Do the numbers stack up? Lessons from a zero carbon housing estate

Many countries are searching for ways to reduce the energy and carbon impact of housing. The terms net zero-energy home and net zero-carbon home have entered the policy lexicon, without clear definitions and without widespread understanding of the likely policy impact. Is the concept limited to bespoke architect driven buildings for specific green clients, or does it have relevance in the mainstream house building sector and for typical households? When we consider volume house building and contemporary lifestyles, what is the energy end-use reality of so called zero-energy homes? Can government policy instruments deliver housing estates that are thermally comfortable, energy efficient and powered by renewable energy?The Lochiel Park Green Village in South Australia represents a genuine attempt through government policy processes to create a suburb of (nearly) zero-energy homes in a near zero-carbon estate. The development includes 103 highly energy efficient homes of various sizes, all utilising solar thermal and solar photovoltaic sources, and built to stringent environmental urban design guidelines. The energy used and generated at each house is being monitored and analysed to extend our understanding of what happens when families bring their energy habits to near zero-energy homes. Appliance and equipment audits are conducted to extend our knowledge of the energy services utilised in contemporary digital-age lifestyles.This paper provides an insight into the quanta of energy using appliances and equipment that fill our homes and satisfy our ever-growing needs. The paper presents key results from the first two years of monitoring for the initial tranche of houses, demonstrating that although significant reductions in operating energy use have been achieved, few households have reached a net zero energy standard. The research highlights the extent to which our choice of energy systems and our individual behaviour affect the total annual energy use. The energy end-use and energy generation results are examined to identify the contribution of near zero-energy homes to the twin policy challenges of anthropogenic climate change and peak power demand. Using empirical evidence from extensive monitoring, this paper throws new light on the energy use of actual families in contemporary near zero-energy homes.     

Germany's path towards nearly zero-energy buildings—Enabling the greenhouse gas mitigation potential in the building stock

On 19 May 2010, the European Union adopted a Directive stipulating that by the end of 2020, Member States must ensure that all newly constructed buildings consume ‘nearly zero’ energy. In Germany, drastic reductions of energy demand for space heating have already become a policy target over the last decade, both for new and existing dwellings. In this article, we evaluate the impact of past and future policies on the development of buildings with a very high energy performance (VHEP) and on their primary energy demand and emissions. These dwellings account for 4% of all dwellings which have been constructed since 2001 and 1% of the total building stock. We have defined different policy scenarios, all of which assume a gradual increase of requirements for new and existing buildings and a continuation of the support policies that stimulate both new constructions and ambitious refurbishments. In the most ambitious scenario, the proportion of VHEP dwellings will increase by up to 30% of the total stock in 2020 and the share of nearly zero and zero-energy dwellings will then make up 6%. This will lead to emission reductions of over 50% of the 1990 level and primary energy reductions of 25% compared with today.     

Anatomy of a sub-tropical Positive Energy Home (PEH)

Zero energy buildings (ZEB) and zero energy homes (ZEH) are a current hot topic globally for policy makers (what are the benefits and costs), designers (how do we design them), the construction industry (can we build them), marketing (will consumers buy them) and researchers (do they work and what are the implications). This paper presents initial findings from actual measured data from a 9 star (as built), off-ground detached family home constructed in south-east Queensland in 2008. The integrated systems approach to the design of the house is analysed in each of its three main goals: maximising the thermal performance of the building envelope, minimising energy demand whilst maintaining energy service levels, and implementing a multi-pronged low carbon approach to energy supply. The performance outcomes of each of these stages are evaluated against definitions of net zero carbon/net zero emissions (site and source) and net zero energy (onsite generation vs primary energy imports). The paper will conclude with a summary of the multiple benefits of combining very high efficiency building envelopes with diverse energy management strategies: a robustness, resilience, affordability and autonomy not generally seen in housing.     

