S. Schweizer, J.J. Low, L. Subramanian
Keywords: emissivity, low-e materials, coatings, building materials, density functional theory
Summary:Reducing heat transfer through thermal radiation is of main importance for energy efficient building. The emissivity of a material plays a central role in this context. Using low-emissivity (low-e) building materials is a very efficient way to save energy and thus costs . Especially glazings and windows are quite prominent candidates for improving the energy efficiency of buildings. Low-e glass can significantly affect heating, cooling and also lighting costs . Reflective insulation can, however, also be exploited for light-tight/opaque areas of a building , for example by incorporating low-e foils in the house envelope or using low-e materials for advanced insulating attic systems. The importance of low-e materials is not limited to buildings, but plays also a role where insulating against temperature differences is crucial. Reducing the weight of packaging for shipping temperature sensitive goods or insulating operating equipments like pipes or storage tanks can be achieved by employing low-e materials . Critical aspects of low-e coatings are reducing production costs by using equally-performing cheaper materials, increasing the visible transmittance on transparent materials, the design of controllable and adaptive coatings and the long-term durability [1,4,5]. Molecular modeling is a versatile tool for improving material performance and developing novel materials. Predicting material properties using computational methods can efficiently and cost-effectively support and guide experimentation. We will present density functional theory (DFT) calculations on the radiative properties of low-e materials. It will be shown how simulations can be used to efficiently screen these materials and characterize their properties in order to optimize the performance. References:  B. P. Jelle, S. E. Kalnæsa, T. Gao, Energy and Buildings (2015) 96(1):329-356.  G. Ding and C. Clavero, Silver-Based Low-Emissivity Coating Technology for Energy- Saving Window Applications, Modern Technologies for Creating the Thin-film Systems and Coatings, Prof. N. Nikitenkov (Ed.), InTech, 2017, DOI: 10.5772/67085.  http://www.sigmalabs.com/blog/surface-emissivity-why-it-matters-in-insulation.html (accessed Dec 05, 2017)  G. Leftheriotis and P. Yianoulis, Materials & Solar Cells (1999) 58:185-197.  B. P. Jelle, Solar Energy Materials and Solar Cells (2013) 116:291-323.