This essay has been submitted by a student. This is not an example of the work written by our professional essay writers.
I would like to express my gratitude to my supervisors, Roger Waterhouse for suggesting this study and giving me guidance throughout the project. Personally, this is for my family, my daughter Rufaro and my wife Patricia for her support, patience and for making this experience possible. My appreciation is also extended to those that took time to respond and or provide me with information to assist me with this study.
The house construction industry in Australia has a poor history of investing in research and for developing innovative construction materials. Buildings cannot be designed without consideration of their energy consumption and impact on the environment (John et al., 2005).
High-profile and commercial buildings are built using modern construction techniques whilst the housing sector does not seem to benefit from these methods available. When considering the house building industry, the need to adopt a sustainable approach is exacerbated by its fragility and sensitivity to change.
Australia has the highest number of owner occupation in the world at 70% with only 3% of Australian houses designed by an architect (Fairleight, 2006). "Many of the new project homes being rolled out across metropolitan areas in Australia are reproduction designs of past styles and often poorly designed to suit environmental conditions and often are placed together in ways that create dull uninspiring environments." (Chris Johnson, NSW Government Architect, 2004). According to Flannery 2005, Australia has the highest per capita greenhouse emissions of any industrialised country - 25 % higher than the US. on 1 January 2003 mandatory energy efficiency provisions were adopted into the Building Code of Australia - amendment 12.
1.2 Sector of research
Housing, as a sector, has two main characteristics with regard to its environmental impact, the technology used to provide building materials and the energy levels consumed by households to meet their human desires or livelihood. As Western Australia's population grows the need for housing is growing and this is has seen a significant rise in terms of State energy demand and CO2 emissions. Environmental impact can be lowered through the reduction of either of these two aspects. In this research as mentioned in the title, we shall focus on concrete being a technology used to building an energy saving house.
1.3 The Research Problem
With the new building codes in Australia demanding more sustainable houses with emphasise on energy efficiency. Traditionally most homes in Australia where built using timber or timber and brick veneer which resulted in greater demand for cooling during summer and heating during winter. There is an apparent gap between the energy rating required by these codes and that of the light weight material houses that exist. The codes demand: Building fabric improvements; Lighting systems (and greater use of natural light); Heating and cooling systems and control improvements (Green Building Council Australia, 2006)
1.3.1 The Solution
The researcher hypothesises that by exploiting the thermal mass of concrete better energy saving homes can be built in Western Australia and surpasses the energy rating requirements.
If the thermal mass of concrete is exploited in residential construction, then this will provide a more energy efficient and cost effective building than traditionally timber and brick houses.
Statement of objectives
- Draw a comparison of energy performance of both real and theoretical concrete house with the timber and brick house.
- Investigate the thermal capacity of concrete compared to other construction materials.
- Research on whether Active Fabric Energy Storage (FES) homes use less energy compared to standard air conditioned homes.
- Identify methods of building an energy efficient house using concrete.
- make recommendations to local builders and house owners on sustainable concrete solutions
- Learn about additional resources and programs available to help reduce energy and usage.
Desk Research (sometimes known as secondary data or secondary research) involved gathering data that already exists either from publications, the internet, journals, in professional newspapers and magazines. It is strongly recommended to carry out a desk research to gain background information on and provides leads that help maximise the research (Wikipedia, 2010). An initial research was undertaken to understand house construction practices in and around Perth. Literature review was conducted from the initial to the final stages of this research. In order to gain understanding and an in-depth knowledge of the research, the following literatures were reviewed:
The need for a paradigm shift
With the new BCA regulations attaining sustainable house construction requires a lot; it requires a paradigm shift in the way houses are designed, material chosen and quality constraints. This paradigm shift forces house construction to be viewed in a much broader picture terms of time (the house life cycle assessments), space (the house as a system setting) and costs (greener cost metrics than pure monetary), than in traditional house construction.
History of sustainable construction
The study of sustainability in construction was pioneered by the Institution of Structural Engineers (UK). Research has found that the share of greenhouse gas emissions from the building sector represents some 25 percent of the total Australian energy related emissions and is increasing at a rate faster than the total energy related emissions (AGO, 1999). Following extensive consultation with the building and construction industry, the Australian Government agreed on a dual approach of mandatory energy performance requirements complemented by voluntary best practice initiatives. Minimum energy performance standards for all new and refurbished buildings were introduced into the Building Code of Australia from 2003, and the Australian Greenhouse Office is providing funding support for industry designed and delivered best practice initiatives. The development of Green Home Guidelines by Sustainable Solutions consultants was commissioned in 1992 by ACF. The guidelines emphasised:
- using of materials having low environmental impact
- minimise the use of energy and the utilising low energy greenhouse impacting sources
- Reducing loads on infrastructure such as water supply, energy supply, storm water, and sewerage.
- Features facilitating environmentally sound lifestyles
- A high standard of comfort, security, aesthetics, and a healthy environment
(ACF Green Home Guidelines, 1993)
Thereafter calls for tender to design and build a Green Home were made by the Australian Government. The tender was awarded to David Oppenheim architects and Hotondo builders. The project was clouded by lack of experience in entrepreneurial promotion and lack of clear project parameters. The project was further compromised by the change of government with the new government giving it less priority. Without the necessary support from the Department of Planning and Housing the project lost momentum (Henry Okraglik 2003). Tenders were also called to develop materials for the Good Residential Design Guide project, later to be branded "Your Home", with the explicit goal of creating a single guide to reducing the environmental impact of Australia's housing stock. Although there have been a fair number of sustainable developments no one is collecting data on them and there are few economic incentives for property developers to build sustainable homes as the cost of using new technology is far greater than traditional methods. Sunrise Homes Tasmania has written 'The Australian Guide to Affordable Sustainable Housing Manual'. The Sustainable Guide answers and deals with all of the obstacles to Partnership Advancing the Housing Environment (PATHE) reaching its objectives in energy efficiency. PATHE was developed to demonstrate and promote the technologies, design principles and practices that can improve significantly the quality of Australia's built environment (Sunrise Homes).  Affordable Housing National Research Consortium completed some studies on finding solutions to affordable housing problems in Australia which recommended that government should subsidise sustainable housing by private developers (Berry, 2001).