Defining zero carbon and zero energy homes from a performance-based regulatory perspective

The development of a framework for defining net zero energy and net zero carbon homes has seen significant progress over the past decade. With anthropogenic climate change the principal driver, numerous governments are moving to regulate homes at or near a net zero energy or net zero carbon performance level. What has been missing in the literature is a discussion of how the basic principles of performance-based building regulation will shape the definition. The very nature of performance-based regulation as a legally contestable instrument shapes and limits the content of a regulatory definition. This paper examines the recent literature on zero energy and zero carbon building definition frameworks, explores the key characteristics of performance-based standards and determines practical definitions that could be adopted within performance-based building codes.     

Zero energy homes – Are they economically viable?

Whilst net zero energy homes are espoused in many policy circles, and many bespoke examples have been constructed to demonstrate their technical feasibility, there is a scarcity of evidence demonstrating such a standard would be economically rational, particularly for large scale housing development where orientation and aspect may not always be optimal. Drawing on energy monitoring evidence and construction economics associated with a nearly zero energy housing estate in Adelaide, Australia, this paper explores the economic feasibility of the net zero energy home policy in warm temperate climates. The results demonstrate that using economic tools and assumptions typically applied for building energy regulatory policy changes, net societal economic benefits significantly outweigh costs. The clear economic outcomes, combined with expected health and productivity benefits from improved levels of thermal comfort, should provide security to policy makers to progress home energy standards towards net zero energy performance.     

Towards zero energy homes down under

The concept of net zero energy and zero emission home has been a goal for those involved in the sustainable building industry. It is now becoming a reality in many parts of the world with an integrated approach of passive design, energy efficient appliances and local renewable generation. The paper describes the activities in Australia focussing on reducing energy use from the housing sector. It describes the regulatory approach of energy performance for housing which involves developing a house energy rating tool covering the building envelope as well as major energy consuming appliances. It also describes the implementation process which comprises gradually more stringent regulations coupled with financial inducements.The paper describes a world leading new Australian housing development where net zero energy homes are being built and enjoyed. It tells the story of how this outcome is being achieved starting with the planning process and developing environmental guidelines. The paper describes the innovations being used in order to achieve net zero energy homes and reports on energy monitoring results and feedback from householders.     

Assessment of current Dutch energy transition policy instruments for the existing housing stock

This research assesses to what extent current Dutch energy transition policy instruments for the existing housing stock can fulfil local executive actors’ needs and instigate adoption of energy efficiency measures by them. This is done by studying energy policy instruments for the existing housing stock in the Netherlands and in other European countries, and by an empirical research, which analyses barriers and needs of local executive actors. We found that, despite current Dutch energy transition policy instruments for the existing housing stock seem to fulfil local executive actors’ needs to a large extent, complementary policy instruments are needed to stimulate and pressure the incumbent renovation regime. A long-term oriented financial rewarding system is needed to build up a structural market for the deployment of renewables, to increase the number of specialist jobs in the building sector, and to stimulate the development of integrated, standardized, building components. Furthermore, a long-term oriented financial rewarding system for energy efficiency investments in housing renovation projects, and a low VAT rate applied to energy efficient renovation measures, are needed. Finally, enforcement possibilities and sanctions (fines) should become an integrative part of Dutch energy certification regulation to make the certificate become part of a value chain.     

Energy consumption and economic growth for selected OECD countries: Further evidence from the Granger causality test in the frequency domain

This paper aims to reexamine the causal relationship between energy consumption and economic growth for 20 OECD countries. To that end, we employ a Granger causality test in the frequency domain which allows us to distinguish short (temporary) and long-run (permanent) causality. The empirical results could be summarized as following. First, in terms of causality running from GDP to energy consumption, there is a temporary relationship for Australia, Austria, Canada, Italy, Japan, Mexico, the Netherlands, Portugal, the UK, the USA, and a permanent relationship for Austria, Belgium, Denmark, Germany, Italy, Japan, the Netherlands, Norway, and the USA. Second, in terms of causality running from energy consumption to GDP, there is a temporary relationship for Austria, Denmark, Italy, the Netherlands, Norway and Portugal, and a permanent relationship for Belgium, Finland, Greece, Italy, Japan, and Portugal. The main implication of our finding is that the energy policies should take into consideration not only the causality direction between economic growth and energy consumption but also whether it is temporal or permanent and furthermore authorities must design policy actions accordingly.     

