Building Sector and Energy Consumption - Essay Example

 Introduction The objective of building energy assessment should be to valuate the overall energy impact of the building. This requires a life cycle analysis (LCA) approach in order to properly assess all the building energy implications. A common shortcoming of virtually all the building energy regulation schemes and most of the building certification schemes is that they limit their energy assessment to the building operational energy requirements, leaving aside the embodied energy (EE) accumulated in the materials and equipments implemented in the building through their manufacturing, transport, implementation and end of the life recovery processes. This becomes more critical as building operational energy efficiency is increased, since under these circumstances the building EE adopts a higher relative weight in the life cycle energy consumption.(Tavil, 2004; 111–118) Hence, if EE considerations are not included in building energy regulation or certification schemes, it is possible that buildings with low life cycle energy consumption are discarded because of not fulfilling the regulative (operational) energy consumption levels, or that they reach a lower certification than other buildings with higher life cycle energy consumption. (Edwards, 2001) In Germany and the United States there are even energy certification schemes (‘Plus Energie Haus’ in Germany and ‘Zero Energy Haus’ in USA) based on the concept of the net production of operational energy (negative operational energy consumption). In Fig. 1 we show the evolution of the accumulated energy consumption (LCA) for two 150 m2 dwellings, an ‘average’ one and another with pretensions of energy efficiency on basis of its reduced operating energy demand. The ‘average’ building implements materials with relatively low embodied energy and a limited amount of HVAC equipment. (Guo, 2003; 1413–1422) The ‘efficient’ building implements relatively high embodied energy materials and is more intensive in HVAC equipment. The energy ‘efficient’ building achieves a 30% reduction in heating energy demand. The LCA shows how, even with a long analysis period (100 years), the energy ‘efficient’ building may consume more energy than the ‘average’ one if care is not taken about its EE. Evolution of accumulated energy consumption for two 150 m2 dwellings, an average one and another with pretensions of energy efficiency on basis of its reduced operating energy demand. (Laustsen, 2003) The results presented in Fig. 1 assumed a rather low increase in operational energy efficiency, but even with higher energy efficiency improvements we may find similar results with lower life cycle periods. The ‘average’ building implements materials with relatively low embodied energy and a limited amount of HVAC equipment. The energy ‘efficient’ building achieves an 80% reduction in heating energy demand and 40% reduction in cooling energy demand. The LCA shows how, even with a very significant reduction in operating energy consumption, the energy ‘efficient’ building may consume more energy than the ‘average’ one in relatively short life times if no care is taken about its embodied energy. Life cycle analysis for two 150 m2 dwellings, an average one and another with pretensions of energy efficiency on basis of its reduced operating energy demand, for a life time of 30 years. (Addis, 2002) The effect of transportation energy requirement becomes also evident in this case, being the highest energy contribution for the ‘average’ building, and the second one, after the embodied energy, for the energy ‘efficient’ building. From a building energy point of view, these distributed urbanization schemes offer more chances for energy efficiency measures and application of renewable energy technologies than centralized urbanization schemes. It is just through transportation energy requirements that sustainable building considerations interact with the higher structure sustainable urbanization approach. Instruments for Building Energy Assessment Building energy assessment, extended to its design, construction, and useful life, allows for a proper quantification of the building's energy implications, and hence provides the basis for appropriate planning in the sector. Given the high relative weight of the sector in the country's energy balance, the very limited penetration of energy assessment tools in it and its high inertia to incorporate changes, there is a clear need to develop normative and mechanisms that structure the application of energy assessment in the building sector. (Mithraratne, 2004; 483–492) However, it is of paramount importance to establish clear objectives for the different actions to undertake, and to structure those actions so that they effectively facilitate, instead of hinder, the internalization of energy assessment in the building sector. (Oral, 2004; 281–287) The two main mechanisms to articulate the participation of energy assessment in the building sector are energy regulation and energy certification. Energy Regulation Energy regulation has a perceptive character, and its objective should be to establish and limit the upper bound for the buildings energy consumption. With its normative character, energy regulation establishes the minimum, and often the only, building energy assessment tools that will be introduced in the sector, and has therefore a high responsibility in the internalization of energy assessment. (Kwok, 2003; 1019–1026) The success of building energy regulation in effectively controlling