Australian legislation on sustainable construction
Different States have different laws and codes of construction in Australia meaning there is no umbrella rule governing house building in the country. A Sustainable Cities report was tabled by the House of Representatives Committee on Environment and Heritage. Till now, the Committee still awaits government response. The aim of the report was to examine issues and policies related to the development of sustainable cities. The establishment of an Australian Sustainability Charter that sets key national targets across areas including water, transport, energy, building design and planning was recommended by the Committee.
In New South Wales a land tax rebate program was introduced by the state government for affordable housing providers whilst this is not the case in other states.
In the State of Victoria, a mandatory 5 star home energy rating standard was implemented from July 2005. This legislation means every new home constructed from 1st of July 2005 has to obtain an energy rating of 5 stars for the building envelope plus a rain water tank or a hot water system must be installed. The standard is expected to be included in the national building code.
In Australian Capital Territory (ACT) all new houses must have a minimum ACT House Energy Rating of 4 stars and the ratings of new and existing houses must be displayed prior to any sale.
Planning concessions have been incorporated into planning schemes as an incentive for developers to produce affordable housing. Though density bonuses are commonly used concession, local authorities have relaxed other regulations such as design standards, approvals processes and assessment fees. The use of these mechanisms erodes community and environmental standards. Performance-based planning principles introduced into planning schemes have created opportunities for design-related relaxations to be accepted. The government should be noted that taxes influence prices and therefore behaviour, and can be used to discourage activities that damage the social or natural environment. However the government has introduced the Photovoltaic Rebate Program where subsidies for residential and community installations of PV cells and solar hot water systems are rewarded. HIA argues that there is a need for an operational definition of sustainability that contains concepts that can be practically applied by decision-makers at the grass-roots level. The approach to defining sustainability for implementation must distinguish between sustainable urban growth, traditionally the role of the planning system and sustainable building performance, typically addressed through technical building and plumbing regulation." HIA suggests a nationally coordinated approach for regulation of sustainable construction. In terms of regulation, it is the view of HIA that the Building Code of Australia (BCA) is the most appropriate tool for the regulation of sustainable construction measures to ensure its prominence as Australia's mandatory code for design and construction.
Life Cycle Assessment
LCA is defined by the International Organization for Standardization as the "compilation and evaluation of the inputs, outputs and the potential environmental impacts of a product system throughout its life cycle." Though some sectors argue that cement production releases CO2 and its embodied energy being too high, concrete has greater benefits that outweigh energy consumed and the front-end labour.
Why do we need LCA?
- For any improvement to occur one needs to measure it first
- BCA is demanding houses with environmental credentials (energy efficient).
- House owners are increasingly in need houses that demonstrate environmental performance and cheaper to run
How is LCA works?
The below figure shows the stages of LCA with reference to our concrete house LCA methodology, which is tailored to the meet the requirements of BCA.
Goal and scope
At this stage the question to be answered by our study is set. In this research our question is whether concrete house are better performing in terms of energy efficiency compared to timber and brick veneer houses
Here the life cycle is outlined and information on building materials, thermal capacity and energy consumption of the house is gathered over the whole lifetime. The data is then presented in an inventory table.
In this stage the energy consumed over the study period is assessed. This allows the total energy consumed to be calculated and the house given an energy rating inline with the BCA regulations. Up to this point, LCA is firmly objective as it will show us what the energy rating is and the thermal capacity. Impact assessment will then be used to produce a single numerical score by weighting each category and summing them up into a single score.
Value engineering (VE) is an organised approach to identify and eliminate unnecessary cost. Unnecessary cost in this case is the high energy bills associated with the cooling and heating of most homes in Perth. VE is a systematic method that may be used to improve the energy efficiency of Australian houses by examining function. Value is a ratio between function and cost. Value can be increased by improving the efficiency or reducing the energy consumption. It is important in value engineering that basic functions are kept and not reduced due to value improvements (Wikipedia, 2010). Residential accommodation will benefit from value engineering solutions in order to achieve the BCA regulations' objective of energy efficient houses, improve the quality of houses and decrease the demand for resources.
Concept of Value Engineering
A purchase engineer by the name Lawrence Miles came up with the concept of value engineering while working for general Electric Company. He was assigned with the task of purchasing material but was unable to do so at times due to shortages. He had to come up with alternative materials and it is during this process that he noticed that some of the substitutes performed better than the original material, hence the birth of value engineering (Construction information services, 2008). In our case if timber and brick houses cannot achieve the energy efficiency levels desired alternatives need to be found and we seek to test and prove the use of concrete as a way of achieving high energy efficiency levels of Australian houses.
In this research VE is used to increase the energy efficiency of Perth houses by considering the thermal mass of concrete and the benefit of building concrete homes and balancing this against the costs incurred in delivering it. The task then becomes to increase the value or decrease the cost.
