|The potential heating value of wood is about 7,200 BTUs per pound. We can burn 20 pounds or more of wood per hour in a 48" Rumford and, if the fireplace is about 50% efficient, your BTU output would be about 72,000 BTUs per hour (7,200 x 20 x 50%).|
July 30, 2001
Your website was very helpful.
We are considering putting a 48" Rumford in our new home and would like to know what the BTU output will be per hour with the doors open and doors closed. Do you have any information that will help us answer this question?
From: Jim Buckley [mailto:email@example.com]
Sent: Monday, July 30, 2001 12:06 PM
To: Jim Passage
Subject: Re: New construction
The potential heating value of wood is about 7,200 BTUs per pound. We can burn 20 pounds or more of wood per hour in a 48" Rumford and the fireplace is about 50% efficient so your BTU output would be about 72,000 BTUs (7,200 x 20 x 50%).
Glass blocks over 90% of the radiant heat (see tech14.html) but, curiously, does not reduce the efficiency much - in the lab. With the doors closed apparently the energy goes into heating the brick mass of the fireplace instead of heating the room radiantly.
These are rough numbers and may not be very useful. The 48" Rumford fireplace is capable of heating a large open room without glass doors. Closing glass doors dramatically reduces the effectiveness if not the efficiency. It may drive the heat into the brick but the brick may be outside and in any case is too thick to get hot enough to transfer heat to the house effectively. Rumfords are good radiant heaters and not very good mass, air or water heaters.
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