Biochar as a tool for evaporative cooling?

Okay, the title sounds crazy and probably is, but biochar that is fully saturated with moisture is really hard to dry out.

So much so that when I complete a biochar burn in a barrel, I seal the barrel with dead-wet biochar and pack it in. It's one of the few things that will fully kill the burn and seal the barrel. This seriously works. The char underneath is dry.

So I'm speculating -- could a fully saturated biochar roof add cooling inside a building? Like a chicken coop or something? Could it create an evaporative flow from the top (black, hot) to the bottom (wet, cool)?

For the first time in years I have enough rain (for the moment anyway). So I can't hope to test this nutty proposition anytime soon.

What do you think of my crackpot idea? Worth an experiment?

Interesting thought. Biochar holds something like 5x its weight in water so the moisture retention is definitely real. I could see it working as a passive cooling layer on a coop roof, especially if you could rig a simple drip system to keep it saturated during the hottest part of the day. The evaporation would pull heat away from the surface the same way a wet towel on your head works. Whether it's worth the effort vs just painting the roof white and adding ventilation, not sure, but as an experiment it sounds fun.

Test it.  Build a couple desk top “houses”, one with, one without biochar.  I’d be interested in seeing if mixing lime in with the biochar would lighten it color wise and improve reflectivity.