Design Implications on Embodied Energy
Unlocking the re-use potential of ANALYSIS: Facades glass façade systems
The distribution of initial embodied energy for building elements differs with each building. Cole and Kernan conducted research on a threestorey office building found that the façade typically contributes around 25% of the total initial embodied energy as highlighted in figure 2. [3] The relative contribution to the initial embodied energy (EE) is likely to continue to rise in significance due to the broad design possibilities that are explored to minimise operational energy (OE).
Rebecca Hartwell1, Dr. Mauro Overend1 1
University of Cambridge, Department of Engineering, UK
Abstract
Play it again… and again… (i)
The ubiquitous insulated glazing unit (IGU) has been referred to as a monstrous hybrid consisting of a mixture of materials or assemblies of components from which it is not economically feasible to salvage the raw materials after their current life. In recent decades there has been an increase i n the use of glass within façade sys tems with little consideration for end-of-life (EoL) recovery. Technical improvements focused on improving operational energy of glazed façades can have unintentional negative consequences on the ability to recover high-value material. This research aims to assess the opportunities of avoidable waste through a comparative life-cycle impact assessment (LCIA) bound to the EoL stage and evaluate the reclamation potential of glass and aluminium from an existing curtain-walli ng glazing unit in different recovery scenarios. A framework for the assessment of recovery potential of glass façade designs is proposed. Further, the technical challenges that prevent glazing systems from exploiting their re-use potential, in terms of the separation of laminated glass and adhesive connections, have been reviewed to direct future experimental research on glass façades designed for disassembly and re-use.
(ii)
Stuff ~ daily to monthly
Space Plan
EMBODIED ENERGY (GJ)
~3 years
Services
~7-15 years
Initial
25 Years
Skin
~20 years
50 Years
100 Years
Structure
~ 30-300 years
Site Work
Structure
Envelope
Finishes
COMPONENT
Services
Construction
Site
~ eternal
Building "Shearing Layers"
Figure 2: i.) EE contributions over a typical building service life [3] ii.) Building split into service lives of elements [4]
The significance of the EE attributed to the façade is scaled up considerably when the whole building lifespan is taken into account. This is commonly referred to as recurring EE and highlighted in figure 4(i) over, 25-, 50-, 100-year building lifespan. The building envelope is significant in terms of recurring EE, in that, in relation to the structure, it typically requires more frequent maintenance and replacement of parts. The failure rate of the IGU has been the subject of recent study. [5], [6] The multi-component nature of the building envelope can create significant challenges in disassembly and the reclamation of glass and other materials from existing systems for re-use or recycling of component parts at EoL. [7], [8]
unlocking re-use potential in facades
Introduction ARebecca Growth in Function Hartwell and Dr. Mauro Overend from the University of Cambridge, Glass façade systems have evolved to serve numerous functions and UK, discuss overcoming theto traditional issues of being a hybrid product meet complex technical requirements. When it comes design for End-of-life can ultimately be defined as the inability for the system to fulfil disassembly, arise asto to whether is a system trade-off when itquestions comes theirthere eventual re-use and recycle… its design function or meet new requirements. Changing user A growth in function
Glass systems have evolved serve numerous comEarly façade aesthetically-driven glasstofaçade design functions consistedandofmeet a small plex technical requirements. When it comes to design for disassembly, questions material mix involving monolithic glass and mostly mechanical arise as to whether there is a system trade-off between meeting improvements connections. During the 1970s-80s, glass envelopes became more in operational energy and the ability to recover glass and other materials for performance-driven and began to incorporate high-performance re-use at their end-of-life (EoL). double-glazing, glass coatings adhesively-sealed to improve Early aesthetically-driven glass and façade design consisted units of a small material 1 1 Rebecca Hartwell , Dr. Mauro Overend air-tightness, acoustic and thermal insulation and sun-protection. The mix involving monolithic glass and mostly mechanical connections. During the volume of glass in buildings has since grown; triple-glazing units (TGUs) 1970s-80s, glass envelopes became more performance-driven and began to 1 University of Cambridge, Department of Engineering, UK and double-glazing units (DGUs) with coatings are nowandconsidered incorporate high-performance double-glazing, glass coatings adhesivelysealed units to improve acoustic and thermal and essential elements of lowair-tightness, and zero energy buildings. TGUsinsulation and coated sun-protection. The up volume of glass in buildings has since grown; triple-glazing DGUs now make 2% and 12%, respectively, of the existing glazing are considered type distribution The units ubiqu(TGUs) itous iand nsuldouble-glazing ate(EGD) d glaziin ng the uunits nit EU. (I(DGUs) GUSuch ) hawith s bsystems ecoatings en referconsist rednow to aof s amore essential elements of low and zero energy buildings. TGUs and coated DGUs now monsmaterials trous hyband rid cmore onsistipermanent ng of a mixtconnections ure of materivia als othe r asuse semof blieadhesive s of make up 2% and 12%, respectively, of the existing glazingearly type distribution sealants. [2] comp onents fr[1], om w hichWhilst it is nosingle-glazing t economicallyunits feas(SGU) ible to sand alvage theuncoated raw (EGD) in the EU. Such systems consist of more materials and more permanent DGUs for 44% and 42% of the EU EGD, respectively, the mateconnections rials afstill ter taccount h e i r c u r r e n t l i f e . I n r e c e n t d e c a d e s t h e r e h a s b e e n an units via the use of adhesive sealants. [1], [2] Whilst single-glazing field meet incre(SGU) ase ofand i n building tearly he uuncoated srefurbishment e of gDGUs lass still wtoithaccount in faenergy çafor de44% sperformance ysand tem42% s wiof th standards l i t t l e the EU EGD, continues tor grow consrespectively, ideration fo d-ofwhich -of lifebuilding (Esuggests oL) rrefurbishment ecovthat ery. the Tecto hlarge nimeet cal amount imenergy proveof m eglass nts in theenfield performance building stock in lower-performance systems will soon be considered focusstandards ed on imcontinues proving otopegrow rationwhich al enesuggests rgy of gthat lazethe d falarge çadeamount s can hof aveglass in