UNDERSTANDING CLIMATE FOR ENERGY EFFICIENCY
Weather and climate is perhaps the most complex of all end use related measurements. The drivers for space heating and cooling energy consumption are a combination of weather, building shell thermal performance (including materials, insulation, glazing, orientation and shading), occupancy and zoning within a house (the latter 2 being user related effects). Measurement of heating and cooling energy consumption is of little strategic value unless there is also an assessment of the impact of the other 4 key elements - weather, building shell, occupancy and zoning. An example of an appliance that is also partly affected by weather and climate is household refrigerators and freezers. Ambient temperature has a substantial impact on the underlying energy consumption for these products, so at a minimum the indoor temperatures need to be measured as part of a monitoring program. Lighting is also partly affected by weather and seasons, and some other end uses may also show seasonal effects (eg dryers and hot water). Knowledge of climate is a requirement for energy efficiency in house construction. It enables designers to optimize natural energies to create comfortable homes. Since climatic data is often very technical, its implication in building design is often limited. There are climate classifications to provide a general outlook of climatic condition of a place. However, a building designer needs more precise information regarding climate, so a rigorous climate analysis is necessary. In order to exploit the climate to comply with the thermal needs of a building, it is critical to analyse the climate type within which the site is located and to collate relevant data that will inform an appropriate strategic design. The different climate regions of the world are commonly categorized in terms of their thermal and seasonal characteristics (e.g. hot-dry, warm-humid, composite, moderate and cold).Climate data for the purpose of this paper is obtained for Perth Airport. Climate data over a period of 63 years have been used for analysis. Perth experiences a Mediterranean climate, characterized by hot, dry summers and mild, wet winters. Requirements of heating or cooling are best described by heating/ cooling degree hours. Heating/ cooling degree hours are the sum of every hour, multiplied by the number of degrees the outside temperature is above or below the comfort temperature. Upper comfort temperature is set according to the neutral temperature (Szokolay, 1982) for each month to respond to the changing characteristics of the climate. Lower comfort temperature has been taken 18°C for the year round. Summer and early autumn months require cooling; from mid autumn to spring, heating demand is very high in Perth. In total, 85% of the time has heating demand and 15% of time has cooling requirements
The Mahoney tables (Koenigsberger, et al., 1973) provide results of thermal comfort analysis using primarily temperature and humidity data, and make recommendations for pre-design guidelines. These pre-design conditions are classified under certain climatic groups or indicators. The Mahoney tables involve six indicators (i.e., three 'humidity indicators', H1- H3, and three 'arid indicators', A1 - A3). The Mahoney tables indicate remedial action involving air movements for humid conditions in H1 and H2. Excess downpours may affect the building structure, so adequate rain protection is advised in H3. Similarly, for hot and arid conditions, thermal capacity (A1) is one of the options for making the indoor space comfortable. When the temperature ranges more than 10 degrees Celsius with relative humidity up to 70%, thermal mass is recommended. Climatic zones with night time temperature above the comfort limit and relative humidity less than 50%, which are advised to make provisions for outdoor sleeping (A2). A building with the temperature below comfortable range needs protection from cold wind (A3).
Energy consumption of Australian houses
More Australians have air-conditioning and are using their air-conditioning equipment more often as the climate consists of mild winters with an average temperature of 18 degrees C during the day and 9 degrees Celsius at night. Then the summers are hot and dry with temperatures rising to and above 40 degrees Celsius. This results to increased usage of air-conditioning and has resulted in an increase in the amount of electricity used to operate the air-conditioning equipment. An investment in energy efficiency will reward through lower energy bills.
Most Australian houses perform poorly when assessed against energy or environmental criteria. The Australian Building Codes Board and the AGO are incorporating minimum mandatory energy efficiency measures into the Building Code of Australia (BCA) which will eventually apply to all new buildings throughout Australia. These measures will eliminate worst practice and encourage voluntary best-practise initiatives. A Building Thermal Performance Assessment also known as a House Energy Rating evaluates the thermal efficiency of a new house design. It measures the home's ability to stay cool in summer and warm in winter. The BCA is applicable in all states except NSW and BCA Part 2.6 is the overall regulation mandating Building Thermal Performance Assessments of residential buildings..
MEASURING energy efficiency
How energy efficient is my home? There are two way of checking this in Australia.
- Computer simulation using energy efficiency software, or
- Having a minimum total R-value in the envelope
The first is a good way to determine energy efficiency because it accounts for the many factors that improve energy efficiency (eg thermal mass, insulation, orientation & design features such as appropriately located windows). The second method, however, is limited in its effectiveness because it relies only on R-value (or thermal resistance, the measurement for insulation). The University of Newcastle and computer simulations by Energetics Energy Consultants have found that the R-value in similar houses produces very different energy consumption results. The frequently used methods of complying with the energy efficiency requirements of the BCA are using the Deemed to satisfy and thermal calculation methods. These can be calculated using AccuRate and FirstRate softwares respectively.
DTS allows for the house to be assessed relatively quickly and easily. The only problem is that its not applicable to all designs and not flexible for improving designs.
Thermal Calculation(star rating)
This is a rigorous and responsive way of analysing a building. If a building does not exceed the annual energy allowance then it is considered to be compliant. The energy usage of the house is then given a rating with this mwthod may not necessarily satisfy the requirements of DTS. However thermal calculation is a better method for those intending to optimise their house's energy rating.  There are numerous items to considerwhen predicting energy consumption and one may use avariety of energy sources such as electricity, gas, oil and solid fuels,but for most of Western Australia the largest energysources are gas and electricity. This may be measured through estimation or real-time measurement. For our research we shall look at Real-time Measurement.
