I don't have any particular experience or knowledge about how to install these products etc. However, we've just had our metal roof relaid, so I've got a bit of an idea.

My view is that R1.5 is not enough in the kind of climate you're talking about. We've jsut got to about r6 or so, and it has made such a massive difference already.

We had some old r4 batts in the roof, they had worn down and flattened, so I reckon they're about r2.5 now. We added some more r4 batts, then a sheet of vapacheck, which sounds similar to the anticon mentioned below.

I don't really agree with the statement that more insulation means that the heat gets trapped in. It keeps way more heat out to start, so the whole house doesn't get anywhere near as hot. Plus, you can open the house up once the sun has gone, and it cools down pretty quick.

For what its worth, I say get as much insulation as you can - r1.5 will be better than nothing, but it will get cooooold in winter if you don't get any more.

Trav