It’s great to see that more people are sharing the goals of creating greener buildings–even in industries like commercial retail.

A cool roof is a great construction method, though the term has a bit of flex with how it’s used (I’m not sure which method you are using) Some people refer to any light colored roof as a cool roof (which is true, it is certainly cooler). If one is installing an EPDM membrane roof then there’s really no reason it shouldn’t be white. The effect is material and cost difference is negligible. A cool roof can also be two layers of roofing with an air layer that moves between them, effectively allowing the heat gathered on the top to have minimal direct contact with the ceiling and structure below (kind of like a double-glazed window). Both are great methods.

When it comes to CMU block, they do have a lot of thermal mass–especially when filled solid–but their insulating qualities are minimal. An 8″ CMU has an R-value of 1.11. With a solid 5″ of concrete inside, that’s probably another 2.5. Even a double-glazed piece of glass is an R-2. One option to consider for the next time is actually using an insulated CMU block (not to be confused with an NRG Block). These have foam inserts within the cavities and actually bring the R-Value to 6.5, so it’s a big improvement.

Also, from your picture, it looks like you’re installing cladding on the outside of your block wall–maybe aluminum panel or stucco? That space between the vertical rails is prime for insulation. XPS rigid insulation brings an R-Value of 5 per inch, which would help hold in all that cool thermal mass of your CMUs. Maybe you’re doing that already.

Great project and best of luck.