Energy flows within a building
The basic principle of energy flow within buildings is shown below. It is important to understand how these various flows interact within a building to form the indoor climate that we experience. It is the effective management of these flows that helps reduce energy consumption - a critical aspect of the Australian building regulations in respect of energy performance.
From the above figure it can be noted that heat is gained by solar radiation, heating, and the occupants and their equipment. Heat is also lost via air leaks, ventilation, radiation through windows and conduction (transmission) through walls, windows and floors. Heat is stored and released by the thermal mass of the building. The ability of building materials to store and release energy by using its thermal mass has an effect on the energy performance of a building. This is brought about either by natural ventilation, which needs no mechanical assistance, or by active methods, such as forcing air or water through coils or ducts in concrete slabs.
Sustainable development comprises of the three broad themes of social, environmental, and economic accountability, often known as the 'triple bottom line'.
Social sustainability involves considering others and the community. This entails designing for different users' i.e. small families, the aged or users with differing abilities. There should be an allowance for change in lifestyle and needs plus safety and security.
Environmental sustainability is considered and efficient resource use i.e. water, waste management and energy use. House designs need to eliminate the need for high energy consumption through lighting, cooling and heating. Passive solar designs and building materials should be incorporated in designs.
Economic sustainability entails designing a cost effective house. Use of materials with a long life and low maintenance is crucial. Other expenses must provide long term savings. It is important to choose the correct design and material to avoid additional costs later.
Sustainable Construction is an application of sustainable development in construction ,encircling matters such as tendering, site planning and organisation, material selection, recycling, and waste minimisation. Stern has been defined Sustainable construction as "an approach to construction that makes optimal use of resources (material, energy, space and money). This includes the resources used in constructing, its operation and maintenance, and its eventual disposal" (Stern and Knapp, 1993) 'Sustainable construction is development that meets the needs of the present without compromising the ability of future generations to meet their own needs' (Brundtland, G, 1987). It is crucial to reduce energy consumption in homes because of the significant role this can play in combating unsustainable levels of energy use. According to the Australian Government and the Design and Construction industries (2008), space heating and cooling and water heating accounts for 63 per cent of household energy use. Concrete homes are durable and have cost-saving features.
Benefits of sustainable concrete construction
The main benefit of using concrete is its high thermal mass which leads to thermal stability, saving energy and producing a better indoor environment for the home dwellers. The use of concrete optimises the benefits of solar gain there by reducing the need for heating fuel. combined with air-conditioning, it reduces the energy used for cooling by up to 50% hence reducing the energy costs of the home. An intelligent combination of heating, ventilation, solar shading, building structure and night cooling, can further improve the utilisation of concrete's thermal mass, producing houses that are better adapted to increasing temperatures and helping them to remain comfortable without the need for air conditioning. Residential homes themselves account for about 21% of national stationary energy use9 and 18% of water use (Department of the Premier and Cabinet 2006; Australian Greenhouse Office 1999). Concrete is extremely versatile in terms of its structural and material properties hence it will be successful in producing an energy efficient house. Concrete offers an effective solution to the requirements of BCA introduced 1 January 2003. The thermal mass properties of concrete, when considered in the design of buildings, can lead to more sustainable, energy efficient and more environmentally friendly structures that can save money. Fabric energy storage systems, which use ducted air within the concrete slab, provide extra cooling. Compared with air conditioning, these systems reduce carbon dioxide emissions. With Insulating Concrete Forms (ICF), concrete homes look just like a wood-frame house, solid, lasting construction that resists the ravages of bush fires, wind and Time.
Challenges to the Adoption of Sustainable Building Practices
There is a widespread perception that sustainable houses are higher in cost than the marketplace is willing to pay for (Zerkin, 2006). McKee (1998) suggests that houses are not the best place to test new green technologies and designs, as developers and investors are not willing to carry the risk. The barriers to developers choosing high performance green houses centre on the perception of higher first-dollar costs, and that the market is not willing to pay them. Most Lending institutions do not understand the high performance aspects and value of new construction methods in the marketplace such that new approaches are perceived to be risky. Designers, architects and contractors usually don't influence design decisions, sustainability criteria needs to be integrated into procurement, contracts, tenders and commissioning.
The Design Process
There is limited understanding of options by design professionals such as knowledge of available high performance materials and the difficulties in gaining approval of new technologies for building codes. The designer must specify sustainable building techniques and materials for them to be adopted. The Construction Process Lack of skilled labour with knowledge to install and maintain new technology is also a barrier.
Materials and Technology
Within Australia, high performance buildings, with their technological approach to greening the built environment has resulted in increased complexity in projects without appropriate management systems in place to deal with the various issues that arise. These buildings are expensive because they rely heavily on new technologies, frequently developed specifically for individual projects, seemingly designed to outperform the previous one hence they haven't been passed on the housing sector (C. S. Hayles and T Kooloos).
Availability of appropriate information/specifications, especially when choosing appropriate 'green' materials is an issue. Whilst there are websites available regarding 'green' specifications and products, these are not yet sufficient. There is also considered to be a lack of evidence of the benefits of green building in a local context (due to the relative immaturity of the industry when compared to Europe). In addition, evidence of the whole of life benefits of sustainable building in Australia is not yet available, with no local studies completed. Clients' knowledge is often very limited, making sustainable building less attractive if they do not understand what they are paying for (including higher capital costs).
Information on new technologies and the ability of organisations to investigate them during the design process is assisted by schemes like the Commercial Office Building Energy Innovation Initiative - COBEII (Sustainability Victoria, 2006). Methods such as LCA and embodied energy calculations are not used to assess the suitability of materials in Australia. Based upon the responses of those interviewed, materials selection in sustainable building is subject to commercial viability as per conventional construction.
