Other than the need for heating, the concrete floors will need to be sealed or covered as concrete is very dusty and this could cause problems with dirty track and electrical pick-up for your locos. I do not think that humidity will be much of a problem if you use ply for the baseboard construction, also temperature in a loft will far exceed the variations you will get and there are little problems with loft layouts if gaps are left for expansion of the track, and I would think you would have similar conditions for most of the year.
hope this helps, I wish I had some where like that for my layout!
regards
mike g
hope this helps, I wish I had some where like that for my layout!
regards
mike g