Identification of cost-optimal and NZEB refurbishment levels for representative climates and building typologies across Europe

The energy consumptions of the building stock are playing a central role in the energy policy of the European Union. While the Member States are applying the Directives in force, the European Commission is working to update the regulatory framework. Specifically, it is necessary to achieve the great unrealized potential for energy savings in existing buildings. With this aim, the nearly zero-energy building (NZEB) target was introduced, and a comparative methodology framework to calculate cost-optimal levels of minimum energy performance requirements was proposed. This study focuses on the issue of building renovation, and it presents the results obtained with the application of a cost-optimal calculation method for identifying proper retrofit measures to reach cost-optimal levels and NZEB levels. The assessment takes into account an exhaustive set of passive and active renovation options and it was extended to various building types of 60s–70s (residential and non-residential) in a wide range of representative European climatic conditions. A very relevant energy-saving potential was found for all cost-optimal benchmarks, and in many cases, the obtained NZEB refurbishments have resulted interesting also from an economic point of view.     

Comparative assessment of different air-conditioning systems for nearly/net zero-energy buildings

This study deals with the performance of different air-conditioning strategies for achieving the target of nearly/net zero energy in a medium-scale building under various environmental conditions. In particular, vapour compression (VC), vapour absorption (VA), and integration of radiant cooling technology are analysed using renewable energy resources and solar photovoltaic (PV)-based electricity. Four different kinds of air-conditioning configurations are considered: VC-based, VA-based, VC-radiant air-conditioning technology with VC dedicated outdoor air system (DOAS) and VA radiant air-conditioning technology with VC-DOAS. Numerical model validations with the benchmark standards are done for VC- and VA-based systems. In particular, annual electric consumption, electricity generation, thermal load generation among all configurations, emissions and solar fractions are studied. The present study shows that target of nearly/net zero-energy building can be achieved in an efficient manner through radiant VC-based system with VC-DOAS for hot-dry and composite (ie, hot-dry with higher humidity) environment conditions. However, for warm-humid environment, complete net zero is not possible, but up to 74% of net zero target can be assured with VC-based radiant and DOAS. With respect to the conventional VC-based system, the payback period assessment for the most suitable nearly/net zero building cooling system varies in the range of 5-9 years, depending on the environmental conditions.     

The self-sufficient solar house in Freiburg—Results of 3 years of operation

Energy efficiency is the key to buildings with minimized environmental impact. The combination of this approach with active and passive solar energy utilization can lead to purchased energy demand close to zero. Nevertheless, energy autonomy under Central European climatic conditions requires seasonal energy storage, especially energy with a high exergy content. The Fraunhofer Institute for Solar Energy Systems built an energy autonomous house in Freiburg, Germany, in 1992. Highly efficient solar systems are combined with a hydrogen-based seasonal-storage system. Long-term storage of low-temperature heat was avoided by extensive passive solar energy utilization. After describing the project, this paper focuses on the experience of nearly 3 years of operation.     

The influence of the Energy Performance Certificate: The Dutch case

All European Union Member States require an Energy Performance Certificate (EPC) when buildings are constructed, sold and rented. At its introduction the EPC was considered a pioneering instrument, one that would help overcome an information deficit hindering consumer interest in energy efficient dwellings. Now that the EPC has been implemented for several years it is possible to examine its impact. This research draws on data from ex-ante and ex-post assessments of the EPC in a number of countries and presents the results of a survey of Dutch private dwelling purchasers. This survey was based on two sample populations, one received an EPC during property transaction and another did not. Differences were sought between the two samples in a number of areas relating to the adoption of energy efficiency measures. Results show that many projections about the impact of the EPC have fallen short. The EPC was found to have a weak influence, especially pre-purchase. The potential of the EPC in driving energy efficiency improvement in the existing stock is doubted especially if it continues to act independent from a mix of instruments designed to tackle multiple barriers. It is argued that the energy saving potential of existing dwellings, applauded in climate change policy, will remain unexploited if it continues to be assessed subjectively by householders.     

