Hot air rises. Thus they are trap at the upper portion of the house.
Like someone mentioned before. Install the wind turbine ventilators.
Alternatively, install those insulation - rockwool, etc. try searching in the net. This is to prevent the heat from radiating from the attic to the room below (1st floor)

It depend on how much (temperature) you want to cool down. If you want to use it for entertainment, nothing beats installing A/C

depends on what room temp you are looking for. in our kind of weather, the turbine ventilator will not lower the room temp much. Basically, its function is to draw out the hot air that are trap at the ceiling level. If the weather is hot, the room will not be much cooler then outside. Maybe a few deg C lower. That's all. This is from my experience from using them at my previous house

To really have a cool room, nothing beats having an air con switched on. Of course, there is the initial installation cost plus the monthly elect bill

what's the damage for the TCL?

Generally, heat from the outside penetrates into the house from all directions. They can be from the roof, walls, windows or even openings.

Those that are renovating their house (to be exact, hacking and extending their existing perimeter walls) can opt to use the autoclaved aerated concrete (AAC).
These are not the normal red clay brick or the sand bricks. They are concrete product made with fine raw materials entrained with tiny air bubbles and cured under high pressure and temperature. The tiny bubbles slows down the heat transmission through the walls and acts as a heat shield. Thus providing an insulation against incoming heat into the house.

This is not a new material. It was first introduced as a building product in Europe in the late 1920s.

These products are currently being used in the green bungalows in Semenyih

You can refer to here