London Metropolitan University MSc Integration of Renewable Energies in Buildings
Potential of Achieving Comfort Conditions in a Typical Housing Project in the Composite Climate of North India using Passive and Low Energy Ideas MODULE CODE ADP034N
A thesis submitted in partial fulfilment for requirement for the degree of Master of Science.
Hitanshu Jishtu 07031328 September 2008
ABSTRACT Chapter 1
Contents
4
1.0
INTRODUCTION
1.1
A INTRODUCTION OF THE CONTEMPORARY HOUSING IN DELHI, THE CHOSEN SITE.
1.11
Traditional Housing
Chapter 2 2.1
6 8
PROJECT BRIEF- TIVOLI
Introduction of the Project Tivoli
2.2 Site
11 12
13
2.3 Site planning 13 2.4
Typology of Units
14
2.5
Climatic Comfort
16
Chapter 3 3.1
Climate Analysis 17
Composite Climate
3.3 SEASONS
18
19
3.31 SUMMER SEASON
20
3.32
MONSOON SEASON 20
3.33
WINTER SEASON
3.34
MILD SEASON 22
3.4
Prevailing Winds
22 23
3.5 Solar Altitudes 24 3.6
WEATHER DATA
3.7
THERMAL COMFORT 26
3.71
THERMAL COMFORT STUDIES
3.72
ADAPTIVE COMFORT 27
3.73
ADAPTIVE COMFORT RANGE INDIAN CODES (NBC) 28
3.8
GENERAL ENVIRONMENTAL STRATEGIES 29
3rd of June (Summer Season) 30
6Th of August (Monsoon season)
31
7Th of January (Winter Season)
32
Chapter 4
Analysis
25 26
33
4.1
Methodology 34
4.2
EFFECT OF CLIMATE ON DESIGN
4.21
ORIENTATION 36
4.22
EFFECT OF SOLAR RADIATION
4.23
DAYLIGHTING ANALYSIS
4.24
EFFECT OF WIND
4.25
EFFECT OF TEMPERATURE 42
4.3
TAS Dynamic thermal modelling TAS 42
4.31
ANNUAL SPACE TERMPERATURE DISTRIBUTION
4.32
TEMPERATURE PROFILE N-FLAT
45
4.33
ANNUAL TEMPERATURE PROFILE
47
36 37
39
41
44
8
Chapter 5
PASSIVE DESIGN RECOMENDATIONS
5.2
THE BUILDING ENVELOPE
50
5.1
Climatic design for Composite Climates
5.3
IMPACT OF CHANGE IN THERMAL MASS LAYERS 52
5.4 STRATEGIES FOR VARIOUS SEASONS 5.41 SUMMER SEASON
50 58
58
5.42
Winter Season 59
5.43
MONSOON SEASON 60
5.44
MILD SEASON 60
Chapter 6 aNALYSIS OF RECOMMENDATIONS
61
6.1
Comparison of Base case Annual energy demand with proposed recommendations
6.11
Comparing the temperature and cooling loads against base case in North Flat
63
6.12
Comparing the temperature and cooling loads against base case in South Flat
64
6.13
Effect of mixed mode ventialtion on Cooling load
6.12
Annual Space Temperature Disribution.
CONCLUSIONS
69
BIBLIOGRAPHY
70
66
65
62
ABSTRACT North India has extremities of climate. A composite climate where the summers tend to be hot with temperatures reaching up to 45deg C and in winters dropping down to 0deg C. It is a challenge designing for comfort within these parameters as the systems need to be flexible to change course in dealing with the climate. The traditional houses in these climates had through all the years been adapted to offered the flexibility in being suited to the climate. Today’s mass produced housing schemes rely heavily on mechanical means for creating comfortable thermal conditions and are more in tuned for the ease of construction, convenience, profitibility and housing density figures. Climatic comfort as such is as an afterthought to be consigned to mechanical means. Given the high costs and unavailability of energy air-conditioning or heating system is a burden in most of the houses without which the spaces tend to be uncomfortable for a large part of the year. The thesis attempts to suggest strategies by simulating a typical real world housing project in the National Capital Region of Delhi to put it within the comfort zone by using passive systems and low energy consumption technologies which are viable in the situation there. Simulation tools today offer the possibilities to render the conditions and to fine-tune the design to suit the conditions. Right from selecting the right orientation to the area of glazing and shadings can have a great effect on the indoor climate and the strategies can be successfully refined by these simulation tools. This thesis exploits the possibilities offered by the simulation tools of Radiance, Ecotect, TAS and Esp-r to arrive at the conclusions for the suggestions. The existing design prototypes as mentioned are postulated to be out of the comfort band for a large part of the year. The objective ways to find a prototype housing project and study if it meets the parameters of comfort conditions using the adaptive thermal comfort indices. The intent was to find the period it is out of the comfort zone and to suggest solutions using firstly passive design strategies and where unsuitable to reduce the heating or cooling load as appropriate. By incorporating the design interventions it is proved that the buildings can be within the comfort zone for a longer duration of time with passive solutions like orientation, appropriate sunshades and insulation in the building fabric. Where it is not feasible to get the building within the comfort zone entirely the aim is to reduces the heating and cooling load saving energy as compared to the conventional design.
Chapter 1 INTRODUCTION
1.0
INTRODUCTION
The relation between the building and its surroundings is an important criteria which defines the design and the positioning of the building. The thesis will attempt to explore ways to make the contemporary housing design in the composite climate of North India more energy efficient and comfortable to inhabit using passive design strategies to a large extent. At the same time explore ways to reduce the heating and cooling load of a typical model of housing project being built today in that particular mentioned climate. The guidelines to be determined for the energy efficient design include: 1) The impact of solar gains on the heating and cooling load of a building 2) The impact of passive design strategies like shading devices and orientation on the heating and cooling loads. 3) The impact of the insulation and glazing ratio on the heat gain/ loss in the building. 4) The optimisation of the daylight levels in the interiors. The current standards for the energy efficiency in Indian buildings is defined by the Energy Conservation Building Code (ECBC)- 2007. This code specifies the guidelines to be followed to make the buildings energy efficient in the climatic zones of India by specifying the energy conservation measures which should be incorporated to achieve the standard. The thesis will adhere to them and where possible exceed the set standard by taking up a case of a typical housing project in the composite climate of Delhi. The thesis will rely on building simulation tools to explore the hypothesis and verify the strategies to be adopted based on the study of the existing housing design. In the first part a typical housing design is chosen as a prototype. This existing design is modelled and simulated using computer software’s for - - - -
thermal analysis, daylight and sunlight shading Facade performance and optimisation Building aerodynamics and ventilation
The data derived is analysed to formulate methods for energy efficient design by reducing the heating and cooling loads and passive design. A detailed study of the climate is also undertaken with which derivation is got as to the strategies to be adopted to deal with it and use it in a positive manner in the incorporation of the design. Introduction
From the analysis of the data from the simulation and the outcome of the climatic study the suggestions are incorporated in the existing design and verified by the computer simulation for their effectiveness. The study is done as a prototypical study for the housing design and although it is site specific and also relies on the particular chosen design, it can considered as a study of climate specific design for housing in composite climates as it emphasises on basic strategies to be followed in achieving the comfort parameters and energy efficiency targets for buildings.
