screen porch floor insulation

A few years ago we had a swim spa and I installed a 12 x 20 slab (6" thick). We sold the swim spa and currently have a conventional spa which I am in the process of selling due to low use. I am considering building a shed on the slab vs tearing it out. Our township does not require a building permit for sheds under 200 sq ft but it does state that foundations should have a rat wall. [url]https://www.doityourself.com/forum/attachment.php?attachmentid=91395&stc=1&d=1520692532[/url] I'm sure that many homeowners who install small sheds even install a slab and even less probably install the required rat walls. So I guess my inquiry is, why is a slab without a rat wall ok for a swim spa, patio, side walk, etc but once I build a structure (shed) it now is required? I also noticed that their generic wall section they have on the building permit shows the structure sitting on the rat wall/foundation vs on the slab like I would be building.

I am building a shed, and I would love to create a modern look with aluminum trim and cement fiber panels. There are many systems available, such as the EasyTrim Reveals system. However, I can't seem to find places that sell small quantities of trim. The market seems to cater to design/build firms and wholesale sales. Does anyone have experience or advice on finding it for small-scale projects? (My hope is that the shed would be a pilot project for eventually replacing the siding on some/all of the house, but that is a ways down the road.)