Field study on thermal comfort and adaptive strategies in residential buildings in China

This paper fully describes a nation-wide field study on building thermal environment and thermal comfort of occupant, which was carried out in summer 2005 and in winter 2006 respectively in China, illustrating the adaptive strategies adopted by occupants in domestic buildings in China. According to the climate division in China, the buildings in Beijing (BJ), Shanghai (SH), Wuhan (WH) and Chongqing (CQ), Guangzhou (GZ), Kunming (KM), were selected as targets which are corresponding to cold zone, hot summer and cold winter zone (SWC-SH, WH, CQ), hot summer and warm winter zone and temperate zone, respectively. The methodology used in the field study is the combination of subjective questionnaire regarding thermal sensation and adaptive approaches and physical environmental monitoring including indoor air temperature and relative humidity. A total of 1671 subjects participate in this investigation with more than 80% response rate in all surveyed cities. Both physiological and non-physiological factors (behavioural and psychological adaptations) have been analysed.

Competitive Solar Heating Systems for Residential Buildings (REBUS)

Research on solar combisystems for the Nordic and Baltic countries have been carriedout. The aim was to develop competitive solar combisystems which are attractive tobuyers and to educate experts in the solar heating field.The participants of the projects were the universities: Technical University of Denmark,Dalarna University, University of Oslo, Riga Technical University and Lund Institute ofTechnology, as well as the companies: Metro Therm A/S (Denmark), Velux A/S(Denmark), Solentek AB (Sweden), SolarNor (Norway) and SIA Grandeg (Latvia).The project included education, research, development and demonstration. Theactivities started in 2003 and were finished by the end of 2006. A number of Ph.D.studies in Denmark, Sweden and Latvia, and a post-doc. study in Norway were carriedout. Close cooperation between the researchers and the industry partners ensured thatthe results of the projects can be utilized. The industry partners will soon be able tobring the developed systems into the market.In Denmark and Norway the research and development focused on solarheating/natural gas systems, and in Sweden and Latvia the focus was on solarheating/pellet systems. Additionally, Lund Institute of Technology and University ofOslo studied solar collectors of various types being integrated into the building.

Energy efficient and economic renovation of residential buildings with low-temperature heating and air heat recovery

With the building sector accounting for around 40% of the total energy consumption in the EU, energy efficiency in buildings is and continues to be an important issue. Great progress has been made in reducing the energy consumption in new buildings, but the large stock of existing buildings with poor energy performance is probably an even more crucial area of focus. This thesis deals with energy efficiency measures that can be suitable for renovation of existing houses, particularly low-temperature heating systems and ventilation systems with heat recovery. The energy performance, environmental impact and costs are evaluated for a range of system combinations, for small and large houses with various heating demands and for different climates in Europe. The results were derived through simulation with energy calculation tools. Low-temperature heating and air heat recovery were both found to be promising with regard to increasing energy efficiency in European houses. These solutions proved particularly effective in Northern Europe as low-temperature heating and air heat recovery have a greater impact in cold climates and on houses with high heating demands. The performance of heat pumps, both with outdoor air and exhaust air, was seen to improve with low-temperature heating. The choice between an exhaust air heat pump and a ventilation system with heat recovery is likely to depend on case specific conditions, but both choices are more cost-effective and have a lower environmental impact than systems without heat recovery. The advantage of the heat pump is that it can be used all year round, given that it produces DHW. Economic and environmental aspects of energy efficiency measures do not always harmonize. On the one hand, lower costs can sometimes mean larger environmental impact; on the other hand there can be divergence between different environmental aspects. This makes it difficult to define financial subsidies to promote energy efficiency measures.

Using national input-output data for embodied energy analysis of individual residential buildings

Embodied energy (EE) analysis has become an important area of energy research, in attempting to trace the direct and indirect energy requirements of products and services throughout their supply chain. Typically, input-output (I-O) models have been used to calculate EE because they are considered to be comprehensive in their analysis. However, a major deficiency of using I-O models is that they have inherent errors and therefore cannot be reliably applied to individual cases. Thus, there is a need for the ability to disaggregate an I-O model into its most important 'energy paths', for the purpose of integrating case-specific data. This paper presents a new hybrid method for conducting EE analyses for individual buildings, which retains the completeness of the I-O model. This new method is demonstrated by application to an Australian residential building. Only 52% of the energy paths derived from the I-O model were substituted using case-specific data. This indicates that previous system boundaries for EE studies of individual residential buildings are less than optimal. It is envisaged that the proposed method will provide construction professionals with more accurate and reliable data for conducting life cycle energy analysis of buildings. Furthermore, by analysing the unmodified energy paths, further data collection can be prioritized effectively.