Introduction
1.1 A INTRODUCTION OF THE CONTEMPORARY HOUSING IN DELHI, THE CHOSEN SITE LOCATION. The contemporary housing is a far contrast from the traditional housing in India. The progressing economic situation has changed the dynamics of housing and the more demanding people have become. Gone are the small low rise individual houses and the new trend is are housing estates being put forward by developers which have all amenities within the estate. The houses have all modern functional requirements with regard to modern lifestyles and rely on mechanical means to cool and heat the interiors.
1.11 Traditional Housing The traditional houses of the region had been adapted to be functional in the climatic and site specific context. The house planning followed the courtyard type of houses which ensured the house was shaded and in sun at the same time throughout the day. This made the space multi functional throughout the year as the same space could be used according to the season. The shaded spaces in the summers and the sun lit spaces in the winter. The design was most appropriate for the climate and most low rise houses in the older towns and cities follow this pattern.
fig. 1 courtyard house in Delhi: Source : author
They had specific characteristics like thick stone walls and roof which provided a thermal mass to balance the temperature and the insulate from the outside vagaries of the temperature. The climatic aspects of this house design have been well documented and studied and were appropriate for the lifestyle of the people in those times.
Introduction
The forts of the region are a classic example of the way the climate was overpowered to make the conditions comfortable to inhabit. The kings and the other noblemen would live in the forts which were usually a series of courts which had connected rooms. These courtyards had landscaped gardens and water pools which effectively altered the micro climate to make it comfortable.
Fig. 2: Courtyards in Palaces: 2a. Oberoi Palace Hotel, Udaipur. 2.b. Oberoi Jai Mahal, Agra www.oberiohotels.com
Changing lifestyles which have followed the globalised world have changed the pattern of housing as well. The courtyard houses have now been replaced down the years with multi-storeyed houses. As the pressures on the land have increased the land prices getting way beyond reach the obvious answer has been to go higher up and towering housing blocks are now becoming more and more common. With most developers trying to economise they seem to be the way forward now. The growing metropolis has altered the surroundings and encompassed them within. Today Delhi itself is a city with a population of over 15 million inhabitants (2001 Census data, Survey of India). The trend which had started from the major metropolis in India has started to trickle down to the small towns as well which have felt the pressures on the scarce land and it has become difficult to see any regional features in the architecture of different places. The same block design, material palette and design feature gets replicated everywhere. The comfort conditions to be provided gets relied on air-conditioning which helps to moderate the climate within the interiors.
Introduction
The reliance on mechanical systems for climate control has inevitably been putting a huge pressure on the energy demand situation and it is in this context the government introduced the ECBC-2006 code which has the guidelines for energy consumption to be specified for particular building types. This forces a rethink on the current thinking which delinks the environmental design and performance from the buildings and makes it imperative to use technologies to utilise passive climate control systems and renewable systems to make the buildings comfortable to inhabit.
figure 3. Typical housing estate in Delhi: source:
Introduction
10
Chapter 2 PROJECT BRIEF- TIVOLI
Chapter Overview
In the context of this thesis study a typical example of contemporary housing project has been selected for analysis and to see how it could be adapted to utilise passive systems to achieve comfort conditions and to reduce the heating and cooling loads. The Tivoli Holiday village at Daruhera is within the National Capital Region of Delhi has been chosen for this purpose. The detail of this project is described in this chapter.
2.1
Introduction of the Project Tivoli
The city of Delhi encompasses the surrounding areas and a vast area known as the National Capital Region (NCR) is what comprises of the extended city. Daruhera is one of the up coming regions of Delhi which till a few years ago was on the absolute outskirts of the place but is now seeing a lot of development as the city expands outwards. A number of developers have proposed projects there and the ‘Tivoli Holiday Village is being undertaken by T.G. Buildwell Pvt. Limited.
Fig. 5: Artists representation of Tivoli Holiday Village at Daruhera. ACPL Consutants, Delhi
Project Brief_Tivoli
The project proposes 1-3 bedroom apartments and some villas on the site. The whole project is a self contained township and includes a health club and business centre incorporated within the estate. The housing is arranged in 5 towers with each having a different cluster layout.
12
2.2 Site The site is located at Daruhera, in the satellite town of Gurgaon. The area has been developed by dividing the land into different sectors and each being developed by a different development company. The distance from the international airport is almost 20 Kms and to the centre of Delhi is almost 50 Kms.
figure 6: Site Location ACPL Consutants, Delhi
Figure 7: Site Plan ACPL Consutants, Delhi
2.3 Site planning The zoning has been done by keeping the residential blocks in the back and the club house and the business centre as the focus. The residential blocks are oriented on a manner to create a parkland in the centre. The whole campus has underground parking as well as parking under each of the tower blocks on the ground floor. The whole structure is thus raised up on stilts.
Project Brief_Tivoli
13
2.4
Typology of Units
The residential units are arranged in 14 storeyerd tower blocks with each block having a different arrangement of housing cluster combination. The residential units comprise of studio flats and 1-3 bedroom units with the top floor having a duplex pent houses on each block.
figure 8: Cluster plan 2 bedroom apartment
figure 9: Cluster plan single bedroom apartment
Project Brief_Tivoli
14
Figure 10: artistic impression of Tivoli Holiday Village ACPL Consultants, Delhi
Figure 11: Cluster plan Studio apartment
Project Brief_Tivoli
15
Figure 12: cluster Plan 2 Bedroom Apartment
2.5
Climatic Comfort
The housing project is a high spec one and relies on air-conditioning for the living areas to create comfort conditions. Split AC units in each of the living areas and bedrooms linked to the outside units are proposed to provide comfort cooling. For ventilation the air infiltration through the windows is supposed to provide for the necessary required air changes. No separate heating system is proposed and the same air conditioning units can be used in the reverse cycle to provide for the heating in the winter season.
Project Brief_Tivoli
16
Chapter 3 Climate Analysis
Chapter Overview The climate of the site was analysed to determine the strategies which could be adopted for passive climatic design. The chapter details out the climatic analysis and the outcomes for determining these strategies. To see how the housing project interacts with the surrounding and the spaces between the buildings can interact will form the character of the project. Optimising the landscape and the architecture to harmonise the passive design of the building keeping in consideration the sunlight, daylight and wind factor is essential to study the climate of the place.
India has different climate zones and it ranges from the cold climate of north to the hot and humid of south India. In between is the composite climate which has the huge seasonal variation to be easily categorised into any one part.
Figure 13: Climatic Zones of India: ECBC-2006.
3.1
Composite Climate
The composite climate is characterised by extremities of climate. There is no clear defined climate like hot or cold which is prevalent through the year. Rather the conditions vary to quite the extremities, being hot in summers and cold in winters.
Designing for climatic comfort using passive technologies thus becomes a challenge because both heating and cooling needs are required to be met. Doing this with passive systems is at the same time more challenging. For the purpose of evaluation of the climate to come up with strategies to define comfort conditions the weather data has been obtained from the ISHRAE (Indian Society for Refrigeration and Air-conditioning engineers).
