But but but why? How? It's counterintuitive.
Dont get you, do you mean that the fire is essentially behind "glass" and you think that you get less heat??
See below, also you can control the rate of burn by the dampers in the stove so if the room is hot or you just want to turn down the heat you simple turn the little knobs on the fire. Very safe to use no sparks etc. The metal also acts like a storage heat and disipates heat out even when the fires has died down. My wife could never be bothered with the old open fire messy and she found them hard to light, but she just opens the dampers and theres a sort of rod at the top which opens an extra vent and whoosh the fire takes off. Most mornings all your left with is some ash in the ash tin take it out a rub with a fire brush a wipe of the glass with a damp cloth and your good to go. The only downside is sometimes when I sit down I tend to fall asleep with the soothing flames and the lovely heat.....but that could be my age
A wood burning insert may be used to refurbish an existing fireplace, or to finish a fireplace in a new construction. Wood burning fireplace inserts are self-contained and relatively easy to install, with all the components needed to provide the warmth of a real wood fireplace in one energy-efficient package. The front of the wood burning insert is generally encased in glass, and an adjustable fan blows a stream of heated air into the room through vents.http://www.wisegeek.com/what-is-a-wood- ... insert.htm
The crackle and aroma of a nice, warm log fire is very enjoyable for many people. And, while non-renewable fossil fuels such as coal or gas do burn cleaner than wood, they cannot truly duplicate a wood fire. Unlike coal or gas, wood is a renewable resource. However, open wood fireplaces provide inefficient heating, allowing most of the heat to escape right up the chimney. A wood burning insert is made to be extremely energy-efficient, and to provide a cleaner burn than a wood furnace or typical fireplace.
Heating efficiency is measured in British thermal units (BTUs), with around 25 to 30 BTUs recommended for each square foot of space (approximately .304 square meters). A wood burning stove insert will achieve about 75% efficiency compared to around 25% for an open fireplace. It is clear that wood fireplace inserts far outpace open fireplaces in energy savings, providing an inexpensive, alternative heating source. By installing a wood burning insert, consumers can enjoy the natural heating properties of a wood fireplace while minimizing environmental damage.
The Sustainability Ireland site confirm the figures http://www.sustainability.ie/energyefficient.html