Building performance evaluation and simulation for existing buildings of composite climate: A case of Delhi
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Building performance evaluation and simulation for existing
buildings of composite climate: A case of Delhi
Emeline Renthlei1 and Abraham George2
1,2
Indian Institute of Technology, Kharagpur, India
1
emerenthlei@gmail.com, 2abrahamiitkgp@gmail.com
Abstract: In the beginning of Delhi Master Plan 2021, existing buildings of Delhi are energy intensive
which add to the cooling load and energy requirement. The study aims to reduce energy use in existing
buildings through the use of passive cooling strategies, after building performance evaluation is carried
out; to highlight the importance of passive cooling strategies and their relevance with two case studies
of built-forms in Delhi which differ in their design, location and function. The performance of the
buildings in its existing condition is monitored in two extreme climatic conditions; summer and winter.
Exploration and experimentation of passive strategies are done on two built forms through modelling
using the environmental tool IESVE, to determine optimum design solution. The key findings of
modelling are the importance of response of each building element to its environment. Appropriate
insulation of the roof drastically changes the adjacent internal environment due to the amount of solar
radiation falling on it. Design of overhangs must be done in relation to the altitude angle of solar
radiation and depth of window. Selection of strategies based on micro climate and design of buildings in
harmony with the environment is also crucial for cutting down energy consumption.
Keywords: Building Performance Evaluation, Passive Strategies, Modelling, Simulation
1. Introduction
Though it is easier to build a new environment-friendly building, one cannot ignore retrofitting of
existing buildings since they consume 36% of the total energy globally (International Energy Agency
2017). Electricity consumed annually by existing buildings in India is more than the total electricity
consumed by all buildings that will be constructed over the next 20 years (The Energy and Resources
Institute 2013). With significantly growing energy demand in buildings, power shortage and increase in
Carbon emissions have been experienced. Improved efficiency of existing buildings through building
retrofitting represents a high volume, low-cost approach to reducing energy use and greenhouse gas
emissions (Luisa F. Cabeza 2018). Policy and planning documents define eight types of settlements in
1
Research Scholar, Department of Architecture and Regional Planning, Indian Institute of Technology
Kharagpur, India Pin: 721302. Tel: 91-7308970585 E-mail: emerenthlei@gmail.com
2
Corresponding author: Associate Professor, Department of Architecture and Regional Planning, IIT
Kharagpur, India Pin: 721302. Tel: 91-9434742367, E-mail: abrahamiitkgp@gmail.com
Revisiting the Role of Architecture for 'Surviving’ Development. 53rd International Conference of the
Architectural Science Association 2019, Avlokita Agrawal and Rajat Gupta (eds), pp. 527–536. ©
2019 and published by the Architectural Science Association (ANZAScA).
528 Renthlei E. and Georege A.
Delhi, only one of which is termed ‘planned’. The planned colonies account for about 23.7% of the total
estimated population whereas; the unplanned colonies together make the remaining population of
76.3% (Centre for Policy Research 2015). The new Master plan of Delhi 2021 aims to develop 27,000
hectares in the City to meet growing demands (Delhi Development Authority 2010). Construction in
Delhi is time sensitive; as is the case of any fast-growing city and many constructions are done without
proper management. Not all existing buildings are designed ‘energy efficient’ or ‘climate responsive’.
Therefore, importance of retrofitting should be taken a serious concern by the Government,
stakeholders and homeowners.
According to the Central Electricity Authority annual report 2017-2018, electricity consumption in
Delhi is more than all the metro cities put together (Central Electricity Authority 2018). The power-cuts
and shortfall in electricity experienced in Delhi during the months of June and July could directly be
attributable to air-conditioning (Lall 2007). Hence, it is inevitable to ensure appropriate Building
Performance. An evaluation method as a regulatory means is hence appropriate.
