Something to watch for with a tile roof

no, the very expensive 4 baht thin cinder block things. work very well without insulation. they always put down there concrete and wire, then a row of block on one edge, i simply added another row on the other edge, with few inches of air in between. outside hot to touch, inside, cool as can be. too easy, too cheap.

With my house I added 2" fiberglass batts in the void between the double block walls. It more than doubled the R-value for around 5,000 baht for 52 meters of outside walls. When the walls were going up, but before adding the insulation, on a sunlit wall you could only feel a little difference between the inside surface of the second wall and an interior wall but after the insulation they both felt the same. The added insulation probably won't make much difference with the windows open but I think it will help when the AC's are on.

When I purchased my house it has two very long valleys, however as the Thai's tile so the the valleys have a small space between the tiles, it meant that birds, leaves and anything else that liked to spend time in the shadow used it.
After about three years I had the same thing happen, water inside the house.
I contacted my local roofer Thai and I made him cut the tiles so that the valley gap was about 3 inches wide. NOW no leaves, birds or anything else and no water inside the house.
I have guttera and tanks to catch the water, they in itself do not affect water off the roof. Insulkation would just hide a probelm until it got bad.
Just check the gap in the valley if you cannot see the underlying steel or aluminum sheet, have the gap made wider, an electronic tile cutter willdo the trick. it saves thousands in replacing a roof, and all the hassle that goes with a repair. it is not a repair just a commonsense approach to a simple problem made more difficult as Thai builders lack in commonsense.

The other thing that caught me is in roof valleys is something similar to to what I saw in this post.
invalid roof flashing. If the flashing material is not sufficient it will lead to repairs since the default stuff they sell for the metal that sits under the valley is too thin and the water will slash in during a heavy rain!