This particular paper suggests an alternative method of defining a temperature condition of enclosures at variable air temperature through developing estimates of a temperature condition of enclosures by means of balance ratios (alternative to a method of Fourier) and defining deep penetrations of temperature under variable boundary conditions of the mixed type. Subject of this research paper is walls and temperature condition of walls. Integrated ratio of thermal balance allows one to refuse Fourier's method (orthogonal decomposition) favoring a method of Cauchy's thermal balance leading to the solving a task for the ordinary differential equations. Assessing the heat accumulative ability of walls will solve an energy saving problem.