Building Performance Evaluation is a useful method to understand and enhance the level of
performance; to upgrade the effectiveness and efficiency in producing quality and well-maintained
buildings. All buildings require a level of performance and a standard of management throughout their
life that can provide and sustain conditions suitable for the well-being of their users (Kamaruzzaman
2011). Building performance simulation has become an accepted method of assessment during the
design as well as during the operational life of built forms (Olufolahan Oduyemi 2016). The complexities
in the design process is increasing and building performance simulation tools help to find the optimum
results and solution for the performance of buildings (IES Virtual Environment User Guides 2019). These
can be applied for finding the best retrofitting solution for an existing built form. There are many passive
design technologies that can be applied for retrofitting of existing buildings, and selecting the optimum
strategy yields the appropriate performance. The simulation tool which is selected for the project plays
an important role in the selection of optimum design solutions. Thus, the research intends to
understand the effects of different simple retrofitting strategies for the existing housing stock in Delhi
and extend to other cities as well, through building simulation tool, Integrated Environment Solutions
Virtual Environment (IESVE).
2. Methodology
Integrated Environment Solutions Virtual Environment (IESVE) is a tool used widely for new building,
renovation or retrofitting projects and the software allow designers to test different design options, to
identify optimum passive solutions, compare low-Carbon technologies, and draw conclusions on energy
use, CO2 emissions, occupant comfort, lighting levels, airflow, and many more. It allows one to design
and operate comfortable buildings that consume significantly less energy and incorporate low-Carbon
and renewable technologies (IES Virtual Environment User Guides 2019). With the help of the Ap locator
(weather and site location editor), the climatic condition of a particular site can be acquired and these
data can be modified and altered to match the required conditions. IESVE programs facilitate a full
dynamic thermal modelling of building and consequent energy consumption with APACHE calculations
and simulation (Central simulation processor which enables one to assess every aspect of thermal
performance as well as share results and input) (IES Virtual Environment User Guides 2019).
Five retrofitting strategies are selected, among many strategies, to make retrofitting more cost
effective and practical for this particular simulation project. These selected strategies will not be
burdensome for implementation for the homeowners and the community. They are:
Building performance evaluation and simulation for existing buildings of composite climate: A case of 529
Delhi
a) 1200mm overhang for windows and openings, where applicable.
b) Integration of 100mm rock wool insulation (U-value of 0.6 W/m2K) on the roof and floor
c) double glazing with 12mm air gap (12mm gap is used to avoid bulky window frame and double-
glazing windows have 0.4 mm to 20mm gap depending on the type of gas-filled) for windows and
openings where applicable,
d) Manual Night cooling mechanism
e) Responsive Roof insulation
2.1 Study area
Delhi has composite climate and is predominantly hot so too, distinct cool and humid seasons.
Cooling is essential and heating is a requirement because most of the population is used to hot climate
and many buildings do not aid thermal comfort. Two buildings are selected for performance evaluation
and simulation model which are different in location, function, orientation and occupancy.
2.1.1 Eastend Apartments
15/903, Mayur Vihar Phase-1 (Extn.), Delhi – 110 096
Eastend Apartments has 1306 apartment blocks of 8 – 9 storeys. The selected flat is on the 9th floor.
Figure 1: Eastend apartments (Source: Author)
2.1.2 Chelsea West Architects Office
S-468 First Floor, G.K Part 1, Delhi – 110048
Figure 2: Chelsea West Architects Office (Source: Author)
Greater Kailash Part I was developed in the early 1970’s. The selected flat is a residential one on the first
floor of a 5-storey building which has been converted to suit the requirement of the architecture firm.
530 Renthlei E. and Georege A.
2.2 Building Performance Evaluation
While Building Performance Evaluation can cover the entire life cycle of the building (including
construction, postconstruction, early occupancy and in-use stages), Post-occupancy evaluation (POE) is
limited to the in-use stage of a building (Rajat Gupta 2019). A Post-occupancy Evaluation was performed
for both the buildings through Energy Audit, Temperature Monitoring and Occupancy Satisfaction.
