The Sustainable Housing Challenge
4.2 Dwelling Scale
4.2.1 Planning and Design
In many developed countries, there is some form of planning process involved in the provision of housing (see Chap. 2). In addition to the ability to set local requirements for design, quality, and performance, planning systems have a critical role in deciding how land is used and where development should occur [10–13]. The decision of what land can or cannot be used for has important implications for environmental, social, and economic outcomes for a range of stakeholders. For example, the planning system can set parameters for areas that are to have higher, or lower, density development which then immediately influences the type of housing that can be provided, as well as its affordability. In other areas, the rezoning of land from industrial or agricultural to residential can unlock significant financial value for the landowner. Furthermore, it is in the planning system where decisions on climate risk typically sit, such as determining if dwellings should be built in an area with a particu- lar climate risk such as flooding or bushfire. These planning system deci- sions present opportunities for improvement of design and sustainability outcomes but can also create negative outcomes if not done properly. For example, after significant flooding events through urban centres on the east coast of Australia in 2022, it was revealed that many local planning authorities were using historical climate data to make decisions about flood risks. Some researchers suggested that this had led to some houses being built in areas we should not be building in, considering future cli- mate changes [14, 15].
The planning system is typically also responsible for the design and layout of proposed development sites. This means that before any dwell- ings are designed, materials and technologies are selected, and construc- tion methods are confirmed, that lot layout of vacant or underdeveloped land is done in a way that maximizes sustainability outcomes. For exam- ple, optimizing orientation can reduce the costs for design, materials, technologies, and construction methods to achieve improved
performance outcomes. Conversely, if lot layout is done without consid- ering orientation, it can negatively impact dwelling performance.
Research from Australia shows that the difference between the best and worst orientations for a minimum regulated performance house in Melbourne was as much as 35% and that higher performing dwellings had less variance from worst to best orientations [16]. Research on the benefits of orientation in other locations has also found significant per- formance improvements. For example, Elnagar and Köhler [17] found thermal performance improved by 7% for a residential dwelling in Kiruna (Sweden), 15% in Stuttgart (Germany), and 22% in Palemo (Italy). In the UK, Abanda and Byers [18] modelled a house and found a 5% differ- ence in thermal performance between the best and worst orientations and this translated this to an energy saving cost of about £900 over 30 years. Abanda and Byers [18] demonstrate that orientation is not just about reducing energy consumption but it has a wider impact on afford- ability and liveability, an outcome that is only likely to increase with a changing climate and increasing energy bills.
Additionally, planning systems address the question of density of hous- ing. Arguments for density include the need to house growing popula- tions close to amenities as well as for housing affordability outcomes.
However, density should not be done at the expense of good design prac- tices. In relation to environmental sustainability, there is disagreement across the research as to what is optimum in relation to density and diver- sity of dwellings. From a purely energy perspective, research has shown that detached housing is more energy intensive from dwelling operation compared to medium-higher density housing. However, this depends on what is under consideration, as higher density housing requires increased energy for things outside the dwelling such as elevators, communal light- ing, and heating/cooling [19–23].
It also depends on what other considerations are included. Research undertaken in Adelaide (Australia) compared energy consumption and emissions across the life cycles of apartments within the city centre and detached homes in the suburbs. This research found that the total deliv- ered energy consumption of apartment households was lower than the suburban households [24]. However, the authors found that, when
looking at greenhouse gas emissions, the total per capita emissions typi- cally exceeded those of the detached suburban households.
The challenge in the density discussion is that when housing gets built upwards, it often results in higher embodied energy1 consumption due to the requirements of the structure and results in lower occupants/dwell- ings in comparison to lower density housing. Highlighting the complex- ity of this issue, Estiri [22], analysed more than 12,000 dwellings in the USA and found that lower density suburban households consumed 23%
more energy than higher density inner city households. Again, depend- ing on the metric, the data could be interpreted differently with the research showing that those living in the higher density city housing had a 22.6% higher energy intensity compared to the detached suburban homes. Roberts et al. [25] found that, with apartment occupants, it was not just the difference in energy consumption, but also how and when the energy was consumed which was different to detached housing. This could have broader implications for energy generation and energy grid stability. As we move towards consuming more renewable energy we are already seeing a need to better align energy consumption with when energy is being generated [4].
In an interesting analysis of more than 73% of housing in the USA, Goldstein et al. [26] explored the carbon footprint of housing across the country. They calculated that if cities were to meet Paris 2050 goals, there would need to be an increase in density of 19%. In some cities, such as Boston, the required increase in density was more than 50% (increasing to an approximate 5000 residents/km2, which the study authors say is a critical threshold for residential energy sustainability targets). The authors also argued that densification has wider benefits for affordable housing, largely through the provision of more housing options in well- established areas.
