Open topped enclosures do not, and cannot work, as you are experiencing first hand. Having the heat lamps and CHEs outside on top creates a chimney effect that draws all the heat and humidity up and out and pulls in cold dry room air to replace it. Most of the electricity you are burning is just going up and into the room. Covering the top is better than nothing, but it doesn't solve this problem.A few weeks ago we got a Brazilian Cherryhead red footed tortoise, but we are first timers and learning. It was born 6/3/2022. I bought a larger enclosure for it so it will last it a couple of years before we transition them outside. I have looked through threads for hours and figured it was time to ask for specific advice. Since the top is mesh we purchased plexi glass and cut it to fit the front half and then I put foil besides the lamps to try and retain heat and humidity/moisture. I have a sensor by the bulbs to keep the temp there at 92, and then I have a sensor on the opposite end that usually is around 80. Do you have any tips on how I can keep the temperatures higher in the “non-bulb” areas? And keep humidity higher and more consistent? Currently I spray down the enclosure morning and night and it usually keeps around 60% humidity in between.
What you need is a large closed chamber with all of the heating and lighting inside. For a CH, I would also eliminate the basking area in favor of just having a warm over all ambient temp. Radiant heat panels mounted on the ceiling are a much better way to go than CHEs too. Either heating method needs that thermostat. When you switch to a closed chamber, you will be amazed at how little electricity it takes to maintain the correct warmth and how easy it is to keep things both humid and dry at the same time.
Your tortoise needs humidity, but be careful that you don't cause a case of shell rot on the plastron from having substrate that is too wet too much of the time. Having a large closed camber allows you to easily maintain 80%+ humidity with dry substrate.