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An adequate window system is one of the most important retrofit strategies for effective energy conservation of a building, because the U-value and solar heat gain coefficient of windows have enormous impact on the heating and cooling loads of buildings. Therefore, this paper presents methods for improving the energy efficiency of existing residences that have various window sizes and envelope insulations, through a window retrofit using optimal U-value and solar heat gain coefficient values. Furthermore, the window retrofit strategy has been standardized using analysis of the correlation between the properties of the retrofitted window and energy saving rates. The results show that the annual heating and cooling energy demand decreases by 7.9–16.7% when changing the U-value of the windows in a poorly insulated house, and that the relationship between the lower U-value and energy saving is strong for poorly insulated houses regardless of window size. However, for houses with better insulation and larger window sizes, the total energy usage decreases by 18.4–29.7% when the solar heat gain coefficient is lower, and the energy saving effect of the U-value decreases while that of the solar heat gain coefficient increases.Practical application: This study was focused on improving the energy efficiency of existing residences by applying retrofitting technology. By exploration of the contribution of the specific qualities of windows and the thermal envelope (insulation) system of buildings via simulation, it was determined that it is necessary to adjust the U-value and SHGC of retrofitted windows, in relation to the thermal performance and window-wall ratio of an existing residence, to achieve high energy efficiency. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured the thermal performance of different window systems. [•] We also analyzed their effects on building energy savings in S. Korea. [•] The maximum ratings of the southern region and Jeju Island are Ratings 1. [•] The maximum ratings of the central region is just Ratings 2. [•] We suggest more specific and local criteria of the certification system. [ABSTRACT FROM AUTHOR]

Abstract: Solid adsorbents comprising 50, 70, and 90wt.% heteropolyacid Fe2.0SiW12O40 (Fe–HPA) and mesoporous cellular foams (MCFs) have been synthesized by wetting impregnation. The adsorbents were characterized by various physicochemical, thermal and spectral techniques and the CO2 adsorption capacity of the adsorbents were investigated. The structure of Fe–HPA on the surface of the support was confirmed by TEM, SAXS, XRD, SEM, FTIR, 29Si MAS NMR, and XPS. XPS of the Fe 2p3/2, 2p1/2, 3p and W 4f7/2, 4f5/2, 4d5/2, 4d3/2 confirmed the presence of typical Fe(2+) and W(6+) in the adsorbent, respectively. The adsorbents showed a very high adsorption capacity due to the chemisorption of CO2. The CO2 adsorption capacity of a 70wt.% Fe–HPA–MCF sample was 111.8mg/g-adsorbent at 25°C. This result indicated that the reported iron (Fe2+) complex could be used as an efficient adsorbent for the separation of CO2. The adsorbents displayed excellent CO2 adsorption capacity and were thermally stable and recyclable. [Copyright &y& Elsevier]