Hmm, I have a collection of that I have put into outer sleeves in the 1990's in Tucson. Then I have moved to the Pacific Northwest about twenty years ago. I have never seen any evidence of mold or any other problem.
Record Storage Problem
Outer sleeves are a problem. I know that is going to be a contested statement, but it has been my experience over decades of collecting that often as not records stored in outer sleeves develop mold. This was first suggested to me in the early 1970s in Seattle, a Mediterranean Climate, and I thought OK maybe it is a concern in certain regions. Then I encountered it in San Diego, a Semi-Arid Climate. Currently I am sorting through a large estate collection in South Florida, that reportedly has always, ALWAYS, I am assured, been under air conditioning. Most of the records are protected by outer sleeves and most have mold. This is about 8,000 records. So you may wish to rethink your strategy. What is the priority: The vinyl or the jacket?