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Energy Savings in buildings

Energy Savings in buildings

Energy savings in buildings
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Technologies and measures which are aimed at reducing the use of energy in buildings could have several advantages, such as lower energy bills, increasing comfort of living or working, and reduced impact on the environment, including reduction of CO2 emissions. The options considered for energy savings particularly leading to CO2 emission reductions include the following:

  • Use of renewables for heating, cooling and electricity;
  • Improvements to the building envelope, including materials, natural ventilation and daylighting; and
  • Improvements to building services, including heating, mechanical ventilation and air-conditioning.

Included in the latter category are: commercial offices, retail, warehouses (excluding industrial), hotels and catering, transport and communication (building-related energy use only), sport and leisure including libraries and theatres, education (schools and universities), health centres, hospitals, government and other buildings including churches, mosques and community centres. Within buildings energy saving can take place through refurbishment of existing property or by building new buildings which replace old buildings and/or which energy performance is better than that of existing buildings.

Introduction

Buildings’ energy consumption in the EU represents about 30% of total EU energy consumption and between 25 and 40% in OECD countries (OECD, 2003). Developing countries have less efficient building stock where it is even more important to improve on energy efficiency of the building. In the EU-25, in 2003 total CO2 emissions amounted to 3.8 Gtonnes of which 479 Mtonnes were household emissions (12%) (EU, 2005). In the UK, the domestic sector represents about 28% of CO2 emissions and within that space heating is 53%, lighting and appliances 22%, and water heating 20%. Cooking contributes only 5% (UK DTI, 2006).

Technologies and measures which are aimed at reducing the use of energy in buildings could have several advantages, such as lower energy bills, increasing comfort of living or working, and reduced impact on the environment, including reduction of CO2 emissions. The options considered for energy savings particularly leading to CO2 emission reductions include the following:

  • Use of renewables for heating, cooling and electricity;
  • Improvements to the building envelope, including materials, natural ventilation and daylighting; and
  • Improvements to building services, including heating, mechanical ventilation and air-conditioning

In general, energy use in a building depends on:

  • the purpose of the building;
  • the envelope design and materials;
  • the heating, cooling, ventilation and lighting systems;
  • how long the building is used for each day;
  • density of occupancy;
  • topography of the site; and
  • external factors such as the weather and the behaviour of the occupiers, e.g., in turning off unwanted lights.

When considering the sources of CO2 emissions from buildings, also so-called ‘life cycle CO2 emissions’ of building should be taken into consideration, such as the emissions related to production of building materials, as well as downstream waste disposal from construction and renovation of buildings. The main design considerations which should be taken into account in the buildings for energy efficiency measures include the following:

  • The orientation and form of the building to improve daylighting: Preferably, a building should face north. According to Lawrence Berkeley Labs in the USA, lighting controls such as occupancy sensors have been shown to save significant electrical energy in commercial buildings (LBL, 2006). However, the success rate depends on having well-monitored building sites. Advanced control strategies that require a systems approach, such as daylighting and load shedding, were less successful. For strategies such as daylighting which require the electrical light levels to respond to the external daylight input to a room, a lighting control system is needed. However, since the manufacturers supply components rather than systems, these components do not necessarily work well when put together as a system. This could hold especially for dimming resulting in complaints at the poor performance. Similar problems are faced with advanced shading systems for controlling solar heat gain through building windows. Linking the lighting controls with building envelope controls is also a problem particularly for motorised blinds, louvers and the variable transmittance electrochromic windows. Such system improvement processes could benefit from involvement of the users of the building on commission.
  • Warming and ventilation: Buildings can be designed to be naturally ventilated with considerations such as inlet and outlet aperture sizes for the air flow being important. Air conditioning using electrical energy is second only to lighting in terms of energy demand in buildings. In California, it amounts to 14% of peak demand. Low energy cooling systems are therefore very important and involve a number of technologies and considerations. For example, natural ventilation and evaporative cooling allow heat to be dissipated from the interior to exterior without refrigeration. Effective cooling of occupied spaces needs technologies such as displacement ventilation or radiant cooling, so that the temperature of the air or water cooling medium does not have to be as low as normally required. The distribution system is important as well, so that the losses are reduced either by using water, or by sealing ducts. Chilled beams in the ceiling of occupied spaces are known to be very effective.
  • Managing the effects of solar gain and the use of less energy intensive services equipment: For instance, improvements could be achieved in the field of humidity control.
  • The supply of energy to buildings is a focus for improvement through consideration of such measures as:
  • Borehole cooling,
  • Heat pump,
  • Combined Heat and Power (CHP),
  • Biomass heating,
  • Gas powered cooling,
  • Wind power electricity supply,
  • PV electricity supply,
  • Heating water by solar collection (70% of hot water can be provided in this way),
  • Solar thermal space and water heating,
  • Passive cooling by use of thermal inertia, and
  • Solar assisted cooling.

