Air Conditioned Buildings In Energy Efficiency Construction Essay

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With the advancement in technology humans have adopted many techniques which give them relief and pleasure rather considering the factor how much energy and resources are being consumed. Like air conditioners if we talk has become the part and parcel of life in these days and people on the other side are willing to pay high price for it but what it can be mitigated by adopting natural ventilation (NV) which not only would save energy consumption and will conserve resources for the future generation. As non- renewable resources are depleting, climate is changing across the globe which has lead an alarming threat towards health and environment due to the harmful emissions which in turn has made awareness in improvising energy efficiency in buildings and other residential apartments.

Natural ventilation is the process in which the air is supplied in and removed through an indoor space by natural ways i.e. without any mechanical system. It works on the principle of airflow outside of the building caused by the difference in pressure between the buildings and surroundings to provide occupants comfort and natural ventilation (Green 2010).

Natural ventilation has old historical importance from ancient times to modern era. As global diversification in terms of land, climate and culture in relation to human needs has led to factors considering the designs. Talking about hot and arid regions of Arabs traditional buildings have been modified to the sources of energy available which helps in reducing humidity and enhanced natural ventilation. Wind catcher was introduced to achieve occupants comfort in the buildings for many centuries from early Pharonic periods (Shorbagy, 2006).

Heat capacity also plays a vital role in natural ventilation. In comparison to rural areas, urban areas have high heat capacity because of density of materials being high and high thermal conductivity as ground is more populated and has less to none insulating layer above.

From the background studies, figures have shown the variation in adoption of natural ventilation to being mechanical ventilation or even hybrid (mix of natural and mechanical ventilation). Orientation of the buildings, thermal masses, and thermal zone and buffer spaces all factors contribute to NV. In relation to the height of building, maximum width accounts for maximum natural ventilation.

Coventry University situated in Coventry, UK is an eye library due to its high energy efficient design spread over an area of 10,000m2. It fully optimizes the daylight conditions for natural ventilation thus saving energy consumption on a largely wider scale in comparison to air conditioned buildings.

In adoption of natural ventilation many factors come into play that may be technical, financial or other psychometric conditions. In technical aspects, initial investment is an important factor as to cut the energy consumption of air conditioned buildings, initial infrastructure is needed. People have general assumption that how NV going to work over air conditioned conditions and has a fear in adopting as they might not investing money in wrong task. Many people are not sound enough to have any of ventilated systems in their houses because of their inability to buy due to financial crises.

Natural ventilation has advantages over air conditioned buildings in terms of reduced running costs because of lower energy consumption, less capital cost, lower transport energy in relation to fans, lower noise pollution which may occur due to air conditioners (Jones, 2003).

1.2 Literature Review

Energy Efficiency

Energy efficiency accounts for the reduction of usage of energy for the given activity in regard to heating, lightening or ventilation systems. The amount of energy consumed is in relation to how good the technology is and how better organized and managed the building is. Basic factor on which energy efficiency depends is the design of the building and its constituents including walls, floors, foundation, doors and the roofs.

The building operation also accounts for the energy being consumed and the material of what building is composed off. In commercial buildings the main energy consumption is generally through heating and cooling systems and by implementing the automatic control or smart control energy consumption can be significantly reduced.

Embedding energy efficient features into old buildings is bit difficult as all the retrofitting will have to be done and it will be cost oriented but in new construction of the buildings it can be easily integrated and helps in attaining energy efficiency (EPRI, 2004). Carbon dioxide (CO2) emissions are also produced from the building sectors but they generally go unnoticed as attention is mainly to the major contributors of pollution such as transportation and industries.

1.3 Steps for case studies

Ysbyty alltwen, porthmadog uk

This is a community hospital which was completed in 2008.

The building is designed according to the topography, ecology and geology to provide the staff and patient with friendly therapeutic environment of high quality. This building is designed around an internal winter space suitable for proposed natural ventilation and heating strategies.

The building incorporates many environmental friendly features like:

Patient area is covered with large areas of glazing so as to provide enough sunlight, natural ventilation and excellent natural views to patients for quick recovery.

In clinical areas a mixed method of ventilation is used which uses natural ventilation and where natural ventilation is not possible, mechanical ventilation is used.

For heating and hot water, a biomass boiler is used.

In the patient area, to fulfill the heating requirements a concrete structure is used which provides thermal mass for heating. For natural ventilation, the winter garden and light wells are used which create a pleasant stack atmosphere.

To maintain and control the environment in the building, a building monitoring system is adopted.

The building roof is designed to collect and retain the rainwater. The site also uses a rainwater attenuation system with a surface lagoon.

The building design is very good and the building has achieved two awards for its perfect and sustainable design. The two awards are the national gold award and the national champion award.