the energy consumption in the sector will be to a great extent associated to the adopted energy performance indicator and to the promoted energy assessment tools. Nowadays, building energy regulation in the different countries is very inhomogeneous regarding these two elements, as well as regarding the pretended upper bound for building energy requirements, even in the frame of the EU as shown in. (Edwards, 2001) In the absence of any other mechanism, energy regulation lays down the basis for the energy consumption in the building sector, and hence, should allow for a clear quantification of its implications both at national and at consumer level. Energy Certification Energy certification is mainly a market mechanism whose main objective is to promote higher energy performance standards than the regulated ones. To reach this objective, energy certification must provide a clear and detailed information about the building's energy performance (energy labelling), allowing for the straight comparison between different buildings. As well as with energy regulation, the indicators implemented in the energy certification will condition its capability to reach the pretended objective. (Guo, 2003; 1413–1422) The indicator implemented in the energy regulation should be included among the indicators provided by the energy certification in order to clearly situate the certification on the reference regulated level of energy performance. The energy assessment methods upon which energy certification is based, as well as their transparency, are key elements for its success as shown by the Danish experience. A well implemented energy certification scheme must allow for, and promote, a clear quantification of design concepts with potential for building energy consumption reduction, such as bioclimatic architecture, passive solar heating, passive cooling, passive ventilation, integration of renewable energies, …, always guaranteeing some given comfort levels. (Laustsen, 2003) This is the only way to stimulate the market introduction of all these recommended design strategies from an energy point of view, but with a quality guaranty that avoids their discredit. Energy certification may have a compulsory or voluntary character. Compulsory energy certification schemes may introduce some additional burdens on the administration, while voluntary ones do not. (Addis, 2002) However, only through a compulsory energy certification scheme, can this mechanism develop all its potential for energy improvement in the building sector. Voluntary energy certification schemes have a limited scope and not always succeed to send the appropriate signals to the building market. (Kwok, 2003; 1019–1026) A good energy certification scheme, with a compulsory character and a demand for short period actualization, allows quantifying the actual energy state of the building sector, and monitoring its evolution in time, as well as promoting and evaluating the energy efficiency measures introduced in it. A proper energy certification scheme gives an added value to the building and allows the assignment of economic incentives to drive the building sector towards sustainability. Building Energy Analysis A building is a very complex energy system, especially when allowing a high degree of interaction with its surrounding environment (bioclimatic architecture, solar passive design) with the aim of improving its energy performances. Therefore, given the high relevance of the building sector in the energy consumption, the introduction of rigorous energy analysis tools, capable to appropriately assessing the operational energy implications of different design options, should be promoted. Because of the lack of tradition in energy analysis within this sector, the role of the normative (compulsory regulation and certification schemes) is of paramount relevance to reach an effective introduction of energy analysis tools in the building sector. (Tavil, 2004; 111–118) The appropriate assessment of building operational energy requirements, and especially of those designs with a higher energy saving potential, requires the use of a complete and detailed dynamic energy simulation tool. This tool should include a detailed thermal modelling, the possibility to evaluate many different HVAC systems, and the capability to properly assess the effect of the different couplings found in building energy analysis: building with its HVAC system, thermal and air flow processes, inertial ground coupling. (Guo, 2003; 1413–1422) The appropriate use of such an energy tool requires a considerable degree of qualification and training, and therefore requires the incorporation of additional resources, both for the building design team as well as for the Administration that should control the regulation and certification schemes. It is obvious that these additional resources will not be incorporated, and therefore energy analysis will not be internalized by the building sector, unless the appropriate signals are sent from the Administration. (Oral, 2004; 281–287) Building energy impact can go far beyond its operational energy consumption, partially affecting other factors like transport energy demand for working displacements. This is recognized in some building energy certification schemes as the leadership in energy and environmental design (LEED) certificate, promoted by the US Green Building Council. However, care should be taken to avoid that such certification schemes permit a relaxation in the building operational energy assessment by allowing a partial compensation with