Optimizing the thickness of a straw outer wall of a building for sows in a view to achieving cost-effective heat insulation

V. Dimova*, D. Georgiev

Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 22 November 2020; accepted for publication 16 April 2021)

Abstract. The aim of the study is to determine the optimum thickness of the surrounding wall structure of a building for nursing sows by using heat insulation from straw and different fuel (pellets and dry wood) for heating the building. To achieve the purpose, 6 models of walls made of environmentally friendly panels with wooden skeleton, thermal insulation from pressed straw bales and double-sided clay plaster have been developed, such that the accepted thickness of the thermal insulation layer is respectively: 20, 25, 30, 35, 40 and 45 cm. The construction value of the finished wall is determined by adding the value of the construction and assembly works on the construction site to the value of the preparation of the panels (in a workshop), including the payment of labor, materials and additional costs for the implementation of clay plaster and waterproofing membrane. The annual energy losses through 1 m2 of the enclosing wall and the annual heat insulation costs (as a sum of annual energy cost and the depreciation deductions) are determined through the described methodology and verification of condensation of water vapor on the inner surface of the wall was carried out. The results of the research show that by using pellets for fuel, the optimal thickness of the thermal insulation is 45 cm, and by using dry wood it is 35, 40 and 45 cm. All studied models of enclosing straw wall meet the hygienic requirements for preventing condensation on their inner surfaces.