in an open fireplace, plenty of indoor air will get sucked up the chimney along with the combustion gases, with the result that in many cases having a wood fire burning in your fireplace actually cools the house down overall rather than heating it.
With a properly installed natural gas fireplace you should not have to worry about either passive air escape up the chimney when the unit is not in use, or the fire sucking too much indoor air up the chimney along with the combustion gases. In fact you can even buy outdoor-venting units, which draw their air intake from outside. Your installer should line your chimney with a metal chimney liner so that the exhaust gases are not in direct contact with brick, because natural gas combustion gases can damage brick over time. When this chimney liner is properly installed it effectively seals the chimney at the top because the chimney is capped around the liner.
Of course you can get all this with a wood fireplace insert as well: a sealed chimney without having to worry about baffles, an extra source of heat in your home, and an outside air source for combustion.
Choosing between a wood fireplace insert and a natural gas fireplace insert is a question of convenience, cost, and environmental factors. It is certainly more convenient to flick a switch and have a natural gas fireplace come on or go off at a moment's notice (and provide instant heat when you need it). I have a wood fireplace insert and while I love the warmth and the homeliness of a wood fire, and the fact that burning wood is essentially carbon-neutral because trees are a renewable resource, it is definitely not that convenient. It's hard work hauling in the firewood even if it's delivered to my front porch; it's messy; it takes a while to start the fire; and when the fire burns it throws off so much heat that the living room turns into an inferno while the rest of the house gets colder and colder, since the furnace stops running when it detects all that heat in the living room. From a cost perspective, firewood could be free (my uncle heats his house entirely with scrounged oak and maple pallets from local hardwood flooring stores) to very expensive, while natural gas is typically reasonably priced but can be expected to go up over time. From an environmental perspective, you are trading off the extra CO2 emissions from burning natural gas to the extra soot emissions from burning wood, which can cause local air quality problems in your own neighborhood.
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