Expert: Richard Taylor, AIA - 11/23/2008

Question
I am wondering if installing an airtight glass door for my masonry fireplace might help significantly with heating costs by burning firewood slowly inside the fireplace with the doors shut.

Answer
Marty - thanks for your question!

The simple answer here is no - you'd cut off all the combustion air in the fireplace and would not be able to sustain a fire at all.  You'd also create a significant combustion gas hazard in your home.  Most definitely DO NOT try this!

Any change to your existing fireplace must be done by a qualified, experienced professional mason.

There are "sealed" glass fireplace units available in the marketplace but they are gas-only units, not wood-burning.

If you want to get the absolute most use of the available BTUs in wood for heating, your best bet is probably a wood-burning stove.  Because they're typically made of cast iron, they radiate a very large percentage of the heat generated by combustion,as opposed to a masonry fireplace where much of the heat generated goes up the flue.

Alternatively, your existing inefficient masonry fireplace can be converted to a more efficient type, but you need a professional mason to do it.  The "Rumford" style masonry fireplace is a more efficient shape, and reflects more heat back into the room.  Many existing masonry fireplaces can be converted to Rumfords.  It's not cheap, however!

Finally, you can purchase a "Grate Heater" for your fireplace.  It's essentially a series of tubes that you insert in your fireplace and built the wood fire on...the tubes heat up and a fan pulls air through them (heating the air) and into the room.  Try this link for one product (this is not an endorsement): http://www.americanchimneysweeps.com/the_fireplace_heater.htm

Hope this helps,

Richard Taylor, AIA
www.rtastudio.com
www.rtaplans.com