In my projects in Poland usually when we aim to achieve heat island option 1. points with non-roof "open-grid pavement" strategy we mean permeable grass pavers, just like the ones on the picture, of course 50% unbound: https://kb.pl/static/site_media/uploads/images/plyta-azurowa-polbruk-ekologiczny-meba.jpg
However, recently I was asked if using gravel or some other king of aggregate instead of grass inside grid openings is an acceptable strategy. The building owner would like to give up on grass for aesthetic and water saving reasons.
After reading the definition of open-grid pavement I wonder if aggregate would be acceptable. I think it still would be a loose substrate supported by a grid, so it seems compliant. Do you have any thoughts on this?
Thanks in advance!