other ‘more easy to reach’ certification points. The goal to achieve a real internalization of energy analysis in the building sector should be integrated in the energy regulation and certification schemes, since the building energy operational demand will always constitute an intrinsic contribution in all buildings, while other energy contributions may be more dependent on higher structures like urbanization, social organization, and technology development, which may change with time and that are often not accessible by a single building design (they belong more to the urbanization certification sphere than to that of the individual building). The Relevance of Live Cycle Analysis The objective of building energy assessment should be to valuate the overall energy impact of the building. This requires a life cycle analysis (LCA) approach in order to properly assess all the building energy implications. A common shortcoming of virtually all the building energy regulation schemes and most of the building certification schemes is that they limit their energy assessment to the building operational energy requirements, leaving aside the embodied energy (EE) accumulated in the materials and equipments implemented in the building through their manufacturing, transport, implementation and end of the life recovery processes. (Mithraratne, 2004; 483–492) This partial view on the life cycle energy impact of buildings may be misleading, and may send wrong signals to the building market leading it away from the sustainability path. This becomes more critical as building operational energy efficiency is increased, since under these circumstances the building EE adopts a higher relative weight in the life cycle energy consumption. (Laustsen, 2003) Hence, if EE considerations are not included in building energy regulation or certification schemes, it is possible that buildings with low life cycle energy consumption are discarded because of not fulfilling the regulative (operational) energy consumption levels, or that they reach a lower certification than other buildings with higher life cycle energy consumption. Under these circumstances, building energy regulation and certification schemes are not able to reach their main objective, and become limited or even market distorting mechanisms. In Germany and the United States there are even energy certification schemes (‘Plus Energie Haus’ in Germany and ‘Zero Energy Haus’ in USA) based on the concept of the net production of operational energy (negative operational energy consumption). However, in order to reach these low (or even negative) operational energy demand levels, these buildings often must incorporate a big amount of materials like aluminium, stainless steel or glass, and additional HVAC equipment, significantly increasing their EE, in such a way that the life cycle energy impact of these buildings is not as favourable as their certification pretends. In Fig. 1 we show the evolution of the accumulated energy consumption (LCA) for two 150 m2 dwellings, an ‘average’ one and another with pretensions of energy efficiency on basis of its reduced operating energy demand. The ‘average’ building implements materials with relatively low embodied energy and a limited amount of HVAC equipment. (Oral, 2004; 281–287) The ‘efficient’ building implements relatively high embodied energy materials and is more intensive in HVAC equipment. The primary energy demand of the ‘average’ dwelling is 70 kW h m−2 year−1 for heating and 50 kW h m−2 year−1 for cooling. The energy ‘efficient’ building achieves a 30% reduction in heating energy demand. The LCA shows how, even with a long analysis period (100 years), the energy ‘efficient’ building may consume more energy than the ‘average’ one if care is not taken about its EE. Evolution of accumulated energy consumption for two 150 m2 dwellings, an average one and another with pretensions of energy efficiency on basis of its reduced operating energy demand. The results presented in Fig. 1 assumed a rather low increase in operational energy efficiency, but even with higher energy efficiency improvements we may find similar results with lower life cycle periods. The ‘average’ building implements materials with relatively low embodied energy and a limited amount of HVAC equipment. The ‘efficient’ building implements relatively high EE materials and is more intensive in HVAC equipment. (Tavil, 2004; 111–118) The energy ‘efficient’ building achieves an 80% reduction in heating energy demand and 40% reduction in cooling energy demand. The LCA shows how, even with a very significant reduction in operating energy consumption, the energy ‘efficient’ building may consume more energy than the ‘average’ one in relatively short life times if no care is taken about its embodied energy. Life cycle analysis for two 150 m2 dwellings, an average one and another with pretensions of energy efficiency on basis of its reduced operating energy demand, for a life time of 30 years. (Guo, 2003; 1413–1422) The effect of transportation energy requirement becomes also evident in this case, being the highest energy contribution for the ‘average’ building, and the second one, after the embodied energy, for the energy ‘efficient’ building. Energy transportation results are presented to show that they may have a very significant contribution to LCA. From a building energy point of view, these distributed urbanization schemes offer more chances for energy efficiency measures and application of renewable energy technologies than centralized urbanization schemes. But