Conference PaperPDF Available

Abstract and Figures

One approach to supporting the implementation of sustainable activities by industry sectors is the use of climate targets. Such climate targets have potential to be used in design and rating tools for buildings and to support government regulation for the building and construction sector. In this study, the climate targets for New Zealand residential dwellings were calculated based on assigning the global carbon budget (for limiting temperature increase to 1.5 or 2.0 °C during 2018-2050) to three building typologies: detached, medium-density housing and apartments. These budgets were assigned to the pre-existing and new-built dwellings using building stock projections for the nominated period. Separately, the climate impact of new-built dwellings in each of the three residential typologies were assessed using Life Cycle Assessment methodology. For New Zealand residential buildings, new-built dwellings exceed their 1.5 °C climate targets by a factor of 6.7, 6.8 and 10.9 for detached, medium-density housing, and apartments respectively. For the 2.0 °C climate target, these factors are 4.8, 4.8 and 7.7 for detached, medium-density housing, and apartments respectively. The results show that about two-thirds of the climate impact of residential dwellings for the period 2018-2050 is associated with pre-existing dwellings rather than new-builds. The operational energy used for space heating, water heating, lighting and plug loads makes the biggest contribution to the climate impact for all typologies of pre-built residential dwellings. For new-built residential dwellings, both the operational energy and the construction materials/products contribute most of the climate impact.
Content may be subject to copyright.
IOP Conference Series: Earth and Environmental Science
PAPER • OPEN ACCESS
Application of Absolute Sustainability Assessment to New Zealand
Residential Dwellings
To cite this article: S J McLaren et al 2020 IOP Conf. Ser.: Earth Environ. Sci. 588 022064
View the article online for updates and enhancements.
This content was downloaded from IP address 118.92.213.72 on 23/11/2020 at 10:47
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution
of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
Published under licence by IOP Publishing Ltd
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
1
Application of Absolute Sustainability Assessment to New
Zealand Residential Dwellings
S J McLaren1,2, C Chandrakumar1,2, D Dowdell1,3, L. Bullen1,2 and R Jaques3
1 New Zealand Life Cycle Management Centre, c/o Massey University, Private Bag
11222, Palmerston North 4442, New Zealand
2 School of Agriculture and Environment, Massey University, Private Bag 11222,
Palmerston North 4442, New Zealand
3 Building Research Association of New Zealand (BRANZ), Judgeford, Porirua 5381,
New Zealand
S.McLaren@massey.ac.nz
Abstract
One approach to supporting the implementation of sustainable activities by industry sectors is
the use of climate targets. Such climate targets have potential to be used in design and rating
tools for buildings and to support government regulation for the building and construction sector.
In this study, the climate targets for New Zealand residential dwellings were calculated based on
assigning the global carbon budget (for limiting temperature increase to 1.5 or 2.0 °C during
2018-2050) to three building typologies: detached, medium-density housing and apartments.
These budgets were assigned to the pre-existing and new-built dwellings using building stock
projections for the nominated period. Separately, the climate impact of new-built dwellings in
each of the three residential typologies were assessed using Life Cycle Assessment methodology.
For New Zealand residential buildings, new-built dwellings exceed their 1.5 °C climate targets
by a factor of 6.7, 6.8 and 10.9 for detached, medium-density housing, and apartments
respectively. For the 2.0 °C climate target, these factors are 4.8, 4.8 and 7.7 for detached,
medium-density housing, and apartments respectively. The results show that about two-thirds of
the climate impact of residential dwellings for the period 2018-2050 is associated with pre-
existing dwellings rather than new-builds. The operational energy used for space heating, water
heating, lighting and plug loads makes the biggest contribution to the climate impact for all
typologies of pre-built residential dwellings. For new-built residential dwellings, both the
operational energy and the construction materials/products contribute most of the climate impact.
1. Introduction
One of the targets of the United Nations Sustainable Development Goal 12, Responsible Consumption
and Production, is to “encourage companies, especially large and transnational companies, to adopt
sustainable practices and to integrate sustainability information into their reporting cycle” [1]. However,
there is much debate about what is meant by “sustainable practices”. One approach for supporting
sustainable practices in climate change management that is rapidly gaining traction, is setting absolute
targets for greenhouse gas (GHG) emissions. These targets are derived from a global carbon budget
which is the maximum amount of GHG emissions (usually measured in tonnes CO2eq) that can be
emitted over a defined time period whilst keeping warming of the Earth’s atmosphere below a threshold.
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
2
The threshold is commonly defined as an observed global mean surface temperature (GMST) of 1.5 or
2.0 °C [2], or 1 Watt per square metre increase in top-of-atmosphere radiative forcing [3], relative to
pre-industrial levels. The global carbon budget is divided between different countries, industry sectors,
products, and/or individuals using a chosen sharing principle. Common sharing principles include
“equal per capita” where the budget is divided equally between all people, and “grandfathering” where
the budget is assigned to countries or industry sectors in proportion to their relative contributions to the
global climate impact in a chosen reference year [4, 5].
