Longwave (infrared) radiation is exchanged between exterior building surfaces, the ground and the sky. This process affects exterior surface temperatures and hence building energy consumption. Current approaches to modelling this exchange in building and microclimate analysis tools are discussed. There are various shortcomings, the most significant concerning radiation exchange between building surfaces at different temperatures. This work implements improvements to the longwave exchange processes in the EnergyPlus simulation engine, allowing improved calculation of surface temperatures and thus of heating and cooling loads. The improvements cover ground temperature assumptions and the coupling of other building surfaces. The coupling of radiative transfer was achieved by means of a timelag; it is shown that for small timesteps this approach is adequate. The new approaches are compared to the existing implementation in EnergyPlus for arrangements including a street canyon and shading devices. The combined impact gave an increase in surface temperature of up to 6 degrees C, with an average change of 2 degrees C. This caused a decrease in annual heating load of 18% and an increase in cooling load of 19%. This confirms the importance of accurate longwave radiation modelling both for buildings in dense urban areas and for buildings with external shading devices. (C) 2014 Elsevier B.V. All rights reserved.