This paper presents a comprehensive model for analyzing the thermal conditions of buildings through a system analysis methodology, focusing on heat and energy efficiency indicators, the impact of external climate on thermal conditions, and annual heat consumption for heating. Utilizing trigonometric series and harmonic oscillation, the study formulates analytical functions to simulate the thermal regime of buildings, determining heating periods and heat consumption. Factors such as heat devices, air permeability, and heat transfer coefficients are considered in detailed models to calculate heat losses and optimize energy consumption. An analysis of heat energy savings in a higher education institution highlights the effects of internal heat capacity and heating system adjustments. Additionally, this research incorporates thermal imaging inspections and the Blower Door system to detect structural defects and abnormal insulation properties. Recommendations from field tests on residential, public, and industrial buildings include insulation upgrades and adjustments to materials, aiming to enhance energy efficiency. The study underscores the importance of accurate environmental parameter representation and provides standardized methods for assessing and improving building thermal performance.