The building sector is particularly relevant for consideration when setting climate targets. Building
construction and operation account for 36% of global final energy use and 39% of energy-and process-
related CO2 emissions according to the 2019 Global Status Report for Buildings and Construction [6].
Research on climate targets for residential buildings to date has focused on assessment of the climate
target for a single residential building or housing for one person over one year (e.g. [7,8,9]) or
commercial building for one year (e.g. [10,11]). Such targets are country-specific due to the large
international variations in construction materials, climate conditions and energy mixes. Furthermore,
although most of these studies account for population growth up to 2050, they do not account for the
growth in the number and size (i.e. floor area) of buildings, and changes in building typology makeup.
These factors are potentially significant in determining the climate target for residential buildings. For
example, in New Zealand detached residential buildings are being built with larger floor areas, the
number of occupants per household is declining, and more residential medium-density housing (MDH)
and apartments are being constructed relative to detached houses [12].
To account for changes in the building stock up to 2050, Chandrakumar et al. [13,14] proposed
integrating building stock projections into the calculation of the climate target for buildings. Essentially,
for residential buildings, this involves calculating the numbers of pre-existing buildings of different
building typologies (e.g. detached, MDH, apartments) and their projected service life, up to 2050. This
is added to the number and size of new-built buildings of different building typologies, up to 2050. The
gross floor area used over this period by different building typologies (measured in m2·yr) provides a
basis for assigning the building sector’s climate budget to an individual dwelling in each building
typology. It should be noted that the distinction between pre-existing and new-built buildings is
important because the climate target needs to account for the construction of new buildings but this is
irrelevant for pre-existing buildings as those GHG emissions occurred prior to the time period for which
the carbon budget is calculated.
In this paper, the method developed by Chandrakumar et al. [13,14] is applied to the residential sector
in New Zealand. It extends the previous study’s methodology on detached residential houses in New
Zealand [14], applying it to the remaining two residential typologies: MDH and apartments.
2. Method
A set of five residential dwellings, built recently to meet the New Zealand Building Code, were chosen
and modelled using LCA: three detached houses (DH), one medium-density house (MDH) and one
apartment (AP). A general description of these buildings is presented in Table 1.
The method involved calculating four results for each residential typology:
The climate impact of each new-built residential dwelling over its service life (taken as 90
years), divided into different life cycle stages (Section 2.1), and a pre-existing residential
dwelling operating between 2018-2050.
Projected total stock of pre-existing and new-built residential buildings for the period 2018-
2050 (Section 2.2).
The climate impact of the total stock of each building typology for the period 2018-2050
(Section 2.3)
The climate impact and climate target for a new-built dwelling of each typology for the
service life of the dwelling (Section 2.4).
A more comprehensive description of these calculations is available in [14].
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
3
Table 1. Characteristics of each building typology used in the study [15]
2.1 Climate impact of pre-existing and new-built dwellings of each typology
The method for calculating the climate impact of each new-built dwelling is described in [14]. The
functional unit was defined as the ‘construction and occupation of a residential dwelling over its
reference service life’. For this study, a service life of 90 years was considered for residential dwellings
(as previously estimated in [16,17]).
Inventory data were categorised into the following life cycle stages: product (modules A1-A3),
construction process (modules A4-A5), maintenance (module B2) and replacement (module B4),
operational energy use (module B6), operational water use (module B7), and end-of-life (modules C1-
C4). In this study, it was assumed that the buildings are properly maintained; hence, the life cycle stage
repair (module B3) was not considered. And credits for recycling and biogenic carbon storage were
outside the scope of this study. The GHG emissions related to the operational energy use were quantified
assuming 100% grid-derived electricity as the energy source, and using an annual New Zealand grid
GHG intensity calculated based on the Ministry of Business, Innovation and Employment’s (MBIE)
Reference [18] for each year during the 2018-2050 period (and assuming it remained equivalent to the
year 2050 after that year). Energy use for space heating and cooling was calculated to represent three
different climate zones in New Zealand.
For pre-existing dwellings, as the climate impact data were only required in order to calculate the
contribution to the total climate impact of each building typology between 2018-2050, only the life cycle
stages occurring during 2018-2050 were considered. In other words, modules A1-A3 and A4-A5 were
omitted, and modules C1-C4 were only included for those buildings reaching their end-of-life at some
point between 2018-2050. The climate impacts of the other modules (B2, B4, B6, B7) were only
considered for the projected years of operation in the period 2018-2050 for each pre-existing building.
Energy use for space heating was assumed to be the same as for new-built dwellings (per square metre
of gross floor area) in the absence of more detailed data. This value is similar to values at the lower end
of the (limited) data sets on operational energy use for space heating in New Zealand residential
buildings [19,20], recognising that existing residential dwellings are likely to become more energy-
efficient over the 2018-2050 period. It should, however, be noted that existing dwellings generally have
lower ambient temperatures and higher humidity than new-built dwellings.
