In this article, two types of mathematical models for thermal protection level analysis were developed: the economic and energy ones. Both of which allow to calculate the relevant thickness of the selected insulation material under any climatic and economic conditions with any constant layers of building envelope taken from structural considerations. The factors influencing the models were also evaluated. The main factors on which the economic model depends are the costs of energy and insulation material in the region, the region degree-days, the discount rate and the billing period. The key factors to influence the energy model are the region degree-days and the energy consumption rate for the production, transportation and installation of the insulation material. Comparing the two models developed, the following conclusion can be made: The economic model is practically easier to use, as all of the necessary information could be found in the standards, and in the manufacturer catalogs, it allows to get a more precise and accurate result, while the energy approach requires the data, which sometimes has no public access. But, energy model provides us with a more objective assessment when comparing the level of building thermal protection in different countries.