Wood Buring Fireplace Efficiency
There are several thermal dynamics that come into play with fireplaces and their efficiency. They dictate how efficient a fireplace is going to be. Here are the key factors to wood burning fireplace efficiency.
The biggest is the orientation of the chimney. A chimney is made of brick or block that absorb the heat from the fire built in the firebox. That heat is then transferred (at a much lower temperature) through the brick as it warms creating it's own type of natural heat even after the fire has died. The orientation of the chimney dictates how much of that heat escapes into a house. The best place for a chimney, of course, is right in the middle of the house. This is where the chimney can be utilized the most from floor to ceiling. Unfortunately, with a chimney that is on an outside wall, this heat transfer is significantly less.
If your fire flames up more when you close the doors than it does when you open them, then it is time for new fireplace doors. The doors are meant to cut down on the oxygen flow to the fire making it burn longer and allowing the firebox to collect heat. Good fireplace doors can cost anywhere from $400-$800 depending on the trim package selected.
A fireplace blower gathers the heat from around the firebox and distributes it around the room. Some systems are installed around the entire fireplace, while others are simple the grate that the wood sits on attached to a fan motor and a connection that cycles air through a sealed pipe to draw the heat from the fire and embers. These are add on units and cost between $250 and $350 depending on size and heat output.
Fireplace Overall Efficiency
Overall, fireplaces are not very efficient allowing 50-80% of the heat made to go up the chimney. If the suggestions about are used, average efficiency could increase as much as 20-30%. If you are looking for truly efficient wood burning, however, you have to install a wood burning insert. This is basically a wood burning stove that is meant to slide into your fireplace opening. Most units come with a blower for optimal heat distribution.
Wood burning fireplace efficiency depends on how you use it and how it is constructed. Remember that if you keep a fire going for a day or two or three, that heat stays in the house consistently. It also takes a while to get warmed up from a standard fireplace because of it's recessed design. However, there are few things that can warm the toes and the sole, like a wood fire.