How to design ultra-low energy buildings?

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Features of 1. ultra-low energy consumption building design


In the process of ultra-low energy consumption building design, it is necessary to count and calculate the energy consumption projects of each branch of the building in detail, combine the energy consumption of the building with different energy consumption branches, realize the optimization design goal, and reduce the overall energy consumption of the building through systematic optimization. In the design process, we should closely combine the characteristics of the construction project, rely on the surrounding natural conditions, and establish a more reasonable and perfect architectural design scheme through the close cooperation between different branches and specialties.


Compared with the traditional architectural design method, ultra-low energy consumption building design has the following characteristics:


First, take the building energy consumption index as the ultimate goal, and coordinate and optimize between different specialties.


Second, in the initial design process of the building, it is necessary to strictly control the thermal parameters of the building shape and enclosure structure, calculate and optimize the energy demand of the building, take the energy consumption index as the design goal, and adopt passive and active optimization methods to realize the optimization of the building design. In the design process, it is also necessary to analyze and calculate the renewable energy around the building in detail to see if it can be applied to the architectural design process.


Third, the design of ultra-low energy consumption buildings belongs to the overall optimization. After counting the energy consumption of various departments, systematic optimization is carried out to effectively reduce the overall energy consumption of buildings, so as to determine the architectural design scheme scientifically and reasonably.



Design Method of 2. Ultra-low Energy Consumption Building


The analysis of ultra-low energy consumption building design method, without the use of more rigid theoretical research, the use of which method needs to be strictly in accordance with the performance of ultra-low energy consumption building indicators to start the design, after the use of general, guiding way.


(I) Key Parameter Limit Method


The key parameter quota method is a commonly used method in the design of ultra-low energy consumption buildings. The purpose is to reduce the energy consumption of buildings, and then scientifically and rationally plan the spatial layout, resource utilization, and various constructions of buildings. On the basis of comprehensive principles, strictly control the heat transfer coefficients of external walls, roofs, windows and other building elements, so as to fully meet the living conditions of residents.


The key parameter quota method scientifically and reasonably uses the natural conditions and climate characteristics of the building location, adopts fresh air heat recovery technology, and designs the building as a whole. The biggest advantage of this method is that it does not need to carry out too much simulation calculation. The building materials used are all renewable resources. The use of energy-saving standard control index technology can provide residents with more comfortable and healthier living conditions and increase the service life of the building.



(II) two-way cross-balancing method


The two-way cross-balancing method is used in the building design process, which not only needs to fully consider the optimization degree of the maintenance structure of the building and the design of the efficient heat recovery device, but also fully consider the use of renewable energy. In this way, in the design, we can change the direction of the building and the proportion of windows and walls, and combine the maintenance structure, system equipment, renewable energy and efficient energy of the building. The use of renewable energy can balance the energy consumed by the building to better meet the design requirements of the building.


The main technical features are as follows: First, the use of passive design, the natural ventilation of the building, the lighting state of the implementation of regulation, set the building maintenance structure of the thermal parameters, reduce the building's demand for fossil fuels. Second, through active optimization, the use of energy-saving equipment, such as frequency conversion fans, energy-saving lamps and other effective improvement of system performance. In addition, in terms of energy demand for buildings, this part of the energy supply should come from renewable energy such as natural light and wind energy as much as possible, so as to reduce the use of non-renewable energy.



(III) economic environment decision-making method


This method belongs to a more commonly used ultra-low energy consumption building design method, this method in the specific use of which the effect is more ideal. The use of this method in the design of ultra-low energy buildings can effectively reduce building energy consumption and meet other needs of people for buildings.


Because this method will not only consider the building energy consumption indicators, but also consider the building comfort, economic indicators, in other words, that is, taking into account the energy consumption, economy, comfort on the basis of the three indicators, the architectural design. Compared with the above two design methods, the method of economic environment decision-making belongs to an ultra-low energy consumption building design method that can obtain the best design effect in the end.


Analysis of Carbon Emissions and Influencing Factors of Ultra-low Energy Consumption Buildings in 3.


The main factors of building carbon emissions are the type of building insulation materials, the thickness of building insulation materials, the frame structure of building windows, the area ratio of building windows and walls, the heating form of the building, and the service life of the building.