Sunyani hospital, Ghana

This hospital was completed in 2003. This is the urban funded hospital with 240 beds and was designed to provide long term value for money.

The hospital design is such which uses local material and minimize the future maintenance and costs. The site is gently sloping and provides regular cool ventilation and uses a green ventilation design for natural ventilation which restricts air conditioning to operating facilities only. This is achieved and maintained by using the system of open corridor with 'shallow plans' which are separated by large planted courtyards which ensures cross ventilation through adjustable glass blinds.

The hospital designed is just the single storey, except the department of administrative offices. The big roof of the building overhangs and open corridors are built to provide protection from the sun and the rain.

The large land available was put into good use by the hospital and a human scaled building was made on the abundant land.

The building designed is technology modest and engineering facilities have been provided as generic replaceable section for choice maximization.

To attach the different department's twin streets were designed and open space is left for future expansion of the building and streets.

The hospital has achieved great success. The reviews in 2008 were conducted to estimate the effectiveness and efficiency of design approach, low energy building, low maintenance cost on clinical outcomes and satisfaction report from visitors, patients and staff was very good and the hospital has gone from 240 beds to 400 beds and was attending five percent more outpatients and maternity patients as was anticipated. The patients were fully satisfied. The clinical and environmental success of the hospital has lead to high level of retention of staff as this hospital is in rural Africa and has also lead to rapid increase in the number of doctors and nurses.

Gateway sixth form college, Leicester, uk

This college was built in august 2009 and in UK this college is the most sustainable one. The emission rate of the college is 17.3 kg co2/meter square each year which is more than half less than other conventional college buildings. The emission of this college building is estimated to be two third than the other old colleges. This college fits in the status of the city as Britain's first environmental city.

The Uk performance certificate score has been given to the building with 28(b) scores as compared to the other similar buildings with 46 score.

The building is three storeys and is 11,500 meter square and is designed to fulfill the requirements of 1500 students and also has provision for expansion of rooms at the rear.

The three storey building includes units for administration, building and additional accommodation which is assessed through three storey street with also route for primary circulation and route for dining and living room space.

The building was designed by giving top priority to energy creation and conservation and it is designed to exceed present statutory regulations.

Controlling solar energy and maximizing day light - daylight sensors and fittings consuming low energy are used to minimize the use of electric lighting wherever possible. The middle three storey street is shield from the southern side by brise-soleil. On the south side, solar energy controlling glass has been used.

Visible sustainability - it is not commonly seen that building plant is put on a display but in this case it was put on a display to encourage the college students to show interest in environment by using visible sustainability. Therefore, the energy centre is established in front of the building at most prominent public place with big glazed mirrors offering the excellent view of biomass boiler. A big LCD display is located at the main entrance to monitor the working of wind turbine and PV panels which is also linked with the website. All these features and attributes have attracted many students.

Biomass - chips and wood was used as fuel foe the biomass boiler. As wood chips were used initially, the fuel used was carbon neutral and fully sustainable. The biomass boiler attached with gas boiler generated 80% heating energy and fulfilled the demand of hot water for domestic use.

Natural ventilation - the full building was fully ventilated naturally and windows and instruments of the buildings were attached to building management system which controlled temperature that is cooling and heating in the building. Most of the teaching pods off of the main atrium have exposed precast concrete plank ceilings. This help in controlling temperature changes as it was provided with a thermal mass. Windows was linked to building management system which controlled cooling at night time.

Photovoltaic glass and wind turbine - The photovoltaic laminate was used in the main entrance of the building. Solar energy was also enhanced by the combination of arrangement of PV'S along with solar controlled glazing which generated energy. The site elevation was used for the functioning of wind turbine. A large amount of energy for the college was produced by the PV'S and turbine. In spare times, this system continues to generate and provide energy back to national grid by saving costs of energy for the college.

Sustainable drainage - many number of tanks and swales were made for water storage on the site due to poor drainage system and as the soil was clay impermeable soil which absorb little water.

Harvesting of rain water - the rainwater is collected and stored in tanks of 8400 liters which was used for flushing toilets in the teaching unit. Not only this, measures are also made to use rain water for fire brigade whenever necessary.

Suitability of natural ventilation system

Narrow plan buildings or having a floor plate width of 15m.

Open plan layouts with very less external air and noise pollution.

When modeling usual ventilation, take into report supplementary constructions concerning it as they will alter the effectiveness of the wind hitting the constructing to craft the pressure differentials needed. So, the need for NV arises from carefully understanding the conditions of the place and requirement needed (Heiselberg , 2002).

Research questions

From the research field description the question that arises is as: how natural ventilation in air conditioned buildings can attain energy efficiency? As the NV buildings after 20th century has been based on the concept of air flow in and around the buildings and so more specific questions could be formulated.