For all the dwellings, the climate impact result for each dwelling was calculated using LCA
methodology and following the EN15978:2011 standard [21]. It should be noted that data for materials
represented current manufacturing processes rather than future technologies, and this represents a
limitation of the study.
Building
Gross floor area
(GFA in m2)
Characteristics of building
elements
Total stock size (no. of buildings),
[total GFA in m2]
Pre-
existing
New-
built
By 2018
2018 to 2050
DH
166
198
Timber frame; concrete slab floor;
90 mm wall & plasterboard lining;
double glazed windows; concrete
tile roof
1,304,126
[216,484,916]
527,609
[104,466,582]
MDH
115
114
Braced frame & shear-walled
frame; reinforced concrete floor;
90 mm brick wall; double glazed
windows; steel profile cladding
roof
334,676
[38,487,740]
167,731
[19,118,319]
AP
99
94
Rigid frame; concrete slab floor;
plaster cladding on aerated
concrete blocks; double grazed
windows; steel profile cladding
roof
121,656
[12,043,944]
118,106
[11,127,917]
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
4
2.2 Projected total stock of building typologies 2018-2050
A stock projection developed by the Building Research Association of New Zealand (BRANZ) was
used, which was based on the long-term trend in building consents. It gives the projected numbers of
pre-existing and new-built detached buildings of each building typology for each year from 2018 to
2050.
2.3 Climate impact of total stock of each building typology 2018-2050
The climate impact of the total stock of each building typology for 2018-2050 was estimated based on
the calculated climate impacts of the pre-existing and new-built buildings (Section 2.1), and the
projected numbers of buildings for each year from 2018 to 2050 (Section 2.2).
2.4 Climate target for a new-built dwelling
The procedure for calculating the climate target for a dwelling involves the following steps:
Determine the maximum acceptable amount of GHG emissions that can be emitted globally
while respecting the chosen global climate target during a specific time period (referred to as
the global carbon budget). The approach proposed by [22] was used to calculate a global carbon
budget of 1110 GtCO2eq for the period 2018-2050 using the 2 °C target and 786 GtCO2eq for
the 1.5 °C target.
Assign a share of the global carbon budget to New Zealand based on population projections.
The sharing principle of “cumulative impacts per capita” was applied which meant that 0.06%
of the global carbon budget was assigned to New Zealand for the period 2018-2050.
Assign a share of New Zealand’s carbon budget to the residential building sector based on the
relative contribution of the sector to the country’s total climate impact in 2012 (the latest year
for which life cycle-based data were available, see [23]) i.e. using the grandfathering principle.
This meant that 10.0% of New Zealand’s carbon budget was assigned to the residential building
sector.
Assign the residential sector carbon budget to the DH, MDH and AP building typologies on the
basis of the New Zealand population in each building typology 2018-2050 (measured in cap·yr).
Assign carbon budget shares for the embodied (A1-A5, C1-C4) and operational (B1-B7) life
cycle stages of the residential sector in the same ratio as calculated for the embodied:operational
impacts of the total building stock in 2018-2050 (1:4).
Calculate the climate target (measured per square metre gross floor area) for embodied life cycle
stages by dividing the sector-level carbon budget for embodied life cycle stages by the total
gross floor area of the new-built residential buildings constructed in 2018-2050. Likewise,
calculate the climate target for operational life cycle stages (measured per m2·yr) by dividing
the sector-level carbon budget for operational life cycle stages by the total gross floor area used
in 2018-2050.
Determine the climate target for each new-built dwelling by multiplying the climate target for
the embodied life cycle stage by the floor area of each single dwelling (see Table 1), and
multiplying the climate target for the operational life cycle stage by the floor area and the years
of operation between 2018 and 2050 (i.e. 33 years). Note that, for this calculation, it was
assumed that there was zero carbon budget beyond 2050.
2.5 Climate impact and climate target for new-built dwellings in each building typology
For the residential detached building typology, the climate impacts were calculated for each of the three
dwellings separately and averaged based on their floor areas. For the MDH and AP typologies, data
were available for units in just one building of each typology, so these were used for the climate impact
analysis. The climate impact results were then compared with the climate targets for new-built dwellings
in each typology.
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
5
3. Results
3.1 Climate impact of New Zealand residential dwellings
As presented in Figure 1, the climate impacts of the detached house (DH), one medium density housing
unit (MDH), and one apartment unit (AP) are 233, 135 and 179 tCO2eq, respectively (for a service life
of 90 years) - equivalent to 13, 13, and 21 kgCO2eq∙m-2 ∙yr-1. The higher climate impact (per 1 m2yr)
for the AP dwelling is at least partly due to the floor plan (i.e. long and narrow) of the building used for
the AP typology. Note that these climate impact values do not account for the biogenic carbon in the
timber and engineered woods used in the buildings, and the avoided burden due to the reuse, recovery,
and recycling of construction materials (module D). The majority of the carbon footprint (over the
service life) is associated with the operational stages (78, 76 and 72 % for DH, MDH, and AP
respectively) and is largely related to the operational energy (for space heating, hot water, lighting and
plug loads). The climate impacts of the residential dwellings are comparable to the climate impacts of
residential buildings in other parts of the world, although they are at the lower end of the range (10-90
kgCO2eq∙m-2∙yr-1) [24].
