IBPSA Competition Entry_Harvard GSD

Student Modelling Competition

Design and simulation of a mixed-mode office building Aman Singhvi, Elnaz Tafrihi, Juan M. Yactayo, Nada Tarkhan

Building Simulation 2015

Executive Summary

Introduction This report aims to both establish and test a methodology for designing passive strategies for a naturally ventilated office building. Lighting design, airflow assessment and overall energy usage become integral indicators for design features such as façade design, interior arrangement, program distribution and material selection. In order to ensure a comprehensive process, we have chosen to use simulation tools in a phased manner to ensure that our findings are well informed. The aim of integrating several simulation tools is to capitalize on specialized features and reach a greater degree of accuracy keeping in mind our assumptions and limitations of each tool. Our aim in coupling different testing methodologies is to aid simulation to better inform architectural decisions.

Strategies The process was started with the analysis of the climate using the provided weather file of New Delhi. Since it was apparent that it is a very hot climate, the cooling loads were very high. This was reduced significantly by incorporating a solar chimney to flush out the heat. The second phase of design was to optimize the openings for both thermal performance and lighting. A multi-functional and adaptable facade system was designed based on exact solar angles to shield the building from high solar gains on the South, East and West while simultaneously maximize Northern indirect light to reduce lighting loads. Moreover, each facade was given a different window to wall ratio according to radiation studies. At every design iteration relevant data from CFD results and fuel totals from Energy-plus results were observed. In order to tackle the pollution and high CO2 content in New Delhi, that may hinder a ventilation scheme, we probed into Titanium Di-Oxide’s properties of naturally reacting with harmful Nitrates and Sulphates and reducing them to useful Water and Oxygen. An additional layer of native green plants and climbers ensure cleaner air entering the building further improving air quality.

Finally, the materials of the building were upgraded. Using double glass helped reduce heat gains significantly as well as increasing the insulation of the building construction.

Results The final design of the house shows an annual energy consumption of 69 MWh. This result represents a reduction of 61% from the original Base case model. Using natural ventilation strategies along with other active and passive design features has enabled a 70% reduction in cooling energy needed. The lighting load was also reduced significantly by testing different opening sizes and incorporating lighting controls. The total ventilation hours in the year are 3917, which resemble an increase of 55% as compared to the base case design. Moreover, our design aims to enhance air quality by adding a unique shading and filtration system to the facade that purifies incoming air and reduces CO2 content.

1

Table Of Contents

Our Position on Simulation and Design; “ Simulation tools are to test complex synergies of an idea in a practical scenario.

Using these tools in their appropriate limitations, together in a comprehensive methodology, opens up possibilities of creativity in Design, not only functionality.

Our explorations are in light of a symbiosis between simulation and design.�

Executive Summary ...................................................................................................................................... 1 Nomenclature ...............................................................................................................................................2 Introduction...................................................................................................................................................2 Methodology and Design Workflow..................................................................................................................2

Mixed Mode Coupling strategy.........................................................................................................3

Modelling Plan............................................................................................................................... 4 Climate and Context Analysis..........................................................................................................................5 Base Model Design........................................................................................................................................7

Model Inputs.................................................................................................................................. 7

Results: CFD.................................................................................................................................. 8

Results: Energy.............................................................................................................................. 9 Conclusion..................................................................................................................................... 9 Building Design............................................................................................................................................. 10

Plans and facade details................................................................................................................. 11 CO2 Concept...................................................................................................................................12 Chimney and Ventilation Scheme....................................................................................................................13 Lighting and Shading Design..........................................................................................................................14 Design........................................................................................................................................... 14

Modeling Method............................................................................................................................14 Result............................................................................................................................................ 15 Material Selection..........................................................................................................................................15 Design........................................................................................................................................... 15

Modeling Method............................................................................................................................15 Result............................................................................................................................................ 15 Site Renewable Energy...................................................................................................................................15 Design optimization....................................................................................................................................... 16 Final Results and Conclusion..........................................................................................................................17 Appendices

2

Nomenclature Autodesk Ecotect Analysis: is a software tool for shading studies and Solar analysis.

DesignBuilder: is a software tool for calculating building energy usage, carbon, lighting and comfort performance. The main engine used to perform these calculations is the Energy-plus simulation engine.

DIVA-for-Rhino: is a highly optimized daylighting and energy modeling plug-in for the Rhinoceros - NURBS modeler.

FloVent: is a computational fluid dynamics software that predicts 3-D airflow heat transfer, contamination distribution and comfort indices in and around buildings of all types and sizes.

HoneyBee: Honeybee is an open source environmental plugin for Grasshopper to help designers create an environmentally-conscious architectural design. Honeybee connects Grasshopper3D to EnergyPlus, Radiance, Daysim and OpenStudio for building energy and daylighting simulation.

