An analysis of daylighting performance for office buildings in Hong Kong

Daylighting has often been recognized as a useful source of energy savings and visual comforts in buildings. Occupants expect good daylight in their working spaces. The quality and quantity of natural light entering a building depend on both internal and external factors. In Hong Kong, commercial building accounts for the major building energy use and electric lighting is one of the major electricity-consuming items. This paper studies the daylighting performance and energy implications for office buildings. A total of 35 commercial buildings have been selected in the survey. Key building parameters affecting daylighting designs are presented. Two typical office blocks were further analysed based on a lighting simulation program. The daylighting performance was evaluated in terms of daylight factor, room depth and glare index. It has been found that the daylighting performance for office buildings is quite effective. About one-third of the office areas that are near the perimeter regions have an average daylight factor of 5%. For inner region of deep plan offices, some innovative daylighting systems such as light redirecting panels and light pipe could be used to improve the daylighting performance. In general, the office building envelop designs are conducive to effective daylighting and proper daylight linked lighting controls could save over 25% of the total electric lighting use.     

Energy consumption and the potential of energy savings in Hellenic office buildings used as bank branches—A case study

Energy performance of non-residential buildings and in particular of office buildings used as bank branches is very limited. This paper presents new data from 39 representative bank branches and results from a more in-depth analysis of information from energy audits in 11 typical bank branches throughout Greece. The data was used to derive practical energy benchmarks and assess various energy conservation measures. Accordingly, the average annual total energy consumption is 345 kWh/m². The breakdown of the different end-uses reveals that HVAC averages 48% of the final energy consumption, lighting averages 35% and other office and electronic equipment average 17%. The most effective energy conservation measures reach annual energy savings of 56 kWh/m² by regulating the indoor set point temperature, while the use of HF electronic ballasts and CFL lamps may save about 22 kWh/m² and 29 kWh/m² with and without the use of the external marquee sign, respectively.     

Benchmarking the energy efficiency of government buildings with data envelopment analysis

Constructing an indicator to measure the effectiveness of energy management is important for energy agencies and authorities. This paper uses multiple linear regression method and data envelopment analysis to examine the effectiveness of energy management. First, the regression method using environmental factors is used to calculate the predicted energy usage intensity of each evaluated building. Data envelopment analysis is then employed to calculate overall energy efficiency, using the predicted energy usage intensity as output and the observed energy usage intensity as input. Data envelopment analysis can be further applied to measure the overall energy efficiency in details by examining environmental factors and management factors. Finally, the energy consumption of buildings can be measured to evaluate the effectiveness of energy management. Buildings examined as a case study in this paper are government office buildings in Taiwan. The results show that most of the buildings evaluated to report a higher predicted energy usage intensity have successfully used efficient energy management methods in energy saving.     

Principal component analysis of electricity use in office buildings

Principal component analysis was conducted on five major climatic variables—dry-bulb temperature, wet-bulb temperature, global solar radiation, clearness index and wind speed. Twenty-eight year (1996–2000) long-term measured weather data were considered. A two-component solution was obtained, which could explain 80% of the variance in the original weather data. Monthly electricity consumption data recorded during a 5-year period (1979–2006) were gathered from 20 fully air-conditioned office buildings with centralised HVAC systems in subtropical Hong Kong. Electricity use per unit gross floor area ranged from 163 to 389 kWh/m². These consumption data were correlated with the corresponding principal components using linear multiple regression techniques. The coefficient of determination (R²) varied from 0.76 to 0.95 indicating reasonably strong correlation. It was found that the regression models developed could give a reasonably good indication (mostly within 3%) of the annual electricity use, but the monthly estimates might differ from the actual consumption by up to 9%. Attempt was also made to develop a general regression model for the 20 buildings, which had an R² of 0.84 with a maximum mean-biased error of 18.6% and a maximum root-mean-square error of 21.4%.     

福建省建筑节能工作初步探讨

本文就福建省近两年来在建筑节能推行过程中遇到的各种问题进行探讨,提出设计人员在设计过程中应把握的主要原则,以及现阶段节能工作存在主要问题。本文着重根据福建省地域特点,针对设计、管理过程中经常遇到的难点、疑点进行一些系统的研究和分析并提出了技术措施。     

Energy saving with passive climate control methods in Spanish office buildings

This work comprises case studies of passive indoor climate control techniques, applied to a number of office buildings in Spain. The main objective of the work was to evaluate the effects of using indoor permeable coverings on energy savings, for the same indoor thermal comfort conditions. Previous studies have shown that permeable coverings will lead to optimal indoor comfort conditions, which depend on maximum and minimum monthly mean outdoor temperature and relative humidity values. This work shows that, both in summer and winter, indoor energy consumption decreases with the permeability of coverings. An energy saving potential of 3 kWh/m² per year may be achieved, which leads to the possibility of replacing mechanical HVAC by passive methods in mild climates, such as in Spain and Portugal.     