How the design of the building and natural ventilation are related to each other?

Can natural airflow be used as potential factor in designing a building?

Aims

To figure out what work has been already done in making air conditioned buildings more energy efficient by improvising Natural Ventilation and what else can be added to it further.

To make sure the maximum use of daylight conditions for the lightning in buildings.

To access the energy demand and also considering the combined heat and power with renewable energy of the building

Objectives

To give clear understanding between how change in climate and different buildings situated with respect to places respond to energy demand and balance.

To present the contribution made by the passive (orientation, types of windows) and active (absorption chiller) techniques in effective energy dissipation in buildings.

Examining the quality of air, thermal comfort and minimization of potential dead spots by adopting natural ventilation.

Methods

To evaluate natural ventilation certain parameters like automatic control, smart control and building management systems needs to be understood clearly. The building operations nearly account 40% of all energy consumption in Europe (Allard, 2002).

Automated control system in relation to mechanical and natural ventilation can reduced the CO2 emission to large extent and led to ecofriendly environment. As compared to the traditional HVAC systems which consumes large amount of energy and accounts for carbon dioxide production, adaptive natural systems are inexpensive to install, maintenance cost is low and maintains a sustainable future. Automated programmed windows can be used proportionally to open at their own when a given set of carbon dioxide level is reached in the room.

The manipulation of natural-ventilation arrangements is frequently endowed as a standalone solution. As this can manipulation ventilation in a constructing, there could be conditions whereas it is in fight alongside supplementary HVAC plant - alongside uneconomical results. One example is possessing windows to furnish new air as warming or air conditioning plant is running (Santamoris, 2005).

Such conflicts lead to inefficient and extravagant use of power and can additionally have a negative encounter on the early connection price, as installing a temperature sensor for the warming arrangement and a distinct temperature sensor for the natural-ventilation arrangement is unnecessarily expensive. Making natural-ventilation controls an integral portion of an finished BEMS resolution not merely reduces the early investment price but additionally ensures that all constructing arrangements are working effectually alongside on another.

Also the supply shackle encompassed alongside enumerating and installing a natural-ventilation arrangement can be quite fragmented, alongside disparate design and connection parties involved.

To circumvent such a scenario, possessing a seamless solution from a solitary provider - that additionally takes on the design agent - is most beneficial. This will safeguard the most energy-efficient methods are retained as carrying comfort to users (Rees, 2012).

To technically optimize the use of Natural Ventilation research focuses on tracking three performance criteria (Livermore, 2000);

Energy savings,

Occupant comfort and

Indoor-air quality (IAQ)

The objective is to appropriately test and monitor the building to rate the performance of installed NV under different controlled strategies .experimental framework would be in three phases:-

Testing set up

Data collection

Data analysis

The focus of Phase I is the determination of what NV components and strategies to test, how those tests will be implemented through a testing matrix, and how each control will be developed to track tests developed in the experimental matrix.

Phase II describes a means for collecting data through building sensors, data acquisition software or other sources (i.e., weather stations or occupancy comfort surveys) and organizing them in a database.

After completing tests, Phase III utilizes energy analysis and normalization to determine performance criteria for each strategy and determine the best NV strategy for the building. These strategies will be implemented in an automated control and will be retested for verification.

1. Introduction

For any nation to be socially and economically developing the important parameter is energy. Energy is also vital factor in considering and evaluating outcome of the technical systems on the environment as it is directly related in terms of the emissions to various impacts across the globe environmentally which further includes particulate matter, smog, greenhouse gases and climate change. Construction industry is considered to be the major and vital consumer of energy and other natural resources globally (T.E .Uher, 1999).

The significance of the availability of greenhouse gases and energy consumption is well described during the building operation. But, still having the knowledge for energy being consumed in various manufacturing processes that may be building materials there are other phases like transportation of the building materials, aggregation into buildings and also the extermination of the building is not counted during the energy usage when buildings are determined (J. Adnot, 2004).There is a significant constant rise in Thailand's energy intensity. Its energy consumption in 2001 was accounted 3.06 EJ, which rose six times from 0.53EJ which they used to consume 20 years back. The construction rate of buildings is also increasing in Thailand. There was 35% increase in the constructions of new buildings totaling 268,000 in 2005 as compared to the year 2002 which has added to the high energy intensity of Thailand and also accounted a share of 43% of consumption of electricity annually (EIA, 2008).

To make the energy sector better Thailand government has enacted the Energy Conservation and Promotion Act in 1992 with which the emphasis was laid on mitigating the energy consumption rate under 10% annually from 13% (Chirarattananon etal., 2004).

