insulation
I live in Rajkot, India. Temperature goes above 40 *C (104 *F) for at least 4 months a year.
I live in a single floor house with 3 sides of house and roof is exposed to sunlight.
It's a house built with brick walls, plaster and concrete slabs. flat roof floor is tiled with white ceramic tiles. Outer walls are painted white.
Is there anything I can do to reduce the inside temperature?
I just finished our garage this past summer and here are a few things I did.
I insulated the garage door by cutting pieces of rigid insulation foam to fit into each piece of the garage door. You can glue them on and then seal the edges with expanding foam or caulk.
On the side of garage door I installed weather strips and also on the top/bottom of the door so that it is sealed when the door closes.
If you have any windows I would make sure to seal them (I boxed mine in with wood and then caulked). Also depending how you finished the bottom of the garage walls, I would seal the bottom (my drywall buts up right to the cement floor, so I sealed the space with expanding foam and cut the excess away).
The simple answer is "yes". Every piece of insulation you put in is a bit of heat that's not lost to the outside world. This is better for you as your house is warmer and your fuel bills are lower, it's also better for the environment as you're not using as much energy.
The more complex answer is "it depends". Buying and installing the insulation costs money (you don't say!) so the immediate equation becomes "is this cost less than the money I'll save over X years?". It's the answer to this that will, largely, affect your decision on whether to insulate or not.
The company who wouldn't estimate may be right (for their system) in that it would cost $2,000 (say) to do the work, but you'd only be saving $20 a year on your heating. This would mean it would take 100 years to pay back the cost. Now, if you can find a system that costs less then the proposition becomes more economical. Insulating the ceiling/roof space is a good thing to do anyway.
However, if your primary concern isn't the savings then you might decide to go ahead regardless.
Best Answer
Add a corrugated roof slanting from 1ft to 2ft high with the corrugations pointing to the higher side. Convection will pull the air to the higher side and out, providing some airflow. Insulate the ceilings of your living areas with rigid foam panels to limit heat gain from the roof. Provide awnings above your windows for shading in the summer, especially on the South facing windows, use a passive solar calculator online to size the awnings properly for passive sun heat in winter.