The paper discusses thermal quality improvement in historic buildings. It is based on a case study of a wooden historical building in an architectural style typical of Zakopane, located in the Podhale region of Poland. The building’s historical value and timber structure prevent the application of typical thermal retrofitting solutions. This paper presents an analysis of the possibilities of the improvement of energy performance of a historic building (villa) which included: a review of the available energy performance improvement solutions applicable to this type of building, with a particular focus on applying internal insulation; a technical condition assessment using non-invasive methods, the identification of problematic areas in terms of the thermal retrofitting of buildings with timber walls and decks; in situ tests: thermovision tests which showed the places with temperature distribution field disturbances in the building’s envelope, focusing on thermal bridges; measurements of actual thermal transmittance coefficients for extant partitions; measurements of the building’s airtightness and the microclimate in selected rooms; numerical analysis: an assessment of the influence of the thermal bridges on the building’s existing condition, an analysis of water content changes in wall systems post-insulation. The presented approach enables the improvement of the energy performance of timber historical buildings while preserving the historical value of its architecture. It is innovative because it tries to fill in a research gap concerning a lack of relevant guidelines in Poland. The research questions that the authors asked were as follows. Is it possible to improve the thermal insulation of a building’s wooden walls without adversely affecting the building’s technical condition? With regard to the necessity to meet nZEB (nearly zero energy building) standards, is it feasible to improve the timber walls of historical buildings? The study found that under the correct assumptions and while maintaining a responsible approach to design, it is possible to improve the energy performance of historical buildings without interfering with historical heritage.

Based on modeling and measurements, the authors investigated the performance of expanded polystyrene and lightweight aerated concrete slabs. The objective of the work was to assess the performance of the brick wall (having various thickness and layering) commonly built in the Silesia Region (Poland) in the 1920s and the changes of water content in layers of the flat wall through the measurement of temperature and relative humidity in the selected layers of the masonry wall.

This article addresses the important problem of improving the energy efficiency of historic buildings, where due to the architectural value of the facade, thermal insulation should be placed from the inside. As a part of this publication, the author, on the basis of their own experience and research, presents and discusses selected problems to which special attention should be paid when designing this type of insulation. These are among other things: disturbances in the distribution of the temperature field on the partition; defects related to partial thermal insulation of partitions; the lack of detailed analysis of wall systems in terms of construction and their technical condition; wood decay; the selection of inadequate calculation methods, e.g., the simple method of Fokin–Glaser and many others. The author, on the basis of measurements and computational analysis, presents the methodology of a correct solution of such problems. This significantly simplifies currently applied methods.