from a LCA point of view both options have to be compared including transportation energy requirements. It is just through transportation energy requirements that sustainable building considerations interact with the higher structure sustainable urbanization approach. However, transportation energy is not an intrinsic energy contribution to the building LCA like the other indicated energy concepts. The Need For Appropriate Indicators One of the key points for the success of building energy regulation and certification schemes, in terms of the fulfilment of their objectives, is the main indicator they implement. The indicator these schemes are developed around should be chosen taking into account the targeted objectives. However, it is very common to find regulation or certification schemes based on indicators that do not take into account these considerations and that therefore have a limited effective scope. Based on the objectives for the regulation and certification schemes pointed out in point 2, the following considerations regarding the appropriate indicator may be stated: • It has to be a quantitative indicator of the amount of energy required by the building and therefore be expressed in terms of kW h m−2 year−1 and kW h year−1. Many energy regulation schemes are still based on indirect indicators as steady state heat transfer coefficients, which, as we will show later, may be rather useless for the pretended objectives. • It should be expressed in terms of primary energy demand, and therefore include the efficiency of HVAC equipment and other energy transformation processes (for example, electricity generation). Since the coupling between the building and its HVAC equipment has significant effects on the HVAC efficiency, this requirement imposes important restrictions on the energy assessment tool to be used. (Oral, 2004; 281–287) • It should be based on life cycle energy analysis, and therefore incorporate all building operational energy concepts (heating, cooling, ventilating, DHW and lighting) and the embodied energy. • It should introduce limitations on the overall active energy supply (renewable and non renewable altogether). In some recent building certification schemes this distinction is not made, and therefore may lead to the inefficient use of renewable energy resources which compromises sustainability. For example, a ‘zero non renewable energy house’ could implement a building with a very high energy demand, which however, it is only satisfied with renewable energy sources (biomass, solar thermal, photovoltaic, wind). (Laustsen, 2003)However, both natural and economic renewable energy resources are limited, and therefore such a building, awarded with a high energy certification, could indeed be producing a negative overall impact by preventing the use of these renewable energy resources to satisfy the overall society energy needs. • It should introduce requirements to satisfy an important percentage of the overall energy demand with renewable energy. The Eu Directives and Their Limitations As a practical example, we will now proceed to examine the building energy legislation at EU level in the light of the above stated general considerations, pointing out some of its shortcomings. Already in 1993, the Directive 93/76/CEE [3] clearly pointed to the building sector for its high relevance in the energy consumption and CO2 emissions within the EU, urging to adopt measures to increase the energy efficiency in this sector. Building energy certification schemes where already proposed as a tool with high potential for leading the building sector towards efficiency levels above the regulated ones, recommending the Member States its implementations before 1995. However, the lack of concretion in this Directive, together with the high inertia of the building sector in some countries, has brought about a very unequal implementation of these requirements in the Member States. (Tavil, 2004; 111–118) Nowadays, energy performance demands in the building sector within the EU go from the situation in countries like Denmark and Germany, with rather demanding energy regulations and already established energy certification schemes, to the situation in countries like France and Spain with low regulative demands and without certification processes established at national level. (Guo, 2003; 1413–1422) The Directive 2002/91/CE [4], specific about the energy performance of buildings, pretends to represent an effective advancement and concretion of the action lines indicated in the Directive 93/76/CEE for the building sector, with the aim to achieve the great unrealized potential for energy savings and reducing the large differences between Member States. This Directive establishes a general framework in which the building energy assessment should be implemented, urging the Member States to establish minimum energy performance requirements (regulation schemes), and energy certification schemes that allow driving the building sector to higher energy performance levels than the regulated ones. (Kwok, 2003; 1019–1026) In broad outline, the Directive 2002/91/CE gives an appropriate frame to drive the building sector towards sustainability, but once again presents a lack of concretion that may seriously condition its capability to reach the pretended objectives. Therefore, in spite of its appropriate philosophy, the Directive presents several shortcomings that may limit its effective transposition to the Member States. The main points where the Directive 2002/91/CE presents limitations which condition