The present paper aims to study the influence of the formwork structure on the efficiency of heat treatment (HT) of precast concrete elements (PCE) by solar energy in various climatic conditions. The objects of the study were different types of formworks composed of solar energy equipment for HT of PCE. In total, six types of formworks, made of steel sheet, laminated plywood and timber, with and without insulation were studied. Calculation and experimental study were carried out for humid continental, and subtropical climates. Experimental study was carried out in the laboratory and in the open air. According to the obtained results, the heat insulation material in the formwork structure contributes to increase the strength of concrete. Formwork with heat insulation layer of 40 mm gave the best results. However, the level of the contribution depends on climatic conditions. Heat insulation material in the formwork structure is necessary in humid continental climate. Even the thickness of the insulation layer of 20 mm gives good results and the difference between the concrete strength with thickness of 20 mm and 40 mm is insignificant. On the contrary, in humid subtropical climate, the heat insulation material in the formwork structure is favorable, but not compulsory, since the difference between the concrete strengths is not significant and the strength values, obtained in all six types of formwork, allow it to be removed after 24 hours of curing. © 2021, Chulalongkorn University, Faculty of Fine and Applied Arts. All rights reserved.