Heating Your Home: Why Open Fireplaces Don’t Heat
Author’s note: the following article on home heating is the fifth in an eight-part series.
Open fireplaces have a reputation for polluting air. Actually, a fireplace, when burned hot and fast, creates very little pollution. The trouble is, a hot fire in a fireplace sometimes yields less heat than a smoldering fire. Where does the heat go?
The optimal amount of combustion air contains just enough oxygen to burn all combustible gases liberated by the heat. Any additional air grabs heat and sends it up the chimney. Under some circumstances, fireplaces can so far exceed this air-to-fuel ratio that they suck more heat out of a house than they radiate back into it. The fire actually makes the house colder!
The usable heat produced from the fireplace is primarily radiation, the same heat you feel on your face when you look at the flames. While fireplaces often contain lots of thermal mass (masonry), the unrestricted flow of cool air across this mass prevents it from capturing much heat. Nevertheless, if the damper is closed as soon as the fire burns out, a significant amount of heat will radiate back into the room instead of going up the chimney. Unfortunately, when the fire burns out, many fireplace users give up and go to bed without taking this critical step.
Here’s where pollution enters the picture: instead of burning a quick, hot fire and closing their damper, most people elect to burn their wood slowly to meter out heat.
Slow combustion means that the wood is burning at a lower temperature. At a lower temperature, a smaller portion of the combustible gases actually burn. More gases leave the chimney as smoke and soot (pollution).
With fireplaces, you really can’t win: if you burn a hot fire, you lose most of the heat up the chimney. If you burn a slow fire, you get very little heat, and lots of pollution.
The next article in the series talks about woodstoves.
Previous Articles in this Series:
- Heating Your Home: Thermal Mass
- Heating Your Home: Forced Air
- Heating Your Home: Heat 101
- Heating Your Home: Radiant Heat, Wood Heat
Photo credit: Wikipedia Commons
Glad you’re getting the word out about how to build a clean burning fire. It makes me so sad to see grey smoke coming out of chimneys!
We’re considering building a near-passive home, and are considering a Tulikivi or similar to tide us over the really cold days. Yes, the transportation of the ton of soapstone is a concern, but we’re in Europe, so it won’t be as bad as shipping to the US.
Excellent!
I want to make calculations of heat energy efficient house for cold countries such us Russia, Alaska of USA and Canada. This house use energy of wind and heat energy of soil.
er tI am finding sponsor for this works. The sponsor will be used technologies that will be developed.
See details in this doc-file:
http://simulations.narod.ru/energy_efficient_house.doc
As Philip says, this appears to be a ground source heat pump powered by a wind turbine. The winter cycle makes sense to me, but I was wondering if maybe in the summer cycle, the earth-cooled inlet air might be sufficient for cooling? Also, might the system might be easier/cheaper to build if it were electro-mechanical rather than purely mechanical? (Additional watts are cheaply purchased for wind turbines, so losses due to conversion should be easy to cover.) I would also be worried about being utterly reliant on wind for my heat. While I can’t say I’m a veteran of harsh winters, it’s my impression that cold, windless days occur everywhere it gets cold.
I, too, look forward to seeing your concepts progress.
Your diagram looks a bit like a ground source heat pump combined with a wind turbine.
It’s not really related to the article topic, but it would be interesting to hear more about it as you develop it further.
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Chris,
I read your article “Heating Your Home: Why Open Fireplaces Don’t Heat” with great interest. It is suprisingly not well known that an open fireplace is a loosing battle in heat production in the winter. There are upgrades that help some by trying to bring some of the wasted heat back into the living area but the truth you hit on the head is “it is a loosing proposition” if your goal is heating your home.
It is worth mentioning here that metal dampers in firepalces are also notoriosly bad at stopping air from entering the house and dampers allow heat to escape. If your goal is to stop heat loss and cold air inflitration while you are NOT using your fireplace then you can use a chimney balloon as a damper to stop this from happening.
See new calculation result on the bottom of the page:
http://simulations.narod.ru/ideas/eeh_en.html
I made calculation of cooling of soil with boreholes-radiators.