wrote in message
...
I have a steel barn. Both the roof and walls are steel, and the floor
is concrete. It's very cold tonite, (about 25 deg.) and I just went
to that barn to get something. I noticed the whole ceiling is covered
with frost on the INSIDE. This barn is well closed from leaks and
weather, with only some small spaces along the bottom of the walls,
which are one half inch at most. There are no livestock in there, so
that rules out the breath from animals. About all that is in there is
mostly lumber and other building materials, plus a few lawnmowers and
garden tools. How in the heck does frost get INSIDE?

Thanks

Mark

The same way frost can form on the inside of car windows: severe radiational
cooling coupled with some interior moisture. This can happen if you have a
period of warmer weather with some degree of humidity and then high pressure
moves in with its associated radiational cooling. The moisture remains
inside the building and has not yet equalized with the dryer air outside.
In Western NY now the pressure is a very high 30.8 and I would not be
surprised if some steel barns are frosting up.