Low Slope Roof Systems

Overview

Prior to 1970 thermal efficiency was not a significant performance factor for roof systems. It was common to underlay a roof membrane with one or two inches of high density insulating board, but this was as much to provide an even surface for the membrane as to insulate the roof. This situation changed abruptly when the cost of energy rose dramatically in the early 1970s. Insulation is now the rule rather than the exception for new construction and for re-roofing. This surge towards insulating, coupled with the commercial availability of many new insulation materials and the appearance of a wide array of new membrane systems has brought new flexibility to the roofing industry but also many new concerns. These are "systems" concerns that relate to changes in material environment and to incompatibility between materials. Issues such as heat damage, solvent resistance, fasteners, wind uplift, fire resistance, flute span, thermal performance, construction water, water leak source, water migration, flashing height, thermal expansion, dimensional stability all have systems connotations and will have to be addressed in each of hundreds of different situations until unifying general relationships for roofs acting as systems are established.

The purpose of this project is to initiate a study of the systems attributes of roofing systems. The primary contribution is a compilation of available information, with interpretation and some extension, on whole systems performance, whole systems modelling, and whole systems economics.