Intermediate temperature (100-120 degrees C) polymer electrolyte fuel cells (IT-PEFCs) offer simplified water and thermal management compared to conventional PEFCs, since any water should exist in the vapour phase, allowing for easier removal. The higher operating temperature also facilitates greater temperature differentials between the fuel cell and the surrounding atmosphere, thus easing the thermal management of an IT-PEFC stack. However, the study of IT-PEFC is still a relatively poorly covered field within the literature and thus little information is available on performance characteristics. We therefore present a simple multiphysics model as a quantitative tool for describing the IT-PEFC. This tool is then used to optimise different materials and parameters within an IT-PEFC. Experimental data is presented as a test of the model, and excellent quantitative agreement is demonstrated. Having validated this model, we present a detailed study of the GDL materials in order to understand the influence of different parameters, namely: (i) porosity, (ii) permeability and (iii) electrical conductivity. We report that the optimal porosity for IT-PEFC operation is 40-50%, whereas that the GDL permeability was found to have little impact on the cell performance. Further, we used the model as a design tool: proposing a novel cell design, taking into account the considerable advantages when using a metallic GDL which yielded potential significant improvements in the system efficiency. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.