Efforts were put forward in conservation of energy in assigned industrial and commercial buildings in reference to the building codes which were introduced as a part for this program, but only the operation phase was under focus by these measures and didn't give much consideration to other phases operating on the building accounting for energy savings. So, to reduce the energy consumption by buildings other phases would be given consideration as a future goal for energy efficiency in country. Therefore, energy assessment of the life cycle of building is necessary.

Life cycle analysis (LCA) is a part of ISO 14040 which involves managing environment under specific standards set up for different activities associated with it. It deals with how a process goes through different stages from its origin to its extermination. Here LCEA will be relevant as energy efficiency of the building is assessed and energy is only the vital parameter discussed under. So, a much detailed study of the available energy to buildings can be made. LCEA cannot be compared to the LCA as it is broader in assessing the environment. Despite it, LCEA makes decision easier for energy efficiency outlining the information required for a step by step procedure to reduce consumption of energy from buildings sector.

The buildings sector provides opportunities in an area in urban development for increased energy conservation. Particularly energy use of buildings becomes crucial when referenced towards Thailand's aim for energy security. In Canada, the comparative LCEA of three different structural systems has also been conducted of wood, steel and concrete mixture on three-story building covering around 4620m2 of area. The energy required for operation and demolition of a low energy building in USA and Sweden has also been assessed and in Japan, amount of energy consumed as well as the pollutants emitted due to building construction has also been examined (C. Thormark, 2001). However, in case for Thailand no study exists on the LCEA of office buildings in Thailand. The aim of this dissertation therefore is to demonstrate and discuss the use of LCEA in reference of a typical office building in Thailand.

The objectives of this study are to determine the embodied energy coefficients of materials used in building materials utilized in Thailand; to assess the LCE consumption of a typical office building; to study different life cycle phases and; to provide information which may be effective and can be used as basis for building energy efficiency policies in the country.

2. Research methodology

Various types of commercial buildings exist in Thailand like hotels, hospitals, educational institutes, offices, and department stores so to be aligned with the objective to achieve, a typical commercial building needs to be chosen. Office building stock has the largest share in the electricity consumption in Thailand and accounts for 43% of the total electricity being consumed in the country according to Department of Alternative Energy Development and Efficiency (DEDE). So the office buildings were of much interest as what measures need to take up to reduce the energy cost by lowering the electricity consumption by implementation of any policy or any research results which would be of any benefit in better economic development and energy security in Thailand. The building structure in Thailand is almost similar and has same envelope structure comprising of reinforced concrete and concrete wall system. So the result outcome can be applied to other buildings after analysis in Thailand.

The case study building is located at 14°N latitude in the Bangkok district of Thailand and was eight-story in height. Humidity outside was calculated mean of around 65-70%. The mean temperature variation was from minimum 23 °C-27 °C to maximum 30°C-34 °C. Operating energy required to run the building system is obtained from the national grid. HVAC system is located centrally to cool the building. For the indoor operating conditions set point temperature of 22-24°C was set up and level of humidity inside the building was around 50-60%. Constant supply of fresh air was provided to the occupants of the building by air handling system at rate of 5l/s for the ventilation. The lightning system of the building was full manual. The LCEA of studied building was based on the presumed life of 50 years and materials composing the building structure comprising mainly steel, concrete were taken into consideration. The total gross area of the building was 60,000 m2. The ceiling height of the building was 2.9 m with building's gross volume accounting 9, 12,000 m3. The foundation structure was built from concrete slabs, interior and exterior walls were composed of brick and combination of curtain wall. Flooring was finished with fine ceramic tiles and roof area was flat and made of concrete.

3. Life cycle energy assessment (LCEA) methodology

Two types of methodologies exist for LCA one is based on the process and other is based on the economic input output LCA (EIO-LCA). For the LCA which is process based all the activities are in relation to the all the life cycle operations starting from cradle to grave. Process based analyses are very result oriented and requires huge calculations and data to evaluate and due to this it makes it more wastage of time and cost inefficient. Due to fluctuating design parameters of two buildings the result outcome is not that easy predictable. Therefore, to remove the hassle of LCA process to be used EIO-LCA was created. Only drawback of this method found was incapacity of providing précised results due to aggregation of product in high level but the approach is quite comprehensive.

A different number of issued came up when doing the LCA of an office building due to enormous structure of building, life of the building and different materials embedded inside the building. Additionally, uniqueness of every building leads to less standardization of the production process as compared with most of the goods manufactured. Thus, the whole scenario of buildings complication structure urges the use of other LCA methodology.

With the addition of pros of process and input output based LCA a new hybrid is formulated.

EIO-LCA can give handy knowledge regarding the products which come under IO grade and rest can be taken care by the process based LCA. Thus, for studying this building, a heterogeneous LCA was used. To study and give detailed information regarding the building materials EIO-LCA was used.