Research study undertaken at RMIT University, Melbourne in 2006, which aimed to identify challenges facing the adoption of sustainable building in the Australian commercial sector, identified similar issues to those descried above.
WWF identified six key barriers to development of sustainable homes in Australia:
- Current planning and building regulations that do not promote sustainable homes;
- lack of fiscal incentives
- perceived lack of investor support
- perceived extra cost
- lack of consensus around the definition of a sustainable home
- Perceived lack of consumer demand.
Some investors if given the opportunity and the right drivers to build sustainable houses would take it upon themselves to develop and invest in sustainable housing. For this to occur, solid business cases should be developed such that financial benefits of sustainable buildings are fully understood by the potential buyers and investors.
According to British Standard BS EN ISO 7730 Thermal comfort is a condition of mind that expresses satisfaction with the thermal environment. It involves many physical parameters, not just one. It's possible to design a house with high thermal comfort without relying on air-conditioning. The most important aspect of thermal comfort is the operative temperature. This is the average of dry bulb air temperature and mean radiant temperature of a room. (Think Brick Australia).
This is when a material is able to absorb, store and emit solar heat. Materials with out thermal mass loose heat instantaneously. To change the temperature of high density materials like concrete, a lot of is required thus it is considered to have high thermal mass. On the other hand light weight materials have low thermal mass. Appropriate use of this property will make a difference in energy consumption.
Thermal mass of concrete
By utilising concrete's thermal mass, energy consumption can be reduced as the thermal inertia provided has the effect of smoothing out temperature peaks or troughs and delaying the onset of peaks in internal temperatures, so maintaining a more stable, comfortable indoor environment.
As a heavyweight material, concrete acts as a buffer during the heating season by utilising heat gains, from solar radiation and heat from residents, storing this energy and then releasing it later in the day. Conversely, the ability of concrete to be cooled at night and then release this coolness into the building's interior during the day is another important way in which concrete can contribute to thermal comfort during the summer. Thermal mass has long been known to have a positive influence on energy use and thermal comfort in buildings, but this aspect has not been incorporated into building energy codes until relatively recently. concrete floors and walls have the ability of to absorb internal heat gains during the day, helping stabilise the internal temperature.
As a heavyweight material, concrete acts as a store (or buffer) during the heating season by utilising free heat gains, such as solar radiation and heat from occupants, storing this energy and then releasing it later in the day. Conversely, the ability of concrete to be cooled at night and then release this coolness into the building's interior during the day is another important way in which concrete can contribute to thermal comfort during the summer. Dense, heavyweight concrete provides the highest level of thermal mass. Lightweight insulating concrete provides a lower, but nevertheless worthwhile level. Thermal mass has long been known to have a positive influence on energy use and thermal comfort in buildings, but this aspect has not been incorporated into building energy codes until relatively recently
R- Value (insulation
The R value is a measure of thermal resistance of a building. it is the ratio of the temperature difference across an insulator and the heat flux through it under uniform conditions. The bigger the r value, the better the building insulation's effectiveness. R-value is the reciprocal of U-value.
Calculating the U value of a wall
Calculate the upper resistance limit (Rupper) by combining in parallel the total resistances of all possible heat-flow paths (i.e. sections) through the building element. Calculate the lower resistance limit (Rlower) by combining in parallel the resistances of the heat flow paths of each layer separately and then summing the resistances of all layers of the building element. Calculate the total thermal resistance (RT) from
R t= R upper + R lower
Calculate, where appropriate, corrections for air gaps (?Ug) and mechanical fasteners (?Uf). Calculate the U-value from
U = (1 / RT) + ?Ug + ?Uf
The standard permits ?Ug and ?Uf to be omitted if, taken together, they amount to less than 3% of the U-value.
The R-value of a building
The R-value of a building element is the TOTAL THERMAL RESISTANCE (RT) including surface thermal resistances of the air on either side of the building element. The total thermal resistance of a planar building element consisting of layers perpendicular to the heat flow is calculated using the expression:
RT = Rsi + R1 + R2 + . . . . . + Rn + Rse
Where: RT is the total resistance
Rsi is the internal surface resistance;
R1, R2, ....Rn are the thermal resistances of each layer, including bridged layers;
Rse is the external surface resistance. (Terry Williamson,2007)
Books on research case studies, journal articles and relevant reports on sustainable construction were sourced to determine the research framework, methodology and questionnaire design.
The data collection process was to try and obtain information on what the industry terms as an "energy efficient house". The research data obtained aimed to discuss the role of concrete in design and construction methods addressing energy efficiency. The data collected was then used to prove the hypotheses that concrete houses in Perth, Australia save enrgy.
To conduct the research I had to identify organisations that have knowledge and experience of energy efficiency in residential homes. Initially I decided to obtain details of organisations involved with the construction of homes which I obtained from the Housing Industry Association (HIA) register of businesses. However a large quantity of organisations on the register do not base choice of building material on any criteria but price. I then decided that information obtained from such organisations was too limited to gain insight into the effectiveness of concrete in energy saving. For me to stay on track with my program of research of collecting data I decided that organisations listed with the Green Building Council of Australia would be in a better position to offer insight as these organisations research more on sustainable construction.
An initial email detailing the research was sent to all the organisations that matched the predetermined criteria. This email articulated the aims of the research. Only a small number of organisations agreed to participate in the research after the initial email, so I did follow-up telephone calls.