the effective transposition of its philosophy to the Member States are as follows: • Lack of clear definition of the main indicator to assess the building energy performance. From the context of the Directive 2002/91/CE it becomes evident that this indicator must be the quantitative assessment of the building's energy performance (kW h m−2 year−1). This is the indicator already implemented in the EU countries with a higher demand on the buildings energy performances or with more advanced implementation of building certification schemes (like Denmark and Germany). It is also the indicator adopted by recent building regulation schemes developed under the umbrella of the Directive 2002/91/CE like in Portugal [Laustsen, 2003]. However, the lack of determination in the Directive 2002/91/CE, together with the non appropriate translations of the English term ‘building energy performance’ to some of the Member States national languages, as in the case of Spain where it has been translated as ‘building energy efficiency’ with connotations of a dimensionless indicator, leaves the door open to the adoption of other indirect indicators that may result completely inappropriate for the objectives of a regulation or certification scheme, and even against the philosophy of the Directive 2002/91/CE. • Unclear requirements for the calculation method used to perform the assessment of the building's energy performance. The Directive 2002/91/CE states several requirements for the calculation method. However, unfortunately it does not go far enough, leaving the door opened to the possibility that the method adopted by a Member States is unable to properly assess specific building energy performance aspects indicated as priority by the very Directive 2002/91/CE (like passive cooling schemes in southern State Members), or even to the fact that the calculation method adopted is not able to properly assess the building energy performance according to the Directive 2002/91/CE. • Indeterminate minimum requirements for the energy regulation schemes. Therefore, no effective legal instrument is supplied to reduce the large differences between Member States, as pretended by the very Directive 2002/91/CE. • Excessive validity period for the certification scheme (10 years), which conditions its utility for controlling the real building energy performance, monitoring the effect of the energy efficiency measures introduced, and propitiate the adoption of new energy efficiency measures on the basis of its technical–economical assessment. • Indeterminate requirements for the implementation of renewable energies in the building sector. • Indeterminate requirements for the scope of the regulation and certification schemes, which will therefore probably be reduced to the project phase of the building (new buildings). • It does not incorporate the LCA for the building's energy assessment, and hence excludes the building's EE from it, limiting the scope from the energy assessment to the operational energy requirements. • It does not specify requirements on the attained thermal comfort and interior air quality levels. Proposal of rational criteria to establish energy consumption limits Rational criteria to establish the regulated limit on allowed energy consumption from the buildings (kW h m−2 year−1) should be adopted. This criteria should be coherent with the pursued objectives (sustainability), the acquired compromises (Kyoto protocol), and the actions undertaken in other sectors. For this purpose a national allocation plan (NAP) should be prepared involving all the sectors. This NAP should be coherent with the first steps in emissions reduction following the Kyoto protocol, and with the final objective to stabilize atmospheric greenhouse gas concentrations at safe levels. From this NAP follows the energy consumption from non renewable energy sources assigned to the building sector, and dividing it by the projected building surface in each period (including new and existing buildings), the average limit value of kW h m−2 year−1 for the building sector is derived (an internal allocation plan within the building sector may then be applied to particularize this limit among the different building types). Within this framework the main role of building energy certification would be to push the market ahead from the regulated limits in each time period, facilitating therefore the attainment of the final objectives. The short time period (50 years) available to reach a very drastic reduction in greenhouse emissions, requires the participation of the certification scheme to supplement the increasingly demanding regulation limits in such a way that they can be achieved. All the data needed for this approach are available at national level, and therefore its implementation should be rather straight forward. Any other approach that pretends not to look straight into the eyes of the central issue will lead to a delay in implementing the required actions. Regulation limits for the building sector derived independently from the other energy sectors, just do not make sense. On the same way, actions undertaken in other sectors (like the greenhouse gas emission allowance trading) without rational and coherent measures imposed on the excluded sectors may be useless. (Kwok, 2003; 1019–1026) Regulation limits for the building sector derived independently from the other energy sectors, just do not make sense. On the same way, actions undertaken in other sectors (like the greenhouse gas emission allowance trading) without rational and coherent measures