The construction industry can act as one of the keys to successfully combatting climate change. Around 30 to 40 per cent of primary energy is consumed by buildings for heating, cooling, ventilation, lighting, cooking and other activities. The resultant CO2 emissions account for more than one third of the global total. Xiaotong Gao of Saint-Gobain Research Shanghai explains that although the construction of low-energy buildings can help to address this problem, promoting them in China is a challenge.
Up to 70 per cent of China’s energy is supplied by coal-fired power stations. Consequently, catastrophic amounts of air pollutants, such as carbon dioxide (CO2), carbon monoxide (CO), suspended particulate matter (PM), nitrogen oxides (NOx), sulphur oxides (SOx), polycyclic aromatic hydrocarbons (PAHs) and heavy metals, are released into the atmosphere. This causes multiple environmental problems like smog and acid rain and contributes to health issues including chronic respiratory diseases.
A recent example of extreme pollution was witnessed in Shenyang, Liaoning Province, on 8th November 2015, when the recorded peak concentration of PM2.5 exceeded 1,400µm/m3. This astonishing deterioration in air quality was widely acknowledged as being caused by the city’s coal-powered heating systems being fired up for the winter. Clearly, reducing buildings’ energy consumption will be critical for China’s sustainable development.
To reduce energy consumption in buildings there are three key technical aspects that must be addressed: ensuring buildings are properly insulated, adopting clean energy sources and employing efficient downstream technology, such as heating and cooling equipment. None of these can solve the problem on its own, so advanced solutions for all the three are needed.
Proper insulation plays a fundamental role in reducing a building’s energy consumption. A poorly insulated building can be compared to a car with a leaking fuel tank: to conserve fuel, the first thing to do is to stop the leakage. Similarly, to reduce a building’s energy consumption, thermal leakage through walls, windows, the ground and roof needs to be prevented, thermal bridges at various building elements need to be avoided or protected, and the airtightness of the building envelop needs to be sound. A well-insulated building can save up to 90 per cent of energy expended on heating and cooling, significantly reducing the overall amount of energy used and subsequent CO2 emissions and air pollution, not to mention the reduction in operational costs.
Products and solutions for low-energy buildings are already available and have been for years, yet low-energy buildings are still not as popular in China as anticipated. This is not primarily due to cost, as the cost of insulation materials is only a fraction of the cost of the whole building. Therefore, in order to successfully promote low-energy buildings several other factors must also be considered.
First, nowadays, developers and contractors will engage several suppliers and evaluate a huge number of products before selecting materials for insulation, moisture control, mortar, glazing and roofing. This involves high costs related to communication and coordination and it raises legitimate concerns over quality control due to a lack of alignment between the various products from the different suppliers that are ultimately selected. Manufacturers that can offer a wide range of products and one-stop solutions are therefore more desirable: it is more likely that the quality and performance of the building envelop can be assured because the integration of different products and materials takes place during the product design and manufacture stage.
Second, solutions must be designed with due consideration given to a building’s function, the local climate and attributes of the building’s occupants. A low-energy building designed for Shenyang cannot be adopted in Guangzhou because of the differences in temperature, relative humidity, solar angle and strength of solar radiation. Similarly, solutions that are suitable for schools will be different from those for hospitals, apartments and shopping malls, because the activities and needs of the occupants are completely different. Thus, a deeper understanding of building sciences and occupant preferences is required in order for the building industry to be able to provide localised and specialised products and solutions that satisfy the needs of different customers.
Third, the demand for low-energy buildings has to be stimulated among potential end-users. The general public needs to be educated on the importance of low-energy buildings for maintaining a desirable living environment, the available products and solutions that can reduce energy consumption in their homes, offices and classrooms, and how their choices and actions can ultimately help to save our planet.
This is not an action that should be undertaken solely by government and educational institutions, all stakeholders of the building industry should participate. For example, demonstration buildings are a useful tool of communication, however, most of them are accessible only to professionals. Making demonstration buildings accessible to the general public will allow them to see, touch, feel and understand low-energy buildings, which, in turn, will increase their interest in and desire for low-energy buildings. It is ultimately increased demand from end-users that will raise the low-energy building market to a higher level.
Last, but by no means least, a low-energy building must be liveable, meaning it should provide a high quality indoor environment. Optimum thermal comfort, adequate daylight, proper room acoustics and clean fresh air are all conditions that are better for the health, productivity and psychological well-being of a building’s occupants.
Traditionally, Chinese customers tend to sacrifice comfort to save on energy bills. An example of this can be witnessed in Shanghai during the winter, when the indoor temperature of a typical apartment can drop to as low as 5°C, which is far below the suggested comfort temperature of 18°C to 24°C in building codes and literature. In these instances, well insulated walls and windows can make a significant difference by preventing heat loss.
Research by Carnegie Mellon University’s Centre for Building Performance and Diagnostics also shows that productivity in offices can be improved up to three per cent with good thermal comfort; up to 11 per cent with good air quality; up to 15 per cent with good natural light; and up to 20 per cent with good acoustics. Ensuring a high level of comfort will therefore clearly make low-energy buildings more attractive to building owners and end-users alike.
According the Ministry of Housing and Urban Rural Development’s 2013 annual report, China then had a building stock of 37 billion square metres, which had increased at a speed of 10 billion square metres per year since 2009. This high rate of growth poses a significant challenge to the overall aim of reducing energy consumption and improving building quality. At the same time, it presents an enormous opportunity to the building industry to introduce new technologies, products and services.
In addition to energy efficiency, one-stop solutions and customised design, an end-user orientated strategy and a high level of occupant comfort are the keys to promoting low-energy buildings in China, which will eventually play a major role in reducing energy consumption and CO2 emissions, and improving air quality.
Mr Xiaotong Gao obtained his Ph.D. in Materials Science and Engineering from Drexel University, Philadelphia. He joined Saint-Gobain Research Shanghai (SGRS) in 2011, where he is the leader of the Building Physics Platform. The Platform covers research projects of building energy efficiency, thermal comfort, daylighting, room acoustics and indoor air quality, and supports the group strategy of Sustainable Habitat in APAC.
Saint-Gobain, the world leader in the habitat and construction market, designs, manufactures and distributes high-performance and building materials providing innovative solutions to the challenges of growth, energy efficiency and environmental protection. The company takes a long-term stance for its actions in order to produce for its customers the products and services that will facilitate sustainable construction and day-to-day living.