Occasionally my guys shiver too, although the house is never too cold that they would be shivering for that reason. I don't think it's an actual problem, but i can't say why they would be doing it either.
Well now we're just entering a confusing language barrier. Long pants as in jeans or cargo pants, rather than short pants like 3/4 pants or shorts.To an english dude, that sounds really kinky! it made me laugh, I presume pants to you are like joggers or similar?
Over here PANTS are PANTS if you know what I mean
They go lovely with a big wooley jumper!