3.1 Embodied energy

Data was made available from government databases of Thailand for calculating the building materials embodied energy intensities. The previously described method is used here and it uses contributions made by the energy sectors in relation to the building materials sectors. National average prices of various materials obtained from Thailand government to produce the energy consumed in the output of a single unit was multiplied by the energy intensity from the sectoral sector. Then, by obtaining these values the total initial embodied energy per material was verified after multiplying with values of total material which reached the construction site. Different materials wastage factors were also obtained (MOC, 2012).

Energy required for the construction comes from the electricity in use for running the electric machines, diesel fuel utilized by the heavy equipment's and transportation of the of the material on the site

Activities include site preparation, structural and envelope installation, mechanical, electrical equipment installation, and interior finishing. Process-based LCA was applied for this phase. Data on the construction process of the study building site are site specific. The main building elements which formed part of this building substructure were columns, floors, staircases, roof, walls, windows, and finishes. Items such as fitments, sanitary fixtures, appliances, plumbing, electrical and external items were excluded from the study due to the difficulty associated with obtaining these data. All data relevant to construction machines, energy requirement and equipment used on-site, and transportation distances of construction materials to the construction site were obtained. These were subsequently aggregated with the energy consumption for the transportation of building materials to the construction site from their various points.

3.2 Operational energy

Operating energy of the buildings includes energy used for cooling and air flow, lighting and machines procedure, and water source. Only energy was found in the studied constructing. Process-based LCA was utilized to figure out the building's operating power need. This was calculated by evaluating knowledge on mechanical and electrical devices style and design requirements as well because the anticipated use sample on the making (each day utilization 8h/ 5 day/week). As the building age is less than a year and was new at the time of research, so records for its actual electricity consumption exist for a this period only. The results of energy consumption determined by examining the building were matched with current available records for the electricity. The assessed outcomes showed a great correlation thus verifying the calculations with electrical energy intake data. Life span of the materials of which building is made up was used in calculating the energy required in the maintenance phase and subsequent process was followed in estimating the energy requirement in manufacture.

3.3 Building end

The final stage of a building's life involves demolition. The traditional demolition method normally involves disposing off materials into a landfill site. Electrical power consumption at this stage is mainly resulting from the procedure of demolition equipment. Due to absence of data around the electricity requirement of the demolition procedure in Thailand, secondary details were taken into consideration and applied (UNE, 2003). 51.5 MJ/m2 of energy was used to demolish concrete building obtained in the form of diesel fuel. From the available data it was assumed that 0.846 ton/m2 of waste would be generated from the demolition of the buildings.

As the building under research is located in the central area of Bangkok so transportation distance to the landfill site located 50 km on the periphery of Nonthaburi was assumed. The diesel operated truck using energy around 2.78MJ/ton km was used in transporting the demolition materials. Last but not least the total energy required in demolition phase was summed up by the energy used by the demolition machinery and the energy used by the dump truck in transportation of the materials (Chini, 2003). So, total life cycle energy was calculated by the equation given under:-

LCE=EEi + EErec+ (OE-building lifetime) (J)

Where LCE: life cycle energy;

EEi: initial embodied energy;

EErec: recurrent embodied energy (for future maintenance) and

OE: total annual operational energy.

Table 2.

Embodied energy coefficients of key building materials.

Material

MJ/kg

MJ/kg

Ceramic tile

2.2

2.5

Granite

0.7

Brick

1.86

0.97

Gypsum

3.31

4.4

Aluminum (Virgin extruded)

216.5

191,227

Plywood

8.5

10.4

Cement sand screed

0.2

0.1

Glass

17.1

15.9

Concrete (ready mix 17.5 MPa)

1.3

1.0-1.6

Steel reinforcement

11.1

8.9

Structural steel

22.1

35

Steel wire

13.3

12.5

Bulk cement (dry process)

3.6

5.8

Mortar

1.2 (Fine), 1.4 (LWB)

2

Paint (oil)

81.5

88.5(water), 90.4(general)

95.4 (polypropylene), 98.1 (solvent)

Sand

0.1

0.1

It was determined that the embodied energy coefficients were well in co-relation with other studies on same materials with mere deviations. This deviation for some materials could be associated to number of parameters that embrace technological effectuality and quality of data. As an example, brick producing in Thailand has become ascertained to usually be inefficient and technologically deprived. Therefore, on calculating the embodied energy value of bricks manufactured in New Zealand and the ones used in this study showed a large difference due to the poor efficiency of the kiln techniques deployed in Thailand (Lensink, 2005). Discrepancies within the distinctive methodologies and program boundaries used for the calculations within the analysis are {additionally} additional parts to be cause for these variations.