Types of (I) building insulation materials


Building insulation materials are mainly used in the external construction of buildings, which will not affect the use of lighting appliances inside the building, but will have a certain impact on the thermal performance of the building system, thus affecting the effect of building heating in winter and cooling in summer. For the choice of building insulation materials, mainly including PUR, EPS, XPS and rock wool and other materials. According to scientific experimental studies, under the condition of equal thickness of building materials, rock wool insulation materials have the smallest building carbon emissions. Because of this, without considering the thickness of building insulation materials, in order to reduce building carbon emissions, rock wool should be selected as building insulation materials.



(II) the thickness of building insulation materials


When the unified material is selected as the building material, the carbon emission of the building decreases with the gradual increase of the thickness of the building insulation material. However, when the thickness of building materials reaches a certain level, the carbon emissions of buildings are stable. At the same time, when the thickness of building materials is high, even if the thickness of building insulation materials is increased, the reduction effect of building carbon emissions is not significant. Not only that, the building insulation material is too thick will affect the appearance of the building and increase the cost of construction. Because of this, for the cost, architectural beauty and other considerations, if the building material is EPS insulation material, the thickness of the building insulation layer is more appropriate between 160mm and 260mm.


Frame structure for (III) building windows


The building can choose different window structures, such as wood frame windows, aluminum frame windows, PVC windows and various window glass types. Under the same glass material, the building carbon emissions of different window frame structures are measured. Among them, the aluminum frame has the most building carbon emissions, and the wooden frame has the least building carbon emissions. Considering the architectural appearance, the durability of the window frame and the thermal insulation function of the window, the architectural window should choose the aluminum frame. At the same time, considering the impact of the number of layers and performance of glass on the carbon emissions of buildings, regardless of the type of glass, the carbon emissions generated in the glass manufacturing process are much higher than the carbon emissions generated by the use of glass in buildings. Based on this, in order to achieve the goal of near zero energy consumption building carbon emissions, the number of layers of building window glass and the number of layers of windows should not be too much.




(IV) building window and wall area ratio


The carbon emissions caused by building windows are mainly divided into two parts: on the one hand, the thermal insulation performance of windows is poor, and the carbon emissions caused by building cooling in summer and heating in winter are increased. On the other hand, the light transmission function of the window can accept solar radiation, which increases the carbon emission of summer cooling. In addition, the carbon emission caused by the building window is also related to the orientation of the window. The south-facing window receives stronger light radiation, and the carbon emission caused by air conditioning and cooling in summer is more. Experiments show that under the same conditions, with the increase of the proportion of windows and walls, building carbon emissions first reduced and then increased. Based on this, the proportion of building windows and walls should be controlled within a reasonable range, and the heat insulation performance of windows should be paid attention to in the design of building envelope, and the appropriate proportion of wall and window area should be selected.


Heating forms of (V) buildings


Air conditioning and cooling and winter heating of buildings are one of the major components of building carbon emissions. For example, building winter heating methods are mainly divided into solar heating, ground source thermal energy, solar ground source thermal energy and other heating forms. Among them, the energy consumption in the construction of solar heating system is the largest, and the carbon emission of the building is the most in the operation of ground source heat. In addition, based on cost considerations, solar heating technology and heating costs are higher, building heating equipment should choose a combination of solar energy and ground source thermal energy.


Service life of (VI) building


The normal service life of buildings in China is generally 40 years, 50 years and 70 years. The research shows that with the increase of the service life of the building, the carbon emission in the operation of the building increases gradually. However, the energy consumption of carbon emissions in the transport phase of building peripheral materials is gradually reduced. On the whole, with the increase of the service life of the building, the annual carbon emissions of the building are gradually reduced.



Measures and Suggestions for 3. Carbon Emission of Ultra-low Energy Consumption Buildings


(I) energy-saving design according to the building environment


The carbon emission energy-saving design of near-zero energy-consuming buildings should fully consider the external conditions of the environment where the building is located. First, fully test the climate of the building environment, including the average temperature of the building environment, the average duration of building sunshine, the ratio of internal and external temperature difference, wind direction and frequency, average annual rainfall, average annual summer cooling and winter heating days and other data information. Architectural designers can use relevant software to analyze climate data, so as to realize the planning of adjusting the layout, greening environment and orientation in architectural design, maximize the use of external environmental conditions, reduce building energy loss, minimize building carbon emissions, and realize the concept of green and low-carbon environmental protection.