Introduction The aim of this project is to design and test a mixed mode ventilation strategy for an office building located in New Delhi, India. Using the provided weather file, the annual climatic data was analyzed and used for the formulation of a building strategy. The competition requires compliance with thermal comfort ranges i.e. 20.3 deg C to 26.7 deg C (calculated by PMV model ASHRAE 55 handbook of fundamentals 2010) indoors and an assessment of air quality (CO2) when natural ventilation is used.

In addition, the proposed scheme must detail opening sizes, furniture layout and facade details. The design needs to demonstrate that all these features operate under the ventilation scheme while reducing the overall energy demand.

The next section provides the main strategy and software use at every stage in the design process.

Methodology and Design Workflow Mixed Mode Coupling Strategy In order to test a mixed mode building, a natural ventilation schedule needs to be formulated. This schedule would tell us the times at which the external temperature is achieving a comfortable indoor temperature. After knowing this, we would then need to calculate the cooling loads with the use of natural ventilation by deducting the hours where the temperature is satisfactory. CFD and Energy Analysis offer complimentary information that can be used to obtain the above information. Below is a breakdown of the coupling strategy: Step 1: By setting sensors in CFD and running a parametric simulation we can know the outdoor temperature that is satisfying the indoor environment.

Step 2: Run the design builder energy simulation with mechanical ventilation on. This will give you total cooling as well as breakdown of lighting and equipment loads.

Step 3: Remove the cooling energy consumption in hours where the outdoor condition satisfies indoor comfort temperatures. This will then give the total energy consumption.

The details of the ‘IF’ statements used to filter out the hourly cooling data can be seen in Appendix A.

3

Modelling Plan

Natural Ventilation Softwares Main use of Software

Design Sequence 1. Design of Chimney and ventilation scheme

Flovent Assessment of airflow patterns within building volume and indoor temperature

4. Design Optimization

Consumption

DIVA (Rhino Plug-in)

Design Builder (Energy Plus)

Evaluating effectiveness of lighting strategies in achieving target illumination

Calculating total energy usgae of building based on passive strategies designed

- Chimney integration for bouyancy ventilation - window size and location - Shading design

2. Lighting, Openings and shading design 3. Material Selection

DaylightinEnergy

- Glass type - Construction type - Wall materials -Location of desks, shelves and other office furniture -Mechanical ventilation strategy

5. Final Energy Consumption

-Energy consumption breakdown (cooling, heating, lighting etc.) set cooling consumption to 0 in hours when natural ventilation can be used

COUPLING CFD WITH ENERGY SIMULATION

Energy Consumption without natural ventilation

Outdoor temperature when natural ventilation

alone is adequate

- Energy consumption with natural ventilation - Total annual ventilation hours 4

Climate Analysis The Site is located in New Delhi, India.

The climate of New Delhi ranges dramatically from a humid subtropical to semi-arid, varying from year to year. Within New Delhi itself, the wind, humidity levels as well as pollution levels vary depending on which area the site is located in. Nevertheless, pollution is a major concern for the entire city especially in the last couple of years. This adds to the already existing challenges of using natural ventilation in buildings.

Analysis: The Sun Path Diagram and Global Horizontal Radiation diagrams were generated from the weather

file provided using weather analysis plug-ins; Ladybug and Honeybee for Rhino. A major part of the year the site receives radiations more than 800 KWh/m2 where the corresponding average outside temperatures remain above 26 Celsius. This hot zone (marked above) roughly falls between late March to September from 7:30am to 5:00pm. The maximum highs can go up to 46 C. Monsoon starts mid-June and stretches till August where, even though the temperatures are still high, there is very rapid increase in humidity levels.

Furthermore, the entire spectrum of 8760 hours was plotted against temperature in 3D to synthesize total number of hours that fall in comfort range. This gives us a preliminary direction towards forming a ventilation strategy.

5

3Dimensional temperature plot of 8760 hours of a year and their analysis

Jun / Jul May / Aug

East North

Apr / Sept

West

Wind rose : Winter

Wind rose : Summer

Climate and Context Analysis

Comfort Range Internal gains Evaporative Cooling

Wind : Wind speeds and directions for the Summer and Winter months were analyzed separately and found that predominant

wind direction varies greatly from NW, NE and E in Summer to N and NW in Winters. NW is found to be most frequent annually.

Psychrometric Chart Analysis: Since the building is an office building, there are many hours in a year that can be brought under comfort ranges only by these internal gains (shown above). Moreover a major part of the year the building would require some for of cooling and dehumidification. A few summer hours can be made comfortable by evaporative cooling.

