Gas fireplace insert vs. house heat

dmloveJanuary 15, 2007

We have a natural gas forced-air furnace system (new-ish) heating our 100-year old house. The walls of the house is pretty much all insulated but it doesn't maintain consistent temps due to old windows and doors. The first two floors (excluding the unheated attic) are about 3200 square feet, of which about 800 is the kitchen/family room. Since we spend 90% of our time in the kitchen/family room, does it make sense that we would save heating costs by putting in a natural gas fireplace insert in place of the wood burning fireplace we have in their now. Obviously, we're not changing fuels - both the furnace and the fireplace would be natural gas. It's just that it seems we could heat the family room/kitchen without heating the rest of the house as much. Is this right or wrong thinking?

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This is not an easy question to answer as it depends on many variables. Just because you produce heat from your fireplace insert doesn't mean that the heat can be distributed evenly through the house. If the heat from the fireplace is not evenly distributed, you may roast near the fireplace but be cold in rooms away from the fire. If the thermostat is near the fireplace, it will be tricked into thinking that the house is warm and cozy when it is not (this may be your plan - I'm not sure).

Additionally, the house loses a certain amount of BTU's (heat) per hour based on the outside temperature which must be replaced by either your fireplace or the gas furnace (or both) to maintain a certain temperature (this is an important point). If you put in a gas fireplace (and the thermostat is not near the fireplace), the furnace will still have to run maintain the temperature setpoint. The only way around this is to lower the thermostat setpoint.

How is your attic insulation? More insulation goes a long way.

You could also install a wood-burning stove and use your fireplace chimney to run the vent pipe. Other options include a pellet stove, pellet insert, or wood burning insert. These choices would suppliment your gas bill as they are alternative fuels. These choices still depend on location inside the house for heat distribution.

FYI: An open, wood-burning fireplace is a negative heat gain. I am not sure from your post if you burn an open fireplace, but the fireplace sucks out heated air from the house and replaces it with cold, outside air.

    Bookmark   January 16, 2007 at 3:51PM
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Thanks Gary. I should have been clearer about one point -- that we would use the fireplace to heat the family room/kitchen, but NOT the rest of the house. In other words, we'd have a thermostat in the family room/kitchen, and keep the doors to those areas closed and run the fireplace when we're in there, which, as I said, is 90% of our waking hours. The rest of the house would be heated by the furnace but not to as warm a temperature. Does that make a difference in your answer?

    Bookmark   January 16, 2007 at 5:16PM
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I assume you do not want to use wood. A wood insert would be another answer and I know that would produce a positive heat gain for you and do what you want.

I know very little about gas fire place inserts. I think some of them are no better than an open hearth wood fireplace, the open flue lets a lot of heat out, albeit you should be able to close it as soon as you shut the gas unit down. If the gas insert is "air tight", and has a good heat exchanger with a blower, I suppose it could produce a good bit of heat. Check out what the insert(s) advertise. I'd guess from what you say you'd be happy with a unit that could put out 30,000 or more BTUs (per hour).

    Bookmark   January 16, 2007 at 10:00PM
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The gas insert would not lower your gas bill as the "new-ish" gas furnace would be similar in efficiency to the new gas fireplace.

    Bookmark   January 17, 2007 at 8:34AM
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Hum, I read that there are high efficiency gas fireplace inserts. I'm not surprised, and it does sound like an attractive way to heat a portion of the house while leaving the central furnace to hold the rest of the house at some lower temperature. This could lower heating costs as compared with heating the whole house to the higher temperature you want in a given area: Family room...

I'm sitting at the moment next to an air-tight coal/wood stove, burning wood, and it "feels good". It is in the basement, and the temperature here is about 70 degrees, it is about 62 to 64 in the rest of the house, in fact the heat pump (geothermal) isn't running at all as I just turned it back to 60 degrees in preparation for bed. In the case of a heat pump I believe this type of rest period helps the ground loop recover some of the geothermal energy (heat), making the heat pump more efficient for a period when it is again put to work. Well that's another subject not directly relate do the subject, but related to his forum's goals.

    Bookmark   January 17, 2007 at 11:18PM
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The original poster was very vague in describing their current gas furnace as "new-ish". Is it 80% efficient? 90%? Not stated. If the gas insert is slightly more efficient than the gas furnace, they still won't be saving any money on the gas bill because they are running BOTH the gas fireplace and the gas furnace. They are not replacing an inefficient furnace with a more efficient one. They are supplimenting an efficient furnace with an efficient gas fireplace. What about the purchase cost and installation cost of the gas fireplace? Are they free? Probably not. So where's the cost savings?

There is also a life style issue involved. Suppose the new gas insert does a good job of heating the family room/kithen area where they spend most of their time. They then lower the thermostat for the furnace so that rooms heated by the furnace now get colder. Is it OK to have a cold bathroom with cold toilet seat and tile floor? Maybe it's OK for them. Maybe they don't like when their butts freeze to the toilet seat. This is a lifestyle issue.

The idea of the post is to save money which, in my opinion, won't happen. Maybe the idea of post should have been "We are spending money to heat our 100 year old house that is drafty due to poor windows, etc., and we are not feeling very warm in the family room/kitchen where we spend 90% of our time, so we'd like to add a gas fireplace to feel warm in these rooms." Nothing to do with an attempt to save money, but an attempt to feel comfortable.