Local government influence on energy conservation ambitions in existing housing sites—Plucking the low-hanging fruit?

Greater energy efficiency can be achieved in existing dwellings thanks to longer lifecycles, slow replacement rates, and technical innovations. Many such dwellings are located in dense urban neighbourhoods, where urban renewal projects are undertaken. Local government can encourage the setting of ambitious goals as a stepping stone to realizing energy efficiency goals that achieve high levels of energy efficiency. The research question which this paper addresses is: to what degree do local governments influence ambitions to conserve energy in existing housing sites? To examine this issue, thirty-three sites in the Netherlands were studied using a quantitative analysis. The results show that collaboration between local authorities and local actors increases the level of ambition to conserve energy. However, local authorities intentionally selected sites with poor energy efficiency, so it would be easy to meet ambitious energy conservation targets. Collaboration between local authorities and local actors turns out to be the key factor in selecting those sites. Moreover, there is little sign of genuine ambition. This article contributes to the debate on energy conservation policies in local housing sites. The study provides starting points for systematic, empirical research into the realisation of energy conservation in existing housing, especially in large-scale refurbishment projects.     

Current challenges of Germany’s energy transition project and competing strategies of challengers and incumbents: The case of direct marketing of electricity from renewable energy sources

Electricity generated by renewable energies (RES-E) already accounts for 25% of Germany’s electricity supply. This has led to recent discussions for a better market integration of RES-E. The paper examines how competing actors and their ideas on market integration developed new services for direct marketing according to their respective origins and tried to shape the regulatory framework. The paper analyses this process and explains the current shape of the field of direct marketing. Medium-sized structured actors, who favoured RES-E integration via the conventional wholesale power markets, and who formed early close coalitions with RES-E power producers at the same time, have been most successful in terms of market shares. Moreover, they have been very successful for different reasons in building-up coalitions with governance units and influencing the field rules and routines. Based on those findings, the paper will conclude with some policy advices for the future adjustment of the current regulative frameworks. As long as there is no evidence of how RES-E can be integrated most effectively and efficiently, policies should maintain a competition between different direct marketing strategies to find out which strategies serve the best in terms of achieving a successful energy transition.     

A social marketing mix for renewable energy in Europe based on consumer stated preference surveys

Regardless their high potential, renewable energy resources are insufficiently exploited in Europe. This paper examines the potential of social marketing for renewable energy sources. It uses acceptability and willingness to pay results from existing surveys on renewable energy sources and generates a marketing mix for the state, organizations, businesses and consumers. These surveys typically claim to produce results that will be useful for policy making or marketing purposes. However, after they distinguish the parameters that affect acceptability or choice and willingness to pay, they do not go deeper to demonstrate the ways for the exploitation of the results. Therefore, this paper gauges the gap between the results from consumer stated preference studies and the insights generated for social marketing.     

House walls as passive solar collectors: An assessment

The gross solar energy falling on a typical house during the heating season is greater than the space heating requirement. Conventional solar collectors produce hot water, which is then used to meet the domestic hot water and space heating requirements of the house. Such collectors, however, are expensive, and it is only possible to use them to collect a small proportion of the available solar energy. This paper looks at an alternative approach of using the entire wall surface as a passive solar collector, by using an external layer of translucent insulation. Measurements and calculations are reported which show that a wall with a double-glazed outer layer would be expected to show a zero net heat loss over the heating season. This is not considered to be sufficient advantage to overcome the cost and other problems associated with the system.     

The German energy audit program for firms—a cost-effective way to improve energy efficiency?