A systematic methodology for optimising the energy performance of buildings in Bahrain

Today, a great deal of effort is ongoing all over the world to find methods for optimising the energy performance of buildings. Such efforts can be seen in the European Energy Performance of Building Directive (EPBD). This directive aims to ensure energy saving and CO₂ emission reduction without compromising the local conditions and people's comfort. In the Gulf States, however, there is a need for such methods due to their economic and environmental benefits. This study introduces a simple but reliable methodology for optimising building energy performance in Bahrain. The methodology is based on building management systems (monitoring, analysing and targeting future performance), simulation tools and other technologies. This methodology was implemented using Visual DOE and was directly related to collectively gathered data gained form experimental works and practical applications. By means of the introduced methodology, energy consumption was obtained together with energy cost and CO₂ emissions. The applicability of this methodology was demonstrated through optimising a case office building in Bahrain.     

Benchmarking Hong Kong and China energy codes for residential buildings

Mandatory energy codes to curb energy use of residential buildings have been formally launched in China for more than two decades but little has been publicized in literature. Similar codes are not available for residential buildings in Hong Kong, but most residential buildings in Hong Kong, especially public housing estates, are HK-BEAM certified to demonstrate their compliance with regulatory and basic design requirements. Given HK-BEAM is internationally recognized and there are doubts about the effectiveness of the China codes, how the energy efficiency of the HK-BEAM certified buildings compare with buildings in compliance with the China codes is of interest to most building designers and policy makers. This paper describes how the energy efficiency of a case study building in compliance with the China codes compare with the one in compliance with HK-BEAM. The energy simulation by HTB2 and BECRES reveal that the case study building in compliance with the China codes is 51.1% better in energy use. In the study, the relative impact of each compliance criterion on energy use and cooling load has been quantified by sensitivity analysis. The sensitivity values indicate that energy use is most sensitive to air-conditioning operation hours, indoor design temperature, coefficient of performance (COP) of the room air-conditioners (RAC) units, and the envelop characteristics. The results of this study indicate that a HK-BEAM certified building cannot satisfy the China codes requirements. This provides good reference to the policy makers, the building owners, and to the China and Hong Kong Governments when considering reciprocal recognition of building energy codes.     

Basic actions to improve energy efficiency in commercial buildings in operation

Numerous studies have focused on improving energy efficiency in commercial buildings. Engineers and researchers have developed complex methods to improve energy efficiency, but buildings are often managed by non-specialised technicians who need understandable and cost-effective actions to implement in their buildings. This paper presents basic actions on which to base improvements in energy efficiency in commercial buildings in operation. Furthermore, obtained results and details of the implementation of these techniques in various buildings in the Universitat Politècnica de València are presented.     

A study of energy performance and efficiency improvement procedures of Government Offices in Hong Kong Special Administrative Region

A study of energy performance in 19 Government Offices in Hong Kong has been carried out. The characteristics of Government Offices, difficulties and results in assessing their building energy performance are discussed and reported. An average Energy Use Index based on unit floor area has been derived for the Government Offices using energy consumption data in the past three years. A number of factors that are likely affect the energy use in buildings, such as year of construction and total gross floor area are reviewed. Energy management opportunities are identified and proposed after carrying out energy audit to the Government Offices. Operational practices to improve energy performance are also recommended.     

Influence of building parameters and HVAC systems coupling on building energy performance

The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan.The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%.     

Energy simulations for glazed office buildings in Sweden

Highly glazed buildings are designed by architects to be airy, light and transparent with more access to daylight. Their energy efficiency, however, has become questioned. Therefore, energy simulations of single skin office buildings in Sweden were carried out, using a dynamic energy simulation tool. In order to study the impact of glass on the energy use during the occupation stage, office building alternatives with 30, 60 and 100% window to external wall area were studied. Other varied parameters were the building's orientation, the plan type (open and cell plan offices), the control set points and the façade elements (type and size of windows, type and position of shading devices, etc.). The main conclusion is that careful design is needed to ensure low energy use and good thermal comfort, especially for highly glazed office buildings. Careful design of glazed office buildings has to be based on detailed thermal simulations. Especially in fully glazed buildings (in which the façade is more “sensitive” to climatic conditions), proper combination of control set points, glazing and solar shading are crucial for the energy performance.     