Shadow Analysis and Shading Calculations: Analyzed using Ecotect engine, the shading calculations were carried out on various points on each facade to get the aggregate effects of shading by context. This was also analyzed in annual ranges.

Jan / Dec

Combined point shading projections and shadow ranges

South East

Psychrometric chart

Mar / Oct

South West

Mech. Cooling and dehumidification

Shading calculations for points on each facade

Monthly shadow range analysis for 6 mirror months

6

Base Model Model Inputs: CFD and Energy surroundings modelled

Schedule:

In order to construct the base case model, both a CFD and a Design builder model were built.

The two buildings in the immediate context were also modelled in CFD as they would impact the airflow entering the building. The loads data was inputted based on the provided schedules.

Both models were then matched. For the CFD model, a steady state result is simulated. For this reason the worst case scenario (highest loads data) was simulated as blocks with thermal power in their relative locations (lighting, occupants and equipments). According to the schedule provided this was between 9:00 am and 12:00pm and from 2:00pm till 5:00pm on weekdays.

For annual energy consumption, the schedule was inputted in design builder format. This can be found in Appendix B.

CFD Model

Material Properties:

- Construction = lightly uninsulated brick block wall - Window to wall ratio = 30% (all facades) - Window assembly = single glass clear More details on materials for both the base case and re-design can be viewed in Appendix C.

External Environment:

Concerning the external environment modelled, climate data was used as a reference. As the aim is too determine the threshold outdoor temperature at which the indoor temperature is pleasant, the ambient and radiant temperatures were set to 26.7 and 28.7 respectively. The radiation and date were matched to this temperature based on climate data. The inputted radiation was 970 and date was March 21.

Window Operability:

The CFD model assumes that the Eastern and Western windows were open to ventilate both sides of the office, divided by the central atrium. For more details on exact window locations, interior layout and plans, please see Appendix D

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Design Builder Model

Lighting loads increasing occupancy Equipment and occupant loads

Base Model Results: CFD The results shown represent the speed and temperature profiles of sections through the building. The sectional cuts at every floor were taken at a height of 1.0 m off the floor where the occupants would be in a seating position.

Temperature distribution at each floor

The vertical section temperature profile shows that the lowest temperatures in the building can be found on the lowest level. The temperature then increases going up, with the highest temperature in the top floor. A closer look at the building’s radiation exposure shows that this is due to the most exposed surfaces to radiation being the roof and the South Facade. This resembles both an opportunity and a disadvantage to the top floor. Strategies should utilize the air stratification that occurs with higher temperatures that cause negative pressure.

Concerning distribution, the temperatures seem to be uniform throughout each floor. The central atrium space seems to be a an area accumulating heat. This would also need to be addressed in the re-design. The speed profile shows that speeds do not exceed 1.2 m/s. Since the East-West windows are open, higher speeds can be seen with air flowing out the windows, especially at the top floor.

Third FLoor

Temperature distribution

Sensors were placed on each floor to know the temperature at 5 different points.

Carrying out a parametric simulation, the ambient temperature was stepped down in 1 degree Celsius intervals in order to see at what ambient temperature, an internal comfortable temperature could be reached.

Location of sensors

Second Floor

Speed distribution

1first Floor

Southern Facade

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CFD Sensor results The parametric sensor readings indicate that at an external ambient temperature of 20.7 C the indoor temperatures are comfortable and are below 26C. Higher ambient temperatures do not satisfy the comfort range with the present design.

Also chimney sensors indicate higher temperatures in top floors, which indicates air stratification occurring.

Results: Energy

The monthly fuel breakdown shows that the highest annual load is cooling. This peaks during summer months where the temperature is at its highest. The energy required for lighting and equipment is relatively constant through out the year.

The annual Fuel totals are as follows: Total Electricity: 176.35 MWh Normalized Electricity: 370 Wh/m2 x10^3 Room electricity: 21,719 kWh Lighting: 61,290 kWh Cooling: 91,019 kWh DHW: 2,242 kWh Total Ventilation hours in a year: 2527 hours This was obtained by counting the hours in the year (using an excel formula) where the external temperature was between 15C and 20.7 C (as obtained from the CFD sensor readings).

Conclusion

The greatest potential for reducing the energy consumption lies in reducing the cooling load. A natural ventilation scheming incorporating a solar chimney could help flush out the heat and bring in cooler air.

More over, heat gains must also be reduced through glass and material selection as well as shading design. Lighting loads can be addressed through Northern facade openings that bring in natural light and reduced Southern facade openings to decrease heat gains.

The next sections carry out analysis on the above strategies.