The LCE associated with the building under study is 2.2 - 106 GJ within next 50 years over total floor area of 60,000m2. LCEA showed Operation phase accounted for around 80% of the total life phases in energy consumption. Significant share of 16% energy consumption was found from the manufacture phase by LCE. All other phases were not of much contribution to buildings LCE profile.

375 TJ was the initial embodied energy of the office building calculated and is also responsible for manufacturing all other materials used in building. The extent of initial embodied energy 6.7 GJ/m2 in relation to the commercial development ranging from (3.4-19 GJ/m2) was uniform (Pullen, 2000). Over a span of 50 years the annual average energy consumption was 0.87 GJ/m2. Over analyzing the buildings operational and embodied energy, towards the end of the building it has been found that only embodied energy accounts for 15% of the energy used in operational phase, which in turns is quite valuable as it equals to requirement of the operational energy for 11 years. Concrete and steel were present in high amounts and steel and concrete shares were 42% and 35% respectively of the IEE. As the building was made of reinforced concrete structure so the amount of steel and concrete materials was high in the building.

From the quantities of the major resources utilized for in building making 80% of the content is concrete followed by steel and bricks as 5.5% and 13% respectively. Nonetheless, for the reason that steel has much higher embodied energy as compared to that of bricks, its share for IEE is greater. Subsequently, concrete supplies (including bricks) and steel shared around 93 and 5.6% respectively in the full product mass from the building assessed.

The average annual energy consumption (AEEC) of 0.85GJ/m2 for the life span of building was aligned with results obtained. In the referenced research, AEEC of commercial buildings ranges from .5 to 1 GJ/m2  in Australia and was found to be 0.77 GJ/m2. A standards or variable normally utilized for evaluating electrical use throughout the buildings' procedure would be the energy index, expressed in KWh/m2/yr and was assessed 238. This was when compared with distinctly located office buildings conclusion was found that it lies in the perimeter for low rise buildings and other denominated buildings by the Thailand government, and also similar to some other Asian countries.

During the analysis of the current energy consumption within the operational phase of the building showed that the air conditioning was highest in energy use of (6796 KWh/m2) followed by office equipment and lighting load of (1996 KWh/m2) and (1887 KWh/m2) respectively. The share of air conditioning system was found to (about 57%) was close enough when compared with office buildings 51% of Thailand building database (DEDE, 2005).

4. Assessment of potential energy saving measures

To cut the energy consumption of the building numbers of standards were formulated first being to raise the set point temperature of air conditioning system. Even though the advisable indoor temperature set point is about 26 °C but many studies revealed that the temperature comfortable for human body is higher in regions of tropics as humans have the ability to get accustomed to diversifying climate and other psychological variations. In regard to people of Thailand many studies have shown that people in Thailand can live at a temperature higher than the people from west comfortably. Therefore, from the satisfaction level of workers, the set point of air conditioned systems can be 28 °C for the one working in these conditions and can be 31 °C in buildings where workers are working natural ventilated conditions.

Implementing the final results of the locating as an underlying assumption, the influence of an increase in the set-point temperature was examined in the air conditioned system. On further analysis it showed that by increasing the temperature by 1 °C in the system a minimum of 7% reduction will be shown in the mean energy consumption. This result proved to be in accordance with result formulated by (Yamtripat et al, 2005). So by changing the set point from 24 to 26°C, 1.14 - 106 kWh/yr of electricity would be saved and this in turns is equal to its annual operational energy by seven percent on application of this assumption in whole of Thailand

The strategy supplied the chance of deciding the potential once-a-year energy personal savings for Thailand place of work developing stock depending on its electrical power consumption 12,349.87 GWh/yr (DEDE, 2004). Applying the belief which the indoor set-point temperature is enhanced by two °C by Thailand's overall workplace constructing inventory, an analogous calculation showed that 978 - 106 kWh/yr of electrical energy may very well be achieved to the region.

Yet another reasonably basic no-cost possibility assessed with a fact of turning off the electrical load and lightning for about one hour during the lunch break in effect to save energy and is also predicted that air conditioned ventilation would also not be under operation within this time. By doing so there would be no effect on the thermal comfort and the performing activities of the occupants. Switching off the building system for this period of time has been experimented in office buildings in Thailand with the permission considering occupants comfort level and has proved vital in mitigating the consumption of energy (Chirarattananon, 1998).

Despite the fact that same objective can be achieved by other available choices like better efficacy and occupancy sensors, it should be mentioned as aim of this evaluation is to find out the degree of mitigation of the energy that can be achieved. Further it was assumed that if for one hour the air conditioned and other equipment's running in the office are turned off during the whole year 12.54% of annual energy of the building accounting 1.8 - 106 kWh/yr would be saved and if this could be projected for all the office buildings in Thailand the energy consumption will be reduced by 1.1 - 104 GWh/yr.