2.2.1 Energy Audit
Electricity bills for the entire year of 2014 were collected and analysed to assess the electricity
consumption and all appliances in both the buildings were audited as well.
2.2.1.1 Eastend Apartments
The main electricity consumption goes in cooling of the house and other uses are relatively low.
During summer months, the unit of consumption of electricity is almost five times higher than the rest
of the year. These summer months includes May to September and gradually decreases when winter
comes. Heating during winter is done through small electric heaters which can be moved anywhere in
the house. Family take care to switch off unused appliances and lights.
2.2.1.2 Chelsea West Architects Office
Electricity is used for all appliances as well as for cooling and heating. Cooling load is high as the
office remains air conditioned throughout occupancy hours i.e. 8 – 10 h / day. Computers are kept on
even when not in use adding to the cooling load. The amount of electricity consumed during the months
of May to August is more than double compared to the other months due to higher cooling
requirement.
2.2.2 Temperature Monitoring
The two flats were monitored using data loggers for a period of one week during summer (23rd May
– 30th May 2014) and winter (19th Jan – 26th Jan 2014) for evaluation and analysis of the actual
performance. Data loggers, i-buttons, were placed in three rooms and one in the balcony in both the
buildings.
2.2.2.1 Eastend Apartments
Summer readings: The internal temperature remains lower than the outside temperature for most
part of the day with a difference of 80C to 100C with mean minimum. During the night the outdoor
temperature drops to about 50C. The rooms that are monitored have different types of conditioning.
Out of the three rooms that are monitored, only Master bedroom is air-conditioned. The other rooms
have ceiling fans for cooling and they maintain a temperature of about 340C with the active cooling
system.
Winter readings: The internal temperature is higher than the outside temperature by 70C to 90C due
to electric heaters. Master bedroom is occupied most time of the day, since the owners are retired, and
has more internal gains than the other two rooms. Most of the rooms have comfortable temperature of
170C to 210C.
Building performance evaluation and simulation for existing buildings of composite climate: A case of 531
Delhi
2.2.2.2 Chelsea West Architects Office
Summer readings: Temperature reading inside the office is below the external temperature (almost
80C difference during peak hours) during most part of the day. There is a decrease in the room
temperature during office hours when the cooling starts.
Winter readings: Temperature fluctuation occurs outside during sunshine hours and after sunset
there is almost 100C difference between the lower range and the upper range. The internal temperature
on the other hand, remains constant during occupancy hours. The bedroom is rarely occupied and so
has lower temperature than the studio which has more internal gains from computers and other
appliances and from the occupants as well. There is a minimal heating during winter and the room
temperature remains within comfortable range with appropriate clothing.
Unit of Electricity Consumed (kWh)
1400
1200
1000 Eastend
Apartments
800
Chelsea West
600
400
200
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 3: Monthly Actual Electricity consumption for Eastend Apartments and Chelsea west office taken
from electricity bill of 2014 (Source: Author)
2.3 Validation and creation of Base case model
The model was validated with respect to the data acquired from the data loggers through six
iterations. Manual adjustments of parameters like infiltration rate, and small changes in the U-values
were done by trial and error until the simulation results matches the known data. The weather file used
for modelling is taken from ASHRAE design weather database 2014 and the location is Safdarjung, Delhi.
The dry bulb temperature readings were quite different from the monitored outside temperature. This
could be due to the difference of more than 17 kms (for Eastend) and 10 kms (for Chelsea West)
between the study areas and the database for the program. Base case models were made with RMSE of
2.14% and 2.34% for Eastend apartments and Chelsea West office respectively.
The internal temperature differences could be due to variation of internal gains, hours of air
conditioning used, external gains and other factors. The number of air changes due to infiltration is kept532 Renthlei E. and Georege A.
as 0.5 and the air conditioning of the rooms are set to work when the temperature of the room is
greater than 260C during occupancy hours only. The base case model does not take into account the
dessert cooler during the summer months and during winter, the electric heating is left out while
modelling and thus the result in the lower temperature reading. The occupancy hours differ slightly in
Chelsea West office due to extra hours in the office from the fixed hours in the model.
