I plan to put 90mm thick polyurethane insulation between the joists under my wooden floor. However, I am concerned that this will make under the house extremely cold during winter which may make my water pipes and central heating pipes prone to bursting due to frost. As it is a wooden floor, the void has air vents which can't be closed during winter. Is the only solution to make sure all the pipes are insulated? I've noticed that the plastic central heating pipes have not been insulated at points.