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Fuel kWh

25000 20000 15000 10000 5000 0

Jan

Feb

Mar

Apr

May

Jun

Jul

Room Electricity kWh

Lighting kWh

Cooling (Electricity) kWh

DHW (Electricity) kWh

Aug

Sep

Oct

Nov

Heating (Gas) kWh

Dec

Building Design Chimney: Buoyancy driven ventilation by introducing a ‘glass box’ as an extension of the existing shaft to maximize solar gains’ potential as pulling force.

18 people total

Lower occupancy in top levels as there are already high heat gains from solar radiation

24 people total

28 people total

Furniture materials and layout: Interior layout designed to balance occupancy and wind flow paths inside the spaces. The design, material selection as well as placement of furniture is done so as to achieve a path of minimum resistance in the direction of wind flow.

Sectional perspective with macro scheme

Chimney: Optimized for maximizing North Light into the floors and for buoyancy driven ventilation performance

Construction: Using Rat-Trap bond construction technique for increased insulation and 30% material reduction. Glass type used is double low-e Argon filled .

Buffer Space: Layering of facade elements creates a permeable buffer space for heat flush and protection from extreme hot and cold winds.

Facade: Titanium Di-oxide coated facade with native planters and climbers for naturally purifying incoming air from particulates and harmful active gases.

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Plans and Facade Details ENTRY

OFFICE SPACE

OFFICE SPACE

PANTRY

Ground Floor Plan

VOID

OFFICE SPACE

MANAGEMENT PANTRY PRINTER

2nd Floor Plan

ADMINISTRATION

CONVERTIBLE MEETING

VOID

PANTRY

3rd Floor Plan

The facade design plays a crucial role in determining the building’s performance in energy, ventilation and lighting. For this reason, a multi-functional facade system was developed to serve simultaneously as shading device, green layer, pollution reducer, thermal buffer and for aesthetics. The resulting facade is a system of vertical porous members with increased surface area coated with Titanium Di-oxide paint along with a system of season-adjustable planters acting also as movable shading element. Titanium dioxide in the presence of UV light component of daylight reduces harmful polluting Nitrates and Sulphates into water and oxygen.

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OFFICE SPACE

OFFICE SPACE

OFFICE SPACE

CHIMNEY

OFFICE SPACE

OFFICE SPACE

Refer to Appendix F for Detailed Plans

CO2 concept Design Modeling Method

Using the standard “Ventilation for Acceptable Indoor Air Quality” (ASHRAE 62-2001). We were able to obtain average CO2 levels in ppm. These are listed below: Indoor Level generated by occupants - should not exceed 650ppm - assumed to be 650ppm in the redesign - typical CO2 level in air 380ppm - in New Delhi it was recorded as 400ppm - indoor limit- 1,030 ppm The aim of this simulation was to check the indoor CO2 levels we would be getting with an outdoor reading of 400ppm with our re-designed ventilation scheme. The same sensors that were used to measure temperature also measured CO2. A concentration of 400pm was inputted as an ambient quality in the CFD interface.

Result:

The highest recorded ppm was 400. If this is added to the internal level assumed to be 650 ppm then the total would be 1050 ppm which is higher than 1,030 ppm. If this level ever increases by changes in occupancy or external conditions, the fin system and vegetation would reduce the CO2 content from the incoming air. However, the effective contribution cannot be determined accurately.

This pollution analysis carried out in 2015 shows PM 2.5 levels to be all time high in areas of New Delhi.

It is categorized as extremely unhealthy. The facade system’s total surface area coated with Ti02 is calculated to be 5.18 x 106 sq. cm. for EAST and WEST facades, which is enough to reduce majority of the harmful polluting gases at peak time (morning and evening pollution levels).

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Chimney and Ventilation Scheme

Alternative 1

Alternative 2

Staircase Shaft

North Shaft

Design The aim of this scheme is to turn the central atrium space into a solar chimney in order to flush out the accumulated heat gains. This scheme relies on buoyancy driven ventilation where the the negative pressure created at the top would create a suction force and expel the hot air. This was designed to go in accordance with the wind direction so that an extra boost could be provided by the North westerly winds. For the sake of this modeling exercise, a no-wind scenario was assumed in order to evaluate the effectiveness of the solar chimney.

Modeling Method Since the solar chimney should heat up, the exterior Southern Facade was modeled as glass.

In the previous design, the central atrium space was divided in a staircase section and a shaft section. In order to optimize the chimney design two alternatives were tested: - Alternative 1: The Staircase shaft oriented South is used as the solar chimney - Alternative 2: The atrium shaft is used as the solar chimney and elevated to have a South facing glass wall.

In order to eliminate back flow at the top level, the openings from the floors to the chimney were tested at different sizes. A summary of all opening sizes will be provided in the next section where lighting was also tested to determine the optimum areas of external windows as well.