In general, some possible options of energy efficiency in buildings are presented below

energy_savings_in_buildings-1.jpeg

Figure 1: Energy saving possibilities in buildings (Source: Rockwool)

Feasibility of technology and operational necessities

The recent EU Directive on Energy performance of Buildings (European Commission, 2002) applies to residential and tertiary sectors (offices and public buildings, etc.) and involves all aspects of energy efficiency in both new buildings and major renovation. The Directive has four main aspects: a common methodology for calculating the integrated energy performance of buildings; minimum standards for the energy performance for new buildings and buildings subject to major renovation (to be set at the national level); systems for certification of buildings; and regular inspection of boilers and air conditioning and an assessment where boilers are more than fifteen years old.

The UK government announced in March 2006 a new Code for Sustainable Homes which contains:

  • Building regulations for energy and water – A timetable will be set for this code to become mandatory for all new homes and possibly for existing homes.
  • The use of landfill taxes and bans on landfill with mandatory separation of materials – Regulations on the quality of building materials are not so prevalent.

Developing countries usually have a restricted energy supply and energy savings for space heating and cooling, lighting and hot water can free up supplies for other activities and improve security of energy supply as well as improve comfort in the home and provide economic savings on energy bills. The technologies involved are well known and tested and even simple changes can make a difference. There are however many possible approaches depending on the building, its orientation location, and usage so that solutions have to be considered in the context of each building, whether it is new build or refurbishment. Since the techniques and know how are available and in many cases not very sophisticated, technology transfer should be relatively simple and could be well supported by training courses.

The advanced commercial building design may not work well if monitoring and management systems are not in place. There are many barriers to the uptake of the technology for eco buildings of which the main ones are:

  • Grid interconnection arrangements for all decentralised electricity generation including BCHP needs improvement.
  • In buildings which are not occupied by the owner the benefits of the higher investment go to the tenants rather than the investor, which could be a disincentive for owners to invest in energy saving measures.
  • Time pressures can mean that existing building design is the only option for the architect/design engineer in the time available.
    • Fee structures for professionals can work against innovation.
    • Innovation requires new collaboration between design professionals, the construction industry and occupiers of the building, which can be difficult to arrange.
    • Lack of strict building regulations.
    • Lack of training and awareness in architectural and engineering courses.
    • Environmental labelling and information on embedded carbon in materials is insufficient.

Status of the technology and its future market potential

Also in developing countries the energy saving potential is very large, but market penetration of these ideas is even less than in Europe and more needs to be done to raise awareness of the benefits and to transfer the skills and know how as well as the technology. Regulatory standards and incentives are still rare except for China.

There are currently more than 5000 Passive House buildings operating in Europe; the oldest since 1991. The Passive House concept is proven both scientifically and empirically to work well (New Zealand Passive House, 2006). Improvements to building design for non-residential buildings are also all available but there are barriers to the uptake as designers find it easier just to adjust existing designs rather than change their practice. In many cases the eco homes or buildings provide energy savings which make them cost effective but there tends to be a higher up front cost as these designs are not yet standard due to the barriers.

The WADE approach for BCHP relies on established technology and the technical potential is estimated to account for the total national electricity demand for most countries. The potential in all countries is very high for new buildings and for refurbishment of existing housing stock. Energy saving buildings are not different in form from standard buildings and tend to be more comfortable so that social acceptability could be high.

