How should I add a 1.5 inch layer of foam board insulation on the outside of our new house that is under construction?
This barrier can be installed either under the insulation layer or on top. There would be very little difference between applying vinyl siding directly over sheathing or over rigid foam insulation. It is important to make sure that the proper fasteners are used (length and strength) to reach through the added insulation and secure the siding to the building; extra nailers may be required at corners. In addition, the continuity of the weather resistive barrier under the siding system is critical for long term building performance and durability; siding alone may not stop wind driven rain. Some insulation products (properly installed) can serve the function of a weather resistive barrier. It can also provide a thermal break between the framing and exterior, increasing the thermal performance of the wall. View our Home Insulation guide and New Homes guide for more information.
