I'd say I have a loose layer of aspen less than an inch thick I tried to only use so much as to not see through the substrate onto the floor of the RUB, my flat is about 20 degrees (give or take) I have put the heating on to see if that helps the situation at all. My other girl uses ceramic which has no issues with the higher temperature!

Do you think heating the room itself will help to raise the temperatures? I want to get him into a viv asap but I'm in the middle of saving for the proper heating for that and not quite there...