Climate Analysis
18
3.2
DELHI 28ĚŠN, 78ĚŠE
Delhi enjoys a composite climate and has a hot summers and cold winters. The famed Indian summer when it becomes unbearably hot lasts from April to June and is unbearably hot. The rainfall occurs in the months of July- September and it is consistent in these months with the sky overcast. After a transition month the weather again changes to be the opposite of summer with cold nights through to March.
figure 14: Location map Delhi www.
3.3 SEASONS The climate of Delhi can be divided into 4 distinct zones based on the weather profile:
Winter
Mild
Summer Hot & Dry
Summer (Monsoon) Hot & Humid
Mild
Winter
figure 15: weather profile of Delhi: generated using ecotect wether tool
Climate Analysis
19
3.31 SUMMER SEASON • •
• figure 16: weather profile June 3: generated using ecotect weather tool
• • • •
Lasts from April to the end to June This season is characterised with a hot and dry weather. The day time temperature stays in the high 30’s degree Celsius mark and very often above 40̊ C . The maximum temperature does reach upto 45˚ C during some of the hottest days. The night time temperature generally is within the comfort zone or just a little above it. The mean outdoor temperature for the season is 7˚ C above the comfort level. A hot and dry wind from the Thar desert flows during the day time which is known as ‘loo’. The percentage of direct radiation is very high in the season and has up to 10 hours of sunshine.
3.32 MONSOON SEASON •
• •
Climate Analysis
This season starts with the onset of the rains in the beginning of July. The rain brings relief to the high temperature but brings along the high humidity level. The temperature during the day hovers around the 30-35˚C mark and drops to a min. of around 25˚C during the night times. The low diurnal range of temperature is attributed to the high cloud cover which is there in the season.
20
Prevailing Winds
W in d Fre q u e n c y (H rs )
L o c a tio n : N E W D E L H I , I N D (2 8 .6 ° , 7 7 .2 ° ) D a te : 1 st Ju ly - 3 1 st Ju ly T ime : 0 0 :0 0 - 2 4 :0 0 ©
3 4 5 °
N O R T H
5 0 k m/ h
h rs
1 5 °
56+ 3 3 0 °
3 0 °
W e a th e r T o o l
50 44
4 0 k m/ h 3 1 5 °
39
4 5 °
33 28
3 0 k m/ h 3 0 0 °
22
6 0 °
16 11
2 0 k m/ h
<5 2 8 5 °
7 5 °
1 0 k m/ h
figure 17: weather profile August 15: generated using ecotect weather tool
W E S T
E A S T
2 5 5 °
1 0 5 °
2 4 0 °
1 2 0 °
2 2 5 °
figure 18: wind rose diag, July generated using Ecotect Weather tool
2 1 0 °
1 5 0 ° 1 9 5 °
• • •
Climate Analysis
1 3 5 °
S O U T H
1 6 5 °
The percentage of direct radiation is very low compared to the summer season with the sky remaining cloudy through the season. The main characteristic is the very high humidity which remains generally above 80% throughout the season. Higher wind speed though does bring in some relief and is generally considered comforting.
21
3.33 WINTER SEASON • • figure 18: weather profile Dec 22: generated using ecotect weather tool
The winter season is characterised with low night time temperature which falls down up to 4˚C. Generally the temperature in the nights is way below the comfort zone. However in the day time does manage to reach just up to the lower level of the comfort band.
3.34 MILD SEASON •
• figure 19: weather profile Oct 11: generated using ecotect weather tool
Climate Analysis
The 2 transition months of March and October are the only times when the temperatures are throughout the time within the extended comfort band. The temperatures are moderated both during the day and night times and the humidity level is also at a very acceptable level throughout.
22
3.4
Prevailing Winds
Fig 21: Wind Wose patterns of Delhi generated using Ecotect Weather tool
Climate Analysis
23
3.5 Solar Altitudes
fig 23:
fig 24:
Climate Analysis
24
3.6
WEATHER DATA
The weather data for Delhi used in the simulations and for analysis has been sourced from the International Weather for Energy Calculation (IWEC). The summary of the weather data has been included in appendix XX The IWEC data is the result of ASHRAE Research Project 1015 by Numerical Logics and Bodycote Materials Testing Canada for ASHRAE Technical Committee 4.2 Weather Information. The IWEC data files are â&#x20AC;&#x2DC;typicalâ&#x20AC;&#x2122; weather files suitable for use with building energy simulation programs for 227 locations outside the USA and Canada.
Site Plan of Tivoli Hodiay Village at Daruhera: Architect: ACPL Consultants , New Delhi
fig 25:
The files are derived from up to 18 years of DATSAV3 hourly weather data originally archived at the U. S. National Climatic Data Center. The weather data is supplemented by solar radiation estimated on an hourly basis from earth-sun geometry and hourly weather elements, particularly cloud amount information.
Climate Analysis
25
3.7
THERMAL COMFORT
According to Givoni ‘Thermal comfort can be defined operationally as the range of climatic conditions considered comfortable and acceptable inside building’. Thermal comfort depends on a number of factors. The dry bulb temperature, humidity, wind speed are some of the factors which define the comfort parameters. It however varies according to the place from the work being performed, requirement of people and location. Thermal comfort is in terms of sensations of the body how it perceives the sensations of hot, warm, slightly warmer, slightly cooler, cool or cold. It has a more relevant psychological perspective where the thermal comfort is the equilibrium between the heat exchange between the environment and the body. Changing the weather conditions to make them suitable for human inhabitation has been one of the foremost needs for building. The traditional buildings of any place usually reflect the way they modify the parameters of weather inside even though the outside weather conditions are inhospitable. The desert houses of Jaisalmer in India evolved to keep the interiors comfortable even when the outside temperature goes above 45 ˚C,( Sofaee, F, 2004). The same effect is seen through the world wherever people live in difficult climates, the buildings they inhabit modify the climate to make the conditions for achieving thermal comfort. The seasonal variation in thermal conditions changes everywhere on the planet and it is obvious that the houses try to balance and moderate this effect.
