What Makes Log Burners So Efficient?

anotheruser

Compared with an open fire, what makes log burners a lot more efficient giving out heat?
I appreciate the chimney hole isn't as big but a lot of heat must still escape up there? 

theonlywayisup

Partly because you can control a burner and less so a fire.  Not all burners are as efficient as they should be and much like other appliances (boilers) there are good and poor ones.  

Davesnave

In two words, good design. Just like modern cars squeeze more from the energy in fuel, so a good wood burner will achieve a high level of combustion and ensure much of the energy released goes to the room. Good wood burners are easy to light with precise control of air flow, preferably through a well-matched flue that has enough 'draw,' but not too much. Also, the seals on the burner's door(s) need to be sound.

The other part of the equation is having correctly dried wood. Mine is at least 2 years old before I think of burning it. If people hear logs fizzing as the water in them boils away, they're much too wet. This has implications for storage space.

Ectophile

A big problem with open fires is that the hot gases from the fire just go straight up the chimney.  You are relying mainly on radiated heat from the hot wood.  A stove has a baffle plate in the top, so the gases have a convoluted route through the steel stove before they reach the chimney.

With a stove, you can control the air flow.  Once the fire is burning nicely, you can close down the vents, and get the logs to burn more slowly.  With some stoves, there is a recirculation system so that some of the gases from the wood are given a second chance to burn.