Material and component performances are blunt instruments for appraising the thermal performance of structures. A certain amount of consumed energy is attributable to the interaction of building fabric components, where thermal bridges occur. This paper analyses the thermal bridging effect and provides a number of modelled, cost-effective retrofit approaches in Greek single family houses, in order to address thermal bridges and improve the building's energy performance. The impact of thermal bridging on the overall annual heating load was estimated at 13%. The investigated retrofit solutions achieved a decrease of the annual heating energy requirement of 4-10%. The sunspace achieved the highest energy reduction of 10%, offering ‘free’ solar heating at a reasonable payback period.