3.71 THERMAL COMFORT STUDIES Some of the earliest studies in thermal comfort have been done by ASHARAE since the 1920’s. At that time it focused on finding the most comfortable temperature at which the human body feels comfortable. These were later modified to include other parameters of humidity, and wind effect. The significant studies are the Comfort charts (ASHRAE 1967, 1981b, 1985, 1992, 1997). Other significant research was conducted by Fanger who proposed the Predicted Mean Vote (Fanger, 1972). Later these were modified and improved upon by Givoni with the Bio-Climatic Chart (Givoni, 1976)
Climate Analysis
26
3.72 ADAPTIVE COMFORT The way the human body perceives the comfort in a particular climate is not depended only on the parameters of air temperature, humidity and wind speed at the particular space. We perceive the comfort in terms of the external weather factors as well, this is the theory of adaptive comfort’. The theory was put forward in the 1970’s by Nicol and Humphreys. The adaptive model understands that the human responses vary with context and to preserve comfort people adapt to their surrounding conditions. The field studies led to the adaptive modelling approach (Humphreys & Nicol,1998) which aimed at testing an existing comfort index and finding an optimum comfort zone. Humphrey’s and Auliciems (Auliciems and Szokolay 1997) expressed the comfort zone in terms of the notion of thermal neutrality. Auliciems derived the following expression for free-running buildings: Tn = 17.6 + 0.31 To Where, Tn, neutral temperature deg.C To, mean monthly outdoor air temperature deg.C A comfort zone can be then defined with the value of Tn at its center extended by 2K on either side thus giving a lower limit equal of Tn-2 and upper limit of Tn+2. The neutral comfort zone given by Auliciems’ equation is 19-30 deg.C, which suggests that adaptive measures that will be taken by people will make this range of temperatures acceptable for the city of Delhi. Jan Feb Mar April May June July August September October November December
Climate Analysis
ta 13.1 16.7 21.4 28.4 32.4 33.2 30.3 29.7 29.2 25.0 19.4 14.6
tn 21.7 22.8 24.2 26.4 27.6 27.9 27.0 26.8 26.7 25.4 23.6 22.1
tn-2 19.7 20.8 22.2 24.4 25.6 25.9 25.0 24.8 24.7 23.4 21.6 20.1
tn+2 23.7 24.8 26.2 28.4 29.6 29.9 29.0 28.8 28.7 27.4 25.6 24.1
27
3.73 ADAPTIVE COMFORT RANGE ACCORDING TO INDIAN CODES (NBC) The Indian National Building codes (NBC) define the comfort parameters according to the prevalent weather conditions there. They have been formulated after extensive testing to ascertain the temperature, humidity and wind speed combination in which a person can feel comfortable and productive. According to them a person can be comfortable in a temperature of upto 35Ë&#x161;C provided sufficient wind speed is there and the humidity level is low enough.
Climate Analysis
28
3.8
GENERAL ENVIRONMENTAL STRATEGIES
To formulate strategies for the climate different typical days are analysed which can give an overview of the methodology to follow. From the 3 distinct seasons Summer, Monsoon and winter which have been defined for the climate one typical day is selected and analysed.
fig 26:
fig 27
Climate Analysis
29
3rd of June (Summer Season) The summer season as mentioned before is characterised with high ambient temperature which is above the comfort zone most of the time. â&#x20AC;˘
â&#x20AC;˘ â&#x20AC;˘
The ambient temperature is above the comfort band for all the hours in the day and suitable strategies need to be incorporated to cool the place. High insulation from the outside climate would be required to maintain comfortable conditions indoors. The Relative humidity is very low during the day time and it mite be a good idea to incorporate a system of evaporative cooling. The direct solar radiation is very high and requires appropriate shading at least on the glazed portions. It would also be wise to reduce the glazing ratio on the facades receiving direct solar radiation. At the same time this direct solar radiation could be suggested for passive solar applications.
fig 28
Climate Analysis
30
6Th of August (Monsoon season) The monsoon season is characterised by the high humidity levels although the temperature levels are much moderate in comparison to the summer season. â&#x20AC;˘ â&#x20AC;˘
The humidity levels are extremely high and require a ventilation strategy to be adopted. The temperature is fairly constant and remains just above the comfort band, which suggests the utilisation of alternative cooling technologies to be adopted.
fig 29
Climate Analysis
31
7Th of January (Winter Season) The winter season is characterised by low temperature in the night time but high level of solar radiation is also there because of generally clear skies. â&#x20AC;˘ â&#x20AC;˘
The high solar radiation could be adopted to heat the building during the daytime by using it for solar gains High thermal mass could be utilised to stabilise the temperature
fig 30
Climate Analysis
32
Chapter 4 Analysis
Chapter Overview The chosen site is simulated using the simulation tools and the results analysed to arrive at the possible areas for intervention to make the spaces comfortable to inhabit.
4.1
Methodology
The relationship between the building physics and building behaviour is the link which determines the building performance. The building behaviour depends on the natural forces which couple the weather and surrounding conditions to react with the building fabric and mass. the natural forces like gravity, heat transfer and light are in turn affected by variations in local climate. To provide an insight into the building performance requires an indepth analysis of these complex forces which are predicted by the modelling and simulation softwares which are described as follows. The simulation softwares that have been used are: - - -
ecotect for site layout TAS for one typical unit Radiance
fig 31: Model in Ecotect fig 32: Model in TAS
Analysis of Current Design
34
fig 33: site plan Tivoli holiday Village
The whole site plan has also been analysed to see the effect of overshadowing of blocks due to the location. The surroundings at the moment have no built up structures at the moment which could be of concern for overshadowing or wind path blocking in any way. For the purpose of the study one of the block has been chosen and 2 flats earmarked out which have been analysed in detail to fine-tune the suggested strategies for improvement. The two residential units are on the opposite side one facing due north and the other facing south which should contrast with the heating and cooling load requirement within the cluster plan. The same strategy can be replicated for all the different tower blocks but for reasons of duplicity of the same job only one prototype has been studies which can be a ground work for the way the units can be analysed.
fig 34
Analysis of Current Design
35
The 2 blocks chosen are in the current design oriented in the North and the South side, this will evidently put them in contrasting situation as to how they react to the climate. They can thus be assumed to be function as either very good or the opposite and thus analysing these two houses should give a general idea to be adopted with all the other houses in the project.
4.2
EFFECT OF CLIMATE ON DESIGN
4.21 ORIENTATION For passive cooling utilising the sun is paramount. The basic approach is to allow the winter sun in and the summer sun out. On the southern faces it becomes relatively easy by using shading devices to exclude the high angle summer sun and admit the low angle winter sun. The size of the shading though needs to be optimised.
fig: 35
Analysis of Current Design
36
4.22 EFFECT OF SOLAR RADIATION The sunshine hours in Delhi are about 10 per day, barring the monsoon season which has a high cloud cover the rest of the time the sky is generally clear. In the hot season the high solar altitude and the exposed site makes it vulnerable for the SE, SW and the NW facades for high solar gain. Balcony or solar shading devices need to be incorporated and optimised to allow the solar radiation in the winter and keep it out in the summer season. This gain though in the brief winter period would be desirable and a compromise would need to be established to the amount of heat gain and the undesirable one in summer. In winters the clear sky allows for a high deal of incident solar radiation and it will be desirable to utilise it by orienting the facade to it. June 3rd-9am
June 3rd-12 pm
June 3rd- 4pm
Aug 15th-9am
Aug 15th -12 pm
Aug 15th -4pm
Dec 22nd-9am
Dec 22nd-12pm
Dec 22-4pm
fig 36
Analysis of Current Design
37
Summer Solstice-9am
Summer Solstice-12pm
Summer Solstice-4pm
Winter Solstice-9am
Winter Solstice-12pm
Winter Solstice-4pm
fig: 37
Conclusions The analysis of the solar shading onsite suggests that the blocks can receive sunlight for some pat of the day atleast. The chosen block for the study can be tilted to align it to be in line with the N-S axis and this will ensure that ll houses on the floor can receive the uniform amount of solar radiation.
Analysis of Current Design
38
4.23 DAYLIGHTING ANALYSIS This section presents the results of the day lighting analysis for a worst case scenario dwelling for this development to evaluate whether it allows for sufficient daylight within the interiors.
RADIANCE Radiance is a tool which has been developed by the Lawrence Berkley Laboratories. With this it is possible to accurately determine the lighting levels in the building. The day lighting strategy can be fine tuned by the aid of simulation is Radiance. It is possible to invoke radiance through Ecotect. Although this reduces the flexibility of the software it does make things simple to use.
