From the replies I have gathered, some establish developers are indeed using metal deck roofing for even bungalows. This shows that there are indeed better quality metal roof material and insulation techniques available in the market compared to the case I have gone through. However, this info came to me only later, and the case I went through was genuine, which gives ground to believe what I have seen and heard as a poor case of metal roofing and insulation. Hence, prozak53 should now be convinced that there is no attempt at insinuation at all, particularly at developers.
What he should have done should be, if he is in the know, to offer some info on this issue of insulation. Instead he showed 'indignance', and yet, refrain from giving a suitable answer. By talking about something else i.e. lightning - the cause of thunder whereas we are talking of the effect of thunder - loud sound, and by his further talk of the effect of rain, not thunder sound, on metal roofing in his links, he is saying to all readers of this forum that he is dodging the issue, that there is indeed a big problem over the use of metal deck roofing that he wouldn't or can't address at all! This amounts to casting doubts over the qualities of homes offered by the few big time developers that he has so eagerly named.
If I were a staff of any of these developers named by him, I would definitely take him on from here and question over his motive! For a simple reason : if he is genuinely innocent, he shouldn't put his foot into the discussion if he doesn't know about insulation, or if he did know something, what is his reason for withholding the info? Who is he truly trying to cast us against in this forum meant for home buyers? KL Kepong won't be fooled by this, I think.
Like me a post earlier, if you think he is somehow weak in his analytical capacity and is downright idiotic, he might be a happy person that no one knows what he is truly getting at. He rather downgrades his intellectual capacity to let you and I think that he doesn't know the difference between 'cause' and 'effect'. But this is highly unlikely.

It really depends on what we are getting. Sophisticated factory may get double layers insulations (Example:rock wool), residential usually get 1 layer, then again the thickness matter.
Too uncertain I will leave it to luck.
The required thickness base on the density of material.