Dual path promotion, making buildings more energy-efficient

Source: Science and Technology Daily

Introduction

At present, the main difficulties in carrying out near zero energy consumption renovation of existing buildings come from three aspects. Firstly, there are more restrictive conditions for the renovation of existing buildings, so it is better to create more space for new buildings. Secondly, it is more stringent in cost control. Thirdly, there are more issues of socialization. The renovation of existing residential buildings requires the consent of all owners and involves public opinion coordination.

The exterior facade and roof are cleverly equipped with photovoltaic panels for power generation, and the atrium is lit on both sides using sunlight to save lighting and electricity consumption. The design of the staggered half story staircase encourages employees to walk more and take fewer elevators, and there is also a "smart brain" platform for operation and maintenance of the entire building's mechanical and electrical equipment. Recently, the Yangtze River Delta integrated green technology demonstration building has been completed and put into use. This modern office building, with a total construction area of nearly 12000 square meters, has been rated as a zero energy building by the China Building Energy Conservation Association and is the largest single zero energy building in Shanghai.

The construction sector is one of the main areas of global energy consumption and carbon emissions. According to the "China Building Energy Consumption and Carbon Emissions Research Report (2021)", in 2019, the proportion of energy consumption in the entire construction process in China reached 46% of the total national energy consumption. In order to achieve the "dual carbon" goal, the construction industry actively explores the development path of zero energy consumption buildings suitable for China.

How to Realize Near Zero Energy Consumption Buildings

In 2019, the Ministry of Housing and Urban Rural Development issued the national standard "Technical Standards for Near Zero Energy Consumption Buildings", which defined near zero energy consumption buildings. Near zero energy consumption buildings refer to buildings that adapt to climate characteristics and site conditions, minimize heating, air conditioning, and lighting needs through passive building design, maximize energy equipment and system efficiency through active technical measures, fully utilize renewable energy, and provide a comfortable indoor environment with minimal energy consumption. Their indoor environmental parameters and energy efficiency indicators meet the requirements of this standard.

Among them, ultra-low energy buildings are the primary manifestation of near zero energy buildings, while zero energy buildings are the advanced manifestation of near zero energy buildings.

The technical standards for near zero energy consumption buildings in China have to some extent borrowed from Germany's' passive room 'and are stricter and higher in standards. "Professor Yang Wei from the School of Architecture at Tianjin University introduced that in 1991, a villa in Darmstadt, Germany became the first building to adopt the concept of' passive room 'for design and construction, and has been developed to this day, Passive housing has become a globally influential ultra-low energy building technology system and standard.

China has a vast territory, with significant climate differences among different regions. The level of economic development and indoor environmental standards need to be improved, and the architectural characteristics, construction technology, industrial level, and people's living habits are not the same. Therefore, China's near zero energy building standards are more complex and detailed.

For example, China is divided into five heat division zones: severe cold regions, cold regions, hot summer and cold winter regions, hot summer and warm winter regions, and mild regions. Each heat division zone has different energy consumption indicators, including annual heating demand, annual cooling demand, and annual energy consumption for heating, cooling, and lighting, "Yang Wei said.

Although the standards for near zero energy consumption buildings vary among different thermal zones and types of buildings, the most basic technologies are mainly five aspects: enclosure structures with higher insulation performance; External doors and windows with better insulation and air tightness performance; The overall high airtightness of the building; Efficient energy equipment system; Design and construction of non thermal bridges.

Yang Hongwei, an associate professor at the School of Architecture at Tianjin University, introduced that in order to meet the near zero energy consumption building standards, these technologies will lead to a certain increase in building costs and higher difficulty in implementation compared to ordinary buildings.

For example, the airtightness of buildings has a significant impact on energy consumption. To install exterior windows with better airtightness, it is necessary to first choose products that are different from ordinary buildings, and the cost will naturally be higher. "Yang Hongwei said," At the same time, three products are installed, and seven products are installed. If there are leaks during installation, even the best product cannot meet the airtightness standard of the hourly air changes specified in the specifications. This puts forward higher requirements for the technical level of construction personnel.

In the process of building use, it is necessary to optimize usage behavior and equipment operation to reduce energy consumption. For example, setting the opening and closing time of equipment, setting power, and using energy storage equipment can all be coordinated and scheduled through intelligent operation and maintenance systems to improve energy efficiency. In addition to guiding people's usage behavior, smart energy management systems can also assist in improving people's energy-saving awareness and achieving energy-saving while meeting usage needs. For example, by sensing temperature, humidity, brightness, etc. through sensors, it can reduce energy consumption while providing the most comfortable environment.

