The implementation of thermal renovation of residential and public buildings is becoming more and more popular. The need to save energy and reduce the energy demand of buildings is becoming a civic duty. Consequently, sacred buildings should also be adapted to the requirements of modern times. Due to the specific use of these facilities and their mostly large cubature, administrators rarely decide to take such measures. Examples of thermomodernization activities in church buildings can be invaluable as they are an example for administrators of other buildings of this type. The paper presents the following case study: A comprehensive thermal renovation of a church building in Rzerzęczyce.