The design stage is also critical for the sustainability of a dwelling. In many countries around the world, like the USA, Canada, and Australia, the floor area of new detached housing has been increasing for many years, although there are signs that this may have plateaued [27]. The
1 Embodied energy is a calculation of all the energy that is used to produce a material or product, including mining, manufacture, and transport [1].
growth in floor area has not occurred equally around the world or across housing types; other jurisdictions, like the UK and Sweden, have much smaller housing [28]. Furthermore, while the average new detached dwelling size in Australia has grown in recent decades, the opposite was seen for Australian apartments with a rapid increase of small apartments entering the market and prompting some Australian states to introduce minimum design, space, and performance requirements.
The increase in the average floor area of new dwellings has been occur- ring at a time of declining average occupant numbers. It has also occurred across a period of increasing shifts in consumer expectations around housing quality and inclusions. As Ellsworth-Krebs [27, p. 22] states, the trends of ‘increasing house sizes and floor area per capita undoubtedly impact expectations of home comfort and aspirations for the ideal home.
Just as standardization and globalization has resulted in homogenization of indoor temperatures across the globe over the past forty years, so too can increasing floor area per capita shift norms and expectations of how much space is “enough”’.
Increasing floor area has an impact on the design, quality, and perfor- mance of dwellings [29, 30]. Research in the USA found that a 1000 square foot increase in dwelling size would result in a 16% increase in energy consumption for space heating/cooling [31]. In Australia, researchers estimated that each 2% increase in average new floor area would add 1 tonne to a household’s total CO2 emissions per year [32].
Although much of this growth in floor area occurred during the same time that minimum performance requirements were introduced, research has found that the growth of floor area of detached housing has largely nullified energy efficiency gains from these improve thermal performance requirements [33]. It is also not just the floor area that is an issue for sustainability, but that the growing floor area on decreasing lot sizes means there are less opportunities to optimize passive design and address wider issues such as the urban heat island effect [30].
There also needs to be a better match between occupant numbers and house size or number of bedrooms due to the impact on sustainability outcomes. In China, Wu et al. [34] found that removing one person from a household results in an increase of 17–23% per capita residential elec- tricity consumption. In England, Huebner and Shipworth [35] found that if single occupant households with multiple bedrooms downsized by
one bedroom, they could achieve an 8% energy efficiency saving, or a 27% saving if they downsized to a one-bedroom dwelling. The authors also note the range of benefits downsizing has beyond environmental benefits, such as social and financial ones like freeing up larger dwellings for growing families and releasing equity for those downsizing.
These benefits have not only been identified for small occupant house- holds; in the USA, Berrill et al. [36] found that changing 14 million dwellings from family housing to multi-family housing would reduce energy demand by up to 47% per household and reduce total urban resi- dential energy by up to 8%. Clearly, the benefits achieved just from ensuring appropriate household and housing balance will have significant implications for the environment. As McKinlay et al. [30, p. 146] state
[g]overnment policies that attempt to address urban consolidation, green urbanism and housing affordability, seldom consider the dwelling size fac- tor … The size of a dwelling has cumulative effects for sustainability at the scale of both neighbourhood, city and country. If these sustainability goals are to be met, the dwelling scale needs addressing. It can be speculated that neoliberal government attitudes avoid intruding in the private realm of the home, however policy documents need to reflect dwelling size as a funda- mental aspect of sustainable housing.
This is echoed by Cohen [28, pp. 175–176] who writes, “the important insight is that size matters and if policymakers are serious about suffi- ciency – especially with respect to meeting climate targets and commit- ments embodied by the SDGs (Sustainable Development Goals) – it is imperative to devote serious consideration to shrinking floor area”.
However, Huebner and Shipworth [35] pointed out a number of chal- lenges in achieving these outcomes, including a limited number of options for such households to downsize into. Similar arguments are put forward by Ellsworth-Krebs [27, p. 22] who says any focus on restricting increasing dwelling sizes must be done alongside ensuring that alternative housing options “provide[s] adequate occupant satisfaction in terms of privacy and personal space as this is assumed to be a part of moderniza- tion and a driver towards smaller household sizes”. Jack and Ivanova [23]
echo these calls, arguing policy makers must think about new ways to encourage new forms of shared living and downsizing as part of an
approach to reduce residential carbon emissions. Others like Berrill et al.
[36] argue that there needs to be innovation in the use of taxes and sub- sidies to help guide the housing industry and consumers to build the type of housing we need in the future.