I've heard people say that about basements. However, you can use a concrete ceiling with rebar to keep that from happening. Most basements today aren't block, but poured in one piece using removeable molds. This can easily have rebar installed and bent over to pour a concrete ceiling, then build your house on top.
If I ever rebuild, I am going to try to find a gentle hillside, dig into it for a semi-underground home facing east if I build in Alabama.
Reasons are:
1) south and west are hottest so facing east with the open end would make it cooler.
2) north and northwest have colder winds in winter.
3) all recorded tornadoes in Alabama travel from southwest to northeast.
4) building on a hillside would allow for better drainage around the burried ends.
I know someone who did this in Auburn and didn't use any heat or air condition for one year to see what would happen. He said when it got down to 14 degrees, the inside was about 55 degrees, so a little fire in the fireplace took care of the chill. Only used the fireplace 2 days that winter. In the summer when it got up to 102 degrees, his inside was 85, but muggy. He discovered he needed air conditioning more than heat. Said in the winter, body heat, lights, cooking, and showers contributed to heating the home. So he ended up installing an air-conditioning system, but even that didn't cost him much in the summer. His home had about 2600 sq. ft. It faced northeast. He owns a crane company, so he installed prefab concrete bridge sections over his home after installing 12" block walls 14' high. He had a suspended ceiling. This allowed him to install wiring, lighting, and ductwork for his air-conditioning/ dehumidifier system. When you cut out all your heating costs, and 90% of your air-conditioning costs, that is a big savings. The cost of the home sq ft wise was about the same as a conventional home. Last I heard, he was installing a solar water heater/heating system. With some solar panels, he could probably take care of his lighting with LED lights. He only put 2' of soil on top of his home. I told him that one more foot would make him have a constant 60 degrees. My gas formulas for Alabama are figured for mains 3' deep and constant 60 degrees year round at that depth. 2' made him a little hotter in summer and a little colder in winter. The extra foot might have changed his inside temperature by 5 degrees each extreme.