South Flat: June 3rd-9am
South Flat: Aug 15th-9am Dec 22nd-9am
Analysis of Current Design
June 3rd-12 pm
June 3rd- 4pm
Aug 15th -12 pm Dec 22nd-12pm
Aug 15th -4pm Dec 22-4pm
39
North Flat: June 3rd-9am
June 3rd-12 pm
June 3rd- 4pm
North15th-9am Flat: Aug Dec 22nd-9am
Aug 15th -12 pm Dec 22nd-12pm
Aug 15th -4pm Dec 22-4pm
fig 38
Conclusions The analysis of the illumination levels on the working plane suggests that the daylight levels in the south flat are very high and will lead to glare. This leaves suffinet scope to reduce the window to floor ratio which at 28% is quite high. This can easily be reduced to less than 20% and anlysed again to have the daylight levels to be in the region of 300500 Lux. The distribution of light in the north flat is almost unifrom though the areas at the back have less than 100Lux which should be optimised by increasing the number of windows.
Analysis of Current Design
40
4.24 EFFECT OF WIND The wind will have an important role to maintain the comfort conditions in naturally ventilated mode particularly in the monsoon season when the humidity is very high. The position of the apertures will need to be optimised with the inlets in the high pressure zones SE in Monsoon season. The outlets will be better located in the low pressure zones in the NW. During the peak summer season the wind known as loo has a very high temperature. To provide comfort it would need to be pre-cooled before it enters the building. Evaporative cooling will be effective in that climate as the humidity is very low then.
Fig: 39
Analysis of Current Design
41
4.25 EFFECT OF TEMPERATURE The composite climate has the extremities of the weather and in summers it is extremely hot with average temperatures above 35 ˚C and will require some form of cooling system. The aim will be to reduce the cooling load in this case. In winters although the night temperatures are quite cool the day time is still comfortable and by storing the heat during the day in a thermal mass and radiating in the night time it would be possible to create comfortable conditions.
Fig: 40
4.3
TAS Dynamic thermal modelling TAS
Tas is a thermal simulation tool which can predict the internal micro climatic conditions based on the input building design parameters and the occupancy patterns. With this analysis it can be useful to determine the strategies to follow for insulation and glazing areas. TAS Dynamic Modelling (DTM) has been used to investigate the potential of the building in achieving the required comfort conditions. DTM software tracks the thermal state of the building on an hour by hour basis using real weather data, resulting in a detailed picture of the buildings performance. DTM combines several mechanisms to calculate the building response: • Conduction • Convection • Long wave radiation • Short wave radiation- absorbed, reflected and transmitted • Internal Condition- gains from lights, equipment and occupants along with the plant operating hours and natural infiltration rates • Ventilation and air movements from internal natural convection.
Analysis of Current Design
42
fig 40
fig 41
fig 42
The 2 apartments on the opposite sides have been modelled in TAS and each space is converted into a thermal zone and the interactions of the space with each other and the outside is computed in the simulation.
Analysis of Current Design
43
4.31 ANNUAL SPACE TERMPERATURE DISTRIBUTION
6000
5000
No.of hours
4000
3000
2000
1000
0 <20
20>
21>
22>
23>
24>
25>
External - IND_New.Delhi_IWEC.epw
SF-BBedroom 1
26>
27>
28>
29>
30>
NF- BBedroom1
fig 43 100.00 90.00 80.00
Annual Demand (kWh/m2)
70.00 60.00 50.00 87.13 40.00
75.95
30.00 20.00
24.79 29.79
10.00 0.00 North bedroom
South bedroom
base case- with no internal gains
fig44
North bedroom
South bedroom
base case- with internal gains
heating loads
cooling loads
The annual temperature distribution profile suggests that the spaces are above the comfort zone for over 5000 hours in an year and the annual cooling load is as high as 87 KWH/m2 in the south bedroom. One of the bedrooms in each flat will also require a minimum amount of heating though which is minimal at less than 10KWh/m2.
Analysis of Current Design
44
4.32 TEMPERATURE PROFILE N-FLAT
The analysis of the temperature profile in the north flat in a typical day suggests that the space is abovethe comfort zone established for all of summer and monsoon. The internal temperature remains above the ambient temperture all through and suggests the need for natural ventialtion in monsoon whn the night time temperature fall.
fig 45
North Flat- June 3rdSummer
fig 46
North Flat- August 15thMonsoon
Analysis of Current Design
45
fig 47
North Flat- December 22nd - Winter
The winter temperature profile suggests that the spaces are almost within the comfort zone. By proper orientation the solar radiation alone could be used to bring the temperatures within the comfort zone. Annual Space Temperature Distribution- North flat
8000
7000 4993
No.of hours
6000
5600
5668
5307
5000
4000
3000 2481 2524
2000
2766
2915 1000 1286 0 Kitchen
fig 48
929 177
394
Living
Bedroom1
Below comfort
In comfort
Bedroom 2
Above comfort
The annual space temperature distribution shows that the spaces without airconditioning will be out of the comfort zone for almost 2/3 of the time in an year. Intervention is required for heating as well as cooling.
Analysis of Current Design
46
4.33 ANNUAL TEMPERATURE PROFILE SOUTH FLAT The analysi of typical days in the south flat tells us that the space is above the cmfort zone and the ambient temperature throughout the day in peak summer. The same is evident in the monsoon season as well and requires airconditioning to create comfort conditions.
fig 50
South Flat- June 3rdSummer
fig 51
South Flat- August 15thMonsoon
Analysis of Current Design
47
fig 52
South Flat- December 22-winter
The typical winter day has the spaces in the south flat heated up to the upper range of the comfort zone and the high thermal mass of the brick wall ensures the paces remain comfortable throughout. Annual Space Temperature Distribution- South flat
8000
7000
No.of hours
6000
5230 5904
5945
5822
2856
2815
2932
0 Living
0 Bedroom1
6 Bedroom 2
5000
4000
3000
2000
2829
1000 701 0 Kitchen
fig 53
Below comfort
In comfort
Above comfort
The above figures show that the houses are within the comfort zone without airconditioning for a very short duration of hours. They require no heating except for the kitchen but are above the comfort zone for more than half the time.