In 2008, a program was established in Germany to provide grants for energy audits in small- and medium-sized enterprises. It aims to overcome barriers to energy efficiency, like the lack of information or a lack of capacity, and is intended to increase the adoption of energy efficiency measures. We evaluate the program's impact in terms of energy savings, CO₂ mitigation, and cost-effectiveness. We find that firms adopt 1.7?C2.9 energy efficiency measures, which they would not have adopted without the program. Taking a firm's perspective, the program shows a net present value ranging from ?0.4 to 6??/MWh saved, which very likely implies a net benefit. For the government, each ton of CO₂ mitigated costs between 1.8 and 4.1??. Each euro of public expenditure on audit grants led to 17?C33?? of private investment. The cost-effectiveness of the program for firms and the low share of public expenditure underline its value for the German energy efficiency policy mix and suggest that it should be expanded in Germany. Further, the good experiences with the program in Germany should encourage countries which have not yet established an audit program to do so.     

Building performance evaluation and certification in the UK: Is SAP fit for purpose?

Improving the efficiency and performance of the UK residential sector is now necessary for meeting future energy and climate change targets. Building performance evaluation and certification (BPEC) tools are vital for estimating and recommending cost effective improvements to building energy efficiency and lowering overall emissions. In the UK, building performance is estimated using the standard assessment procedure (SAP) for new dwellings and Reduced SAP (RdSAP) for existing dwellings. Using a systems based approach we show there are many opportunities for improving the effectiveness of BPEC tools. In particular, if the building stock is going to meet future energy and climate change targets the system driving building energy efficiency will need to become more efficient. In order to achieve this goal, building performance standards across Europe are compared highlighting the most effective strategies where they are found. It is shown that the large variance between estimated and actual energy performance from dwellings in the UK may be preventing the adoption of bottom-up energy efficiency measures. We show that despite popular belief, SAP and RdSAP do not estimate building energy efficiency but instead attempt to estimate the cost-effective performance of a building and thus create perverse incentives that may lead to additional CO₂ emissions. In this regard, the SAP standard confounds cost-effectiveness, energy efficiency and environmental performance giving an inadequate estimate of all three policy objectives. Important contributions for improving measurement, analysis, synthesis and certification of building performance characteristics are offered.     

Considering user profiles and occupants’ behaviour on a zero energy renovation strategy for multi-family housing in the Netherlands

A number of facade solutions have been developed in recent years to solve the problem of large-scale renovation of housing. In the Netherlands, housing associations have the ambition to achieve an energy-neutral renovation approach, and so, some aim at energy neutrality. However, few address the complexity of multi-family rental dwellings and more importantly, the importance of user behaviour in the actual performance of the buildings. In current approaches, the zero energy target is sought for an average household. In this paper we present an approach to zero energy renovation in which the influence of occupants’ behaviour in building performance is taken into account to eliminate the uncertainties related to energy savings. The results are used to inform the design process regarding the amount of energy production required to reach zero energy performance, and the feasibility of the on-site energy production only with photovoltaic panels. The research showed large statistically significant differences on energy consumption between the different household types, which could contribute to pre-bound effects if these differences are not considered when calculating energy savings and return of investments. When considering scenarios based on behaviour after renovation, the difference between the lowest and the highest heating demand is reduced to 34%.     

Trends in observable passive solar design strategies for existing homes in the U.S.

Passive design strategies are among the most cost-effective methods to reduce energy consumption in buildings. However, the prevalence of these strategies in existing U.S. homes is not well understood. To help address this issue, this research evaluated a nationally-representative sample of 1000 existing homes distributed geographically across the U.S. Using satellite images, each building was evaluated for three passive design strategies: orientation, roof color, and level of shading. Several statistically significant regional trends were identified. For example, existing homes in the High Plains, Ohio Valley, Northwest, and Southern regions show a statistically significant trend towards orientation in the East–West direction, an effective passive design strategy. Less intuitively, in terms of what would seem to be optimal passive design, buildings in the High Plains and Ohio Valley generally have lighter roof colors than buildings in the warmer Southwest region. At the national level, no statistically significant trends were found towards the passive design strategies evaluated. These trends give us no reason to believe they were a major consideration in the design of existing homes. Policy measures and education may be required to take advantage of the opportunity for cost-effective energy savings through more widespread passive solar design.