Construction students across Europe will soon be able to learn about the latest in green building techniques through a brand-new, web-based programme for which the Centre for Alternative Technology (CAT) will provide information on eco-building techniques and case studies for the programme. Course organisers found there was little or no environmental content in mainstream construction courses in Italy, Bulgaria, Greece and the UK, so they decided to team up with partners in these countries to look at their different needs. The programme will also help educate lecturers whose knowledge often comes from conventional construction methods. Funding for the project has been agreed under the Leonardo Da Vinci European Community Action Programme for Vocational Training. In the UK in February 2005, a new guide for new homes construction ‘Ecohomes’, compiled by the UK-based Building Research Establishment, was unveiled by the Government Office of the Deputy Prime Minister. It has four levels of achievement from ‘Pass’ to ‘Excellent’. For this guide, a top-10 of barriers was established through a survey of 300 housing associations and a panel of experts came up with solutions. WWF have a UK campaign called One Million Sustainable Homes and in collaboration with government, industry and consumers is aiming to bring sustainable homes into the mainstream of construction in the UK (WWF, 2006). Advice is also available for planning a green office, whether it involves an office move or refurbishment, in the form of some simple steps to reduce the ecological footprint of a building (WWF, 2006a).

In the residential dwellings sector the concept of a Passive House has been developed. The concept originated in Darmstadt Institute in Germany from superinsulated houses built in USA and Canada in the 1970s. However, it has still to be put into practice in many countries and is well beyond any building regulation standards. The house is passive because it heats and cools itself so that there is no requirement for additional energy, except for appliances. In the European context the specifications are as follows (Passivhaus Institut, 1996):

  • an annual heating requirement that is less than 15 kWh/m²/year (4755 Btu/ft²/yr), not to be attained at the cost of an increase in use of energy for other purposes (e.g. electricity); and
  • the combined primary energy consumption of living area of a European passive house may not exceed 120 kWh/m²/year (38039 Btu/ft²/yr) for heat, hot water and household electricity.

At this level, the combined energy consumption of a passive house is less than the average new European home requires for household electricity and hot water alone.

A Passive house has an indoor air temperature which is above the minimum of 18°C recommended by the World Health Organisation, and which is maintained year round without the need for heating appliances. The key features distinguishing a passive house as given by the Passivhaus Institut (1996) are listed below.

energy_savings_in_buildings-2.png

Figure 2: Key features of Passivhaus (Source: Passivhaus Institute)

Taking this concept further to a totally sustainable construction concept, the ‘S-House’ was built by the Center of Appropriate Technology (GrAT/Gruppe Angepasste Technologie) at the Vienna University of Technology. They developed an integrated total concept combining all relevant aspects of sustainable building methods that also meet the high standard of energy for the passive house method (S-House, 2005). It only uses building materials that are from renewable raw materials. These materials can be recycled after completion of the building lifetime. The materials used were wood and straw and new technical solutions were developed during the project so that the concept and practical techniques could be applied elsewhere. The building is fireproof and the noise insulation is also good.

An alternative approach has been adopted by the World Alliance for Decentralised Energy (WADE) who promote a Building Cooling Heating and Power (BCHP) approach where combined heat and power units are promoted over grid systems. They have an economic cost model which demonstrated that this local energy approach provides the opportunity for using the heat normally lost in large electricity generating stations for space heating and cooling. This means that costs are avoided for transmission and distribution networks and efficiency is high (WADE and Climate Group, 2005).

There are many examples showing that the construction of a low energy building, whether domestic or non-residential, is possible. For instance, Ireland’s first passive house was opened in November 2005. Capable of both heating and cooling itself, the house is a demonstration project sponsored by Sustainable Energy Ireland, and is independently certified by the Passive Haus Institute in Germany. REEEP/UK Foreign and Commonwealth office have financed a number of projects in this area. An example is the project carried out by the Institute for Market Transformation based in the USA. The aim was to improve and secure engagement for energy efficiency codes for buildings. As a result of this project the Republic of Kazakhstan and the Russian Federation have adopted a new energy-saving building code with IMT’s help in Spring 2005 (IMT, 2006).

In China, according to an article in February 2005 (Chinese Embassy in India, 2005), an increase in green energy efficient buildings is expected in the next fifteen years according to the Vice minister of Construction. China has adopted a target of converting all existing buildings into energy saving buildings by 2020 and new buildings will have higher energy standards saving 65%/m2 of current building energy use at only a 5-7% increase in capital costs. The buildings of China presently have poor energy performance consuming 2-3 times the energy consumed by developed countries. The CDM was seen as one mechanism through which this could be financed.

