I second what Mauro has said.
Here are some resources for cold storage for photographic materials:
http://www.nps.gov/museum/coldstorage/npscoldstorage.swf
http://ccaha.org/uploads/media_items/hbcu-cold-storage-references.original.pdf
For a museum where I volunteered during my studies, I used Mark McCormick-Goodhart’s 2003 report on using the CMI method as an easy and budget-friendly solution for a small collection that is consulted infrquently. It requires regular monitoring, but it seems like a viable solution if executed correctly.