Figure 1. Climate impact and targets of New Zealand residential dwellings. CF= carbon footprint; CT=
climate target; DH= detached house; MDH= medium density house; AP= apartment.
3.2 Climate impact of New Zealand residential buildings up to 2050
The climate impact of New Zealand residential buildings in 2018-2050 is projected as 170 MtCO2eq,
by scaling up the climate impact of both pre-existing and new-built residential dwellings using the stock
projection approach (see Figure 2). According to Figure 2, the pre-existing residential buildings
contribute 63% of the total climate impact, whereas the new-built buildings contribute 37% of the
impact. Considering the building typologies, the largest contributor of the total climate impact is DH
(77%), followed by MDH (14%), and AP (9%).
Considering the individual life cycle stages, operational energy use is the largest contributor of the
total climate impact of the residential buildings (59%), followed by the product stage (16%). The third
largest contributor to the climate impact of the residential buildings is maintenance and replacement
stage (13%).
The large difference in the climate impact between different residential buildings is due to the relative
numbers of those three typologies that are projected to exist during 2018-2050. Furthermore, the large
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
6
contribution of the operational use stage for the residential buildings can be explained by the fact that
this stage contributes the highest share of the climate impact of any building over its service life.
Figure 2. Carbon footprint of total building stock of New Zealand residential buildings up to the year
2050.
3.3 Climate targets for New Zealand residential dwellings
The calculated climate targets, consistent with the 1.5 C global climate target, for new-built DH, MDH
and AP (over a 90-year lifetime) are 35, 20, and 16 tCO2eq. (for dwellings of each typology with gross
floor areas shown in Table 1).
When an alternative global climate target (i.e. 2 C) was used, the climate targets for the chosen
dwellings (from Table 1) increased to 49, 28 and 23 tCO2eq respectively (a factor 1.41 increase
compared with the 1.5 C targets, see Figure 1).
4. Discussion and Conclusions
This study applied the absolute sustainability assessment framework developed in [13,14] to calculate
climate impact and targets for a range of residential dwellings in New Zealand. The results of the
analysis show that none of the New Zealand dwellings assessed in this study are aligned with either the
1.5 or 2 C climate goals. A new-built DH exceeds its 1.5 C-consistent climate target by a factor of 6.7,
whereas new-built MDH and AP dwellings exceed their climate targets by a factor of 6.8 and 10.9,
respectively. For the 2.0 °C climate target, these factors are 4.8, 4.8 and 7.7 for DH, MDH, and AP
respectively. However, arguably it would be preferable to represent the targets in terms of a generic m2
and/or per occupant rather than per dwelling, to represent the fact that occupants can choose to live in
larger or smaller dwellings, and/or co-inhabit with others, as well as choose between dwelling
typologies.
When the climate impact of the total stock of New Zealand residential buildings was compared with
the assigned share of the 1.5 C global budget for 2018-2050, the stock’s climate impact (170 MtCO2eq)
exceeded its climate target (47 MtCO2eq) by a factor of 3.6.
These results therefore indicate that substantial efforts (i.e. a reduction of approximately 72%) are
required to enable the residential building sector in New Zealand to achieve the 1.5 C global climate
target. According to Figure 2, more than one third of the residential building stock’s climate impact in
2018-2050 is associated with new-built buildings. Prioritising mitigation of these embodied emissions
will contribute to avoiding or postponing the transgression of the climate target (Chandrakumar et al.,
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
7
2020), and biogenic carbon storage in construction materials is particularly relevant. At the same time,
initiatives such as retrofitting and refurbishment of pre-existing buildings, and design that prioritises
mitigation of the climate impact of new-built buildings, are crucial for reducing the climate impact of
the residential building sector.
Further work to improve the analysis includes: modelling the climate impact of a larger set of
dwellings in each building typology, accounting for the anticipated increased energy efficiency of pre-
existing (through retrofitting) and new-built buildings over the next few decades, updating the electricity
mix scenarios used in the analysis, and incorporating the updated electricity scenarios into calculation
of the climate impact of construction materials. For the climate budget calculations, further work
includes: using a more recent baseline year to assign the climate budget between sectors and building
typologies, and examining the influence of different sharing principles in calculation of the targets.
However, overall, the approach described in this study has potential to be used to set climate targets
that enable the building and construction sector of a country to align their operations with a global
climate target, such as the 1.5 or 2 C. As the approach accounts for the projected future growth of the
building sector, it is “future proof” and as such is complementary to the commitments of a growing
number of countries across the world to achieving net zero carbon status between 2030 and 2050.
