unheard

Are you close to the plant? That's the only situation when delivery costs are not a significant part. Or your roof is grossly overpriced. Three roofs - all made by a local Bluescope franchisee. Two Bluescope Zacs in 2 different profiles - one is PU insulated, another is with thin stuff. The third is Bluescope Colorbond - PU insulated.

????

Have you ever purchased a metal roof? It doesn't sound like...

Well, yeah... And then another thread comes up later on with a similar question. Filled with speculation and unnecessary arguments. Just like this thread...

Delivery costs is another big expense that is usually not factored into the overall price.

Sorry, what's your point again?

Is that hard to deduct based on the available info? The question is by how much more. We can only hope that OP shares his price discovery findings after obtaining price quotes. Threads like this regularly spring up around this forum without much of a follow up.

You haven't mentioned if you've already planned or priced out the rest of your house project. Just a word of advice...(Please disregard if money is no object). It's only natural to desire the best available materials. But the vast majority of us don't have a luxury of unlimited budgets. The Roof is not the only component that determines overall quality of a structure. Quality of the builder, walls, windows, ceilings (insulation), doors, thermal design/house orientation, shading, furniture and amenities... All will have to compete for and be balanced out within your particular budget. You've mentioned that you don't want to build a hot box. The super-duper roof alone won't help you in achieving a well insulated dwelling.

But why would it matter for the inside facing sheet? Why to overpay for extra protection? Unless roofing over a facility dealing with corrosive chemicals.

It won't produce any rust on the surface of the thinly coated material - no need for multi-layer treatments similar to the out facing site which is exposed to UV, acid, salts, dirt etc.

How's spray foam related to this discussion?

Thank you for bringing this up. Bluescope is considered to be the best and most expensive option for coated roof material. But they're not the only game in town. There at least several other, cheaper suppliers of roofing metal selling in this market. My understanding is that the other options would be coming from Chinese and Korean manufacturers. The non-affiliated with Bluescope shops normally sell cheaper roofing metal which is roll-formed in the exact same way, more likely on the same or similar machinery, including PU foam mixers. The only difference is the core material.

The thin glued-on insulation layer is not the type of 25mm PU foam that's produced by mixing two liquid streams that's made right at the roll-forming line. The thin material is made off-site and comes in rolls. That's the only difference that matters to this discussion. The thin stuff can be made out of anything including bubble wrap. Let's keep things simple.

Why would coating matter on the bottom sheet? What's so critical about that? It wouldn't be exposed to any elements.

Sounds like a good plan!

Yeah, from what I remember from my last purchase the shop has offered three types of the underside finishes: silvery side of the foil facing out, white side out or a layer of plastic white sheet. I'm not 100% sure about plastic though since I've never considered or looked into that option.

Roof condensation is a risk in colder climates.

Yeah, 7.5cm of insulation wouldn't add much on top of the already performant 2.5

That's right - Bluescope sells metal sheet. But it also has a franchised network of roll -forming shops throughout Thailand. Those shops are usually being an easily accessible source in the whole of Thailand of the single-skin Bluescope-branded metal roofs (in most cases). They roller-form Bluescope's metal into a desired profile, apply PU or the other type of thin insulation and cut finished sheets to size and deliver to location.

There's an underlining layer of what looks like aluminum foil. The foam layer stiffens up the sheet. It feels almost solid, not wobbly. 25mm thick insulation works just fine in my experience. Upon delivery the roof stayed under the hot Sun and the underside remained barely warm to touch.

But we're not talking about spray foam here. What do you see being wrong with this design that's been used in Thailand for many years by now? Or rather why wouldn't you use it on your own house?

@sometimewoodworker @Kwasaki Are you guys talking about thick PU foam or the thin type of insulation that is glued on.to the metals surface? From what I've seen on this board that's the silvery thin material that does tend to separate after a number of years, especially when exposed to elements. It's not made out of PU!

I love this metal sandwich system! But at the same time I also like the "regular" panels without the extra cost of the second metal sheet (would be nice to know the price difference).

Sorry to repeat, but what's exactly the failure? His words: "In all probability a layer of silver backed PU foam will provide a similar, if not better, result at less cost though it’s common for lower quality installs like this to breakdown." What kind of breakdown of PU foam? Can you please describe or point me to any evidence?

Second that! Not only interesting but also super helpful for anyone considering insulated metal roof options.