The materials used and U values for base case mode are:
Eastend Apartments Chelsea West Architects Office
Elements Material/modelling U values Material/modelling U values
assumptions (W/m2K) assumptions (W/m2K)
Floors/ Ceiling 150mm thick RCC slab 2.61 150mm thick RCC slab with 2.71
with ceramic tile ceramic tile
Partition wall 150mm brick wall with 1.53 150mm brick wall with 1.67
plaster and paint finish plaster and paint finish
Roofs 150mm thick RCC slab 2.38 150mm thick RCC slab with 2.14
ceramic tile
External walls Brick wall of 230mm 2.06 Brick wall of 230mm 2.06
thickness thickness
Windows Single glazing with 5.32 Single glazing with wooden 5.32
wooden frame frame
Table 1: Materials and U-values used in simulation model for both the buildings (Source: Author)
2.4 Analysis of Simulation
The simulation process is done separately for each of the five strategies and the results were
recorded. The last stage of the simulation process is a combination of all five strategies. Table 2 shows
the comparative result for the two buildings. It is evident that the cooling load of the two buildings
decreases to 38% and 32% and most effectively when all five strategies are applied.
2.4.1 Eastend Apartments
There is a little change in the thermal performance when overhang of 1200mm is introduced.
Although there is a decrease in the cooling load, this is offset by the increase in the heating load since
the overhang remains the same length throughout the year regardless of the angle of solar radiation.
Thermal Insulation (rock wool) of 100mm thick on the roof reduces the overall energy consumption
mainly due to reduction of the cooling load and a small reduction in the heating load as well. On the
hottest day the peak internal temperature drops by almost 20C due to roof insulation which reduces the
solar gain substantially since it is the element which receives the most solar radiation and installation of
insulation materials prevents heat from penetrating into the liveable area. The integration of 100mm
insulation (U-value of 0.6 W/m2K) on the roof and floor has the most effect on the energy consumption
as the cooling load decrease to almost 22% less than the base case model. There is a great improvement
in the U values of the building components. The windows are set to open only when the internal
temperature goes higher than the outside temperature. The peak day temperature sees the lowest
temperature during 04:00 hours in the morning and from that point onwards the temperature is slowly
rising but the internal temperature remains almost 1.5oC lower throughout the day as compared to the
base case without night cooling, which means that the thermal mass of the building helps to retain theBuilding performance evaluation and simulation for existing buildings of composite climate: A case of 533
Delhi
cold. There is not much variation with the overall performance when the glazing is doubled and coating
on the outside, and the amount of heating requirement is higher than a building with single glazing but
this is neutralised by the reduction in cooling load. The peak solar gain in the south side bedrooms
decreases by 0.4 kW, although there is not much change in the peak room temperatures. The cooling
load reduces by 2480 KWh which amounts to 38% reduction when all the passive strategies are applied
on the model. The peak internal temperature is reduced to 5oC throughout the day resulting in more
comfort.
2.4.2 Chelsea West Architects Office
With the introduction of an overhang of 1200 mm, the internal peak day air temperature reduces by
20C as compared to the base case peak day temperature. The reduction is more distinct in the
conference room and the principal’s office since they face south. Insulating the floor, external walls and
the ceiling, on the other hand reduces the cooling requirement substantially by 2100 KWh, which is
22.8% from the base case. The peak internal temperature on any given day is lower by 4oC to 5oC in
almost all the rooms. Insulation of the floor and ceiling does not have too much effect on the thermal
condition of the room since they are an internal element shared between the lower floor and the upper
floor respectively and offers little to the improvement to the thermal mass. There is no heating
requirement when the building is insulated. Night cooling helps to maintain a 2oC lower internal
temperature form the base case and the lowest temperature is between 04:00 hours and slowly rises
until it reaches a peak point after 18:00 hours, but by this time the rooms are not fully occupied and it is
still lower than the base case temperature. The reduced temperature is maintained during the main
occupant hours. Cross ventilation helps the effectiveness of night cooling and the thermal insulation
retains the coolth within the rooms. Night cooling is more effective in rooms having larger windows and
greater number of windows. Double glazing windows do not have much improvement to the
performance of the building and they do not reduce the internal temperature although a slight decrease
in the solar gain is noticed. The windows are mostly facing south and they are long and have larger
width without overhangs so the solar radiation can still heat up almost the entire length of the window.