    Bookmark   January 18, 2007 at 8:51AM
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Lots of good points. I face the issue of not using my current and old wood insert in my main floor fireplace. It is a source,now, of odor during warm weather. My options seem to be to remove it and put in a better damper, or install a new unit with a sealed/air-tight SS pipe. This cost about $4K, depending on the insert. So, while I enjoy a wood fire in the fireplace/insert, the $4k puts a high price tag on it and I may forgo the enjoyment of a wood fire in that device.

Still, if one can justify the cost of installation on the basis of enjoyment (cold butt not withstanding), then why not try to do it in a way that provides an incremental financial (not depreciated) value?

    Bookmark   January 18, 2007 at 12:27PM
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These are all good points, and I'm enjoying reading the different takes on this issue. FWIW, saving money would be nice, comfort would be nice, both would be even nicer.

    Bookmark   January 18, 2007 at 1:05PM
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I clipped this post from a previous discussion on gas inserts to provide additional info on the subject.

Posted by: renron on 12.19.2006 at 07:28 pm in Fireplaces Forum

First, DON'T install a ventless fireplace!!!
Even though the MFG.s will tell you the exhaust fumes are OK, do you really want to breathe them? Many people end up with Major Headaches and chronic breathing issues. Does it sound like a good idea to breathe burnt exhaust gasses?
B type flue(vent) pipes are dual thickness pipes. A pipe inside another pipe, suitable for use at 1" or more to flammable materials. Outer casing pipe is sealed and will not conduct air.
D (Direct Vent) type flue(vent) pipes are also dual layers but they are capable of exhausting burnt gas through the inner pipe and importing exterior(outside) combustion air for burning. Think of a straw inside a larger straw. Inside straw blowing, outside straw sucking outside air for combustion. A fan is usually used to help exhaust the burnt gasses.

Details below:
B-Vent (Natural Vent) gas fireplaces are designed primarily for decorative use. Generally they produce a larger and more realistic yellow flame. B-vent fireplaces are sometimes available without a glass window, so many homeowners are attracted to this design because of the open, realistic flame effect; some models do have a glass window so the existence of a window on a fireplace does not define its product classification. Natural vent gas fireplaces use room air for combustion and vent fumes through a vent or chimney that must terminate vertically above the roof line. The key to determining whether a B-vent fireplace will meet your heating needs is to check the manufacturer's listed efficiency rating (gas consumed x efficiency = heat output). While efficient, heater-rated B-vent fireplaces do exist, many lower quality "builder grade" fireplaces have no efficiency rating and, therefore, will not supply substantial heat. In fact, this category of fireplace will often use the greatest amount of gas at the lowest range of efficiencies. If you live in a warmer climate where you want the aesthetics of a fire without much heat, this may be the appliance for you. Likewise, bedrooms and smaller rooms may be a good candidate for a b-vent fireplace, but please check building codes to see if this class of fireplace is approved in your locality or for installation in the room where you'd like to use it. Local/national codes in some areas prohibit the use of b-vent rated appliances, especially in colder climates. Be aware that very "air tight" houses can cause performance problems with b-vent rated appliances, so please consult an experienced fireplace installer who can advise you on the proper installation and use you are considering.

Direct Vent Fireplaces offer the most features with respect to gas consumption, efficiency ratings and venting options. A direct vent fireplace will always have a glass window because these fireplaces are sealed systems using a double walled venting system. Combustion air enters the appliance via one section of pipe while fumes and moisture are vented through the other pipe. Most often, a double wall "pipe within a pipe" system is used. Subject to each model's requirements for distance and offsets, direct vent fireplace venting may be terminated either horizontally or vertically. Efficiency rating will average 65% to 84%, similar to ratings on gas furnaces. Keep in mind that these appliances must "waste" some of the heat produced to create a draft of rising warm air to evacuate the fumes produced without aid of a forced air exhaust system. Think of direct vent fireplaces as a decorative furnace: the beauty of a realistic flame with high efficiency. This appliance is great for primary or supplental heating and for emergency backup heating as most work without aid of electricity. Because this is a sealed system that uses outside air for combustion, direct vent fireplaces are usually the favored choice among those in the fireplace industry because of their greater efficiency and exceptionally reliable performance.
Hope this info helps,
I am a General Contractor.

    Bookmark   January 18, 2007 at 2:41PM
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In our last house, a 1100sf cape in northern Vermont, we had a Fireplace Xtraordinaire propane burning fireplace (model 34 DVL) that served as the only heat source. The house was only 20+- years old, but wasn't insulated as well as homes are now, and the windows weren't the greatest. The fireplace heated the 2 floor space easily, however, we burned a lot of propane, and I would not recommend the unit as a whole house heater because of that. However, in your application I think it would work well, the unit can really pump out the heat, the flame looked fairly realistic, the unit performed flawlessly for the 3 years we owned the house and it looked great.

We liked the look so much and were so impressed with the quality of the Travis Industries products that we're using a FXP wood burner in the home we're currently building.


Here is a link that might be useful: FXP gas fireplaces

    Bookmark   January 22, 2007 at 10:24AM
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