Acknowledgements
This study was financially supported by the Building Research Association of New Zealand.
References
[1] UNDP 2020 “Sustainable Development Goals. Goal 12. Responsible Consumption and Production”.
Available at: https://www.undp.org/content/undp/en/home/sustainable-development-goals/goal-
12-responsible-consumption-and-production.html
[2] IPCC 2018 Summary for policymakers. In: Global warming of 1.5°C. An IPCC special report on
the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse
gas emission pathways,in the context of strengthening the global response to the threat of climate
change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai,
H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla,A. Pirani, W. Moufouma-Okia, C. Péan, R.
Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock,
M. Tignor, and T. Waterfield (eds.)].
[3] Steffen W, Richardson K, Rockstrom J, Cornell SE, Fetzer I, Bennett EM, Biggs R, Carpenter SR,
de Vries W, de Wit CA, Folke C, Gerten D, Heinke J, Mace GM, Persson LM, Ramanathan V,
Reyers B, and Sorlin S 2015 Sustainability. Planetary boundaries: guiding human development
on a changing planet Science 347(6223) 1259855.
[4] van den Berg NJ, van Soest HL, Hof AF, den Elzen MGJ, van Vuuren DP, Chen W, Drouet L,
Emmerling J, Fujimori S, Höhne N, Kõberle AC, McCollum D, Schaeffer R, Shekhar S,
Vishwanathan SS, Vrontisi Z, and Blok K 2019 Implications of various effort-sharing approaches
for national carbon budgets and emission pathways Clim. Change.
[5] Chandrakumar C, Malik A, McLaren SJ, Owsianiak M, Ramilan T, Jayamaha N, & Lenzen M
(2020) Setting better-informed climate targets for New Zealand: the influence of value and
modeling choices. Environ. Sci. Technol. 54(7) 4515-4527.
[6] Global Alliance for Buildings and Construction, International Energy Agency and the United
Nations Environment Programme 2019 2019 Global status report for buildings and construction:
Towards a zero-emission, efficient and resilient buildings and construction sector. (Nairobi:
UNEP).
[7] Brejnrod KN, Kalbar P, Petersen S, and Birkved M 2017 The absolute environmental performance
of buildings. Build. Environ. 119 87-98.
[8] Hollberg, A., T. Lützkendorf, and G. Habert 2019 Top-down or bottom-up? How environmental
benchmarks can support the design process, Build. Environ. 153 148-157.
BEYOND 2020 – World Sustainable Built Environment conference
IOP Conf. Series: Earth and Environmental Science 588 (2020) 022064
IOP Publishing
doi:10.1088/1755-1315/588/2/022064
8
[9] Zimmermann M, Althaus HJ, and Haas A 2005 Benchmarks for sustainable construction: a
contribution to develop a standard. Energy Build. 37(11) 1147-57.
[10] Russell-Smith SV, Lepech MD, Fruchter R, and Meyer YB 2015 Sustainable target value design:
integrating life cycle assessment and target value design to improve building energy and
environmental performance J. Cleaner Prod. 88 43-51.
[11] Hoxha E, Jusselme T, Brambilla A, Cozza S, Andersen M, and Rey E 2016 Impact targets as
guidelines towards low carbon buildings: Preliminary concept, 36th International Conference on
Passive and Low Energy Architecture, Los Angeles, USA.
[12] MBIE, Pacifecon and BRANZ 2017 National Construction Pipeline Report 2017 Wellington:
Ministry of Business, Innovation and Employment.
[13] Chandrakumar C, McLaren SJ, Dowdell D, and Jaques R 2019 A top-down approach for setting
climate targets for buildings: the case of a New Zealand detached house. Paper presented at
Sustainable Built Environment (SBE) Conference, Graz University of Technology, 11-14
September 2019. IOP Conference Series: Earth and Environmental Science 323(1) 012183.
[14] Chandrakumar C, McLaren SJ, Dowdell D and Jaques R 2020 A science-based approach to setting
climate targets for buildings: the case of a New Zealand detached house Build. Environ. 169
106560.
[15] BRANZ 2020. Unpublished BRANZ data and projections.
[16] Johnstone IM 2001 Energy and mass flows of housing: a model and example Build. Environ. 36(1)
27-41.
[17] Johnstone IM 2001 Energy and mass flows of housing: estimating mortality Build. Environ. 36(1)
43-51.
[18] MBIE 2019 Electricity demand and generation scenarios: Scenario and results summary. (MBIE
4872) Wellington: Ministry of Business, Innovation and Employment.
[19] Isaacs NP, Camilleri M, Burrough L, Pollard A, Sville-Smith K, Faser R, Rossouw P & Jowett J
(2010) Energy use in New Zealand households: final report on the household energy end-use
project (HEEP) BRANZ Study Report 221. Judgeford: BRANZ Ltd).
[20] Pollard A & Buckett N (2010) Clawback of heating services in Beacon research homes Report
HR2420/12 for Beacon Pathway Limited (Judgeford: BRANZ Ltd).
