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The current energy system leads to the possibility of ending up in energy disaster. It is suggested by many researchers that societies have to change from the current paten to new pattern which depends on two primary principles, efficiency and renewable energy resource in order to avoid energy disaster [1-2].
Many of the advances in energy sector have been driven by the need to cut down cost and new requirements, such as environment, efficiency, etc.The availability of adequate and reliable energy supplies to maintain economic growth and to improve living standards. Associated with energy consumption, there are environmental and health impacts which have been discussed and analyzed only during the last decade. In particular, the burning fossil fuels have increased significantly levels of carbon emissions. The carbon emissions are believed to have a major impact on changing global climate by increasing temperatures.The high global temperatures could affect agricultural production, and sea level heights. Moreover, the emissions from coal-fired power plants have caused significant impact in the form of acid rain over trees, crops, and animals [3-4].
Environmental impacts are not limited to fossils fuels but include other energy sources. Dams for hydroelectric power plants have altered major rivers and harmed fish and wildlife. Storage of nuclear waste from nuclear power plants can be radioactive and affect the health of present and future generations.Unfortunately, the damages are not localized to areas where energy is produced or used but are rather global. The emission of hydrocarbon, sulfur oxides and nitrogen oxides are causing severe health problems throughout the world [3-4].
To maintain economic growth and reduce the staggering environmental impacts of conventional energy resources, energy conservation and energy efficiency has to be considered as a clean source of energy. Indeed, improvements from energy efficiency can avoid the need to build new power plants that use conventional energy sources at little costs and with no adverse environmental impacts.
Moreover energy efficiency and energy conservation have other beneficial impacts including:increase the economic competitiveness: investment in energy conservation provide a better return than investment in energy supply, stretch the availability of the limited non- renewable energy resources and gain time for possible development of renewable and reliable energy resources such as solar energy and decrease air and water pollution and thus improve health condition.
In the world there is a vast potential for energy efficiency that has begun to be tapped in only few countries. This potential exists for all energy end use sectors including buildings, industries and transportation. One of the main challenges in this new millennium is to reduce cost and lower the environmental impacts. Therefore energy efficiency can have beneficial impacts on the economic competitions, the environment and the health [3-4] .
The energy sources primarily used in Sri Lanka includebiomass, hydroelectric power and Petroleum. Biomass used mostly for household cooking accounts for more than 52.9% of the primary energy supplied in Sri Lanka during 2000. More than 70% of the total electrical power used in Sri Lanka is generated from hydroelectric power plants in 2000 and 50% in 2010 [5].
Sri Lanka imports most of its energy in the form of petroleum products. Therefore, energy conservation means less reliance on energy imports and, thus, less greenhouse emissions.Over the last 20 years total energy consumption in Sri Lanka has increased by about 40%,while the population increased at a steadily rate of above 2% per year, the per capita used remained almost constant [5].
Electrical energy use can be divided into three end use categories: Residential, Commercial & Industrial sectors in Sri Lanka. The industrial sector accounts for almost 38% of the total electrical energy consumption of the country. Meanwhile the residential & commercial buildings used respectively 37% and 21% of the total electricity consumed in Sri Lanka [5]. Therefore it is prime important tocarry out some energy conservation programs for buildings & industries in order to reduce the demands of electrical energy in Sri Lanka. Residential and commercial buildings account for almost 60% of total energy consumption in Sri Lanka. Lighting, appliances & HVAC equipment account for most of the electricity consumption in non-residential building. The potential for energy conservation for both buildings & industrial sector remains large in Sri Lanka.
Since the oil embargo of 1973, significant improvements have been made in the energy efficiency of new buildings. However, the vast majorities of the existing stocks of buildings are more than a decade old and do not meet current energy efficiency construction standards. Therefore energy retrofits of existing buildings will be required for decades to come if the overall energy efficiency of the building stocks is to meet the standards.
Investing to improve the energy efficiency of building provides an immediate and relatively predictable positive cash flow resulting from lower energy bills. Moreover, several large industrial and commercial buildings have established internal energy managements programs based on energy audits to reduce waste in energy use or to comply with specification of some regulations and standards.Other building owners and operators take advantage of available financial incentives typically offered by utilities or state agencies perform energy audits and implement energy conservation measures.
In the 1970s, building energy retrofits consisted of simple measures such as shutting off lights, turning down heating temperatures, turning up air-conditioning temperature and reducing the hot water temperature. Today, building energy management includes a comprehensive evaluation of almost all the energy systems within a facility [3].
Generally, architects, engineersand quantity surveyors to respond to many considerations including structuraland esthetics design the envelope of a structure. Before the oil crises the energy efficiency of the envelope components was rarely considered as an important factor in design of a building. However, now several standards and regulations have been developed and implemented to improve the energy efficiency of various components of building envelopes. For energy retrofit analysis, it is helpful to determine if the building was constructed or modified to meet certain energy-efficiency standard. If it is the case, retrofitting of the buildingenvelope, may not be cost effectiveespecially for high-rise commercial buildings. However, improvements to buildings envelope can be cost-effective if the building or industrial facility was built without any concern for energy efficiency such as the case with structure constructed with no insulation provided in the walls or roofs.
Moreover, the building envelope retrofit should be performedafter careful assessment of the building thermal loads. For instance in low-rise buildings such as residential and small commercial buildings or warehouse, the envelope transmission losses and infiltration loads are dominant and the internal load within these facilities typically low.
Hotels use significant amounts of energy for daily operations and recreational activities. This basically can be seen in building climate control and general services in the hotel. These are composed of passive cooling, energy management and control systems (EMCS), central cooling system, ice storage, desiccant dehumidification, in addition to laundry and kitchen equipments. In many facilities, energy costs are the second-highest operational costs after payroll. Such considerable cost of energy is due to using technology and different sources of energy to provide comforts and conveniences to hotels' guests. A growing concern has been addressed regarding the high amount of energy that hotels consume for their operational purpose. Moreover, numerous studies lead in studying energy use and hotels environmental performance [6-9]. Such studies have been able to enhance hotels’ performance by achieving good operational practices in these hotels.
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