The thermal mass of the building is improved after addition of insulations and this retains the coolth due
to night cooling. Heating requirement is eliminated completely and cooling load reduces to almost 32%.
Passive Eastend Apartments Chelsea West Office Remarks
design
strategy
Double Cooling load reduces slightly but Does not help in reducing Dose not have desired
glazing heating load increases heat gain due to size and effect due to location
position of windows of openings
1200mm Slight decrease in cooling load but Most effective on the Length should be
overhang increase in heating load in winter south side openings adjustable depending
since the length of the overhang on the angle of
remains the same for both seasons. radiation534 Renthlei E. and Georege A.
Night Reduce the internal temperature Reduce the internal Cheapest mechanism
Cooling by 1.50C during peak hours temperature by 20C. Most provided the external
effective in rooms with temperature should
larger size openings be lower than the
internal temperature
Roof Reduction of 20C in the internal No direct contact with Optimum solution for
Insulation temperature during summer roof top floor apartments
months. Reduction in overall
cooling load
Overall Cooling load reduced by 22% as Reduce the cooling load Insulation the entire
insulation compared to base case. Insulation by 22.8% from the base envelope is the most
of walls and roof is most effective case. Peak internal effective strategy to
as they cover the maximum area temperature drops by 50C reduce cooling load
in most of the rooms.
Insulation of the walls is
most effective
Combined Internal peak day temperature is Internal peak day
Strategies 50C less than the base case. temperature is 50C less
Cooling load reduces by 38% and than the base case.
no heating is required in winter Cooling load reduces by
32% and no heating is
required in winter
Table 2: Analysis of Simulation for each Passive Design Strategies (Source: Author)
Cooling load (MWh)
10
9
8
7
6
Eastend Apartments
5
4
Chelsea West
3
2
1
0
Base case Double 1200 Night Roof Overall Combined
Glazing overhang cooling insulation insulation
Figure 4: Total cooling load for Eastend Apartments and Chelsea West office simulation (Source: Author)Building performance evaluation and simulation for existing buildings of composite climate: A case of 535
Delhi
3. Discussion
It was observed that Responsive Roof insulation is the most effective way of reducing cooling load
and overall energy consumption for a top floor apartment. Night cooling is the simplest mechanism
applied for this simulation to reduce the internal temperature effectively but, the automated windows
will not be applicable in practical use. The change in glazing type alone, without external shading, have
little effect on the overall performance since the size of opening remains the same and solar radiation
already penetrates through the glasses. It was also noticed that the overhang does not have a large
impact since most of the windows are located in areas where shading is provided by either vegetation or
by the neighbouring buildings. Appropriate thermal insulation of wall and roof prevent heat from
penetrating into the internal space and is most effective when combined with responsive and passive
night cooling for attaining thermal comfort.
4. Limitations of the model
External Errors: User errors like inaccurate input data, misinterpretation of output or simple
mistakes made during the course of modelling. Limitations of expertise in using the software can lead to
a different output and is very sensitive when designing for a specific cooling requirement. Modelling
calculations may not match the actual requirement. Over or underestimation of total internal gains can
seriously affect the results, although appliances audit can be made for the exact hours of use and user
behaviour can only be assumed.
The number of occupants varies especially in the office building. The occupancy profile being set
always takes into consideration a fixed number of people; this might overestimate the total internal
gains as well as the cooling requirements. The weather data used might not be up to date and slight
variation in temperature can change the comfort temperature in the area and most weather files are
taken at a specific location of a city and the micro climate of the site having greenery and water body to
cool the temperature might not be considered.