[21] CEN 2011 CEN EN 15978 Sustainability of construction works- Assessment of environmental
performance of buildings- Calculation method, Brussels: European Committee for
Standardisation p64.
[22] Rogelj J, Luderer G, Pietzcker RC, Kriegler E, Schaeffer M, Krey V and Riahi K 2015 Energy
system transformations for limiting end-of-century warming to below 1.5 °C, Nat. Clim. Change
5 519.
[23] Chandrakumar C, Malik A, Ramilan T, McLaren SJ and Lenzen M 2019 Understanding New
Zealand’s consumption-based greenhouse gas emissions: an application of multi-regional input-
output analysis Int. J. Life Cycle Assess. 25 1323-1332.
[24] Chastas P, Theodosiou T, Kontoleon KJ and Bikas D 2018 Normalising and assessing carbon
emissions in the building sector: a review on the embodied CO2 emissions of residential buildings
Build. Environ. 130 212-226.
... The proposed approach was recently applied by McLaren et al. (2020) to calculate 1.5°C consistent carbon budgets for three common types of residential dwellings in New Zealand, e.g. newly built single-family detached house, mediumdensity house and apartment. ...
Article
Full-text available
Target values for creating carbon budgets for buildings are important for developing climate-neutral building stocks. A lack of clarity currently exists for defining carbon budgets for buildings and what constitutes a unit of assessment—particularly the distinction between production- and consumption-based accounting. These different perspectives on the system and the function that is assessed hinder a clear and commonly agreed definition of ‘carbon budgets’ for building construction and operation. This paper explores the processes for establishing a carbon budget for residential and non-residential buildings. A detailed review of current approaches to budget allocation is presented. The temporal and spatial scales of evaluation are considered as well as the distribution rules for sharing the budget between parties or activities. This analysis highlights the crucial need to define the temporal scale, the roles of buildings as physical artefacts and their economic activities. A framework is proposed to accommodate these different perspectives and spatio-temporal scales towards harmonised and comparable cross-sectoral budget definitions.
Article
An LCA-based absolute environmental sustainability approach was used to assess the performance of New Zealand office buildings in the context of climate targets for the period 2018–2050. It was found that the carbon footprint of the New Zealand office building sector for 2018–2050 (8566 ktCO2eq) exceeded the carbon budget (2140 ktCO2eq) by a factor of 4.0. The new build stock contributed approximately 55 % of the total office building sector carbon footprint. Operational energy use accounted for 86 % and 36 % of the existing and new build stock carbon footprints, respectively. Raw material supply, construction and manufacture contribute 53 % of the new build stock carbon footprint. For an individual new build office over a 60-year service life, the carbon footprint (1259 tCO2eq) exceeded the carbon budget (236 tCO2eq) by a factor of 5.3. A sensitivity analysis of the results to various input parameters was undertaken. It was found that methodological choices can significantly increase or decrease the available carbon budget and the carbon footprint. The use of alternative global climate targets or grandfathering years, inclusion of mechanical, electrical and plumbing (MEP) and tenant improvement (TI) elements, and providing an alternative post-2050 use stage carbon budget for a new build office resulted in a >25 % change compared to the base case. The study highlighted the need for more accurate assessment of MEP and TI elements in New Zealand office buildings, and up-to-date and accurate multi-regional input-output consumption-based GHG emission data for New Zealand.
Article
Full-text available
Climate change mitigation requires the construction of low/zero-carbon buildings, and this is a challenge for designers. The use of Life Cycle Assessment (LCA) provides useful information to support eco-efficiency improvements and therefore, to reduce the climate impacts of building designs. However, it does not provide information about whether a proposed design aligns with achieving the global climate target of limiting global warming to below 1.5°C or 2°C. This study, therefore, introduces an LCA-based top-down approach for setting climate targets for the whole life cycle of buildings in terms of greenhouse gas emissions. It involves assigning a share of the 2°C global carbon budget for 2018-2050 to a country, to the construction sector of the country, and finally to a building. The approach includes a stock model that accounts for the projected growth in the number of buildings and associated climate impacts in a country up to 2050. The proposed approach was applied to a detached house in New Zealand, the most common residential building type in the country; it was found that the climate target of a New Zealand detached house over a 90-year lifetime is 71 tCO2eq. This modelling approach has potential to guide designers and other interested stakeholders in development of building designs enabling the building sector to operate within a selected global climate target (such as the 1.5°C or 2°C target).
