Historic buildings constitute a specific group of buildings where the possibilities of improving energy efficiency and comfort are significantly limited because of the existing construction features and heritage values. Each building has a different history so the scope of renovation and/or retrofitting must be determined individually for each building. This article presents the methodology of measurement and diagnosis of features of particular importance for energy performance and comfort improvements, based on the example of a historic masonry building located in southern Poland. The first research question was which of the comfort conditions have been exceeded according to measurements. The second issue concerned the necessary extension of the basic determinants of comfort, beyond measurable qualities. A multi-faceted approach to the comfort assessment is proposed, including qualitative research that applies the additional criterion of aesthetic comfort. During the case study diagnosis, the acceptable level was exceeded in thermal, acoustic and aesthetic comfort. The first two may be addressed by optimized technical measures whilst the latter through a research-through-design that addresses the complex relationship between the perceiver and what the environment affords. The solution reflects the need to meet demands for retrofits that are energy-efficient and aesthetically pleasing while minimizing any negative impacts on the heritage and the environment.