I did not use any supplemental heating device, so i think it is hard to create a cool part as 26 degree.
Now I am using the plastic tub, with cover. only the cover has metal net to exchange air. I am thinking to make a couple of holes at tub body to make better air flow, does it works for lower humidity?
and I put one bag of desiccant, made by carbon and sth else, i am not sure it will help to lower the humidity, but at least worth to have a try.
As my girlfriend just mentioned, here is Thailand, high temp and high humidity..