Old buildings that represent and maintain historic values often have poor indoor conditions and energy efficiency. The aim of this work was to evaluate the influence of building structures on airtightness and energy performance of certain historic building types. In this study on-site measurements, dynamic simulation and questionnaires were used. Significant differences between the levels of the airtightness of the historic houses exist in the studied region. No statistically significant correlation was found between the structure types and the envelope tightness. The typical air leakage places of the studied houses were at the junctions of the envelope structures. Measured air exchange rates indicated that the level of ventilation is insufficient in some of the houses while some are too leaky. If the airtightness of the naturally ventilated house is improved, the acceptable ventilation rate has to be guaranteed. Tightening the envelope and moving from natural to mechanical ventilation was the most effective way to improve the indoor conditions and energy performance.