Integrated Life Cycle Energy and Greenhouse Gas Analysis of Exterior Wall Systems for Residential Buildings

Reza Broun,Hamed Babaizadeh,Abolfazl Zakersalehi,Gillian Menzies

doi:10.3390/su6128592

Reza Broun, Hamed Babaizadeh + Show 2 more

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https://doi.org/10.3390/su6128592

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Abstract

This paper investigates the breakdown of primary energy use and greenhouse gas (GHG) emissions of two common types of exterior walls in the U.K.: insulated concrete form (ICF) and cavity walls. A comprehensive assessment was conducted to evaluate the environmental performance of each exterior wall system over 50 years of service life in Edinburgh and Bristol. The results indicate that for both wall systems, use phase is the major contributor to the overall environmental impacts, mainly due to associated electricity consumption. For the ICF wall system in Edinburgh, 91% of GHG emissions were attributed to the use phase, with 7.8% in the pre-use and 1.2% in end-of-life phases. For the same system in Bristol, emissions were 89%, 9% and 2%, respectively. A similar trend was observed for cavity wall systems in both locations. It was concluded that in each scenario, the ICF wall system performed better when compared to the cavity wall system. The results of the sensitivity analysis clearly show that the uncertainties relevant to the change of the thickness of the wall are quite tolerable: variable up to 5%, as far as energy and greenhouse emissions are concerned.

Highlights

In 2012, the U.K. residential sector consumed nearly 29% of total primary energy and emitted million tons of CO2 equivalent
This study quantitatively examines the breakdown of the primary energy use and greenhouse gas (GHG) emissions of two common types of exterior wall in the U.K., insulated concrete form (ICF) and cavity wall, over the entire lifetime
The ICF wall system is associated with the lowest energy demand and GHG emissions; the cavity wall system has 10% and 12% higher GHG emissions for Edinburgh and Bristol, respectively

Summary

Introduction

In 2012, the U.K. residential sector consumed nearly 29% of total primary energy and emitted million tons of CO2 equivalent. It was estimated that 47% of the life cycle energy use in residential buildings is attributed to the use phase, which is mainly for heating purposes [1]. During the use phase of a typical building, the heat balance significantly determines the overall energy consumption and can constitute up to 80% of the total life cycle energy. The building envelope has the largest impact on consumed energy in the use phase [2]. Heat exchange between the inner and outer leaf of exterior walls depends on using materials or layers of materials with different thermal conductivity [3]. Replacing traditional exterior walls with more energy efficient walls can reduce the operating energy up to 30% [4]

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