(II) energy-saving design based on building wall mechanism


According to the climate data collected from the building field survey, the surrounding structure of the building should also fully consider the influence of climate conditions, and carry out the relevant design work of energy saving and emission reduction. For example, if the area where the building is located is hot all the year round, the peripheral structures such as building walls should mainly use heat insulation materials, carry out external shading design, and air flow ventilation design for windows and internal buildings to avoid carbon emissions caused by indoor temperature cooling.


If the area where the building is located is relatively cold all the year round, the building walls and windows should be made of materials with good heat insulation performance and low thermal conductivity to improve the sealing of the interior of the building and ensure the illumination time and intensity of the interior of the building. According to the above analysis, the building wall structure should be designed differently according to different climatic conditions, so as to realize the low energy consumption effect of energy saving and emission reduction, and further reduce the carbon emission of the building.



Upgrading and Innovation of Energy-saving Equipment in (III) Building System


The main sources of building carbon emissions are indoor air conditioning and cooling and the use of winter heating equipment. Among them, traditional energy heating methods such as natural gas and coal consume more energy and have a huge impact on the environment. Based on this, the carbon emissions of near-zero energy consumption buildings should be combined with the characteristics of the building to optimize and upgrade the energy-consuming equipment and drive innovation. For example, if the area where the building is located is hot all the year round, the combination of fans and air conditioners can be used inside the building to improve the speed of indoor air flow, expand the cooling effect and cooling range of air conditioning, and reduce the energy consumption of air conditioning. as a supplementary role to make up for the shortcomings of objective conditions.



4. the use of renewable energy in building system equipment


Renewable energy can reduce the loss of other non-renewable energy, reduce building carbon emissions, and reduce the pressure of the ecological environment cycle. For example, if the area where the building is located is relatively cold all the year round, the building can use solar energy and ground source heat pump integrated heating, especially in higher latitude areas, the average daily heating time is longer, and 1/2 of the year is in the heating state., Building heating pressure is greater. Based on this, the building can be placed on the roof of the solar equipment, the use of light conditions for building power supply, to maximize the conversion of solar energy. Not only that, under the future development plan of carbon cycle and carbon peak, scientific and technological innovation drive will pay more attention to the conversion and use efficiency of new clean energy such as solar energy, reduce the cost of building development and use, and achieve near zero energy consumption of buildings.



Specific application cases of 5. ultra-low energy consumption building design


In a construction project in Zhejiang Province, the construction area is 6228 square meters. The completion of this construction project marks that China's architectural design technology is close to the level of zero energy consumption. This construction project adopts a two-way cross-balance method, focusing on energy saving and comfort, analyzing energy consumption, environment and economy, and comprehensively analyzing the surrounding environment, maintenance structure and economy of the building.


Nowadays, with the continuous improvement of people's living standards and the continuous enhancement of aesthetic consciousness, the use of two-way cross-balance method can make the building and the surrounding environment to achieve integration. In order to better carry out the architectural design and achieve the goal of reducing the energy consumption of the building, set the thermal parameters of the maintenance structure, add appropriate green design to the roof, do the work of protecting the thermal bridge and heating and heat insulation in place, and strengthen the thermal insulation performance of the building. In the design of building energy system, the width and height of the building, the pillars supporting the building use two-way cross-balance method, the use of natural light, natural cold source, reduce lighting energy consumption, while ensuring good ventilation and lighting performance of the building.



This building is built in the subtropical monsoon climate zone. It is hot and dry in summer and warm in winter. High temperature water should be selected for refrigeration and air conditioning, and cooling radiation method should be used on the ground. The heating and air conditioning system uses a floor-standing condensing module. High and low temperature gas boiler, according to the climate conditions change, at any time to adjust the indoor temperature.


In the planning of ultra-low energy consumption building design, it will also apply the knowledge of economy, aesthetics, nature and other aspects, requiring coordination between multiple disciplines, scientific and reasonable planning, and under the premise of fully meeting the needs of multiple parties, let the city The overall planning becomes more perfect.


Source | Urban Construction, No. 6, 2022; Frontier of Engineering Management, No. 16, 2022

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