"INTRODUCTION The term ""metal building"" is used to describe buildings typically used for commercial@ manufacturing and many other applications. Metal buildings generally are relatively fast to construct@ require low maintenance@ and offer flexibility in design@ construction and expansion (Newman 1997). For these reasons@ metal buildings are widely used in U.S. and are becoming popular elsewhere. In general@ energy savings considerations have not been a significant factor in the design and construction of metal buildings. That situation is changing due to concerns about higher energy prices and a better understanding of building science in the industry. Proper use of insulation materials in metal building roofs and walls will likely improve the energy efficiency of these structures. Some common metal building insulation materials are fiberglass@ foam board@ spray-on cellulose and pre-insulated panels. A more recent development is the use of spray-in-place polyurethane foam. All of these insulation materials are installed on-site during the construction. Fiberglass insulation with an appropriate facing is predominant in metal building roofs and is also widely used for the walls. During the late 1990s@ the American Society of Heating@ Refrigeration and Air-Conditioning Engineers (ASHRAE) Standing Standard Project Committee (SSPC) 90.1 Envelope Subcommittee incorporated specific maximum allowable U-factors for metal building roofs and walls into ANSI/ ASHRAE/IESNA Standard 90.1-1999. Recently ASHRAE and other industry organizations have recognized that Standard 90.1 should be revised and updated to account for a more accurate understanding of the installation of insulation in metal building roof and wall assemblies. The work described here is part of a larger effort to develop a three-dimensional mathematical model for heat transfer in metal building roof and wall assemblies that contain fiberglass as the main insulating component. Our objective is to have an experimentally validated model that incorporates the key geometric features and material properties of these assemblies. Part I of this work@ presented here@ describes the mathematical model and its validation. Part II shall present a selection of computed results obtained using this model on the overall heat transfer coefficients (U-factors) for several metal building roof assemblies. There are many different ways of installing fiberglass insulation in metal building roof and wall systems. In this paper@ we will focus on a Standing Seam Roof (SSR) assembly and describe the formulation and validation of a heat transfer model for this configuration."