A huge amount of energy is consumed and a huge amount of carbon dioxide is emitted into the atmosphere in the operation of buildings – both residential and commercial.
However, it would be possible to drastically reduce the amount of energy consumed by buildings, and drastically reduce our energy bills, if energy use were made more efficient.
Building energy efficiency is a complex issue. Firstly, it is essential to distinguish between primary energy and delivered energy.
Primary energy is energy in nature that has not been subject to any conversion or transformation. It includes fossil fuels such as oil and coal, or renewable sources such as wind and solar. Delivered energy, or site energy, is the amount of energy delivered to an energy user. It may include oil, gas or electricity.
Energy consumed in buildings, both residential and commercial, accounts for 20.1 per cent of the total delivered energy consumed worldwide, according to the International Energy Outlook 2016 by the US Energy Information Administration (EIA).
Delivered energy consumption in buildings worldwide is predicted to increase by an average of 1.5 per cent per year from 2012 to 2040, and in the non-organisation for economic co-operation and developed (non-OECD) nations, consumption of delivered energy to buildings is predicted to grow by 2.1 per cent per year in the same period, according to the EIA report.
Energy consumption in the residential sector includes energy used for heating, cooling, lighting, water heating, and consumer products.
In the report, residential energy use is predicted to account for about 13 per cent of total world delivered energy consumption in 2040.
In the commercial sector, energy is consumed by heating and cooling, lights, refrigerators, computers, and other equipment. Examples of commercial sector buildings include retailers, office buildings, government buildings, restaurants, hotels, schools, hospitals, and leisure and recreational facilities. Total world delivered commercial sector energy consumption is predicted to grow by an average of 1.6 per cent a year from 2012 to 2040 and is the fastest-growing energy demand sector.
Lately in Australia, several workshops and forums were conducted to discuss ways of improving buildings’ energy efficiency. The forums were established by a consortium consisting of the Australian Institute of Refrigeration, Air Conditioning and Heating (AIRAH); City of Sydney; the Energy Efficiency Council; the Green Building Council of Australia; UTS Institute of Sustainable Futures; NABERS (National Australian Built Environment Rating System); and the NSW Office of Environment and Heritage.
The most recent forum – focusing on mid-tier commercial buildings – was conducted in Sydney on June 13. Mid-tier buildings are generally smaller than 10,000sq m, typically built before 2000, with a lower level of energy efficiency than premium buildings.
Australia’s peak body for energy efficiency, cogeneration and demand management, is the Energy Efficiency Council – a not-for-profit membership association aiming to make cost effective energy efficiency measures standard practice across Australia.
The National Construction Code (NCC) sets the minimum requirements for the design, construction and performance of buildings throughout Australia.
The NCC is an initiative of the Council of Australian Governments (COAG) developed to incorporate all on-site building and plumbing requirements into a single code. The NCC is a set of technical provisions that allow for variations in climate and geological and geographic conditions.
The National Energy Efficient Building Project (NEEBP), which started in 1912, aims to help achieve better energy efficiency in new buildings, renovations and additions. The NEEBP is led by the Government of South Australia’s Department of State Development and is co-funded by all Australian states and territories through the COAG Energy Council.
According to the Department of the Environment and Energy, Australian households are directly responsible for about one-fifth of Australia’s greenhouse gas emissions. Heating and cooling accounts for 40 per cent of household energy use, water heating accounts for 21 per cent, appliances and equipment including refrigeration and cooling account for 33 per cent, and lighting accounts for 6 per cent.
Insulation, which acts as a barrier to heat loss and heat gain, is crucial to reduce heating and cooling bills. Half of the energy used for heating or cooling can simply leak out without insulation. Insulation should be installed in accordance with the relevant Australian standards and the NCC. Insulation must also meet the minimum requirements for R-values (which measure resistance to heat flow) and care must be taken to ensure appropriate clearances are met around electrical wires and appliances.
There are two main types of insulation: bulk insulation, which acts as a barrier to heat flow between the home and the outside; and reflective insulation, used to deflect radiant heat and keeping the home cool in summer. Bulk insulation – used in homes located in cooler climates – comes in batts, rolls, boards and can be made of glass wool, polyester, natural wool or recycled paper. Reflective insulation – used in homes located in hot and sunny climates – is usually made of shiny aluminium foil laminated onto paper or plastic.
