Erik,
 
A good sized cage would be better than letting your ferret near the hot tub.
 I know a woman who had two of hers drown in her hot tub.  After the first
one she had drained all but about 2 inches of water from the tub, only to
find her second one dead a few days later in the tub.  Also a greenhouse may
easily reach 90 deg plus along with high  humidity.  You gotta keep these
guys cool and 90 is too warm for any length of time.
 
The 7 hours in school is OK providing you give him lots of time out of the
cage and lots of attention when you get home.  After a while, you'll find him
looking forward to your coming home to play with him.
 
Dick B.
[Posted in FML issue 1147]