High Energy-Efficient Windows with Silica Aerogel for Building Refurbishment: Experimental Characterization and Preliminary Simulations in Different Climate Conditions

Cinzia Buratti,Michele Zinzi,Elisa Moretti

doi:10.3390/buildings7010008

Abstract

The paper deals with the potential of high energy-efficient windows with granular silica aerogel for energy saving in building refurbishment. Different glazing systems were investigated considering two kinds of granular silica aerogel and different glass layers. Thermal transmittance and optical properties of the samples were measured and used in building simulations. The aerogel impact on heat transfer is remarkable, allowing a thermal transmittance of 1.0–1.1 W/(m2·K) with granular aerogel in interspace only 15 mm in thickness. A 63% reduction in U-value was achieved when compared to the corresponding conventional windows, together with a significant reduction (30%) in light transmittance. When assembled with a low-e glass, the U-value reduction was lower (31%), but a moderate reduction in light transmittance (about 10%) was observed for larger granules. Energy simulations for a case study in different climate conditions (hot, moderate, and cold) showed a reduction in energy demand both for heating and cooling for silica aerogel glazing systems, when compared to the conventional ones. The new glazings are a suitable solution for building refurbishment, thanks to low U-values and total solar transmittance, also in warm climate conditions.

Highlights

Glass façades have an important role in buildings in terms of energy demand, thermal comfort, and daylighting: the main total energy losses can depend on the windows, especially in highly glazed buildings
The paper deals with the potential of high energy-efficient windows with granular silica aerogel for energy saving in building refurbishment
Aerogel windows seem to have the largest potential for improving the thermal performance and daylighting in glazing systems, because of very low thermal conductivity and density, together with good optical transparency and acoustic insulation [4,5,6,7,8,9]

Summary

Introduction

Glass façades have an important role in buildings in terms of energy demand, thermal comfort, and daylighting: the main total energy losses (up to 60%) can depend on the windows, especially in highly glazed buildings. Opaque silica aerogel-based materials, such as flexible blankets and aerogel-based plasters and concrete, have recently appeared on the market [10,11] Silica aerogels, both in monolithic and granular translucent form, can be used in high-insulated nanogel windows: transparent monolithic panes were developed 20–30 years ago, but their application in glazing systems has still not penetrated the market, and few prototypes have been manufactured for research purposes [12,13]; for these reasons, Buildings 2017, 7, 8; doi:10.3390/buildings7010008 www.mdpi.com/journal/buildings. The most popular systems are multiwall polycarbonate panels for skylights, roofs, walls, structural panels for continuous façades, and insulated glass units Many of these innovative solutions can be found in schools, commercial and industrial buildings, airports, etc., especially in the US and in Northern

Methods

Results

Conclusion