The Application of Silica-Based Aerogel Board on the Fire Resistance and Thermal Insulation Performance Enhancement of Existing External Wall System Retrofit

Kuang-Sheng Liu,Shin-Ku Lee,Chia-Hsing Hsieh,Xiao-Feng Zheng

doi:10.3390/en14154518

Abstract

Due to the need of good thermal performance, external wall insulation (EWI) is usually made of materials that are not fire resistant and sometimes flammable. That restricts its application to a particular circumstance such as limited building height. Hence, a material with good thermal insulation and fire resistance performance would allow EWI to be more widely applied. This paper introduces a novel material: a silica-based aerogel porous board, which differs itself from mainstream products available in the market because of its outstanding properties, such as low density, high surface area, low thermal conductivity and superhydrophobicity. Herein, its thermal insulation and fire-resistant performance were tested and compared with commercial products. The cone calorimeter analysis results indicated that the aerogel porous board could improve the fire resistance performance. Moreover, the evaluation of thermal insulation performance suggested that the application of an aerogel porous board on the external stone wall of existing buildings can decrease the U-value by 60%. Through the detailed insight into the case-study, it is quite clear that the carbon impact of building stock could be greatly reduced by means of a coherent set of building envelope retrofitting actions based on this innovative heat insulation material, without compromising the fire safety.

Highlights

Building energy retrofitting has become increasingly important as the energy consumption in the building sector represents a significant proportion in the overall energy consumption [1,2,3]
The PU or PS foam board is an excellent material for thermal insulation, it is highly combustible and its application comes with a fire risk
The method for preparing the aerogel porous board includes the steps of: (a) adding a 50–70 vol.% MTMS containing methyl groups and a 0.1–0.3 vol.% surfactant into water, mixing evenly and carrying out hydrolysis to get a mixed aqueous solution; (b) mixing the 12–16 vol.% of mixed aqueous solution with 5–6 vol.% of 0.1–0.2 M ammonium hydroxide (NH4OH) and a remaining percentage of an organic solvent according to the percentage by volume and mixing by the magnetic stirrer until the solution obtained clear color in the hydrolysis reaction for emulsion polymerization to get a water-in-oil (w/o) lotion emulsion; (c) subsequently, the wet gels were shaped in a 10 cm × 10 cm × 1.5 cm steel mold at 150 ◦C in an oven for 24 h

Summary

Introduction

Building energy retrofitting has become increasingly important as the energy consumption in the building sector represents a significant proportion in the overall energy consumption [1,2,3]. External wall insulation (EWI) plays a very important role in building the energyretrofitting process because it is able to reduce the building energy demand, improve the indoor acoustic environment and extend the life span of the buildings by cutting down the heat loss through building fabric, filtering incoming external noises and preventing the formation of condensation in the wall [4,5,6]. The EWI with good thermal performance, when installed correctly, can significantly reduce the energy demand of the building. The PU or PS foam board is an excellent material for thermal insulation, it is highly combustible and its application comes with a fire risk

Methods

Results

Conclusion