I live in a duplex bungalow. The room on the first floor is about 250 sqft but has only two windows of 12 sqft each. The roof is at 10 ft level. The roof is open to sunlight and is used to dry clothes so I cannot do anything with the roof. I have aircon but it just does not cool the room. The temperature outside ranges between 36 degrees to 42 degrees. We have comfortable temperatures of 14 to 24 degrees for one month only. So please advise.
If you can't re-insulate the whole house it might be possible to insulate just your room. Since you're already using an air conditioner the lack of effective thermal mass once you do that shouldn't matter much. But it depends on the extent that you're allowed to modify the house.
What we are considering doing in our house is somewhere between building a new room inside one of the existing ones, and lining the walls and ceiling with insulation. The simplest version of this is European-style wall hangings. Find something insulating and hang sheets of it on the walls. Optionally weave the material into decorative tapestries.
If you can get sheets of polystyrene or better foam+foil insulation, you can layer those on the walls and ceiling of the room and tape the gaps. That will obviously make the room smaller, but should be fairly effective. Doing the same with the floor is more difficult, and you will probably need a dedicated underlay material. But simply laying down a layer of flooring ply or new floorboards over the top of the existing floor will help.
The next step, which will take even more of the room space, is to build a whole new layer of wall inside the existing one. Normally you will do a stud/timber frame wall, with any wall insulation, and no exterior cover (because the existing wall does that job). We are looking at using coolstore panels (steel/foam sandwich) instead to get better insulation and better sealing.
With any of those the big problem is the window. You still need to be able to open it, but windows are normally very poor insulators. If you can afford a double glazed window that will help a lot, and may be the single most effective change you can make (as well as the least obtrusive, but also the most significant change to the building structure). There are a range of DIY double glazingideas around, one or more of which might suit you. If you get direct sun on that window a shade or shutter will also help, if you can add that to the outside of the building.
There are safety issues to consider. You need to avoid anything that makes the window unusable as a fire escape, for example, and you should consider ventilation more generally. Also think about what happens to moisture that gets between the existing wall and any insulation - if you get sheets of mould behind the insulation you could make yourself quite sick.