Article
Full-text available
Purpose Consumption- and production-based accounting approaches for national greenhouse gas (GHG) emissions provide different insights to support climate policymaking. However, no study has yet comprehensively assessed the consumption-based GHG emissions of the entire New Zealand’s economy. This research, for the first time, quantified New Zealand’s GHG emissions using both consumption- and production-based accounting approaches and considered the policy implications for adopting a consumption-based approach over a production-based approach. Methods A global multi-regional input-output (MRIO) analysis was undertaken to calculate the consumption- and production-based GHG emissions of New Zealand for the year 2012. The MRIO analysis was based on the Eora database, which accounts for 14,839 industry sectors from 189 countries. Given the sectoral classification of each country is quite different and in order to ease interpretation of the results, the industry sectors of each country were classified and aggregated into 16 key sectors, and GHG emissions were calculated for those key sectors. Results and discussion The MRIO analysis showed that New Zealand’s consumption- and production-based GHG emissions in 2012 were 61,850 and 81,667 ktCO2eq, respectively, indicating that the country was a net exporter of GHG emissions in 2012. The dominant contributors to the consumption-based GHG emissions were the other services and construction key sectors (each representing 16% of consumption-based emissions), followed by food and beverages (14%), transport and equipment (12%) and financial and trade services (11%), whereas the dominant contributor to the production-based GHG emissions was the agriculture key sector (representing 52% of production-based GHG emissions). The results of the study provided two key insights to support climate mitigation activities and policymaking. First, the consumption- and production-based accounting approaches results have different rankings for the most dominant sectors contributing to New Zealand’s GHG emissions. Second, only the consumption-based accounting approach enables the quantification of the embodied emissions in New Zealand’s trade activities, and it indicated that a large proportion of GHG emissions are embodied in New Zealand’s trade activities. These insights, therefore, have important implications for future policies that could positively influence the consumption patterns of New Zealand citizens and the production structure and efficiency of New Zealand’s trade partners. Conclusions This research quantified New Zealand’s GHG emissions using both consumption- and production-based accounting approaches. Given the two accounting approaches provided different insights, both approaches should be used in a complementary way when developing climate policies. However, implementation of a consumption-based accounting approach to support development and implementation of climate policies and instruments requires further consideration.
Article
Quantifying greenhouse gas (GHG) emissions and setting emissions budgets for anthropogenic systems are influenced by several value and modeling choices. This study, for the first time, quantified the influence of choice of GHG accounting approach, GHG metric, time horizon, climate threshold, global emissions budget calculation method, and effort-sharing approach, taking New Zealand (NZ) as a case study. First, NZ’s production- and consumption-based emissions were quantified using multi-regional input-output analysis and applying different GHG metrics (global warming and temperature potentials) and time horizons (20 and 100 years). Second, global emissions budgets for 1.5 °C, 2 °C, and 1 Wm⁻² climate thresholds were estimated. Budget shares were then assigned to NZ using two effort-sharing approaches (grandfathering and economic value), and emissions were benchmarked against the assigned shares. Finally, the analysis was undertaken at the NZ sector level. The results showed that, for each GHG accounting approach, NZ’s total emissions exceeded their budget shares, irrespective of the choices; the largest source of uncertainty was the choice of global emissions budget calculation method, followed by GHG metric, climate threshold, effort-sharing approach, and reference year for the grandfathering approach. The sector-level analysis showed that, while most sectors exceeded their budget shares, some performed within them. The ranking of uncertainty sources was quite different at the sector level, with the choice of effort-sharing approach providing the largest source of uncertainty. Overall, the study indicates the importance of handling value and modeling choices in a transparent way when quantifying emissions and setting emissions budgets for anthropogenic systems.
Article
Climate change mitigation requires the construction of low-carbon buildings. The use of Life Cycle Assessment provides useful information to support eco-efficiency improvements and therefore, to reduce the climate impact of buildings. However, it does not ascertain whether a proposed design aligns with achieving the global climate target of limiting global warming to below 1.5 °C or 2 °C. This study, therefore, introduces a science-based approach for setting climate targets for individual buildings using a whole-of-life cycle perspective. It involves assigning a share of the 2 °C global carbon budget for 2018-2050 to a country, its construction sector, and finally to each life cycle stage of a building. A stock projection model is used to account for the projected growth in the number of buildings and associated climate impact in a country up to 2050. The approach was applied to define a climate target for a New Zealand new-built detached house of 198 m2 gross floor area, the most common residential building type in the country. The weighted average climate impact of three New Zealand new-built detached houses was compared with the defined climate target. The results showed that the climate impact of new-built detached housing exceeded the climate target by a factor of five. When the climate impact was compared with the climate targets at each life cycle stage, exceedances were a factor three to five higher across the different life cycle stages. The proposed approach has potential to guide designers and other interested stakeholders to operate the construction sector within planetary boundaries.