Net Energy Analysis of Double Glazing for Residential Buildings in Temperate Climates

Energy used in buildings is a major contributor to Australia’s energy consumption and associated environmental impacts. The advent of complex glazing systems such as double glazing, particularly in northern America and Europe, has partially closed a weak thermal link in the building envelope. In milder climates, however, building envelope features may not be as effective in life cycle energy terms, i.e. including the embodied energy of their manufacture. A net energy analysis compares the savings in operational energy to the additional requirements for embodied energy, in terms of the energy payback period and energy return on investment. The effectiveness of double glazing is determined for an Australian residential building. A wide range of building operation regimes was simulated. These results support the principle of installing double glazing in residential buildings in Melbourne, Australia, at least in terms of net primary energy savings.

An analysis of factors influencing waste minimisation and use of recycled materials for the construction of residential buildings

Residential building construction activities, whether it is new build, repair or maintenance, consumes a large amount of natural resources. This has a negative impact on the environment in the form depleting natural resources, increasing waste production and pollution. Previous research has identified the benefits of preventing or reducing material waste, mainly in terms of the limited available space for waste disposal, and escalating costs associated with landfills, waste management and disposal and their impact on a  building company's profitability. There has however been little development internationally of innovative waste management strategies aimed at reducing the resource requirement of the construction process. The authors contend that embodied energy is a useful indicator of resource value. Using data provided by a regional high-volume residential builder in the State of Victoria, Australia, this paper identifies the various types of waste that are generated from the construction of a typical standard house. It was found that in this particular case, wasted amounts of materials were less than those found previously by others for cases in capital cities (5-10 per cent), suggesting that waste minimisation strategies are successfully being implemented. Cost and embodied energy savings from using materials with recycled content are potentially more beneficial in terms of embodied energy and resource depletion than waste minimisation strategies.

Estimating demolition costs for single residential buildings

With the increasing stock of aging structures, building
demolition is becoming achallenging research field from
the perspective of management. As the converse of
construction, management of demolition puts forward some
new management themes or adds some new contents
even though the same issues are faced in construction
management. This research aims to develop a quantitative
approach to estimate the costs of a demolition project. A
cost analysis method is presented to systematically break
down the cost components involved in the demolition of
a structure. Due to the lack of robust research in theory
and systematic summary in practice to date, the economic
performances of demolition will be studied through acase
study, and the majority of parameters are derived from
actual experiences in practice. The proposed demolition cost
estimation method is applied to the actual form of building
elimination (Scenario 1), and further comparison is carried
out with two other elimination methods, which are the newly
developed deconstruction (Scenario 2) and mechanical
demolition (Scenario 3). Deconstruction is found to be the
most profitable in this particular instance, and is closely
followed by the actual form.

Case study of demolition costs of residential buildings

Building demolition is one of the most common activities in the construction industry. Several demolition techniques are commonly used, including mechanical demolition, deconstruction and hybrid demolition. Although deconstruction has been advocated for its environmentally friendly approaches, the cost comparison of a demolition project under different techniques is rarely researched. In this paper, the cost of a demolition project is broken down to input and output costs, which are further broken down to more countable sections. Through an empirical study in Victoria, Australia, project costs of mechanical demolition, hybrid demolition and deconstruction are investigated. It is found that deconstruction has the greatest profitability among the three techniques. Hybrid demolition, which is the actual technique adopted by the contractor, has a slightly lower profit, and mechanical demolition is the most expensive. Although deconstruction has the best overall economical performance, the small extra gain comes with increased complexity and risk that deters demolition contractors from its attempt. It is found in the paper that an optimized demolition project strategy exists between hybrid demolition and deconstruction with the greatest profitability among various building demolition techniques.

A new paradigm for sustainable residential buildings

This paper explores a new paradigm in housing, where dwellings will be pre-fabricated, modular, energy efficient, transportable and use renewable and/or recyclable resources. The paper reviews previous attempts to produce housing, which meets some of the criteria for this new paradigm. Their advantages and disadvantages are discussed. An approach towards a new type of modular prefabricated unit is proposed. A preliminary energy analysis, comparing a present relocatable classroom construction with one upgraded, is provided as an example towards low energy building operation. Finally, conclusions are drawn about the requirements of future housing if we are to progress towards sustainability.

