I am about to insulate a suspended timber groundfloor in a 1930s semi. The joists are 2"x5" with about 400mm of air space below. The pipes currently run below the floor, and the pipework is a mess, with very little insulation. As I need to reroute pipes anyway, am I best running them between the joists, within the new floor insulation or keep them under the floor but obviously insulate them. The pipes will be running perpendicular to the joists, so I would need to drill holes in the joists.