Moisture under mattress solutions please

We keep Reflectix under our mattress and don’t have a problem with condensation under our mattress. We didn’t do “testing”, but DW and I both noticed less cold air around the edges of the mattress after adding Reflectix.

Try using a mattress pad (water resistant or water proof) if you aren’t already. Just an idea.

Install HyperVent under your mattress.

When I had a boat the recommendation was for a cross fiber material used for filters. I think it is available at the big box hardware stores in large sizes. Cut it to fit and put it under the mattress.

There are also solutions made for boats but they are more expensive.

Have a look at the Froli mattress foundation.

We do have several topics about the issue. Some members are using special mats design for boats, so boating forum might give better responses.
I had the moisture issue when we full timed in camper during the wettest California winter in last 50 years.
My solution was to get two 4" plastic pipes used for irrigation, drill lot of big holes in them and stick under head side of the mattress.
That was giving air flow in critical area and occasionally I would move the pipe to different part of bed, sticking small electric heater on the side.

BTW, Reflectix does a great job handling radiant heat, but it has low R value and does very little good for handling conductive heat transfer which occurs under a mattress. I would remove it since it might be contributing to the condensation.

I lift up the mattress, hold it up with a foot stool and let my fan dry out the area under the mattress. In cold, damp weather I might need to do that every couple of weeks or so. In hot, dry conditions I can skip it entirely. Regardless of conditions I check for dampness under the mattress every few weeks.

The area under my mattress was raw plywood. I greatly decreased the condensation problem when I applied several coats of paint.