The UK Department for International Development (DFID) has funded research on energy in buildings. An example is a project (R6478) on Thermal Comfort and Design for schools in the North West Frontier province of Pakistan where a number of schools were modified to reduce indoor air temperatures in summer and increase them in winter (Hancock, 1998). Three strategies were identified through computer simulations: increased roof insulation, cross ventilation, and roof and wall shading. The project influenced local architects to set up a group to encourage passive design. Another project (R5493) was able to compile a database on comfortable conditions in commercial buildings in different cities with a view to minimising the heat and cooling loads (Nicol et al., 1997).

Contribution of the technology to social development

There are many sustainability benefits from improved buildings technologies. Comfort and quality of life in the improved indoor environment is a major factor as well as the savings in energy costs and the security of supply that low energy requirements impy. There are knock-on effects with improvements in health and low indoor air pollution though the use of more benign paint alternatives and finishes.

Contribution of the technology to economic development (including energy market support)

In terms of energy consumption, 25 to 40% of energy used in OECD countries is in buildings, which is comparable to 938 to 1500 million toe. According to OECD (2003), there is a potential to reduce by 80 to 90%, but this will depend on real regulatory progress. The technology is affordable in that the overall energy savings will offset initial capital cost increases and the costs relative to traditional buildings are not a great deal higher. Improvements to the energy efficiency of a home are well tried and reliable.

Contribution of the technology to protection of the environment

Environmental impacts are associated with the extraction of resources upstream in the building supply chain and the disposal of waste from construction or refurbishment. OECD (2003) points out that the construction sector accounts for between one third and one half of commodity flows by weight and also a significant proportion of total waste. This implies a need for recycling/reuse of building materials.

Climate

According to WADE and Climate Group (2005), the BCHP approach in apartments, hotels, schools, hospitals, etc., alone, in a high uptake scenario, could cut total CO2 emissions in Canada by 16% by 2020. In the USA, there are 3500 MW of BCHP and the mitigation potential for CO2 is that 20% of total emissions growth could be displaced. Passive houses reduce energy demand by a factor 10 with consequent 90% reduction in associated GHG emissions.

There do not appear to be many activities in this area in developing countries though in China there is some interest in energy saving buildings. In China, BCHP is not so common and large municipal CHP is the norm. It is estimated that about 11% of growth in CO2 emissions could be displaced by the use of BCHP. Similar to China, India does not have BCHP, and WADE estimates a displacement of 16% of India’s CO2 growth by 2020 on the high scenario (WADE and Climate Group, 2005). The benefits in reduction of energy demand in terms of electricity for a developing country are high as energy supply is usually limited. In particular, cooling can be a large demand which can be drastically reduced by sustainable construction.

Financial requirements and costs

Сosts associated with improved energy efficiency in buildings, such as the passive house, are only slightly higher than in normal buildings, but they yield large savings in energy bills. A BCHP approach, depending on what technology is used, also has higher initial costs, but also yields savings through provision of cheaper heat and electricity. However, a maximum benefit would be gained by a combination of energy efficiency and selection of an appropriately rated energy source or sources. In overall energy supply cost terms, energy economic modelling has shown that the BCHP approach not only yields savings at the national level, but also avoids new power plant costs.

Within the EU, financing opportunities for energy saving technologies in buildings are provided by the Intelligent Energy for Europe Programmes SAVE and ALTENER. The EU Thermie programme under the Transport and Energy Directorates-General supported the CEPHEUS (Cost Efficient Passive houses as European standards) project from 1998 to 2001. It involved the construction of about 250 housing units to Passive House standards in five European countries, with in-process scientific back-up and with evaluation of building operation through systematic measurement programmes (CEPHEUS, 2006). They showed that cost-effective passive houses could be built in heating load climates. Under the Intelligent Energy Europe SAVE programme, a new project called Passive-ON (2005-2007) builds on the experience of CEPHEUS and other projects on passive cooling strategies for Mediterranean.

The funding of projects in developing countries through REEEP, GEF, GVEP are well known. UNEP also funds capacity building activities and technology transfer support, as well as research and policy design. In general, the EuropeAID programme has funds for projects in the area of energy. The EU also facilitates transfer of know how and technology through its Asia-Invest programme which has funds of over € 20 million. Launched in 1998 it supports the exchange of experience, networking and matchmaking among European and Asian business organisations (mainly SMEs), to promote the greater integration of European and Asian companies and the transfer of know-how and technology between Europe and Asia.

References

The Climate Technology Centre and Network (CTCN), UN City, Marmorvej 51, 2100 Copenhagen, Denmark.