Finally. in a final test to evaluate suction power. Two opening orientations were tested for the top of the chimney- one South facing, the other as a roof opening.

Temperature distribution

Result A significant improvement can be seen from the base case. Since heat is flushed out, the top floor temperatures have decreased greatly. Both alternatives are very similar in speed and temperature distribution. The second alternative was selected for two reasons, these are listed below: 1- No obstruction in airflow: the Staircase shaft could interrupt buoyant flows which would slow down the speed of air being flushed out.

2- No openings in core wall- the central staircase wall would not need to be punctured in the second alternative. The structural integrity of the building would not be affected. The next set of studies analyze chimney opening location and opening areas.

13

South opening of Atrium shaft

Speed distribution

Lighting and Shading Design Daylight Availability 350 Lux / 4 AB / Base Case

Daylight Availability 350 Lux / 4 AB / Design Case

Ground floor has underlit areas

major Improvement in over-lit areas

Uneven distribution of light at perimeter and corners

Achieved good light distribution around periphery

A large amount of direct heat gain and overlit areas

Reduced overlit spots indicate less heat gain

1. Northern Light - expanded North Openings 2. Shading to reduce over-lit areas and heat gains 3. Lighting controls 4. Having several smaller openings helps in even temperature distribution indoors 5. Facade fins have closed and open configuration Total Electricity: 106.3 MWh [ Room electricity: 21,719 kWh, Lighting: 17,994 kWh, Cooling: 64,782 kWh, DHW: 2,242 kWh] Altitude angle

Height of window

Width of window

Horizontal Projection

Area of openings (each floor)

East Facade

550

1.6 m

0.6 m

0.8 m

5.76 m2

West Facade

550

1.6 m

0.6 m

0.8 m

5.76 m2

North Facade

-

2.4 m

0.6 m

0.8 m

17.28 m2

South Facade

CALCULATED AREAS

600

1.2 m

0.4 m

0.8 m

17.28 m2

Chimney

-

0.8 m

2.5 m

-

5.20 m2

Chimney at the top

-

2.5 m

2m

-

5.00 m2

Ground Floor

Design

Both the base case and design case have analysis grid of 50X50 cm and at a height of 60cm above each floor. Inputting the provided weather file simulations were run on DIVA daylighting software using ‘Daylight Availability Metric’ keeping Lux threshold at 350 and ambient bounces as 4. All geometry were modeled with as much details as possible.

First Floor

Modeling Method

Result

From an energy perspective, the re-design of windows and use of lighting controls reduced the lighting load by 70%. This greatly reduced the total energy consumption of the building. Adding the buffer layer and shading screen, shielded the building from direct sun exposure and reduced the cooling load by 29%. From a daylighting perspective; overlit areas were reduced to only 4% of occupied time.

Over-Lit

25000

Second Floor

20000 15000 10000 5000 0

Jan

Feb

Mar

Apr

May

Jun

Jul

Room Electricity kWh

Lighting kWh

Cooling (Electricity) kWh

DHW (Electricity) kWh

Aug

Sep

Oct

Nov

Heating (Gas) kWh

Dec

14

Material Selection The aim of changing materials was to reduce heat gains and hence reduce the cooling load. By changing both the glass and external wall properties, we could test their impact on the total energy consumption of the building.

A closer look at the gains data and heat balance shows that there is significant gains from lighting and solar gain.

Enhancing the glass performance could help tackle this issue.

Gains Data

Design

Modeling Method

The construction selected was an insulated brick/block wall with a U-value of 0.156 (W/m2-k). The glass was upgraded from single pane glass to double glazing, clear, low-e, argon filled. More details on the material properties can be seen in Appendix C. 25000

Result

Total Electricity: 84 MWh Room electricity: 21,719 KWh Lighting: 17,917 KWh Cooling: 42,394 KWh DHW: 2,242 KWh

20000 15000 10000 5000 0

The biggest reduction was in cooling energy which was reduced further by about 34%.

Calculations

It is found that the roof receives a maximum of 1817 KWh/ m2 of Solar Energy annually.

We have total roof area as 150 m2, total roof area available for Solar PV panels is 70% of 150 m2 = 105 m2 Total energy received by the roof which is available as potential renewable energy = 1817 KWh/ m2 X 105 m2 = 190,785 KWh Considering the efficiency of Photo-Voltaic panels is 15%, the maximum harnessed solar energy would be = 190,785 KWh X 15% = 28,617 KWh (Approx.)

Hence, a further reduction of 28,617 KWh (28.6 MWh) in electrical loads can be achieved by utilizing solar energy potential which is another 34% reduction in total energy. Also, the optimum angle of rotation for solar panel with horizontal axis was found to be about 280 - 300.