浅论建筑节能

主要阐述了我国目前建筑节能的情况,并指出近期的工作目标,提出了建筑节能的有效技术措施,从而在保证和提高建筑舒适性的前提下,不断提高能源利用效率。     

办公建筑节能设计影响因素分析

针对《公共建筑节能设计标准》中对建筑热工设计的规定,结合工程实际,计算分析了办公建筑节能设计的影响因素,供设计参考。     

Cost assessment of concrete and steel types for office buildings: An exploratory study

This paper presents a set of regression models which incorporates concrete and steel types in modeling the costs of office buildings. To these ends, three typical office buildings with seven and 15 stories have been designed by the help of a commercial software taking into account the Turkish practice. In each project C-16, C-20, C-25, C-30 and C-35 concrete classes and S-220 and S-420 steel types were used for dimensioning purposes. Rough construction costs were then calculated for different combinations of concrete classes and steel types. The findings of the study revealed that column dimensions decrease following an increase in a particular concrete class. However, this decrease stops after C-30. Furthermore, an average cost difference of 16% was observed between the steel types S-220 and S-420.     

Towards a multi-objective optimization approach for improving energy efficiency in buildings

The energy sector worldwide faces evidently significant challenges that everyday become even more acute. Innovative technologies and energy efficiency measures are nowadays well known and widely spread, and the main issue is to identify those that will be proven to be the more effective and reliable in the long term. With such a variety of proposed measures, the decision maker has to compensate environmental, energy, financial and social factors in order to reach the best possible solution that will ensure the maximization of the energy efficiency of a building satisfying at the same time the building's final user/occupant/owner needs. This paper investigates the feasibility of the application of multi-objective optimization techniques to the problem of the improvement of the energy efficiency in buildings, so that the maximum possible number of alternative solutions and energy efficiency measures may be considered. It further shows that no optimal solution exists for this problem due to the competitiveness of the involved decision criteria. A simple example is used to identify the potential strengths and weaknesses of the proposed approach, and highlight potential problems that may arise.     

Comparison of thermal comfort algorithms in naturally ventilated office buildings

With the actual environmental issues of energy savings in buildings, there are more efforts to prevent any increase in energy use associated with installing air-conditioning systems. The actual standard of thermal comfort in buildings ISO 7730 is based on static model that is acceptable in air-conditioned buildings, but unreliable for the case of naturally ventilated buildings. The different field studies have shown that occupants of naturally ventilated buildings accept and prefer a significantly wider range of temperatures compared to occupants of air-conditioned buildings. The results of these field studies have contributed to develop the adaptive approach. Adaptive comfort algorithms have been integrated in EN15251 and ASHRAE standards to take into account the adaptive approach in naturally ventilated buildings. These adaptive algorithms seem to be more efficient for naturally ventilated buildings, but need to be assessed in field studies. This paper evaluates different algorithms from both static and adaptive approach in naturally ventilated buildings across a field survey that has been conducted in France in five naturally ventilated office buildings. The paper presents the methodology guidelines, and the thermal comfort algorithms considered. The results of application of different algorithms are provided with a comparative analysis to assess the applied algorithms.     

Cost effect of earthquake region and soil type for office buildings in Turkey

In this study, the change in the load-bearing system cost of a reinforced concrete office building has been investigated in relation to the earthquake regions and soil types. Three different office projects each with five stories were investigated. The structural design calculations have been made according to four different soil types and four different earthquake regions. According to each combination, concrete, steel and formwork adopted approximations were calculated to reach the rough cost of each office building. The changes in the cost of projects according to the soil type and earthquake region were examined with multiple regression analysis and analysis of variance. In general, the change in cost has been observed around 22% between first and fourth soil type and 14% between first and fourth earthquake region.     

A survey of building envelope designs for commercial buildings in Hong Kong

Nearly 1 million m² of gross floor area is represented by the survey which identified four different building envelope designs. To enable judgements to be made on construction cost and time, a comparative study was carried out based on a 40-storey generic office building.     

Towards a universal energy efficiency index for buildings

The growing worldwide demand for energy is basically satisfied through natural resources such as oil or natural gas generally acknowledged as being responsible for climate change through greenhouse gas emissions. The building sector accumulates approximately a third of the final energy consumption. Consequently, the improvement of the energy efficiency in buildings has become an essential instrument in the energy policies to ensure the energy supply in the mid to long term, and to meet the targets stated in the Kyoto Protocol. During the last decade and being sensitive to this fact, many national governments and international organizations have developed new regulations to achieve those targets. One of these regulations is the European Energy Performance of Buildings Directive but, to date this certification does not follow a standard procedure which is universally accepted.This paper aims to contribute to this standardization, proposing an energy efficiency index for buildings that relates the energy consumption within a building to reference consumption. The proposed energy index can be obtained in a simple manner by combination standard measurements of energy consumption, simulation and public databases. Furthermore, the index is upgradable whenever new data are available.