Shingles have a 50 year life span, in my experience the polycarbonate panels start to get brittle and crack after five. Any roof that is face screwed only last as long as the rubber washers (about ten years)

How would your HO Ins. company feel about that type of roof?

They are used on exterior spaces or barns because it's not as important what's underneath them. The cheap ones you are looking at (non-commercial spec) will probably not achieve the wind rating you require. Many other downsides making it the improper product, google it. Just stick to shingles.

Miami approves.

I haven't asked to my insurer, and want to know more about building codes for it too. But I'm just asking because I really believe would be a good idea if allowed.

On the last patio roof I did, I've used almost no screws, I put some 1.5 x 1.5 wood strips over the panels to reduce potential leaks and increase resistance to wind. So far much better than using screws only.

I cannot see the building dept. or your home owners insurance company allowing that type of roof on a home. Even more so in Florida as there is no way that would survive a hurricane in my opinion.

Well you didn't click on my link then.

Yes Joseph, thanks for the link. I believe I'll ask them directly. I know the material is approved in Miami-Dade and sold in HD and Lowes, but my doubt is, specifically about the application, in this case re-roofing over shingle.

The point being missed is not whether Miami approves a polycarbonate panel, it is also the system of fastening and flashing of water penetration that withstands the high winds. Realize that a commercial product specification (meaning products not at HD or Lowes) may have tested compliance when adhering to their fastening/flashing, but that does not apply to DIYing panels you buy on sale for a patio roof, where the patio does not have wood sheathing, insulation, and drywall that would have severe consequences with water penetration.

Your inspiration for this is cost basis only, so I challenge you to get bids on this method, including all end closures, penetration boots, warranties, attic venting, and structural calcs of putting it over existing shingles that will compare with just a tear-off and asphalt shingle.