Two forms of traditional dwelling were identified during a study tour of Greece. A representative Athenian dwelling from the Plaka district, next to the Acropolis, was selected for study using the TAS degrees thermal analysis software. The predictions from the computer simulations indicated that, if the building considered was used either as originally intended or when adapted for modern living, comfortable internal conditions would ensue during both the summer and winter seasons. The south-facing hayati (i.e. the upper-floor-level entrance verandah) was fitted with removable glazing. This feature had a beneficial effect on the temperatures for the adjoining rooms during the summer and winter seasons. The improved summertime performance may, in part, explain the frequent occurrence of this usually unglazed passive-solar feature in the vernacular domestic architecture of mainland Greece. The behaviour of a well thermally insulated version of the dwelling was also modelled. Whilst such a dwelling was more energy efficient, having significantly reduced energy loads for the space heating required at the present time, a tendency was detected for part of the upper floor accommodation of the insulated building to over-heat during the summer months. This suggests that there is a need to evaluate, and consider carefully, the thermal behaviour during both summer and winter when contemplating the refurbishment of such historic dwellings for conservation purposes and compliance with the thermal thrift requirements of the proposed building regulations.