imposed on the excluded sectors may be useless. Conclusions In this paper we have analysed the general conditions for the building energy regulation and certification schemes to be effective in controlling and limiting the energy consumption of the building sector. As a practical example, we have presented an analysis of the building energy legislation at EU level, pointing out the limitations that may compromise its capability to be finally translated in effective national legislation, able to reduce the energy consumption in the building sector. One of the key points in building regulation and certification schemes is the indicator implemented to assess the building energy performance. Building energy tools with capabilities to effectively model the energy implications of different design and operational strategies are nowadays available. The internalization of the building operation energy analysis should be favoured by the energy regulation and certification schemes in order to rationally assess the energy saving options and promote the introduction of the most efficient design and operating strategies. In this sense, regulation and certification schemes should be coordinated, to avoid situations like the one in the Spanish proposal where the energy analyst is forced to learn two different calculation codes, one for regulation proposals and the other one for certification, none of which provides any quantitative information about the building energy performance, and therefore a third tool should be learned in order to properly assess the buildings energy performance. Embodied energy considerations and live cycle analysis should be included in energy regulation and certification schemes in order to effectively lead the building sector towards sustainability. This is by far much easier than the adoption of an adequate building operational energy analysis tool for the design phase. Therefore it is surprising that even nowadays embodied energy and live cycle analysis are not considered in what should be thought to be the most advanced building energy legislation. We propose a rational approach to the assignment of the regulated limits on allowed building energy consumption, integrated with the overall national energy consumption and coherent with the established environmental constraints. For this purpose a national allocation plan of greenhouse gas emissions between the different sectors should be carried out, assigning the allowed contribution to the building sector, and performing an integral energy assessment on the building to compile with this limitation. This really seems to be the only approach that can give us some chances to successfully overcome the environmental constraint to our development process in the short time period available. Reference D.W. Aitken, S.T. Bull, L.L. Billmann, The climate stabilization challenge: can renewable energy sources meet the target?, Renewable Energy World 7 (6) (November–December 2004). Directive 93/76/CEE of the Council of 13 September 1993 on the limitation of the carbon dioxide emissions through the improvement of energy efficiency (SAVE), 1993. Directive 2002/91/CE of the European Parliament and of the Council of 16 December 2002 on the energy performance of buildings, 2002. Commission of the European Communities, Green Paper: Towards a European Strategy for the Security of Energy Supply, Brussels, November 2000. PREDAC, Guide for a building energy label, PREDAC project, Comité de Liaison Energies Renouvables (CLER) predac@cler.org, 2003. J. Laustsen, K. Lorenzen, Danish experience in energy labeling of buildings, OPET network, www.opet-building.net, September 2003. J.A. Alcorn and G. Baird, Embodied energy analysis of New Zealand building materials—methods and results, Proceedings of the Embodied Energy: The Current State of Play Seminar Deakin University, Geelong, Australia, 28–29 November (1996). B.V. Venkatarama Reddy and K.S. Jagadish, Embodied energy of common and alternative building materials and technologies, Energy and Buildings 35 (2003), pp. 129–137. Woolley T, Kimmins S, Harrison P, Harrison R. Green building handbook, vols. 1, 2. Londres: E & Spon; 1998. J. Goldenberg, Energia, medio ambiente & desenvolvimento, Edusp, Sao Paulo (1998). Webb R. Building insulation for sustainability-guideline and standards. Proceedings of international conference sustainable building 2002, Oslo, Norway. B. Edwards and P. Hyett, Rough guide to sustainability, RIBA Enterprises, London (2001). N. Mithraratne and B. Vale, Life cycle analysis model for New Zealand houses, Building and Environment 39 (2004), pp. 483–492. Tavil, Thermal behaviour of masonry walls in Istambul, Construction and Building Materials 18 (2004), pp. 111–118. G.K. Oral, A.K. Yener and N.T. Bayazit, Building envelope design with the objective to ensure thermal, visual and acoustic comfort conditions, Building and Environment 39 (2004), pp. 281–287. Addis B. Evaluating the environmental benefits of using structural timber in buildings. International conference sustainable building 2002, Oslo, Norway. F. Haghighat and H. Huang, Integrated IAQ model for prediction of VOC emissions from building material, Building and Environment 38 (2003), pp. 1007–1017. N.-H. Kwok, S.-C. Lee, H. Guo and W.-T. Hung, Substrate effects on VOC emissions from an interior finishing varnish, Building and Environment 38 (2003), pp. 1019–1026. H. Guo, F. Murray and S.-C. Lee, The development of low volatile organic compound emission house—a case study, Building and Environment 38 (2003), pp. 1413–1422. Read More