Article
Buildings are responsible for a large share of greenhouse gas (GHG) emissions. The use of Life Cycle Assessment (LCA) during the design phase can help to improve the environmental performance of buildings. However, designers and clients find it difficult to set environmental performance targets and interpret the results obtained through LCA in order to improve the building design. Therefore, reference values or benchmarks are needed. Current available LCA-based benchmarks have mostly been developed for certification systems on whole building level and do not provide design guidance on material or element level. To close this gap, this paper introduces an alternative approach that supports the design process by providing guidance and encouraging to improve the environmental performance. The aim of this approach is to support exploiting the optimization potential particularly regarding the embodied GHG emissions related to the manufacturing of construction products and to the construction, maintenance and demolition of the building. The concept consists in combining top-down benchmarks per capita derived from the capacity of the global eco system with bottom-up reference values for building components that are defined based on a statistical best-in-class approach (top 5%) using the market share of different construction products. Benchmarks for GHG emissions for new residential buildings in Switzerland are discussed. The results of applying the dual benchmark approach to a case study show that it can facilitate the use of LCA-based tools for design support and promote the optimization of the building-related environmental performance.
Book
The Intergovernmental Panel on Climate Change (IPCC) is the leading international body for assessing the science related to climate change. It provides regular assessments of the scientific basis of climate change, its impacts and future risks, and options for adaptation and mitigation. This IPCC Special Report is a comprehensive assessment of our understanding of global warming of 1.5°C, future climate change, potential impacts and associated risks, emission pathways, and system transitions consistent with 1.5°C global warming, and strengthening the global response to climate change in the context of sustainable development and efforts to eradicate poverty. It serves policymakers, decision makers, stakeholders and all interested parties with unbiased, up-to-date, policy-relevant information. This title is also available as Open Access on Cambridge Core.
Article
Towards zero emission and zero energy buildings, literature reviews highlight the importance of embodied energy and embodied carbon emissions. The current review analyses 95 case studies of residential buildings, as an effort to identify the range of embodied carbon emissions and the correlation between the share of embodied energy and carbon for different levels of building's energy efficiency. The assessment identifies a range of embodied carbon emissions between 179.3 kgCO2e/m2-1050 kgCO2e/m2 (50-year building lifespan) that reflects a share between 9% and 80% to the total life cycle impact. That same share follows similar trends with the respective for embodied energy and ranges between 9% and 22% for conventional, between 32% and 38% for passive and between 21% and 57% for low energy buildings, while the normalised results indicate a sensitivity for the share of operating emissions that relates to the electricity mix. Considering the deviation of the results, even though a two-step normalisation procedure increases the homogeneity and comparability of the sample, the differences in the electricity mix, in LCI databases or even in the overall building design could not be neutralised and confirm the need for further standardisation in LCA. ............(Share link for free full-text PDF download (valid until 25/02/2018): https://authors.elsevier.com/a/1WLhf1HudMs5oL)............
Article
Our paper presents a novel approach for absolute sustainability assessment of a building's environmental performance. It is demonstrated how the absolute sustainable share of the earth carrying capacity of a specific building type can be estimated using carrying capacity based normalization factors. A building is considered absolute sustainable if its annual environmental burden is less than its share of the earth environmental carrying capacity. Two case buildings – a standard house and an upcycled single-family house located in Denmark – were assessed according to this approach and both were found to exceed the target values of three (almost four) of the eleven impact categories included in the study. The worst-case excess was for the case building, representing prevalent Danish building practices, which utilized 1563% of the Climate Change carrying capacity. Four paths to reach absolute sustainability for the standard house were proposed focusing on three measures: minimizing environmental impacts from building construction, minimizing impacts from energy consumption during use phase, and reducing the living area per person. In an intermediate path, absolute sustainability can be obtained by reducing the impacts from construction by 89%, use phase energy consumption by 80%, and the living area by 60%.
Article
Many impacts projected for a global warming level of 2 °C relative to pre-industrial levels may exceed the coping capacities of particularly vulnerable countries. Therefore, many countries advocate limiting warming to below 1.5 °C. Here we analyse integrated energy-economy-environment scenarios that keep warming to below 1.5 °C by 2100. We find that in such scenarios, energy-system transformations are in many aspects similar to 2 °C-consistent scenarios, but show a faster scale-up of mitigation action in most sectors, leading to observable differences in emission reductions in 2030 and 2050. The move from a 2 °C- to a 1.5 °C-consistent world will be achieved mainly through additional reductions of CO 2. This implies an earlier transition to net zero carbon emissions worldwide, to be achieved between 2045 and 2060. Energy efficiency and stringent early reductions are key to retain a possibility for limiting warming to below 1.5 °C by 2100. The window for achieving this goal is small and rapidly closing.
Article
Buildings are the largest consumer of energy and greatest contributor to climate change in the United States—consuming approximately half of energy produced and contributing close to half of greenhouse gas emissions. Building designers, contractors, and owners currently have few methods to effectively control a building’s life cycle energy and environmental impacts during the design phase. Managing and reducing these impacts during design requires rapid information turnaround and decision-making. When left unconsidered, poor environmental design decisions leave potential design value uncaptured. This research combines life cycle assessment (LCA) and target value design (TVD) to rapidly produce more sustainable building designs. By establishing site-specific sustainability targets and using dynamically-updating life cycle assessments, this research demonstrates that buildings can be designed to perform at higher environmental standards than those designed without a target in place. The research also offers unique opportunities to analyze the tradeoffs between design and operational decisions.