I conducted telephone interviews as I was limited by my location to conduct face to face interviews as intended (I'm currently working on a remote construction project where the nearest town is 300km away and I'm in the city once every 5 weeks).
The sample population for this research was selected in a manner that tried to give a fair representation of residential builders, research analysts and government authorities involved in the provision of sustainable construction or development. The networking with staff from Murdoch University's School of Sustainability (Perth, Australia) where the writer normally sits University of Reading exams facilitated the identification of people and organisations having the knowledge of the topic under investigation.
Interviewing was a technique used to understand the reasons and motivations for the differing designs, construction methods and standards used. Interviews were conducted on a personal one-to-one basis. Seven out of twelve people contacted were available for interviewing. The interviews were semi-structured or structured depending on who was being interviewed and the situation of the interview. Interviewing was a means of identifying general patterns, relationships between variables (choice of construction materials and their capabilities) and a statistical measure of the status of concrete house construction methods used to achieve sustainability.
I conducted the interviews appropriately such that my approach to questioning aimed at reducing the scope for bias towards the hypothesis and increase the reliability of the information obtained. Questions were clearly phrased so that the interviewee understood them and were asked in a neutral tone of voice. A full record of the interviews was compiled as soon as it had occurred to ensure the exact nature of explanations provided was not lost as there was a possibility of mixing up data from different interviews (Ghauri et al, 1995, Healey, 1991; Healey and Rawlinson, 1994; Robson, 1993)
It was necessary to carefully word questions with the intention of getting the respondent to express him or herself in depth. Some of the questions required short answers and tried not to annoy the interviewee by having to give simple answers, so caution had to be exercised. Though the interview was focused on asking certain questions, I had a list of topics and questions to cover, these varying from interview to interview. This meant I omitted some questions in some interviews and the order of questions would vary depending on the way the conversation was flowing. These interviews were used as a method of gathering data which was used as a subject of quantitative analysis. The interview began by asking a general question related to sustainable house building which meant to encourage the respondent to talk freely. The subsequent direction of the interview was then determined by the respondent's initial reply (Robson, 1993). Formulating questions for an interview guide: In order to be able to collect quality data of concrete house construction in Australia I needed to snowball sample. Snowball sampling involved interviewing initial contacts in the industry and then asking these contact persons who they think is appropriate to interview- to gain more insight of the industry (Rubbin 1995). The data on who was interviewed is presented in a table in the appendix.
Advantages of interviewing:
The use of open questions allowed participants to provide an extensive and developmental answers which revealed attitudes and facts related to sustainable concrete house construction methods. (Grummitt 1980).
- Interviewing enabled me to obtain accurate/relevant information required for this research through in-depth questions.
- Through Interviewing i was able to investigate motives and feelings of the different construction stakeholders in regard to the use of concrete.
- I used recording equipment and was able to replay the interview at a later stage.
There are various types of bias which need to be considered when interviewing people. The first of these is related to interviewer bias. My comments, tone or non-verbal behaviour may have created bias in the way that interviewees responded to the questions I asked. I may have imposed my own beliefs and frame of reference through the questions which I ask. I may have demonstrated bias in the way I interpreted responses (Easterby-Smith et al., 1991).
- There was a need to set up the interview and this was not simple and time consuming, as well as setting the questions
- There were geographic limitations to whom and where interviews could be conducted.
- Interviews are expensive to expensive to conduct
- Respondent bias - there is a tendency to please or impress, creating a false image, or ending the interview quickly.
- Transcription and analysis can present problems of subjectivity.
I conducted three telephone interviews as an alternative where face-to-face interviews could not be conducted. The interviews were easy to administer and allowed data to be collected quickly at a relatively low cost .
Telephone interviews are relatively cheap and quick, allowing coverage of reasonably large numbers of people or organisations over a wide geographic coverage.
- The disadvantage of a telephone interview is that one may be mistaken for a salesman and cause irritation leading to minimum cooperation
- Straightforward questions are required and respondent has little time to think.
- some people dislike speaking on the phone, finding it difficult to develop a train of thought on the phone and others have developed a staccato telephone manner they are hard to hear or interpret what they say or to coax out much useful information. Most disconcerting is the respondent who, half way through an interview bursts into hysterical laughter, when something funny happens on his/her end during the interview.
In order to prove the hypothesis that concrete house are energy efficient some of the data need to achieve this was collected using a questionnaire. The questionnaire was distributed in such a manner it represented a sample of key housing construction stakeholders and will be subjected to tests of statistical significance. The quantitative and qualitative data is intended to provide an exploratory look at views of construction professionals interested in or who are practicing sustainable design or construction. The questionnaire was structured in such a manner that it startd with a straightforward question to get the ball rolling. It begin with general questions leading to specific as I tried to ensure variety in the questions asked. I used headings for related topics, grouping them in such a manner that the structure was clear to the respondent. The questions invbolved closed questions with pre-assigned response categories or 'yes' and 'no' boxes ensuring all eventualities were covered. Open questions were also used after a closed question in some cases with the intention that the respondents should reply in their own words (Information Management Associates, 2007). The use of closed questions was to enable fast processing of answers and increase the comparability of answers (Bryman, 2004). Before sending out the questionnaire, I pilot tested it on a few different people from my work place who would not be involved in the research but comparable to people to be used in the study. This was to enable the identification of any problems in the questionnaire such as confusing or misleading questions (Bryman, 2004).
The advantages of this method were:
- Cheaper to administer and E-mail was used as the preferred option; however on a number of occasions the direct e-mail address was not correct and the questionnaire had to be sent by mail, which was not very successful.