Analysis of Current Design
48
Chapter 5 PASSIVE DESIGN RECOMENDATIONS
Chapter Overview Based on the Climatic analysis and the base case simulation analysis the recommendations are made for passivc design suited to the climate and site
5.1
Climatic design for Composite Climates
The climate of Delhi is a composite climate and thus requires consideration of strategies for both heating the space and cooling the space depending on the season. With just 2 brief periods in an year in October and March when the temperature is within the comfort band for most part, the rest of the year will require some strategies to counter the effect the adversities of the weather. Based on the climatic analysis and the analysis of the simulation results the strategies which could be adopted for making passive climatic design interventions.
fig 54
5.2
THE BUILDING ENVELOPE
The role of the building envelope is to act as a moderator of the climate, to provide the balance between the heat gain and the heat losses required to maintain a comfortable interior. This calls for using effective shading, high performance glazing systems, good insulation access to thermal mass and the use of natural ventilation in the respective season where feasible. In the context of Delhi the facades are most vulnerable to solar radiation as the 14 storeyed tower blocks are exposed out without any shading from the surrounding. The only shading is provided by the overshadowing of the different blocks. Excessive glazing should therefore be avoided on the facades. Effective shading though can easily be done by optimising the depth of the balconies and putting vertical shading devices to counter the effect of low morning and Recommendations
50
evening sun in the west facade without loss of light. The environmental performance of a building depends on a number of different factors. The environmental performance of the facade system on a building is one of the influential characteristics determining overall building performance. The protective shell of the building is the facade and the better this works the less work is required internally from the mechanical systems to maintain good occupant comfort levels. This has a direct influence on the energy consumption of the building. The ideal insulation strategy to follow for composite climates needs to be optimised again depending on the desing and the site conditions. This needs to counter the effect of the variations in the temperatures through the day and the year and the amount of solar radiation falling on the facades. Choosing the glazing type will have an impact on both the illuminance levels in the building and the solar heat gains. By choosing a glazing with an emissivity of 0.1 the heat gains can be reduced when the sun is high and the incident solar radiation to the surface glazing causes increase in indoor temperature and cooling load. For the south east and south west vertical shading devices are recommended in order to reduce the heat gains when the sun is low. For morning performance optimised east facing glazing with both horizontal and vertical shading devices is a preferred approach. For afternoon performance, a double glazed unit should be installed comprising of solar control glass for the outer pane and low emissivity(Low-e) glass for the inner pane. The solar control glass prevents unwanted solar radiation entering the summer months and the low emissivity glass reduces the heat loss from inside during the winter months. The low- e glass also blocks heat radiated from the outer pane of glass when it heats up.
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5.3 IMPACT OF CHANGE IN THERMAL MASS AND LOCATION OF INSULATION LAYERS
fig 55
To provide an acceptable internal environment in hot climates, one of the traditional methods that were used was heavy weight construction (low u-value construction). The thick walls of stone or brick gave a huge time lag and the heat transfer co-efficients thus offer good U-values. They are able to absorb a large amount of heat without a marked increase in the temperature of the interior space. However they take a long time to heat up or cool down and as a result the advantage of solar radiation falling directly on them cannot be taken instantaneouly. On the other hand the light weight consturction offers the flexibility to heat up the space faster during the day which is very useful in the cold winter months. However, during night-time when the out-side air temperature is low heat loss by a lightweight structure is higher than a heavyweight structure, as proven by Victor Olgyay of Princeton University. He made a graphical comparison of a lightweight structure having a 2hour time lag with a 9-inch brick structure with a time lag of 10 hours. Each structure had the same u-value of 0.268 btu/ft2. However, in the lightweight structure insulation was placed inside whereas in case of heavy weight structure insulation was placed outside the building envelope.
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fig 56: Comparing thermal behaviour of heavy and light construction: source: Building Environment , Balwant Singh Sainai
Interpreting the graph it comes across that though the total daily heat transmission is same for both in amplitude, the period of transmission is different. The heavyweight is better off during daytime whereas the lightweight performs better during night-time. It can thus be inferred that for the rooms to be occupied during day-time, heavyweight construction would be required to reduce heat gain and rise in internal temperatures; whereas night-time active areas construction should be lightweight so that they may cool off quickly at night to prevent need of air-conditioning.
5.31 EXTERNAL INSULATION AND INTERNAL THERMAL MASS The grouping of the external insulation and internal mass-produces both a high thermal time constant and a high diurnal heat capacity. It helps in stabilising the fluctuating internal temperature when the windows are kept closed for the whole day and night. In Delhiâ&#x20AC;&#x2122;s climate the summershave a diurnal temperature range which is quite high at
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53
12-15 deg.C. When the building is ventilated during the night-time and kept closed during the day-time it can effectively cool down the mass and absorb, the solar energy transmitted through windows along with heat generated within interior spaces of the building during day-time, with relatively small rise of the indoor temperature.
5.32 EXTERNAL THERMAL MASS AND INTERNAL INSULATION Such construction has comparatively low thermal time constant and negligible diurnal heat capacity as the internal insulation separates the mass from the interior space. Thus, it will act as a lightweight building and will follow the external air temperature when ventilated. The reduction in day-time temperature is mainly determined by the thickness of the construction if the windows are kept closed. This combination is of great advantage for space to be used during nighttimes and during the monsoon season as the heavy mass provides protection from the strong winds and the internal insulation can enhance the cooling rate at night.
5.33 PARAMETRIC STUDY TO DETERMINE WALL TYPE AND CONSTRUCTION To study the affect of thermal mass and insulation in the climate of Delhi a parametric study was done by testing the effect of different combination of wall material and insulation on the same room in esp-r. The study was conducted by by creating a room 5M X 5M x 5 M with 20% window to floor ratio. Keeping all conditions identical 6 different combinations of wall types as explained below were tested. a) Brick Wall with insulation in between Conductivity Density Specific Heat Thickness 1 Brick 0.96 2000 50 100 2 Insulation .10 100 750 100 3 Brick 0.96 2000 850 100 U-Value 1.15 a) Brick Wall with no additional insulation Conductivity Density Specific Heat Thickness 1 Brick 0.96 2000 850 200 U-Value 2.1
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b) Brick wall with insulation on the outside Conductivity Density Specific Heat Thickness 2 Insulation .10 100 750 100 3 Brick 0.96 2000 850 200 U-Value 1.04 c) Brick wall with insulation on the inside Conductivity Density Specific Heat Thickness 1 Brick 0.96 2000 850 100 2 Insulation .10 100 750 100 U-Value 1.04 d) Sandwich of Aerated Autoclaved Concrete (AAC) Block wall with insulation in between. Conductivity Density Specific Heat Thickness 1 AAC block 0.45 850 650 100 2 Insulation .10 100 750 100 3 AAC block 0.45 850 650 100 U-Value 0.85 e) AAC Block wall with insulation on the outside Conductivity Density Specific Heat Thickness 1 Insulation .10 100 750 100 2 AAC block 0.45 850 650 100 U-Value 1.08 f) AAC Block wall with insulation on the inside Conductivity Density Specific Heat Thickness 1 AAC block 0.45 850 650 100 2 Insulation .10 100 750 100 U-Value 1.08 The room was simulated for all the 4 typical days selected for study and the results are summarised:
SUMMER SEASON â&#x20AC;&#x201C; (APRIL â&#x20AC;&#x201C; JUNE) On a typical day the resultant temperatures are higher than the comfort zone. Whereas during the day time the light weight AAC block wall with insulation on the outside is showing the best possible reduction in temperature. The heavy thermal mass of brick wall with insulation on outside or a sandwich layer stabilises the temperature through the day and it remains more or less constant.
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55
For an air-conditioned building this may be the best option but for a naturally ventilated building the night time cooling in this climate demands the building to cool down for the night time. The AAC blocks with insulation on the inside cools down the fastest and is able to loose heat almost instantaneously.
fig 57: parametric study generated using esp-r
MONSOON SEASON â&#x20AC;&#x201C; (JULY â&#x20AC;&#x201C; SEPTEMBER) During the monsoon the diurnal range of temperature is less and the direct solar radiation is also very less. Because of this the direct gain as a result is not too much and almost all cases follow a similar profile. Here again the low thermal mass of AAC blocks and external insulation helped keep the temperatures lowest. The high thermal mass without the insulation (case a) has a fluctuation in the temperature whereas the thermal with insulation on the outside ot a sandwich has a very stable profile. The AAC blocks with insulation on the inside shows the high fluctuation in the daily temperature and is able to cool down very rapidly but remains way above the comfort zone in the day time.
