No reason why that couldn't work. Of course you wouldn't use it to heat a large room, or expect to raise the temp to 75 degrees in cold weather, but it could certainly make a substantial difference in an enclosed space where you couldn't have a fire. In response to other posts, regular bricks and concrete block may crack when heated in fire, but they will not explode. The moisture bricks and concrete blocks absorb escapes easily without danger. However, some (but not all) river rocks and shale rock can explode. Several times I've seen such rocks liven up a sleepy group gathered around a campfire.