As most of us are finding out since July 1st, the new building codes are more stringent, requiring greater energy efficiency. Simply translated – this means higher construction cost. Now even higher insulation values are needed to demonstrate energy compliance – and for attics, this can be a real challenge. While batt or blown insulation still provide an excellent R-value in attics, the need for greater thickness of insulation presents a problem in the heel of a conventional roof truss (the eave area). The problem is that there’s just not enough room for the thicker stuff, and jurisdiction plan reviewers and inspectors are ‘pinging’ contractors for using conventional truss designs in combination with thicker attic insulation. The foul lies in the fact that when insulation is compressed in the eave area, it doesn’t retain the same insulation R value. The building code recommended solution is to design roof trusses with a raised heel (see photo). The raised heel in the eave area provides the extra room in the eave for the required insulation thickness. This will work, but it’s definitely more expensive to build than a conventional roof truss design.
Other options to provide additional attic insulation are as follows. You could consider spray foam insulation on the underside of the roof deck. Icynene and similar products offer a greater insulation R-value per inch in comparison to batt and blow-in insulation and can provide better sealing characteristics. However, this method is typically more pricey than batts or blow-in attic insulation, and may not provide a savings in comparison to the raised heel design. Another alternate solution to the raise roof truss heel is to insulated the eave perimeter of the conventional roof truss design to an uncompressed level of thickness. Of course, this may then require greater insulation thickness to the inside of the eave perimeter in order to provide overall compensation toward energy compliance. In most cases this is the least expensive approach to solve this problem, but also the least energy efficient solution.