The World Green Building Council (GBC) wants all buildings to be 100% net zero carbon by 2050 – and that includes our homes. In terms of their call to action, all new buildings must operate at net zero carbon by 2030.
Various types of action can be taken to help make net-zero carbon a reality, all of which relate to minimizing greenhouse gas emissions and maximizing energy efficiency. Since house size is a key factor in determining the consumption of energy, it's not surprising that some researchers have found that even small reductions in floor areas can offset at least some of the inevitable extra costs associated with zero energy housing.
Technically, net-zero energy buildings generate all their energy needs on-site. But, because that isn't feasible – especially for residential buildings – engineers specializing in mechanical, electrical, and plumbing (MEP) engineering designs in Chicago, New York, Toronto, Delhi, London, Sydney, Cape Town, and all the cities and regions in the world, aim to ensure buildings are as energy-efficient as possible and can draw their energy needs from renewable sources.
In its 24-page Advancing Net Zero Status Report released in 2019, the World GRB lists four key principles:
⦁ The need to measure and then disclose the data relating to carbon, which is the ultimate metric that must be tracked so that operational net-zero carbon emissions can be measured.⦁ The necessity to reduce broad demand for energy and prioritize energy-efficiency so that buildings will perform efficiently and not waste energy uneccesarily.
⦁ The requirement that whatever remaining demand there is for power should be supplied from sources of renewable energy, preferably from on-site sources, otherwise from offset or off-site facilities.
⦁ The need to improve "verification and rigor" so that over time embodied carbon (from the entire building lifecycle) and other impact areas like zero water and waste will be included.
Assessment of Affordable Low-Carbon Housing
As we get closer to the World GBC's 2030 and 2050 net-zero carbon goals, it is essential to assess the relationship between renewable energy systems and house sizes. Policies relating to official ratings also play a vital role.
Right from the start, a pressing issue has been the upfront costs that result when residential house design follows the low carbon model. Even though it isn't usually substantial, and invariably leads to much lower running and maintenance costs, there is a consumer mindset that is difficult to change. There is also a general lack of consumer, and even building industry, knowledge.
What people need to realize is that by reducing energy consumption in the built environment, not only do greenhouse gases reduce but so do the costs of operating and maintaining the building.
The supply of energy for housing in most parts of the world is unsustainable long term, and even though the benefits and advantages of low-carbon, zero-energy houses have been known for a while, houses designed to meet low carbon needs remain in the minority. This is changing where cities, states, and countries have introduced policies that have made the World GBC net-zero carbon goals mandatory, in the UK and California for example.
A UK research paper, Homes as machines: Exploring expert and public imaginaries of low carbon housing futures in the United Kingdom, published in 2016, examines how experts envisage low carbon housing. It also looks at the policies and standards that have been implemented in an endeavor to reduce the demand for energy in the residential sector, together with renewable energy used by the sector, as well as ways of improving the sustainability of new-build housing.
The initial vision put forward in 2006 was that houses needed high energy efficiency and to make use of renewable energy sources that would be acceptable to the supposedly environmentally aware consumers who would buy or build them. By 2015, this had changed and the vision had shifted to affordability and energy security, even though the need to reduce the carbon emissions associated with housing hadn't changed. For this reason, building regulations were tightened and sustainability requirements were added.
A more recent vision advocates energy-efficiency measures that will reduce home energy bills. The largely passive, smart house, with a high-tech automated approach to home energy control, is another vision of future housing.
The Importance of Size for Low Carbon Houses
Perhaps surprisingly, there has been minimal research that examines the role of size in the design and performance of low carbon or net-zero carbon houses.
Australian researcher, Dr. Trivess Moore, together with two researchers from the UK, Drs. Stephen Clune, and John Morissey, undertook a study that specifically analyzed The Importance of House Size in the Pursuit of Low Carbon Housing. They aimed to establish just how reducing the size of a house could help make zero energy housing affordable in the future. The study involved:
⦁ Estimating the construction costs of more than 100 affordable housing plans that included three different sized houses: 160, 220, and 250 square meters.
⦁ Forecasting energy demand and estimating the energy consumption costs of each, assuming that all houses utilized reverse-cycle heat pumps for both heating and cooling.
⦁ Undertaking an empirical costing of photovoltaic systems and solar hot water which would be "energy natural" for a 12-month period of time.
⦁ Factoring in the star ratings that are achievable in different Australian cities, from 6 to 10 when the right design principles and materials are used. These are, of course, applicable to all countries in the world, though they are directly affected by climatic conditions.
Of course, the upfront costs were lower for smaller houses, and the larger the house, the more energy was consumed. With improved thermal performance, the total consumption of energy was reduced, partly because there was less need for heating and cooling and partly due to appliances and technologies used that required less energy.
The star ratings impacted on cost, and anything above the 8 star rating was not considered cost-efficient even though thermal performance and comfort were not negated – and these qualities improve with higher star ratings.
More importantly, the study found overwhelmingly that reducing the size of a house by just 5-10% could offset the costs associated with net-zero energy needs. Environmental benefits were also increased.
In practice, reducing the size of a house requires architects and engineers to concentrate on smart, sustainable designs that meet the individual needs of homeowners and inhabitants. But ultimately, this approach will make houses more affordable.
So, should modern home design go small to meet low carbon needs? The answer is relative, but reducing sizes will help to achieve net-zero goals. However, all the goals of sustainability must combine with size because size alone will not necessarily make houses affordable.
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