I'm looking to replace an existing vinyl sheet floor in a bathroom in a seasonal home that is unheated in the winter. I'd like to use a loose lay vinyl sheet for both ease of installation and it seems logical to me that allowing it to expand/contract freely would be best given the extreme temperature range to which it will be exposed. Right now I'm looking at USG's Fiberock underlayment for this project. I'm aware that most vinyl sheet manufacturers have a low temp limit of 50F or so and have been told that the issue is with the product becoming brittle and cracking. Not sure how true that is but there is no foot traffic in the winter so I'm hoping that's not an issue. I'm looking for some general advice in terms of whether this plan makes sense or if there are better material choices that will stand up to the unconditioned environment.