I am in the process of building one in Somervell County. I am using the "Earth-Sheltered Solar Greenhouse Book" as my guide, though it doesn't completely fit with the Texas climate. My hole is 12' x 12' x 4.5' deep, and I expect to have a 7' wall on the north side. I think 3' deep is adequate as long as the north side wall is higher. Right now I'm leaning towards 6" concrete walls all around, though I may go with 8" concrete blocks just because they're easier. I want to grow lettuce, lemon grass, cilantro, and tomatoes year-round, and keffir lime and meyer lemon, too. Drainage is the issue in my area since there's lots of limestone rock and I really want to use gravity for drainage. Ventilation is a big issue, too, since the summers get so hot here. A friend had good experience with the temperature-controlled ventilation windows sold by major gardening suppliers so I'll probably go with those even though they are expensive. They open automatically when temperatures reach a certain setpoint, 78 or 80 degrees I think. I will try to post pictures as things develop. Growing in Texas is such a challenge!

Thanks for the ideas about plexiglas! I bought a sheet of it at Loew's once and had them cut it to fit my end table, to make a protector to keep it from getting scratched. You've given me the idea of measuring the panes and going to Loew's for a plexiglas sheet, having them cut it to size, and replacing the broken panes with plexiglas for now. It will be cheap and easy. The panes are held in with plastic glazing strips that will slip out. As long as I can get the glass out, it will be easy to hold in the plexiglas with clear silicon caulk & slip the plastic glazing strips back in place. WOW I hadn't thought of that. It will look fine from the street - not an exact match with the other panes but from the street you won't be able to notice. THANKS

eyoung- Here's a link to the store where I purchased the bowl. I don't think they deliver but any nearby outdoor specialty store should have a selection of outdoor bowls to chose from. Just make sure it is a clay fired bowl so it can withstand the heat and tell them what you are using it for so they can make recommendations. http://www.cornercollectiononline.com/gsb.htm The fire ring kit and feather rock was purchased from fire pit outfitters per link below. They do deliver and I ended up with one of the manual spark ignition kits instead of the electronic ignition kits. When you see the pricing, you'll know why! There is also a match lit kit if your budget is tight and you don't mind manually opening the gas valve and lighting the fire ring with a match. Note, the manual kit does not have any flame out protection, so if the flame does go out, the valve will have to be shut off manually to prevent gas from flooding the area and creating a hazardous situation. Both the direct spark ignition and electronic ignition kits have flame out protection. http://firepitoutfitter.com/index.asp?PageAction=COMPANY I then converted the manual kit over to an electronic kit using the components below. Note, you can also buy the electronic ignition kit directly from firepit outfitters but it will cost a lot more than the conversion components I describe below. The advantage, of course, is you won't have to hassle with the conversion and you'll know that the kit will work out of the box if installed properly. Here's the electronic conversion parts. These parts can be found online or at a local HVAC Center or Appliance Parts Center. Gas Valve - Electric Direct Spark Ignition Control Module with flame out detection Flame Sensor - Electric The manual spark ignition kit already has a spark ignitor included in the kit but the flame sensor with the kit is a mechanical one so it needed to be upgraded to electric. The ignition control module will be controlled by our pool automation system and turn the fire pit on/off with the hand held pool remote. Also very important, allowances for air flow are critical to ensure the temperature does not exceed 175 degrees F where the electronics and gas valve are housed to avoid damage to them. This includes adequate intake openings at the bottom of the bowl to allow cool air in and adequate openings around the pan to allow the hot air to escape upwards without restriction. If any of this does not make sense, I would recommend consulting with a local professional such as an electrician, plumber or HVAC technician who has experience making these parts work together safely. Hope this helps!

My answer is based on common sense knowledge, not scientific laboratory or engineer's testing. If someone comes up with an answer from either of those departments, I'll be happy to defer. I think of how many parts of a fireplace surround or hearth of various natural stones or concrete. As long as you're not in the direct "firebox" or chimney area, I don't think the material will be exposed to sufficient heat to cause harm. Keep in mind that the O2 being supplied to the fire is coming from the outside air -- cool air -- washing over the fire pit wall and cap on its way to the fire, ameliorating the effect of heat somewhat. That said, my educated guess could be wrong because that's how educated guesses sometimes are. Hopefully, my answer will not discourage anyone from offering a better one, if they have it.