30 rolls seems like an awful lot, mate - your roof must be huge ! How many square meters are you talking about ? My house is 200 square, and has a very complicated roof, not sure how big, but I know I used around 3,800 cpac tiles, and I think I used around 6 rolls ?
Myself, I went through exactly the same as yourself, and the retailers generally try to sell you whatever they make the most commission on. I would also believe - many of them don't actually know, or have any experience of using foil - it's not a thing your average Thai would bother using. My roof is entirely cpac - even down to the screws, and the cpac reps tried to deter me from using other brands, and naturally tried to sell me cpac foil, and of course it was the best, for sure, and blah blah blah. All unbelievable advertising spiel.
In the end, I went to every retailer I could find, and actually opened every type of foil I could find, and tested the strength in a small corner of the foil. Some of the makes have leaflets, with samples in them, so you can see for yourself, without having to resort to such measures. All of the paper based stuff ripped easily, burned easily, and pushed through easily with just a very small amount of water applied. I couldn't see any of it lasting long if you had a leak in the roof, or a fire. Once you compromise the fabric of these materials with screws, I'm not sure how they would hold up if your roof is breathable, with vented ridges, and the constant airflow / humidity.
In the end, I was lucky, and found some rolls in stock clearance, that should have been around 4,000 baht - reduced to 1,900 baht. The stuff I ended up with was made in New Zealand, (Harvi foil) and was actually listed as agricultural foil (which cpac said was not good to use) - guaranteed for 10 Years against chemical sprays and water, and presumably animals pissing on it - which means in real terms it will last for an age. Very strong - you can't rip it manually, I believe you could actually swing off it if you wanted to. I tried burning it, and it just shrivels up. Retrospectively, this was a good move in a number of ways. Some of the longest horizontal runs on my roof are around 20 meters long, and when I had it installed, if you can imagine one guy at either end of a long run of this stuff, quite a few meters off the ground, trying to pull it tight to screw it down, before applying the tile batons, with the wind getting behind it like a sail, and nearly pulling the poor fellows to their demise - I'm fairly sure the expensive paper based stuff would have ripped to pieces easily.
For all of the claims of other brands, on a very hot day, my house is a good deal cooler than outside, and I haven't rendered, or fitted uv reflective windows yet - the foil works a treat (although my roof is a breathable design). I've used an extra roll I bought for two shelters on my farms, and a rabbit hutch - all corrugated iron roofs, and in direct, blazing hot sun, the heat does not radiate through the foil. It is important to have the air gap between the roof and the foil. The cpac alloy batons allow around 5cm from the foil to the inside apex of the ridge of the tile, if I remember correctly.
I would ignore the manufacturer's claims, and have a look at finding the physically strongest double sided foil you can find - invariably, this will be plastic based sandwiching a woven aluminium reflective surface. Have a look at good quality agricultural stuff, man. In my experience - highly reflective, durable - acts like a secondary roof / water barrier, and much better against the elements. Make sure it's applied horzontally, under the tile batons (or under the joists if your batons are welded steel), with a good overlap from the next piece above (around 20 cm). You don't need to join the edges with foil tape either with this overlap, regardless of what the suppliers / builders say - expensive, and so ridiculously thin / fiddly to use, not durable for sure. If you have breathable vented ridges and soffits the foil wants to start about 50 - 60 cm in from the extremeties of your roof, (usually the second baton up) - convection does the rest.
Have a good look if you have the time, mate - it will pay off in the end.
I wouldn't go with foam, unless insulating a colour bond roof - expensive, and makes it very difficult to trace leaks if you have any.
Edited by Ackybang, 2013-06-30 11:09:24.