5. Conclusion
Building Performance evaluation is a useful and important step in maintaining and controlling the
overall performance of any building, particularly those existing. Improvements, where required, can be
analysed through the evaluation process. Building simulation plays a vital role in selection of the best
design strategies whether at the design stage or at the retrofitting stage. Through building simulation; a
simple design strategy can help to reduce the energy consumption of a building up to 30% reduction.
This will lead to an overall reduction of Carbon emissions in the city to an enormous extend. Building
performance evaluation and simulation, if done at the early stage of design, can ensure minimal to Net
Zero Carbon building.
References
Alex Nutkiewicz, Rishee K. Jain, Ronita Bardhan. 2018. “Energy modelling of urban informal settlement
redevelopment: Exploring design parameters for optimal thermal comfort in Dharavi.” Applied Energy 433-445.
Beker, Rachel. 2008. “Fundamentals of performance-based building design.” Building Simulation 17.
Central Electricity Authority. 2018. Annual Report 2017 - 2018. Annual Report, New Delhi: Government of India.
Centre for Policy Research. 2015. Categirization of settlements in Delhi. Annual, New Delhi: Centre for Policy
Research.536 Renthlei E. and Georege A.
Chaudhary, Juhi. 2017. “Retrofit Buildings to reduce Carbon Footprint.” Indian Climate Dialogue. 21 December.
Accessed May 22, 2019. https://indiaclimatedialogue.net/2017/12/21/retrofit-buildings-carbon-footprint/.
Delhi Development Authority. 2010. Master Plan For Delhi 2021. Delhi: Delhi Development Authority, New Delhi.
2019. Double Glazing Info. Com. Accessed May 18, 2019. http://www.double-glazing-info.com/.
2019. IES Virtual Environment User Guides. Accessed June 1, 2019. http://www.iesve.com/downloads/help/ve64/.
International Energy Agency. 2017. UN Environment and International Energy Agency (2017): Towards a zero-
emission, efficient, and resilient buildings and construction sector. Global Status Report 2017. Annual, United
Nations Environment Programe.
Joytirmay Mathur, Rajeev Kathpalia. 2008. “Design of Passive cooling system for a building in composite climatic
conditions in India.” International Journal of Sustainable Design 10.
Kamaruzzaman, Maszuwita Abdul Wahab and Syahrul Nizam. 2011. “Building Performance and Evaluation Methods:
A Preliminary Review.” 2nd International Conference on Project and Facilities Management. Kuala Lumpur: 2nd
International Conference on Project and Facilities Management. 10.
Lall, Ashok. 2007. “The DNA of Metropolitan Growth and the Prospect of Sustainability - New Delhi an Indian Case
Study.” LafargeHolcim Foundation for Sustainable Construction. Accessed May 22, 2019.
https://src.lafargeholcim-foundation.org/dnl/ab079427-b3e4-47d7-864e-f7535a89ce85/F07-WK-Grn-lall02.pdf.
Luisa F. Cabeza, Alvaro de Gracia, Anna Laura Pisello. 2018. “Integration of renewable technologies in historical and
heritage buildings: A review.” Energy & Buildings 16.
Olufolahan Oduyemi, Michael I. Okoroh. 2016. “Building performance modelling for sustainable building design.”
16.
P. Hoes, J.L.M. Hensen, M.G.L.C. Loomas, B. de Vries, D. Bourgeois. 2018. “User Behaviour in whole Building
Simulation.” Energy and Buildings 8.
Rajat Gupta, Matt Gregg, Sanyogita Manu, Prasad Vaidya & Maaz Dixit. 2019. “Customized performance evaluation
approach for Indian green buildings.” Building Research & Information 47:1, 56-74.
The Energy and Resources Institute. 2013. Roadmap for Incorporating Energy Efficiency Retrofits in Existing
BUildings. New Delhi: The Energy and Resources Institute.You can also read