Major share of the electricity consumption in the building is basically the air conditioned systems and HVAC system running centrally chiller water system and which can be replaced with high efficacy and lesser capacities of chillers. The detailed option for chiller to be replaced is down below:-

Technical data for chiller scenario.

Water-cooled centrifugal compressor (>300 ton)

Capacity (kW/ton) base case

Capacity (kW/ton) replacement option

Chiller 1

0.65

0.45

Chiller 2

0.64

0.45

Chiller 3

0.63

0.45

Chiller 4

1.32

0.45

Chiller 5

1.32

0.45

An assessment on the electricity use with the constructing using the substitute options for the chillers was carried out plus the effects obtained in contrast with that of the base situation. The end result indicated that by utilizing the substitution choice of chillers rather than the base configuration, a 17% decrease in operational energy might be achieved and this also saves tremendous amount of energy. Thus efficient energy equipment in making of office buildings should be given consideration.

Windows can significantly absorb and transmit sunlight which in turns increases the cooling buildings cooling load. So, to reduce the energy and solar consumption enhancing windows performance was also considered in buildings. The ratio of window to wall in the building studied was 0.5. As larger window area is used as a sale objective in majority of Thailand the window wall ratio lies within the range of 0.3-0.5 for buildings used as offices. So it was calculated if in given building wall window ratio is changed to 0.45 and 0.35 there would be a decrease in operational energy by 2% and 6.24% respectively.

Glazing and deciding appropriate selection of the size of windows used in the buildings can help in reducing the heat transmission still maintaining adequate entry of light and views within the building. So, based on this selection of window size and glazing materials in use different material was used in place of the base material and result was evaluated.

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Specification

Base case

Option A

Option B

Thickness

6 mm

6 mm

External pane 6 mm

Shading coefficient

0.29

0.26

0.26 (total)

U value (W/m2 K)

5.24

4.6

1.1 (argon filled)

SHGC = SC - 0.87

0.253

0.226

0.226

Visible light reflectance (%)

16

8

14

Visible light transmittance (%)

9

41

30

Solar energy transmittance (%)

6

33

15

Solar energy reflectance (%)

12

7

11

Source

Bill of materials

A

B

Base case = Heat Strengthened Blue Reflective glass SS514; Option A = Heat Strengthened Gray Reflective glass SS514; Option B = High performance Blue double glazed unit with 16 mm argon filled cavity, 6 mm clear inner glass.

The outcome advise that by using solution A as an alternative to the base, holding the ratio of window-wall (WWR) at 0.5, a reduce of about 0.6% while in the building's operating electricity need could possibly be accomplished. While using the exact WWR, option B performed well by lowering 3.7% of the operational energy of the office building in comparison to current situation

Recycling recovered making elements with the conclude of daily life of the developing is undoubtedly an spot the place attainable reductions can be received while in the LCE profile of building's via a reduction during the original embodied electrical power needed for production making components. Recycling is used below given that the general idea for reuse and materials recycling. The prospective positive aspects of recycling are saving of all-natural uncooked components and vitality at the same time as lowering of landfill room.

Recycling the materials recouped at the time of demolition of the building is an aspect where buildings LCE profile can be reduced by reducing the embodied energy required in the initial phase of manufacturing materials for the building. Reprocessing is utilized here as the finished believed for reuse and physical recycling. The possible benefits of reprocessing are saving of raw materials occurring naturally, energy and also reducing area under landfill. Though, the degree of asset varies reliant on physical kind and form of reprocessing. A possibility can't be denied to reduce embodied energy of the building by reprocessing the materials recovered at the buildings end life.

Energy saved was calculated on the basis of the previous methodology delineated and final result obtained showed reprocessed materials over the life span of the building reduces initial embodied energy up to 9% and 1.49% over the life cycle of the building.

At the end life of building it is usually taken down and results in the large chunks of bricks and other concrete materials which leads to formation rubble and which is generally disposed of to open sites in Thailand and are not recycled, which in turns have the ability to be recycled. But, in recent times due to advancing technology and science much attention is given to recycling of rubble. Data from the European countries suggest that what which was considered to be waste because of inherent value is now been considered to be importance as rubble obtained from the demolished building can be used as a substitute in place for virgin aggregate in using as road base, pavement ingredient which will save energy spent in manufacturing concrete from it. Also the energy wasted in mining and processing to make concrete would be saved.

To give clear scenario of what potential does recycled rubble have by substituting virgin aggregate the contents of waste obtained from the demolition of building were utilized and proportions of different materials in the waste was measured by using an equation below:-

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Qx=A-Gav-Px=Qp-Px (J)

where Qx: quantity of demolition waste material x in tons;

 A: gross area of building in m2; 

Qp: project demolition waste generated in tons;

 Gav: average waste generation rate (18.99 kg/m2 for new non-residential buildings);

 Px: average composition of waste material x in %.

