Is my fireplace efficient?

September 19, 2005 5:58 PM

How energy (in)efficient is my gas fireplace?

I just moved into a new house and it has a really nice gas fireplace in it. When we crank it up it warms the living room really nicely. On a cold winter day would it be more efficient to heat up the whole house to 69 degrees, or to heat the whole house to 63 degrees and crank up the fireplace to warm up the main room?

posted by crapples to home & garden (4 comments total)

Well let's see here:

http://www.google.com/search?q=gas+fireplace+efficiency brings up, as a top hit, a link to Union Gas which says

"Generally speaking, natural gas fireplaces range in efficiency from about 20% to 70%. By choosing a higher percentage rating you’ll enjoy more energy savings."

While http://www.google.com/search?q=gas+furnace+efficiency brings up the U.S. Department of Energy telling us that furnaces range from 78% to 97% efficiency.
posted by five fresh fish at 6:34 PM on September 19, 2005

But that doesn't actually answer the question. Heating the entire house using an efficient furnace could still require more energy than just heating a single room with a less efficient fireplace.
posted by Rhomboid at 7:31 PM on September 19, 2005

if you dont know the efficiency either your heater or the gas fireplace, you're going to have a hard time solving this one.

google for R value calculations heating for some pdfs on estimating the heat loss in your home.

i'd say the most direct approach is empirical. during a time of year when the temperature is pretty constant from day to day, measure 1 day's worth of gas usage with the first approach and then 1 day's worth of gas usage with the 2nd. this way you don't really have to worry about the estimation of heat loss and heater efficiency. if the outside air temperature varies too much, you can always scale the gas difference by the temperature ratio, since the heat loss is linear in the delta between indoor and outdoor temperatures.

of course, you have to be careful not to use a whole bunch extra hot water or do a wildly different amount of cooking on each of those days. or you could do the experiment over multiple days to try to smooth out non-heater related gas usage. in my old house, the heater usage totally dominated the cooking/water heater by a long shot.

i am crazy, so i've spent a lot of time doing experiments like this, on both gas and electric consumption.
posted by joeblough at 11:50 PM on September 19, 2005

A lot would depend on what technology you're using to heat the rest of your home. If it's electrical for example, then somewhere along the line a lot of fuel will be getting burned to produce the electricity which will then be converted back to heat. This is not good for the environment and probably not brilliant for your bank balance.
posted by biffa at 3:16 AM on September 20, 2005