mattress moisture barrier

I have thought to use a foundation dimple type moisture barrier, fabric side up to prevent moisture under the mattress. We have not experienced moisture under the mattress yet though as it is a cheap stuffed spring type that has lots of air moving through it. No collection of moisture seems to occur.
This is one type of the dimple sheet.
Another alternative I've thought to use is a section of cedar lattice fencing. Two of them lain over each other under the mattress would provide larger venting channels. Quick cheap and easy...