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56
fig 58: parametric study august 15 generated using esp-r
WINTER SEASON (Nov-Feb) The cold climate has a utility for thermal mass in stabilising the temperature. This is infact helped due to the high solar radiation which gets trapped as heat and keeps the night time temperature stable. The AAC blocks with external insulation which perform well for summer conditions are not suitable in this climate as the temperature remains way below the comfort zone.
fig 59: parametric study Dec 22 generated using esp-r
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57
5.4 STRATEGIES FOR VARIOUS SEASONS 5.41 SUMMER SEASON The summer season will require strategies to
1)
Reduce heat gains from the building fabric
This can be done by: •
•
•
•
Orienting the building to reduce the footprint of the solar radiation received. By reducing the exposed area to the direct sun the heat gains should get reduced which will reduce the cooling load Improve the insulation level of the building fabric. Using insulation on the external face of the building which can reduce the external influence of hot weather can vastly improve the cooling load requirements. Insulating materials can range from simple air gaps in the walls to advanced materials specifically tailored for the effect. Optimise the glazing ratio. The Glazing is the most vulnerable area for heat gains in summers if it is in an exposed area which receives direct sunlight. Optimising the glazing ratio will needs to be balanced to achieve the desired illumination levels in the spaces and the heat gains it will cause. Use insulated glazing system like double glazing which has a marked improvement on the insulating property as compared to the single glazing. This will reduce the heat gains from the surroundings.
2) •
•
Reduce Internal gains
Internal sources contribute the heat gains in a space and the strategy for summer needs to be to reduce them to avoid this heat gain The heat gains from the lighting fixtures can be significant. Using firstly energy efficient lights can reduce this gain. Secondly the control system needs to be defined which can switch on and off the lights according to the usage pattern.
3) Reduce temperatures by apppropriate Ventilation strategies •
• •
Recommendations
Ventilation requirements are crucial for health reasons and they need to be optimised in the building heat flow dynamics to reduce the heat indoors. The summer temperatures although quite high, have a low humidity level and can benefit from evaporative cooling. The rate of air changes need to kept at a minimum if the outside temperature is way above the comfort level. The minimum standard to be followed can be the ones from ASHRAE standards for residential buildings.
58
5.42 Winter Season The average temperature in the composite climate of Delhi in winters is much below the comfort band. The strategy to be adopted is to keep the interior temperature above the ambient ones.
1) •
•
•
•
The temperature variation in the interior and the exterior suggests use of insulation to reduce the heat loss from the interiors. This is the same as for the summer season Orient the building to gain more direct solar radiation. Since this contrasts with the strategy for summers an optimisation needs to be made on this respect. Optimise the Glazing ratio of the building fabric: The heat gains that can be made from the glazed areas need to be optimised to check the vulnerability of the glazed surfaces to aid in heat loss due to the low U value. Utilise insulated glazing which can reduce the heat loss from the interior
2) •
Recommendations
Reduce heat Losses from the Building Fabric
VENTILATION
The ventilation rate has to be optimised to fulfil the requirements of comfort and health while at the same time to reduce the outflow of heat from the interiors.
59
5.43 MONSOON SEASON The High humidity and temperature requires a different strategy from the hot summer season for the monsoons.
1) • •
•
The temperature generally hovers around the low 30’s and it is essential to provide a insulating fabric from this high temperature. The temperature in the night time though does go down and is in the high 20’s which could essentially be used for free cooling in the night time. The incident solar radiation is quite low and as such the effect of shading would not be apparent,
2) • •
Reduce heat gains from the building fabric
Ventilation strategy
The high humidity makes wind flow very essential, but it renders evaporative cooling as useless in this weather Night time cooling could be utilised as the wind speeds are generally quite high.
5.44 MILD SEASON •
•
Recommendations
With the weather conditions favouring human comfort it would be an advisable strategy to bring the outdoor climate indoors as much as possible. The heat gains from the interiors and the atmosphere could be channelled to the outside to create comforting conditions.
60
Chapter 6 aNALYSIS OF RECOMMENDATIONS
Chapter Overview The recommendations put forward in the previous chapter have been incoporated in the base case design and simulated again to quantify their effectiveness. The chapter analyses the two scenarios and discusses the impact of passive strategies in reducing the energy demand and creating comfort conditions.
6.1 Comparison of Base case Annual energy demand with proposed recommendations List of assumptions of both the baseline and the current design buildings made for the thermal modeling simulation program Proposed Recommendation
Base case building 1.0 1.1 1.2
Facade treatment
2.0
Construction properties U-Values of Transparent Constructions-Glazing U-Values of Opaque constructions
2.1 2.2
28%
20%
Bedroom, living room windows shaded by a horizontal overhang on all facades on all orientations
Fixed shading devices, same as the current design and additionally vertical shading on east and west windows
Single glazing 5.71
Double glazing with 12mm air gap 1.8
1.1
2.21
External Walls (bedrooms)
2.4
2.22
External Walls (Living)
2.4
0.8
2.32
Internal Walls
2.53
2.53
2.33
Slab
2.65
2.65
2.34
Opaque Doors
2.35
Door/ Window Frames
3.0
2.6
2.6
5.88
5.88
Internal Conditions – Internal Gains- Living Rooms and Bedrooms
a.
Infiltration
0.5 ach
b.
Ventilation
0 ach
0 ach
c.
Lighting Gain
12 W/m2
6 W/m2
d.
Occupancy Sensible
e.
Occupancy Latent
2.5 W/m2 2 1.3 W/m
2.5 W/m2 2 1.3 W/m
f.
Equipment Sensible
g.
Equipment Latent Thermostat Temperature Settings
h.
Analysis of Recommendations
Building Design Window to gross wall ratio
7 W/m
2
0.5 ach
4.5 W/m
2
-
-
Air conditioned (25°C)
Air conditioned (25°C)
8am-7pm
4.0
Occupancy Schedule
4.1
Day-time occupancy
8am-7pm
4.2
Evening occupancy
6pm-9am
6pm-9am
4.3
Lighting Schedule
6pm-11pm
6pm-11pm
5.0
Apertures for Natural Ventilation
5.1
Apertures
(none)
5.2
Aperture Function
(none)
On all windows
Opens when the zone’s dry bulb temperature is between 20 °C and 29 °C
62
6.11 Comparing the temperature and cooling loads against base case in North Flat Chart1
600.00
40.00
500.00
35.00
400.00
30.00
300.00
25.00
200.00
20.00
100.00
15.00
0.00 1
fig 60:
Cooling Load (W)
Dry Bulb Temperature (deg.C)
Comparison of Temperatures and Cooling Loads in the North flat on June 3rd (Summer) 45.00
2
3
4
5
6
7
8
9
10
11
12
13
External Temperature (deg.C) Proposed Design-Bedroom1 Dry Bulb (deg.C)
14
15
16
17
18
19
20
21
22
23
24
Base Case-Bedroom1 Dry Bulb (deg.C) Base Case-Bedroom1 Cooling Load (W)
Proposed Design-Bedroom1 Cooling Load (W)
100.00
Page 1
90.00
80.00
75.95 69.23
Annual Demand (kWh/m2)
70.00
60.00
50.00
45.74 42.34 39.02
40.00
30.00
26.13
20.00
10.00
fig 61
0.00 base case
w/f ratio optimised
Mixed-mode ventilation
U-values (opaque)optimised
U-values (glazing) double glazing
internal gainsoptimised as per NBC standads
Annual heating and cooling loads- Bedroom 1- North flat
The above figures show how the energy demand to keep the space at the comfort conditions decreases with the application of each recommendation. With just the application of mixed mode of ventilation and window to floor ratio optimised the the energy demand per annum when the demand falls from base case scenario of 75KHh/M2 to 45KWH/m2. After all the recommendations in place the energy demand can be as low as 25KWH/m2 per day. The cooling load on a typical summer day reduces from a peak of 500W to 300W only.
