I know it can get pretty confusing, but it shouldn’t necessarily be. While any Sauna can heat the body, you need one that is effective and health beneficial.
Although a normal sauna can get hot, it doesn’t have as many health benefits since the heat doesn’t penetrate the skin. A far-infrared sauna will cost you more on the electricity bill and is not very healthy since your body is exposed to much more electromagnetic fields.
Using a near-infrared light will give so much benefit since near-infrared light heats the body effectively rather than the entire enclosure. On a more succinct note, you will get the health benefits of light therapy such as stress relief, anti-oxidation, cellular healing, and deep skin penetration.
Using a high quality near-infrared bulb to build your sauna is by far, a better option.
Stay Healthy!
Grace.