Result 28

0

15

Total Electricity : 55.4 MWh

(Please see enlarged images in Appendix G)

To further decrease the energy consumption of the building, we looked into potential for harnessing solar energy on the site. An annual solar radiation simulation was run using DIVA simulation software and energy received per unit roof area is calculated based on analysis of specific points.

Annual Solar Radiation Analysis : NW and SW Perspectives

Site renewable energy

Jan

Feb

Mar

Apr

May

Jun

Jul

Room Electricity kWh

Lighting kWh

Cooling (Electricity) kWh

DHW (Electricity) kWh

Aug

Sep

Oct

Nov

Heating (Gas) kWh

Dec

Design Optimization Opening to chimney

Furniture Layout

As can be seen in the vertical section, the furniture does not interrupt flow patterns. The external windows are high enough to bring in air above the workplace and likewise, the chimney inlet has a high opening. This means that the air circulation is above the occupied zone and hence the air is not stagnant. This can be seen on the plane in the section mapping the air speed.

Mechanical Ventilation

In times when natural ventilation won’t be used, mechanical cooling must be provided. Below are the proposed considerations and design attributes.

Location

As indicated in the diagram, the distribution points can be adjacent to the facade, in the direction of airflow. Units can be placed at a height of 0.6m above the ground so as to serve the occupied zone as cooling the whole building volume could be wasteful.

Peak load reduced

In reference to system sizing, one of our main goals was to not only reduce cooling hours but also the peak annual load. Reducing the highest load in the year would mean a reduction in the system size.

In the Base case the maximum hourly load reached is 50 kWh. In the re-design this has been reduced to 30 kWh. This resembles a 40 % reduction.

Technology- Absorption cooling

Absorption cooling could be used to provide for the building’s cooling load. Since solar radiation is high, thermal solar collectors on the roof could be used to provide for the systems hot water input.

Through an endothermic reaction with lithium bromide as the refrigerant, this hot water could be used to cool the building.

proposed distribution points for mechanical ventilation

16

Base Case

Final Results Energy Totals

25000

The final results show a reduction of reduction of 61% in total energy demand from the original base case model with a final demand of 69 MWh. The cooling demand on its own has been reduced by 70% by both ventilation strategies and other design upgrades. The total annual ventilation hours have also increased by 55%. Details of

10000

20000 15000

5000 0

the sub components of the fuel totals at every design iteration can be found below.

Jan

Feb

Mar

Apr

May

Jun

Jul

Room Electricity kWh

Lighting kWh

Cooling (Electricity) kWh

DHW (Electricity) kWh

Aug

Sep

Oct

Nov

Dec

Heating (Gas) kWh

Final Re-design 25000 20000 15000 10000 5000

An additional energy produced by Solar Photo Voltaic is 28,617 KWh which brings down the total energy to 55.4 MWh from 84.2 MWh ( 34% further decrease). Using site renewable energy will lead to a total 68.5% reduction from the base case.

CFD Sensor Readings In the re-design the sensors in the space show that an ambient temperature of 24.7 C satisfies indoor comfort temperatures while using the buoyancy ventilation scheme.

It is important to not that initially the model was constructed to only be operated by convection. A resimulation with wind (average speed of 2m/s) shows that at an ambient temperature of 25 C indoor temperatures are comfortable. This is because the wind force would aid in flushing out internal gains.

Details of the cooling calculations based on the wind temperature threshold can be found in Apendix A.

0

Jan

Feb

Mar

Apr

May

Jun

Jul

Room Electricity kWh

Lighting kWh

Cooling (Electricity) kWh

DHW (Electricity) kWh

Aug

Sep

Oct

Nov

Heating (Gas) kWh

Dec

Speed Distribution

Results: Temperature and Speed Distribution The CFD results below show a significant improvement in overall temperature distribution. As heat is being flushed out by the chimney in the redesign, there is no longer accumulated heat in the shaft area and top floor. In the redesign, at an ambient temperature of 26.7 C, the internal temperature lies within the range of 27 C and 29 C.

Base Case

It is also important to note that due to improved material properties, the construction no longer retains as much heat. This is evident in the section where the floor slabs and wall sections appear to have a lower temperature when compared to the Base case.

Building Automation and Control In reference to the wind driven ventilation scenario, it was important to make sure that the indoor air velocity does not exceed 1 m/s. For this reason we have provided a control sequence for both wind and thermal regulation to determine when to open the windows. This can be seen in Appendix E.

Re-design

Temperature Distribution

Base Case

3rd Floor

Re-design

2nd Floor

1st Floor

Thank You

Team: Aman Singhvi ( asinghvi@gsd.harvard.edu ), Elnaz Tafrihi ( etafrihi@gsd.harvard.edu ), Juan M Yactayo ( jmyactayo@gsd.harvard.edu ), Nada Tarkhan ( ntarkhan@gsd.harvard.edu )

Appendix A- Total cooling calculations The data below was exported from the design builder simulation. The temperature thresholds for the excel functions were obtained from the CFD sensor readings.

