I will be using some metal strip for my roof, not sure what exactly is it, it could be the Galvanized steel roll. My contractor told me is sufficient to block the heat and also help prevent thief coming in.

Nothing can stop the thief to come in. It just slow them down. I got any idea from the Architect when I ask him for opinion. His house is using rebar (Reinforcing bar) on the roof. You know the thick steel mesh that contractor use for putting Reinforce Concrete. He put this on the wood that hold the clay roof. What he did is "Clay roof -> wood -> Rebar"

I was considering this option, but the cost is higher and need to do lots of reinforcing on the wood to stand the weight of the roof and medium thick Rebar.

IF anyone is rebuilding a house, this is also one good option to slow down the thief entering your house.

I don't prefer this type of instillation. First heat still trap between the roof and ceiling, second when you want to do wiring work got to dig out the insulation.

Is actually nightmare for pipe and electrical maintenance. Also for house owner using light bulbs with ballast. And if house pipe or roof got leaking, can growth mushroom :-) .

I ask similar vendor before of the points above. Can never give me satisfied answer.

Water leak without the insulator will be able to spot earlier. With the insulator the water will absorb into larger area, and may risk ceiling going collapse especially for plaster ceiling. Cleaning up the mess of absorb water maybe challenging.

I do see some benefit, it absorb the pump sound.

Us, au, even japan have code to follow and they enforcer it very tight. You should see their workmanship especially japan. I handled my previous company tokyo office relocation. I can you, their new complete empty office block before renovation is near perfect, the floor, roof, finishing is dam perfect. Even much better than our contractor here after renovation.

over here as long can work is ok.

Ask your contractor build up the wall. Is your house old house? Only the 49ers house use that, maybe summer in 80s

You never check before ask them come over?

Hope you did not pay them any deposit. The coolbatt things and similar are heavy so need wood or further strengthen your Plaster ceiling before putting it.

Put in support than ask them come over. Usually they have the contractor can help you, did you all them if they can provide.

Not your job, but knowing in advance will help you decide and execute faster.

Not your job, but knowing in advance will help you decide and execute faster.