The energy performance of a building is evaluated using the Nationwide House Energy Rating Scheme (NatHERS) using software based on research by the CSIRO. The software models a house plans to estimate the amount of energy it will need for heating and cooling. Taking into account hundreds of factors, including the building’s construction, local climate and orientation, the rating system scores a house between zero and 10 stars.
Other countries also have several initiatives in place to improve building energy efficiency and reduce greenhouse gas emissions.
Germany initiated a far-reaching transformation of its energy system in its Energiewende, which demands a reduction of primary energy consumption by 20 per cent until 2020, and 50 per cent until 2050. To achieve this, the German Federal Ministry for Economic Affairs and Energy (BMWi) proposed a national action plan on energy efficiency in December 2014.
Japan has been implementing the Top Runner Program to set energy use standards for home and office appliances. The program searches for the most efficient model in the market and then stipulates that the efficiency of this ‘top runner’ model should become the standard within a few years. By that target year, each manufacturer must ensure that the weighted average of the efficiency of all its products is at least equal to that of the top runner model.
In the United Kingdom, housing is among the least energy efficient in Europe. In 2004, housing accounted for more than 30 per cent of all energy use in the UK. Despite the progressive tightening of the building regulations’ requirements for energy efficiency since the 1970s, there has not been a significant reduction in domestic energy use. This is probably because of an increase in the number of homes with central heating, the increase in the number of households, and an increase in the number of domestic electrical appliances.
Building regulations in the UK limited the ‘u-value’ – the amount of heat lost per square metre, for each degree Celsius of temperature difference between inside and outside.
In the United States, there are more than 85 million residential and commercial buildings, accounting for about 40 per cent of the country’s primary energy consumption and 39 per cent of US carbon dioxide emissions, according to the EIA.
In his 2013 State of the Union address to the nation, President Barak Obama issued a national goal of reducing energy losses in buildings by 50 per cent in the next 20 years.
The Building Technologies Office (BTO) within the Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy is responsible for developing and deploying technologies that can substantially reduce energy consumption in residential and commercial buildings. The BTO has developed an R&D roadmap for next generation home appliances; emerging water heating technologies; solid-state lighting; emerging HVAC technologies; windows and building envelope; and next generation low global warming potential refrigerants.
Residential appliances such as refrigerators, dishwashers, laundry equipment, and cooking equipment account for more than 12 per cent of US residential primary energy consumption, according to the BTO. The BTO has listed appliance technology options for the near-term (up to two years), medium-term (two to five years), and long-term (five to 10 years).
For example, long-term options for advanced compressor technologies for refrigerator/freezers include: linear compressors implemented in wider range of products, first demonstrations of electrochemical compressors implemented in residential-sized refrigerators, first full-sized residential refrigerators using electrochemical compressors brought to market.
Long-term options for vacuum insulation panels for refrigerator/freezers include improved VIPs implemented in wider range of residential refrigerators. Long-term options for magnetic refrigeration include: development of full-sized magnetic refrigerator, and testing of full-sized magnetic refrigerator in residential settings.
The BTO said solid-state lighting represents a huge opportunity to generate significant energy savings. It said in the US, LED (light-emitting diode) lighting is forecast to account for the majority of installations by 2030.
In its roadmap for emerging water-heating technologies, the BTO has identified many technologies, some already commercialized, and some under development.
Commercialised technologies include an electric heat pump water heater, a residential gas condensing water heater that achieves up to 96 per cent thermal efficiency, and a wireless water heater controller.
Technologies under development include: a carbon dioxide heat pump water heater, a high performance adsorption water heater, a carbon dioxide heat pump water heater for commercial applications, a gas-filled residential heat pump water heater, and a thermoelectric heat pump water heater.
Emerging HVAC technologies identified by the BTO include: a direct current-powered HVAC system to utilize DC power from a solar PV system without inverter losses; raising heat pump performance at low ambient temperature; electrochemical compression systems; new adsorption pairs, and compact heat exchangers; open-source, open-architecture platform that enables smart grid connectivity for demand response; and low-cost sensor network and control scheme where every surface, critical object, and occupant has a sensor.
In general, technological advances will work toward improving energy efficiency, but other developments such as population growth, improved living standards, and a smaller number of people per home, will cause energy use in buildings to increase, making it more difficult to improve energy efficiency.