Hi
I read the same thing about 12 years ago and immediately had to try it out. It's amazing how well this works !
For people weary of exploding rocks, rest assured that ordinary red brick is safe to use. Because it is so porous any water present in the brick is free to check out any time it wants without building up any pressure during the heating process. Though it is not impossible a brick may crack after repeated use, it will not explode !
Ever heard of brick walls detonating in a housefire ? <img src="/images/graemlins/crazy.gif" alt="" />
I once used this trick in an emergency when there was a blackout at around 10.15 PM and it was freezing outside. As the temp inside started to drop I remembered this and fired up the bbq and grilled 8 red bricks, 4 at a time for a little over an hour (75 min. I think it was).
Hauled them inside in wire baskets and although it didn't heat up like a sauna and despite the fact that my home is not that well insulated it did keep the inside temp at a comfortable 18 degrees Celcius (64.4F) during the night till power was restored at around 05:30 AM.
Since I used a charcoal fire for this it may have been hotter than your regular wood fire but I'm not sure.... However I think I got excellent milage from the hotbrick-trick
Regards,
Pharaoh.