There was a previous thread on this some time back (I tried to find it, but failed).

One suggestion was to keep the kilts in a deep-freeze!

There are also bags sold that are air-tight, and have a fitting that lets a vacuum cleaner suck most of the air out of them. That might also be a good idea, after you have thoroughly brushed and steamed the kilt.

No way is cold going to damage the kilt!