The problem is that moisture from your body migrates through the memory foam. Then it condenses on the platform.
If you go to buy a platform bed for the house, to use with memory foam, the platform will always be in something like 2" wide slats with about 2" spacing in between. That is to allow for air circulation so the mattress can dry out.
What I would do is check frequently for moisture under the mattress. If the area is damp, you need ventilation. So you could:
*buy Hypervent
*take out the current platform and build a slatted one
*replace the current platform with some plywood and drill out about half the are of it with holes for ventilation. This would probably be the least expensive option.
In your area it would probably be a good idea to run a dehumidifier any time you are not running AC. But that still wouldn't keep the condensation from your body moisture off the mattress platform.
Single empty-nester in Middle TN, sometimes with a friend or grandchild on board