The Energy Upgrading of Existing Buildings: Window and Shading Device Typologies for Energy Efficiency Refurbishment

Cristina Carletti,Fabio Sciurpi,Leone Pierangioli

doi:10.3390/su6085354

Abstract

Residential buildings built after the Second World War have high energy consumption and inadequate thermal comfort, especially in summer conditions, largely attributable to the high transmittance of windows and lack of effective shading devices. Performance improvement of these components is essential for energy upgrading of existing buildings. This paper shows the results of the research, which aims to evaluate effects on energy consumption and environmental comfort of combined solutions of windows and shading devices applied to a case study representing a typical post World War II Italian building. In this paper, the main typologies of solar control systems are described and evaluated on the basis of a case study in different climatic locations (Berlin, Milan, Florence and Athens). Thermal behavior has been assessed through the EnergyPlus dynamic calculation code, by using appropriate performance indicators for energy and thermal sensation. Starting from performance evaluation of the existing building, different strategies have been assessed: replacement of existing windows with high-energy performance ones and introduction of shading devices and solar control glasses. Finally, a global comparative analysis has been carried out based on energy, acoustic and lighting performances, technical feasibility and management problems. Results of the different solar shading devices assessment are reported in the form of a data sheet.

Highlights

The results show that, if louvers design is optimized, a significant space cooling energy reduction can be achieved in all the cities, especially in Cairo, Lisbon and Madrid where solar radiation is higher in summer
The replacement of windows in existing buildings has become common practice, thanks to tax incentives offered for example in Italy—with the Law n°296/2006, to the ease of implementation and to the synergy of positive effects that the intervention may produce—for example the improvement in the acoustic performance of the facade
It might be useful to combine these shading devices with a building automation system that manages the opening in a dynamic way, in relation to incident solar radiation

Summary

Introduction

Since the building sector is responsible for almost 40% of European primary energy demand, the European Directives 2002/91/EC and 2010/31/EU on energy performances of buildings promote passive design strategies oriented to improve energy performance of the building envelope, in order to reduce heating and cooling loads.Among passive design strategies, those concerning windows and solar shading devices play an important role, since these elements have a relevant impact on energy and thermal behavior of buildings.The connection between internal environment and outside through glazed surfaces calls for three specific requirements:- Control of heat flow through components with a low thermal inertia;- Regulation of solar radiation access;- Provision of adequate visual connection to outdoors and satisfactory level of natural light, avoiding visual comfort detriments (such as glare, etc.).Since conventional windows are the weakest part of the building envelope, as their thermal resistance is much lower than adjacent walls, the first requirement is strictly related to energy efficiency and had pushed forward the development of components—glass panes, frames and window spacers—with low transmittance values. Reduction of heat transfer through windows is possible thanks to the development of several solutions, such as the application of gas layer with a thermal conductivity lower than air, the introduction of low emissivity coating film, the addition of interspaces fractionation with multi glazing systems, metallic frames with multiple air cavities and thermal breaks and the adoption of spacers made of low thermal conductivity materials [1,2]. These improved performances are producing positive outcomes in term of thermal and acoustic comfort

Objectives

Results

Conclusion