Passive envelope solutions to aid design of sustainable livestock buildings in Mediterranean climate

The dairy cattle sector is responsible of significant greenhouse gas emissions such as methane, carbon dioxide, nitrous oxide. The reduction of heat stress of dairy cows plays a crucial role in the improvement of dairy productivity and avoid greenhouse emissions. In this study a parametric analysis about several traditional or innovative passive solutions for building envelope of livestock housing is carried out, with the aim to achieve the thermal comfort of animals without active energy systems. The different energy efficiency measures designed for the building envelope are evaluated on the basis of different indexes for animal comfort, by means of the combination of the Building Energy Performance Simulations (BEPS) and computational fluid dynamics (CFD) simulations. The proposed method starts from the numerical model definition of a semi-closed, naturally ventilated, loose housing system, characterized by criteria traditionally recognized or accepted by the scientific community for designing a dairy cow housing. Different interventions, referred to the shape of the building and its envelope materials, are taken into account, such as cool materials or cross laminated timber, as well as polyurethane insulation or shading systems. Basing on the both temperature-humidity index (THI) and black globe temperature humidity index (BGHI) the optimal building envelope solutions are: opening ridge area with 1.8 m width, window to wall ratio equal to 79%, roof made by polyurethane foam with a slope of 15°. The environmental indexes calculated by means of BEPS numerical models simpler than CFD analysis bring a difference in results by a maximum of 18%. The results can support the decision-making process in the design of a sustainable barn for dairy cows taking animals welfare as reference. Moreover, the methodological approach could be easily replicated for other livestock type or other climatic zones.