Total hourly data

Outside temperature obtained from weather file

Total hourly cooling obtained from design builder simulation with mechanical cooling on

Total hourly cooling after removing cooling when ambient temperature is between 15C and 24.7 C

Total hourly cooling after removing cooling when ambient temperature is between 15C and 25 C

Excel Functions and Explanation

=IF(AND(B3>15,B3<=24.7),0,C3) According to the CFD results, an ambient temperature of 24.7 satisfies indoor comfort conditions when using natural ventilation. Hence when the temperature is under 24.7, the cooling load has been zeroed out. =IF(AND(B9>15,B9<=25),0,C9) When wind is simulated, an ambient temperature of 25 satisfies indoor comfort conditions when using natural ventilation. This is because the wind boosts the heat flushing effect. Hence when the temperature is under 24.7, the cooling load has been zeroed out.

Since all the ambient temperatures are between 15C and 24.7, the cooling has been removed from the natural ventilation scheme (Columns D and E).

Appendix B- Loads Schedule Design Builder SchedulesOccupancy

Equipment

Lighting

Schedule:Compact, Office_OpenOff_Occ, Fraction, Through: 31 Dec, For: Weekdays SummerDesignDay WinterDesignDay, Until: 07:00, 0, Until: 08:00, 0.15, Until: 09:00, 0.6, Until: 10:00, 0.9, Until: 11:00, 0.9, Until: 12:00, 0.9, Until: 13:00, 0.7, Until: 14:00, 0.7, Until: 15:00, 0.9, Until: 16:00, 0.9, Until: 17:00, 0.9, Until: 18:00, 0.5, Until: 19:00, 0.15, Until: 20:00, 0.05, Until: 24:00, 0, For: Weekends, Until: 10:00, 0.05, Until: 11:00, 0.05, Until: 12:00, 0.05, Until: 13:00, 0.05, Until: 14:00, 0.05,

Schedule:Compact, Office_OpenOff_Equip, Fraction, Through: 31 Dec, For: Weekdays SummerDesignDay WinterDesignDay, Until: 01:00, 0.15, Until: 07:00, 0.15, Until: 08:00, 0.4, Until: 18:00, 0.9, Until: 19:00, 0.6, Until: 20:00, 0.4, Until: 21:00, 0.2, Until: 24:00, 0.15, For: Weekends, Until: 01:00, 0.15, Until: 09:00, 0.15, Until: 16:00, 0.25, Until: 17:00, 0.0, Until: 24:00, 0.05, For: Holidays, Until: 24:00, 0.05, For: AllOtherDays, Until: 24:00, 0;

Schedule:Compact, Office_OpenOff_Light, Fraction, Through: 31 Dec, For: Weekdays SummerDesignDay WinterDesignDay, Until: 01:00, 0.05, Until: 07:00, 0.05, Until: 08:00, 0.4, Until: 09:00, 0, Until: 18:00, 0.9, Until: 19:00, 0.6, Until: 20:00, 0.4, Until: 21:00, 0.2, Until: 24:00, 0.05, For: Weekends, Until: 01:00, 0.05, Until: 09:00, 0.05, Until: 16:00, 0.25, Until: 24:00, 0.05, For: Holidays, Until: 24:00, 0, For: AllOtherDays, Until: 24:00, 0;

Appendix C- Material Properties Source (CIBSE Guide in Design Builder) 1- Base Case:

2- Redesign

Wall Assembly: starting with outermost

Wall Assembly: starting with outermost

Layer 1: Brick work, 0.1m thickness Conductivity (W/m-k)= 0.840 Density (kg/m3)=1700 Specific heat (J/kg-K)= 800

Layer 1: Brick work, 0.105m thickness Conductivity (W/m-k)= 0.840 Density (kg/m3)=800 Specific heat (J/kg-K)= 1700

Layer 2: XPS Extruded Polystyene, 0.0795m thickness Conductivity (W/m-k)= 0.034 Density (kg/m3)=1400 Specific heat (J/kg-K)= 35

Layer 2: XPS Extruded Polystyene, 0.2m thickness Conductivity (W/m-k)= 0.034 Density (kg/m3)=1400 Specific heat (J/kg-K)= 35

Layer 3: Concrete block, 0.1m thickness Conductivity (W/m-k)= 0.510 Density (kg/m3)= 1000 Specific heat (J/kg-K)= 1400

Layer 3: Concrete block, 0.105m thickness Conductivity (W/m-k)= 0.510 Density (kg/m3)= 1000 Specific heat (J/kg-K)= 1400