The following assumptions were made based on information obtained, (a) process energy for the production of one ton of virgin aggregate = 51.3 MJ/ton; (b) process energy for the production of 1 ton of recycled aggregate = 37.1 MJ/ton.

4.1 Analysis of energy saving strategies

In terms of mitigating the operational energy of the building an evaluation of certain measures were undertaken and were applied and the most reliable and efficient method was having an effective HVAC system. Second was the stopping electricity supply periodically and third was the WWR reduction enhancing energy saving for about 2%. As artful value of the building with bigger window size is liked in Thailand so small WWR would not be of much acceptance, the next best method of saving energy by 3.69% would be use of lower solar heat gain coefficients with higher performance of the double glazed unit.

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The end results obtained when put together and also considering the fact the potential of recycled materials in reducing the initial embodied energy of the building a total of about 45-50% of the energy can be saved. If the office buildings in Thailand would operate under the conditions formulated above a large amount of total energy can be reduced up to 3.1- 103 GWh/yr equivalent to 28% could be achieved.

.

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Introduction

Based on the LCA of the air conditioned building above similar building of the same dimension was studied for calculating energy efficiency of the natural ventilation of the building as baseline. Some changes were made to face the challenges rising in measuring the natural ventilation. The overall arrangements and structures of the natural ventilated building were same as of the commercial building and much of the concern was given to the energy, airflow and temperature.

Office building is located at distance of 300 meters from the mechanical ventilated building studied above in Bangkok. The building is well spaced, with nearly 25- 35 meters between buildings. The area basically falls in the tropical region of the earth. The variation in temperature was from 22 -31°C at the time of study. The building has an area around 2650 m2 approximately and is three stories in height and is surrounded by the buildings operating under mechanical ventilated conditions.

Building has open space on all the 3 floors starting with first floor on the south side, second floor had both south and north facing open spaces and last floor with north side open. The first floor is closed from all sides of the building and is generally used as conference hall towards the north side. As sometimes due to increase in temperature this floor has the ability to be cooled mechanically but this is done generally on weekly basis and for few hours. The office area opens in main entrance along east to west direction of the building.

The buildings construction description is given below in the table:-

Construction

Materials

Thickness, mm

Glazing

Argon filled double tinted glass pane

29

North roof

Vapor membrane and roofing board

82

South roof

Fiber insulation

155

Insulated panels

Aluminum panels

214

Brick Façade

Fill insulation and cavity wall

410

Table: Construction material Description (DEDE, 2005)

Orientation and U-value of the buildings are given below the table:

Orientation

Façade type

Area m2

U-value W/m2 K

North

Brick façade

80

0.46

Glazing

230

2.2

South

Insulated panels

84

0.46

Glazing

228

2.2

East

Brick façade

264

0.46

Glazing

110

2.2

West

Brick façade

262

0.46

Glazing

102

2.2

Table: Area and U-value of building (DEDE, 2005)

The ventilation operated in the building was buoyancy-wind driven and also the fan assisted ventilation stacks were in effect. At each floor of the building, on north and south facades there were six sets of two occupant monitored windows, a larger window containing the smaller window. Venetian blinds were included in the design of the building to reduce the glare from suns which were manually operated depending upon the requirement of the occupant to permit daylight entry to building. As these blinds were placed to cover the upper windows they hinder the amount of air entering or leaving the building when they are all the way down.

A series of windows shutter commonly termed as louvers were used in series by stack outlet and are also manually controlled. The louvers are opened if the fans are operating. The building is occupied by the occupants on each level and there are approximately 26 people on each floor. Energy efficient lamps are located in the building. By analyzing the energy being consumed and other equipment's use habitation of the building can be figured out. The detailed data was collected from every floor of the building in evaluating the energy consumption of the building.

Window Airflow Rates

Awning type windows were pivoted to the top and would by friction pull of hinge intact. A method for determining the airflow rate was developed as the foundation for natural ventilation is the air drawn from outside atmosphere to provide comfort level and fresh breeze as movement and speed of wind is highly uncertain. To measure the exact amount of wind entering the building a device was made not only to make design of window understood easily but also to maintain balance in the airflow rate. To have an effective area for windows, a rectangular window passage was installed instead of the geometry of awning window which was more complex to understand.

Following data was calculated for the wind speed and effectiveness of opening of window was measured.

Time (sec)

Velocity of air (m/s)

Air volume (m3)

Volume flow (m3/s)

Effective opening (m2)

Effectiveness of window (%)

9

0.476

1.6

0.183

0.366

31

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