Carbon emissions associated with new buildings are being reduced by the increasing stringency of building regulations [1]. It is however, the retrofitting of existing buildings for minimum carbon emissions throughout their expected lifetime that poses the biggest challenge at this time. This paper considers the assessment of retrofitting non-domestic buildings using two different modelling techniques, Static Simulation Modelling and Dynamic Simulation Modelling. A case-study building, located on the campus of University College Cork, was used for the modelling and actual retrofit. This allowed for a comparison to be made between actual measured data and the proposed modelling techniques with regard to thermal energy modelling. The measured data along with the two types of modelled data, gave an extensive data set from which the assessment of the two modelling techniques could be nude. This assessment proposes a modelling technique which is sufficient to base future retrofitting decisions upon. This research demonstrates clearly that fundamental building information, simplified occupancy profiles, simplified weather data and a less time consuming model is a sufficient and adequate means to base retrofitting decisions on. (C) 2011 Elsevier B.V. All rights reserved.