Height and construction costs of residential buildings in Hong Kong and Shanghai

A widely recognised theme of construction economics suggests that the cost of construction per square metre increases as building height rises. However, after many years, research conducted regarding the height and cost issue have established a classic relationship between those two, well known as a U-shaped curve. This paper describes the study of height-cost relationship of high-rise residential buildings in Shanghai and Hong Kong. Initial findings indicated that the curved relationships of height-cost of residential buildings in Shanghai and Hong Kong exhibit different profiles. The differences suggest that, Hong Kong contractors have more expertise in multi-storey and high-rise construction than contractors in Shanghai. The dissimilarities also imply that different sets of criteria should be applied in the judgement of height affects cost in different locations. Many factors could be contributors, such as the history and experience in constructing residential high-rise buildings, location, linkage and relationships to the neighbourhood provinces, design and construction regulations, and government policy on residential construction.

Enhancement of natural ventilation in high-rise residential buildings using stack system

This paper describes the feasibility study on the application of passive and active stack systems to enhance natural ventilation in public housing in Singapore. About 86% of the population is staying in high-rise public housing, known as Housing and Development Board (HDB) flats, which is designed for natural ventilation. The primary objective of this work is to assess the status of natural ventilation in a typical four-room HDB flat using scaled model in the wind tunnel, and to develop an effective passive or active stack system to enhance natural ventilation in the flat. Four numbers of stacks with different sizes were tested at two locations in the flat. The study shows that the passive stack, incorporating the principle of airflow due to buoyancy, does not enhance air velocity in the flat. However, the active stack which operates based on the suction effect induced by a fan fixed at the top of the stack leads to substantial increase in the air velocity at the room and thus meeting the human’s thermal comfort condition. It was noted that the velocities increase along with the increase in the stack size.

Optimising the life cycle energy performance of residential buildings

A holistic approach to low-energy building design is essential to ensure that any efficiency improvement strategies provide a net energy benefit over the life of the building. Previous work by the authors has established a model for informing low-energy building design based on a comparison of the life cycle energy demand associated with a broad range of building assemblies. This model ranks assemblies based on their combined initial and recurrent embodied energy and operational energy demand. The current study applies this model to an actual residential building in order to demonstrate the application of the model for optimising a building’s life cycle energy performance. The aim of this study was to demonstrate how the availability of comparable energy performance information at the building design stage can be used to better optimise a building’s energy performance. The life cycle energy demand of the case study building, located in the temperate climate of Melbourne, Australia, was quantified using a comprehensive embodied energy assessment technique and TRNSYS thermal energy simulation software. The building was then modelled with variations to its external assemblies in an attempt to optimise its life cycle energy performance. The alternative assemblies chosen were those shown through the author’s previous modelling to result in the lowest life cycle energy demand for each building element. The best performing assemblies for each of the main external building elements were then combined into a best-case scenario to quantify the potential life cycle energy savings possible compared to the original building. The study showed that significant life cycle energy savings are possible through the modelling of individual building elements for the case study building. While these findings relate to a very specific case, this study demonstrates the application of a model for optimising building life cycle energy performance that may be applied more broadly during early-stage building design to optimise life cycle energy performance.

Seasonal coolth storage system for residential buildings in Australia

Night sky cooling is explored as an alternative to the conventional cooling technologies using fossil fuels. The night sky cooling method is based on the long wave radiation of unglazed collectors to the sky at night. An evaluation of the night sky cooling system is present for a residential building in three cities of Australia, namely Alice Springs, Darwin and Melbourne. The system comprises an unglazed flat plate solar collector integrated with borehole storage. It uses night sky radiation to reduce the temperature of the ground near to the boreholes. The system was simulated with TRNSYS, a transient simulation program. The simulation results for adequately sized systems show that night sky radiation is able to reduce the coolth storage borehole temperature and the proposed system is able to meet the cooling load of the residential building simulated in three locations. Borehole lengths of 270, 318 and 106 m are required for coolth storage with 90, 260 and 14 m2 collector area for heat rejection in Alice Springs, Darwin and Melbourne, respectively. At the 20th simulation year, the proposed system is able to achieve a system cooling coefficient of performance of 2.2 in Alice Springs, and 2.8 in Darwin and Melbourne.