- After an initial telephone call to a company to identify the relevant person to send to and explain the aims and focus of the research the e-mail was replied within a week. Posted questionnaires responded within 5 working days.
- Without an interviewer present there is less chance of influencing responses and gives people more time to consider their answers.
- Questionnaires may be posted, faxed or sent by email, covering a large range of people and geographic coverage
- A questionnaire removes embarrassment on the part of the respondent and there is anonymity of the respondent.
However there are a number of disadvantages to a questionnaire and every effort was made to tackle these (Bryman, 2001):-
Where a person did not understand or misinterpreted a question there was no chance to explain what the question asked, as such, questions had to be clear and concise.
The questionnaire could not elaborate on open ended questions, such as "were there any unforeseen benefits of energy efficiency?" There is no guarantee that the questions will be answered in order and the questions can not be truly independent of each other. The questionnaire was designed to lead a respondent logically through the process asking about expectations and then experiences, then a number of open ended questions requiring more detail and consideration, if these are read earlier then it is obvious what the direction of the questionnaire is, and the earlier answers can be influenced by this.
One does not know who answers the questionnaire and to reduce the chance of this, questionnaires were sent to companies who had been contacted by telephone first.
A number of companies would not give a name to contact so questionnaires could not be sent to a named individual, only "the project manager",
- Difficult to ask a lot of questions. Initially fifty questions were designed but most managers don't have the time to complete lengthy questionnaires I designed one that would take less than 20 minutes to complete.
- Low response rate was the main problem with relying on third parties for passing the questionnaire.
- Questions have to be relatively simple.
- There is time delay waiting for responses to be returned.
- Need for a return deadline to be set and reminders may have to be sent out.
- One assumes there are no literacy problems and where necessary it's impossible to give assistance where it's required.
- It's not possible to control who completes the questionnaire and there may be a problem of incomplete questionnaires.
- Respondents will read questionnaire beforehand and then decide whether or not to complete it and if they feel it's too long, boring or complex, they may not respond.
- Closed questions are easier to complete. Because people are not expected to write extensively.
- Reduce the possibility of variability in recording answers.
The second stage of the questionnaire was to establish wether the respondent played a role in sustainable construction and if not why?
Tick box where then used for agree/disagree type questions which sought to establish the views on sustainable concrete. These questions were designed to investigate the validity of some of the widely held perceptions of sustainable concrete derived from the literature review. The response showed a positive result towards considering concrete in achieving sustainability. 64% of the respondents showed that 'green concrete' was applicable or important; with 33% having a consideration and only 7% (2 persons) saying it's not important.
Question: Is your organisation committed to any annual sustainability targets?
The common perception across both positive and negative responses was the need for a proven financial return before any investor would consider either developing or investing in sustainable buildings.
Question 5 intended on finding out the current trend and value drivers' in house construction in Perth. This question aimed at collecting/investigating data to be used in fulfilling objectives of the research of determining the methods of construction being employed and the reasons behind these choices.
Question What benefits can home builders and buyers expect from opting for 'green concrete' houses?
There is substantial literature on the benefits of constructing concrete houses compared to brick and timber veneer houses. The intention of this question was to establish whether developer's expectations would be realised on completion of the concrete house.
Overall the perception of sustainable buildings was positive and notably more enthusiastic if sustainable buildings provided not just marketing and differentiated position
When asked if concrete houses would achieve the expected benefits of energy efficiency the results were largely positive, with most respondents indicating that benefits were in line with expected results.
Question 10 was a group of questions in which the respondent had to choose his/her level of agreement with statements given regarding concrete house construction. The responded was only allowed one answer on each statement.
- Concrete provides valuable comparison of performance to other building material types
- The mass of concrete slows down the passage of heat through the wall compared to timber or timber brick veneer
- Concrete has less air leaks compared to timber or timber brick veneer walls
- Insulated concrete walls increase the R-Value of house
- Concrete walls satisfy the requirements of BCA Part 2.6
- Concrete house has high capital costs but has long term savings and added value
- Should concrete house be considered as a route to 5 star energy rating?
From the results we can see that the majority respondents either strongly agree or agree that concrete is comparable to other building materials in providing an energy efficient building.
Again most of the respondents agreed that the mass of concrete slows down the passage of heat, how ever 15% of the respondents were not sure or had no knowledge on the topic.
The majority of the respondents strongly agree showing that it is true concrete walls retain heat either on the inside or outside as they have less air leakages which leads to fluctuations in temperature.
The respondents either agreed or strongly agreed that insulated concrete walls had a higher R-value which means that a house built of concrete has a higher resistance to transferring energy or heat. Although some people may disagree saying that material with a high R-value cost more, one also saves more due to the high resistance.
No body disputes the fact that houses constructed of concrete will satisfy the BCA requirements.
The level of agreement in this question was low as most respondents only agreed not strongly agreeing showing that there is still some doubt or perception on the economic benefit of use of concrete in the long term. A house owner or developer considering concrete house will want to know if the construction technique is effective and would it offer value for money compared to the traditional method of brick and timber. The results obtained were mixed with 73% of respondents saying it did achieve energy efficiency higher than the required level. 4% gave a negative response, with other respondents not sure (20%) as it was still too early in the process or had declined to answer. Generally people agreed that this approach did offer value for money compared timber and brick veneer.
The question was used to test whether respondents would like to see the use of concrete technologies incorporated in the regulations or building codes such as Australian Standards or the Building Council of Australia. No one disagreed although some people were not so sure whether this should be included as it may end up forcing people to build with concrete only. The reason some may disagree with this is that they believe concrete has high embodied energy.
