The best way to protect a wooden floor underneath is to place a moisture barrier (like 6-mil polyethylene) between the insulation and the floor. This will help to prevent the insulation from absorbing moisture from the concrete slab, which could cause the wooden flooring to warp and buckle over time. Another option would be to install an underfloor heating system, which would help keep the concrete slab warm and dry and would therefore not pose a threat to the wooden flooring.

I was thinking of insulating the wooden floor underneath. What is the best way to protect a wooden floor underneath? There are a few things you can do: 1) Use an area rug. This will help reduce the amount of direct contact with the floor and will also help keep your feet warm. 2) Install a radiant heating system. This will heat up the floor from below and will keep your feet nice and toasty. 3) Apply a sealant or wax to the floorboards. This will help protect them from moisture and humidity fluctuations, which can cause damage over time.