Loft insulationI need to insulate my

Loft insulation

I need to insulate my loft. The ceiling of my bedrooms is made of chestnut wood planks. This is also the floor of the lost space. I am thinking of using a foil backed solid insulation such as kingspan and laying this directly onto the boards. My one concern is could this trap moisture ? Any one out there used this or have any other suggestions?

Many Thanks