Quik-Therm CIS is an all in one composite insulation system that deals with all three forms of heat transfer – Conduction, Convection and Radiation. High performance insulation panels keep walls warm. The panels are foamed together; consequently there is no air leakage; and engineered reflective facers send radiant energy back to its source. Basements with Quik-Therm CIS are typically 3 to 5 degrees warmer than basements with batt, poly and studs.
Is a double Vapour barrier created when foam insulation is added to the outside of framed walls?
The real answer is yes. Typically, homes and buildings have interior poly vapour barriers and fiberglass insulation in the wall cavities. The poly is designed to stop moisture from entering the wall cavity and does a darn good job of it – but it’s not perfect. Some moisture always gets in, and some is inherently built in. It’s just the way it is; assuming framed walls continue to be constructed the way they are.
When rigid foam insulation is attached tight to exterior wood sheathing the walls drying path is totally cut off. That means some moisture will be trapped within the wall cavity; it also means humidity in the cavity will be higher. Moisture and mold go hand in hand.
When installing continuous insulation on the outside of batt filled framed walls, follow these instructions and the walls will be energy efficient and healthy. Create at least 1/8″ airspace (no more than 3/16″) between the exterior sheathing and the rigid foam insulation and buy quality rigid foam
insulation that is at least 1.5″ thick.
The double vapour barrier wall design can work, provided the rigid foam insulation is at least two inches thick and all joints, cracks and seams are taped and/or foamed. It works, provided the wall is tight. Attention to detail is critical.