In the transition period from pilot to promotion

Searching for the words "near zero energy consumption building technology standards" on the internet will bring up standards from multiple provinces and cities. Under the framework of national standards, various regions across the country are exploring suitable near zero energy consumption building models.

At present, China's near zero energy consumption buildings are in the transition period from pilot to promotion. The nearly zero energy consumption buildings that have been built are mostly individual cases, appearing sporadically and not being promoted on a large scale, "Yang Wei said.

In fact, from a purely technical perspective, China's current technology can fully achieve the construction of near zero energy consumption buildings or even zero energy consumption buildings. For example, Yang Wei, the zero carbon building work "RCELLS", which won the championship of the third China International Solar Decathlon Competition at Tianjin University, integrates multiple innovations such as architectural design, structure and construction, equipment systems, renewable energy systems, intelligent control, and adopts scalability Customizable modular design that can be promoted on a larger scale.

The economic feasibility is one of the important factors that determine whether near zero energy consumption buildings can be promoted in the future. Near zero energy consumption buildings are relatively high-tech buildings, with higher building materials and construction costs compared to ordinary buildings. The maturity of related products and technologies largely determines their costs and market acceptance, "Yang Wei said.

In terms of fully utilizing renewable energy, the green power ratio of China's current power grid is not very high. If the building itself is installed with photovoltaic technology, due to the high density and large scale of urban buildings, the roof area is relatively limited, and its own renewable energy utilization rate will be constrained to some extent. Therefore, the integration of urban and rural areas and the promotion of green power generation and energy storage scale also contribute to the promotion of near zero energy consumption buildings.

In addition, in the construction industry, implicit carbon emissions and operational carbon emissions each account for approximately half of their total process carbon emissions. Implied carbon emissions mainly come from material extraction and processing, component production, construction and transportation, while operational carbon emissions are generated during the use of buildings. By improving the lifespan of buildings and building components, developing technologies such as material conservation and environmentally friendly building materials, energy conservation and emission reduction in the construction industry can be promoted throughout the entire life cycle, helping to achieve carbon neutrality goals.

Near zero energy consumption renovation of existing buildings is more important

In addition to building new near zero energy buildings, the demand for near zero energy renovation and promotion of existing buildings seems more urgent and grounded.

As of now, the existing building area in urban and rural areas of China has reached 66 billion square meters. The new construction market is becoming increasingly saturated, and large-scale existing buildings urgently need to improve energy efficiency. Therefore, improving and renovating existing buildings is very important and necessary, "Yang Wei believes.

At present, the difficulties in carrying out near zero energy consumption renovation and promotion of existing buildings mainly come from three aspects. "Yang Hongwei introduced that first of all, there are more restrictions on the renovation of existing buildings, so it is better to have more space for new buildings. For example, some technology needs to be added, but the space is not enough, and some materials need to be replaced, but the construction conditions cannot be met. Secondly, in terms of cost control, it is more stringent. For Party A, when renovating existing buildings, they place greater emphasis on cost-effectiveness and time cost. For the renovation of existing buildings, it is necessary to first diagnose the reasons for high energy consumption before coming up with a plan, and spend the money on the cutting edge to see greater benefits. The third issue is that there are more socialization issues, and the renovation of existing residential buildings requires the consent of all owners, involving public opinion coordination.

Yang Wei believes that although it is not easy to carry out near zero energy consumption renovation and promotion of existing buildings, it is not impossible. It can be promoted through both 'top down' and 'bottom up' approaches, "Yang Wei explained." Top down "refers to the top-level design where the government takes the lead, sets overall goals, formulates relevant national and local policies, regulations, etc., and promotes implementation through administrative and incentive measures.

For example, in 2021, China issued the national standard "General Code for Building Energy Conservation and Renewable Energy Utilization" numbered GB55015-2021. This code is a mandatory engineering construction code that puts forward high energy-saving requirements, requiring all newly built buildings to achieve a certain level of energy efficiency. In the future, specialized mandatory engineering building codes can also be introduced for energy-saving renovation of existing buildings to accelerate the progress of renovation work, "Yang Wei said.

In addition, relevant government departments, research institutions, and state-owned enterprises have also made the (near) zero energy consumption renovation and promotion of existing buildings an important research topic, and carried out demonstration project construction.

At the same time, a "bottom-up" approach can also be adopted, for example, for residential buildings, personalized and customized micro renovations can be carried out according to the needs of the owners. For example, residents can add insulation to their interior walls, replace three glass and two empty windows, and establish a stable and balanced heat environment to reduce household energy consumption.