Analysis of Recommendations
63
6.12 Comparing the temperature and cooling loads against base case in South Flat Chart1 (2)
600.00
40.00
500.00
35.00
400.00
30.00
300.00
25.00
200.00
20.00
100.00
15.00
fig 62
Cooling Load (W)
Dry Bulb Temperature (deg.C)
Comparison of Temperatures and Cooling Loads in the South flat on June 3rd (Summer) 45.00
0.00 1
2
3
4
5
6
7
8
9
10
11
12
13
External Temperature (deg.C) Proposed Design-Bedroom1 Dry Bulb (deg.C)
14
15
16
17
18
19
20
21
22
23
24
Base Case-Bedroom1 Dry Bulb (deg.C) Base Case-Bedroom1 Cooling Load (W)
Proposed Design-Bedroom1 Cooling Load (W)
Page 1
100.00
90.00
87.13
77.57
80.00
Annual Demand (kWh/m2)
70.00
60.00
50.00
46.73 42.03 37.43
40.00
30.00
25.13
20.00
10.00
fig 63
0.00 base case
w/f ratio optimised
Mixed-mode ventilation
U-values (opaque)optimised
U-values (glazing) double glazing
internal gainsoptimised as per NBC standads
Annual heating and cooling loads- Bedroom 1- South flat
In the south flat too the energy demand falls from a peak of 87KWH/m2 on a typical summer day to just 25KWH/m2 after the application of all recommendations. Infact due to the change in orientation of the flat it has a zero cooling load can drop to zero in the early moring hours.
Analysis of Recommendations
64
6.13 Effect of mixed mode ventialtion on Cooling load
fig 64
The base case has airconditioned interiors all through the time, yet it is interpreted from the above figure that the cooling load can be shut off in the monsoon with the application of night time cooling by opening the windows and increasing natural flow of air.
Analysis of Recommendations
65
6.12 Annual Space Temperature Disribution.
4500
4000
3500
No.of hours
3000
2500
2000
1500
1000
500
fig 65
0 <20
20>
21>
22>
23>
24>
25>
External - IND_New.Delhi_IWEC.epw
26>
NF- BBedroom1
27>
28>
29>
30>
SF-BBedroom 1
4000 3738 3521 3500
3000
2815
2766
No.of hours
2500
2000
1500
1000
500
fig66
0 North bedrooms
South bedrooms
Base case
Proposed design
With the application of the recommendations for passive design ideas in comparison to the base case scenario the spaces can be made to be in comfort conditions for a longer duration of time. The north bedroom can fuction without any airconditioning for more than 3500 hours in an year as compared to 2750 in the base case. The south facing flats can have he same increased by 1000 hours annually.
Analysis of Recommendations
66
Analysis of Recommendations
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
75.95
South bedroom
87.13
base case- with internal gains
North bedroom
fig 67
67
Annual Demand (kWh/m2)
South bedroom
South bedroom
46.73
Mixed-mode ventilation
North bedroom
45.74
South bedroom
42.03
U-values (opaque)optimised
North bedroom
42.34
South bedroom
37.43
U-values (glazing) double glazing
North bedroom
39.02
Comparison of cooling loads between north and south flats
w/f ratio optimised
North bedroom
69.23
77.57
South bedroom
25.13
internal gains- reduced
North bedroom
26.13
The graph on the previous page shows how the annual cooling load decreases with the application of each recommendation in the spaces. The fact that is elaborated is that the cooling load can be decreased the maximum is by the use of outside weather conditions to cool the interiors. By using a mixed mode of ventialtion the energy demand falls by a third and is the biggest contributor in thepasive design strategy. Each strategy has a marked improvement on the energy consumption load and by the application of these simple techniques the use of energy can be reduced to a third of what the projected energy consuption figures are.
Analysis of Recommendations
68
CONCLUSIONS
The quest to make the modern buildings comfrotable has had a drawback of heavy reliance on energy to keep them in that state. However senitivity in design which takes into account the environmental conditions of the site can result to lower this energy consumption. Simple passive design strategies can be effective to make the reliance on mechanical means lower. The thesis proves with simple methods and adherence to the tightening norms for building construction can lower the dependence to achieve the comfrot standard. The passive design strategeis are vast and in this thesis the basic ones were explored to see how the building can be comfortable and not rely on airconditioning through the year quite easily. However there were many factors which have been assumed and actual site conditions can vary and change the dynacmics of the projected energy consumption figures. the occupancy pattern and the usage of systems has been assumed to be in one strict manner and it will invaribly differ depending ont eh occupants. Basic attempts at harmonising the building to the enviroment does result in lower energy consumtpion and further research may be done to make even the mass produced housing estates like these ones to be totally not dependent on energy needs at all. The norms at the moment in develpoing countries are still in infacny for these and the aspirations of people have driven the need for fully climatically conrrtolled atmospheres to become common. But it is questionable in the approach as the higher energy demand and the reliance on it has pushed the use of such houses in the forefront. With increasing awareness about global warming and environment consciouness the approach towards environmentally suitable buildings is a step in the right direction.
Analysis of Recommendations
69
BIBLIOGRAPHY 1) 2) 3) 4) 6) 7) 8) 9) 10) 11)
Sofaee, F, 2004, ″ Sustainability of Climatic-Sensitive El-ements in the Iranian Traditional Architecture of Hot – Arid Regions″, ICHH 2004, India. Szokolay, S.V, (1997). Thermal Insulation. PLEA Internatinal/ University of Queensland, Brisbane. Cook, J., (1989). Passive Cooling. The MIT Press Cambridge, London. Givoni, B., (1998). Climate Considerations in Building and Urban Design. Van Nostrand Reinhold, New York. Krishnan, A., (2001). Climate Responsive Architecture. Tata McGraw Hill, New Delhi. Yannas, S., (2000). Designing for Summer Comfort. European Commission, Energy Altener Programme. Saini, B.S., (1973). Building Environment. Auliciems, A.& S. Szokolay., (1997). Thermal Comfort). PLEA Note3, PLEA International/ University of Queensland. Energy Conservation building Code 2006, Bureau of Energy Efficiency, (BEE) National Building Code of India (NBC)-2005, www. bis.org.in
Softwares used – Eco-tect TAS esp-r
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