Unlocking the re-use potential of glass façade systems
Abstract
unintunfit entiofor nalfunctional negative cpurpose. onsequences on the ability to recover high-value material. This research aims to assess the opportunities of avoidable waste through a comparative life-cycle impact assessment (LCIA) bound to the EoL stage and evaluate the reclamation potential of glass and aluminium from an existing curtain-walli ng glazing unit in different recovery scenarios. A framework for the assessment of recovery potential of glass façade designs is proposed. Further, the technical challenges that prevent glazing systems from exploiting their re-use potential, in terms of the separation of laminated glass and adhesive connections, have been reviewed to direct future experimental research on gFigure lass fa1: çaCross-section des designedoffoi.)r SGU disasii.) seDGU mblyiii.)anStructural d re-use.Sealant Glazing. Figure 1: Cross-section of i.) SGU ii.) DGU iii.) Structural Sealant Glazing
Introduction 48
asianglass AG 20-1
A Growth in Function
Glass façade systems have evolved to serve numerous functions and
requirements and new developments in the area of construction, may
building stock in lower-performance systems will soon be unfit for lead to façade EoL being reached prematurely ie.considered every 20 years or so. functional purpose. [4] For these reasons, façades pose a clear opportunity to concentrate
Design Implications on Embodied Energy Design implications processing techniques that have a high-value and require more energy-
recovery methods, even more so with the advance of new materials and
Thedistribution distribution initial embodied energy for building elements differs The of of initial embodied energy for building elements differs with intensive manufacture. with building. each building. and Kernan research conducted on office a threeeach Cole andCole Kernan conducted on aresearch three-storey storey office found typically that the contributes façade typically building found building that the façade aroundcontributes 25% of the around total Energy Problem Shift initial embodied energy highlighted in figureas 2. highlighted [3] The relative 25%Whole-Life of the total initialas embodied energy in contribution figure 2. [3] policies energy in building construction heavily focus onisimproving to theExisting initial embodied likelyembodied to continue to rise in(EE) significance The relative contribution to(EE) theisinitial energy likely to the due toOE. theSeveral broad possibilities that to minimise operational have studied how decisions made in the design continue to risedesign inresearchers significance due toare theexplored broad design possibilities that energy (OE). stage of the building envelope such as DGUs with low emissivity coatings are explored to minimise operational energy (OE). and TGUs, solar thermal collectors and building integrated solar Stuff ~ daily to monthly (ii) photovoltaic panels affect the OE. [9]–[11] Consequently, other factors Space Plan ~3 years within the life-cycle of the façade such as EE and recovery potential are Services ~7-15 years often overlooked. Chastas, et al. reviewed previous literature on 90 Initial residential buildings to find the ratio of EE to OE energy. It reported an 25 Years Skin EE contribution of 6–20% in conventional buildings, 11–33%~20inyears passive 50 Years 100 Years buildings, 26–57% in low energy buildings, and 74–100% in net zero Structure ~ 30-300 years how energy buildings. [12], [13] This shifting balance has highlighted Site improvements inEnvelope OE, has increased the relative significance of the EE; ~ eternal Site Work Structure Finishes Services Construction Building "Shearing Layers" affected by the selection COMPONENT of locally-available construction materials and methods; manufacturing energy intensity; recyclability potential; Figure 2: i.) contributions over a typical building service life ii.) Building Figurerecycled 2: i.) EE EE contributions over a typical building service life [3] Building split into content; renewability potential; potential toii.)[3] reduce construction split intolives service lives of[4] elements [4] service of elements waste; life span and durability; and maintenance needs. As the energy required for operation decreases, scenarios with a higher potential The ofthe theEE EE attributed the façade up for Thesignificance significance of attributed to thetofaçade is scaled is up scaled considerably recycling and re-use can have a significant impact on the whole-life considerably thelifespan whole building lifespan is taken account. This when the wholewhen building is taken into account. This isinto commonly referred cycle. [14], [15]. However, with nohighlighted internationally accepted, is commonly referred to as recurring EE and in figure 4(i) to as recurring EE and highlighted in figure 4(i) over, 25-, 50-, 100-year building and pragmatic method forThe assessing and over,comprehensive 25-, 50-, 100-year building lifespan. envelope lifespan. The building envelope is significant in terms ofbuilding recurring EE,comparing in that,isin the recycling potential façade materials terms of the structure, material and choice significant in terms of recurring EE,requires in that,more ininrelation to the it relation to the structure, itoftypically frequent maintenance and their embodied impact when looking at future scenarios for building replacement of parts. The frequent failure rate of the IGU has been the subjectofofparts. recent typically requires more maintenance and replacement refurbishment, there littlebeen incentive for re-use. [16] [17] The failure rate of the IGUishas the subject of recent study. [5], [6] (i)
EMBODIED ENERGY (GJ)
between meeting improvements in operational energy and the ability to recover glass and other materials for re-use at their end-of-life (EoL).
The multi-component nature of the building envelope can create significant challenges in disassembly and the reclamation of glass and www.asianglass.com other materials from existing systems for re-use or recycling of component parts at EoL. [7], [8] 1
