If there is no water leakage issues in your roof/walls of room, then get complete false ceiling & walls of paperboard. Use wallpaper on paper board. Keep approx 6-12inches space between wall and paper board, or use thermopore and then a 6" space, and then the paperboard. If you see constructions in hot & cold areas in europe, this is how its all built because wood is the best natural insulator. One small boiler heats the whole house and one central AC coil removes all moisture to cool the whole house. Its all because of the insulation provided by the wall & ceiling cavities.
Inside walls....use hollow concrete blocks, use thick thermopore, use jumbolon boards & the like, use an air cavity (few inches empty space), use wood, use space filled with fibrewool/glasswool (its the new govt subsidised thing in the UK and makes a huge impact)...etc etc etc. Everything already been discussed in earlier pages. Useful discussion.
Windows are huge heat sources/sinks. Idk why the heck there is a new trend in this hot arid environment to have humongously windows. Maybe to show off how the occupants are steam-roasting in the 2-crore brick oven.
Mud = huge heat capacity.
Its why they use it in heat furnaces!
You are better off with false wall and ceilings with 6-12" wall cavity. Also, use hollow-concrete blocks instead of bricks. Bricks will ruin the comfort level inside unless you make 18-24" thick walls. Even then, after a week of hot weather all that heat will still penetrate inside.
Use cavities! Air is a great insulator.
Take care of windows too. Discussed in earlier pages. If you don't design windows properly, then wall insulation will be pretty much ineffective.