You are right, mine love styrofoam, they are a whole lot yesterday but still ok today, apparently didn't hurt them. I searched and we do not have rice husk in our country for sale in large quantities. I may need to go to a rice factory... I definitely need some insulation from the cement as the temperature drops close to 5C in the barn where the brooder boxes are now.
my friend in Greece ,uses dry pine needles. she said they work well too .
chooks man