Layer 4: Gypsum Plastering, 0.0130m thickness Conductivity (W/m-k)= 0.4 Density (kg/m3)= 1000 Specific heat (J/kg-K)= 1000

Layer 4: Gypsum Plastering, 0.0130m thickness Conductivity (W/m-k)= 0.4 Density (kg/m3)= 1000 Specific heat (J/kg-K)= 1000

Total U-value of Assembly= 0.4 (W/m2-k)

Total U-value of Assembly= 0.4 (W/m2-k) Glass- double glazing, clear, low-e, argon filled

Glass- Single pane- clear 3mm Total Solar Transmission (SHGC)= 0.904 U-value = 6.2 (W/m2-k)

Layer 1: Clear 6mm Layer 2: Window gas: Argon 13mm Layer 1: Clear 6mm Total Solar Transmission (SHGC)= 0.698 U-value= 1.5 (W/m2-k)

Appendix D - Base Case Plans

Ground Floor Plan

3rd Floor Plan

2nd Floor Plan

Appendix E - Controls Temperature Controls Sequence ( Isolated) START TEMPERATURE SENSOR CHECK IF

Wait 15 minutes

T in < 25ºC

Y

N

T out > 27ºC Turn Fan ON

Y

T in < 20.3ºC

Close Windows

CHECK

T in < 25

N

Y

N

T out < 27ºC

Y

T in > 20.3

OPEN ROOF VENT

Y

T out > 15.3ºC

Y

N

Y

N

Wait 10 Minutes

Buoyancy Driven Ventilation MODE

Open Windows N

Open E and W windows

N

Close Windows

CHECK

Is Fan on?

Y

T in - Indoor Temperature T out - Outdoor Temperature Fan - Exhaust Fan

Turn off Fan

Check for Air Velocity at the sensors

NOTE: Sensors for temperaturs are places at the geometric center of each space’s largest surface as well as inside windows avoiding direct solar gains

Wind Velocity Control Sequence (Isolated) Check for Air Velocity at the sensors START AIR SPEED SENSORS

CHECK

Wait 20 minutes

0.5 < V in < 1.5

Y

Y

N

V in > 1.5

N

Is Fan on?

Y

Turn Fan OFF

Wait 15 minutes THEN

N

V in < 0.5 CHECK

N

V in - Indoor air speed V out - Outdoor air speed Fan - Exhaust Fan

Y

V out < 1.5

Y

Close Windows

N

V out > 0.5

N

OPEN CHIMNEY VENTS

Y

Turn Fan ON Open Windows Buoyancy Driven Ventilation MODE with Fan assistance NOTE: Sensors for temperaturs are placed just outside the windows but inside the outermost facade layer ( fins and vegetation) .

Combined Controls Sequence

T in CHECK CHECK IF

Wait 5 mins

T in < 26ยบC

N

T out > 27ยบC

Y

CHECK

Y T in < 26

Wait 20 minutes

T out > 13ยบC

N

T out < 27ยบC

N

V in < 0.5 CHECK

Y

T in > 18

Open Windows

N

Close Windows

Y

N

Y

Close Windows

N

OPEN CHIMNEY

N

CHECK

V out > 0.5

Is Fan on?

Y

Y

Turn off Fan

V in - Indoor Air Velocity V out - Outdoor Air Velocity Fan - Exhaust Fan Chimney - Operable window in each floor and at the roof facing SOUTH

THEN

Y

V out < 1.5 Wait 10 Minutes

Turn Fan OFF

Wait 15 minutes

N Open E and W Windows

Y

V in > 1.5

N

Is Fan on?

Y

N OPEN ROOF VENT

Y

Y

0.5 < V in < 1.5

N

Check V in

Y

CHECK

Turn Fan ON

T in < 18ยบC

Close Windows

Y

T in - Indoor Temperature T out - Outdoor Temperature Fan - Exhaust Fan

Wind Driven Ventilation MODE

Buoyancy Driven Ventilation MODE

Turn Fan ON

Mixed MODE

Appendix F - Detailed Plans

ENTRY

OFFICE SPACE

OFFICE SPACE

PANTRY

Ground Floor Plan

VOID

OFFICE SPACE

MANAGEMENT PANTRY PRINTER

First Floor Plan

Aâ&#x20AC;&#x2122;

A

ADMINISTRATION

CONVERTIBLE MEETING

VOID

PANTRY

Second Floor Plan

OFFICE SPACE

OFFICE SPACE

CHIMNEY

OFFICE SPACE

OFFICE SPACE

OFFICE SPACE

Section AA

Appendix G - Annual Solar Radiation Analysis / DIVA simulation