What do you think are the benefits of using concrete as a building envelop?
WALL CONSTRUCTION OVERALL R VALUE
A model simulation to prove that concrete house is more energy efficient was done using FirstRate software and AccuRate was used in the analysis of the different house types. This was a model of a four bedrooms and two baths house, which is unofficially the standard house being currently built in Australia.
The first model was a concrete house with concrete floors, internal and external walls. The second house was a timber house with concrete floors and the third house was one built from timber and brick veneer.
To ensure that the thermal mass was observed / examined with better accuracy, the same thermal insulation was used.
Results from Accurate
Using Accurate for this approach, the simulation started with a comparison of concrete wall, timber wall and timber brick veneer envelope of a four bed roomed house. (S/V=0.43) with south facing prevailing, located at Rome (center Italy), with continuous system operational modality (20°C heating and 26°C cooling temperature set point for 24 hours/day all over the year).
A house built from concrete showed that it required 8% (6.1 kWh/m2/year) less energy than the other houses built from different type of envelope.
Brick veneer timber house:
Ultra 20: heat flow out R2.6, heat flow in R2.6 + Super 15: heat flow out R2.2, heat flow in R2.2 + Standard 10: heat flow out R1.8, heat flow in R1.8
In both the previous cases, massive envelope results better in energy performances, in particular concerning the heating energy demand. In the second scenario we used different building typologies i.e house size and number of rooms. The aim here was to compare the different envelop performance by varying the S/V ratio of the houses. The results below are given in relation to annual energy demand per square meter. From the above results it was noted that houses with a heavy envelope especially concrete perform better in cases of heating. It was also observed that when the s/v ratio was lowered the heating energy demand was reduced. On the other hand a variation in the S/V ratio was of little significance to the cooling energy demand. This observation also showed that a double storey house has lower specific cooling demand than a single storey with the same orientation and floor and window ratio. The BCA regulations require a house to have a minimum R value of 1.3 for its walls; only aerated concrete walls meet these criteria without any need for insulation. Brick veneer and weatherboard walls have R values of 0.51 and 0.53 and require an addition of insulation to meet these requirements of the regulations.
Insulated concrete forms
Triple the Thermal Value
Because of the triple insulative nature of these forms, ICFs are extremely energy efficient. The R-value of the insulation, coupled with the thermal mass of the concrete, and the elimination of air leakage, makes for an R-40 energy rating or higher. Exterior walls on wood framed homes typically have an R-value of 20 or so. Some companies even guarantee the energy savings in writing and receive the Department of Energy's Energy Star rating to wear on their product. "The advantages are obvious," says Trudeau of building with concrete. "The insulation factor is incredible, so the return on the investment is immediate for the homeowner." Power companies like Nevada Power are even taking a closer look at the ratio of the thermal envelope area (Se) to the conditioned volume (Vc)
The results contain detailed histograms of the various impacts, such as resource energy or greenhouse gas emissions. Two bars are graphed, the average NSW impact and the example set up by the user.
Following the theme of complete transparency, LISA shows the resource energy and emissions associated with the manufacture of each of the materials used. The research results reveal that heating and cooling energy consumption dominates the energy use in the whole life cycle of an Australian house regardless of the construction envelope.
- While the ratio of operational energy:embodied energy ranged from 2.2 to 5.3, the study does suggest that embodied energy will become more significant as design energy ratings increase and the operational energy is proportionately reduced
- Although the brick veneer house consumed more energy initially than weatherboard construction, it performed better in terms of the more significant operational energy.
- The study does not show any clear differences in total life cycle energy consumption between building on a concrete slab or on a timber floor, for either weatherboard or brick veneer construction
- Compared with mud brick and weatherboard designs, embodied energy is relatively high for the more popular brick veneer on slab form of construction.
- Although the mud brick house performs well in terms of embodied energy (construction of house and building maintenance), it does not perform well in relative terms when considering total life cycle energy consumption.
Orientation and good design allows the sun's heat into the home in winter but not in the long hot summer months. Most heat loss is through the ceiling but it can also escape through walls and floor as well.
25%-35% heat transfer in ceiling/roof can occur.
15%-25% heat transfer in walls can occur
0%-15% heat transfer through the floor can occur.
- Double brick walls heat slowly and stay warm for a long time.
- Brick veneer walls respond quicker to temperature changes
- Lightweight walls heat quickly but also cool quickly
- Concrete floors store heat in winter and if managed well do not heat up so much in summer.
- Timber floors lose heat quicker than concrete floors and if the floor is on stumps, then insulation underneath is recommended.
Concrete houses make a statement that the owner is committed to the use of sustainable building materials and is serious about energy savings. concrete and stone have a similar storage capacity, but as concrete also has a high-embodied energy
The Australian government constitutes as a major player in the housing industry through its Keystart programme for first home buyers who constitute a significant figure on the property market. They should enforce laws requiring an integration of sustainable development in house building. According to UNEP financing for sustainable housing is from individuals with high net worth rather than banks and traditional investors. Sustainable construction at the moment is still driven by the early adopters, with the drivers being related to the search for an alternative lifestyle. The research results show that operational energy consumption dominates the pattern of energy use across the whole life cycle of a typical contemporary house design, regardless of construction type.
- While the ratio of operational energy:embodied energy ranged from 2.2 to 5.3, the study does suggest that embodied energy will become more significant as design energy ratings increase and the operational energy is proportionately reduced
- Although the brick veneer house consumed more energy initially than weatherboard construction, it performed better in terms of the more significant operational energy.
- The st