Laying 126m2 of Celotex to Floor ⬇️ When Installing a Heat Pump System in a old house, you need to upgrade Insulation to high spec otherwise it’s a waste of time and can be expensive to run. So we have laid 2 layers of 100mm Celotex staggering the joints and taping the joints on top With a vapour control layer/slip membrane on top, Which stops the reaction between the cement and foil, stops migration of the screed and stops warm moist air cooling and condensing within the floor. Ready for 50 mm