FINAL THESIS_In the search of a Zero Architecture

IN THE SEARCH OF A ZERO ARCHITECTURE

using grasshopper for the design of a Zero Net Energy Library in California

BY AN AUTODESK

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IN THE SEARCH OF A ZERO ARCHITECTURE using grasshopper for the design of a Zero Net Energy Library in California

TFG GArqETSAB

STUDENT

Magdalena Ruiz Cordero

https:// https://lena8ruiz.wixsite.com/portfolio

TUTOR

Manuel Ferrer Sala

EXAMINATION LINE

Technology field TRIBUNAL

Josep Maria Gonzalez

Course 2019-2020

Escuela Tècnica Superior d’Arquitectura de Barcelona

Universitat Politècnica de Catalunya

The aim of this study is to analyse a different way of carrying out the design process within architecture, using the sun, location, orientation and form at the very early stages of the project. It is also the author’s wish to show the importance of, at least, discuss a new concept of architecture already needed in our fight against the greenhouse gas emissions. The Zero Emission Buildings (ZEBs) involves solutions for existing and new buildings, where carbon emissions for materials, production, operation and hypothetical demolition have to be compensated. This paper describes different levels of ambition within ZEB projects, and also clarifies the difference between Zero Net Energy buildings and Zero Emission Buildings. The development of this architecture requires cooperation in a large number of fields and will result in a variety of solutions depending on the context and climate of the location of the building. Therefore, rethinking the design process it is key in order to meet the targets of sustainability and energy demand required.

The hypothesis proposed by the study is to test how solar energy and solar harvesting, daylight and orientation can shape the building form, in order to minimize the energy use during the performance of the building, and covered the rest of the energy demand with renewables on-site, specifically using photovoltaic (PV) panels as another architectural element. To be able to analyse in depth these questions, this paper is a case study inside an architecture competition called “Architecture at Zero 2020”. The paper describes the development of a workflow for the production of a zero net energy library located in the city of Hollister, California, (USA). The design was required to incorporate the programmatic needs of the users of the library and balanced the energy consumption and production of the same, achieving the goals of a net zero energy building. Further information about the contest appears in the Annex section at the end of the study.

The present work deploys two parametric softwares that can be used in Rhinoceros, Ladybug and DIVA 4.0. Both of them are environmental plugins that by importing standard EnergyPlus Weather files (.epw file) in Grasshopper provides a variety of 2D and 3D simulations onto the 3D building model, supporting the decision-making process. Solar passive design among solar active design in kWh/m2 production have been the driven tool in the testing of different buldings forms. Ladybug is used in the preliminar environmental studies of the site, and to find the best tilt and orientation of the photovoltaic panels. Calculations in the total incidence radiation and the electricity production by the PV system have been run with DIVA 4.0.

The proposed method by modeling and simulation compares two final 3D models, both with integrated PV panels in its roofs. The result is a building envelope whose geometry is optimized for the collection of solar energy, while also taking into account other environmental aspects, such as passive solar heating and the implementation of a courtyard. The resulting geometry is redefined to meet the contest program requirements. The zero-net ambitions and emissions are acomplished, although none of the embodied emissions of the project were considerated. The final conclusions are that ZEB projects need ingenious designs and that the use of parametric programs like the ones used in this work can help to democratizes environmental analysis tools, fostering the advancement of environmentally-conscious architecture designs.

key words:

zero emission buildings, net energy, solar design, radiation, building form, public library, daylight, PV panels, parametric design, grasshopper

PREFACE

Before you lies the dissertation “In the search of a Zero Architecture”, the basis of a research that was conducted during my participation at the “ARCHITECTURE AT ZERO 2020” challenge, where the target was to create a zero net energy library for the San Benito County Free Library in Hollister, CA.

This study is motivated after my stay as an exchange student at The Oslo School of Architecture and Design (AHO), where I first used environmental plugins for Grasshopper, such as Ladybug and DIVA, to reach a basic understanding of how climate analysis can materialize in a design response. Since then, sustainability and the integration between architecture and nature have deeply interested me. My overall goals have been to use these digital tools to explore the integration of photovoltaic panels (PV) on sun exposed surfaces in the effort of the library to become energy “autonomous”. Among that, this paper intends also to be a reflection of sustainability and architecture, focusing on the definition of what carbon neutral architecture really means.

I would like to thank my supervisor, Manuel Ferrer Sala, my teachers in the “IN BALANCE” course inside the Master of Architecture AHO Spring 2019 program, and furthermore, my father, Roberto Ruiz Garcia, for his incredible support through my university studies.

INTRODUCTION

“Architects, if they are really to be comprehensive, must assume the enormous task of thinking in terms always disciplined to the scale of the total world pattern of needs, its resource flows, its recirculatory and regenerative processes.”

― Richard B. Fuller, Ideas and Integrities: A Spontaneous Autobiographical Disclosure

It is undeniable that global warming and climate change are caused by humanity. Since the industrial revolution, humans have released over 1.5 trillions tons of CO2 (carbon dioxide) into the Earth’s atmosphere [1]. According to the IPCC1, if we want to keep the global temperature from rising above 2 degrees Celsius in this century, we need to take global actions that involves transitions in land and ecosystems, energy, urban and infrastructure and industrial systems [2]. Certainly, climate change is a complex paradox, where our way of life and density of population are in conflict with our planet balanced. Reduction of greenhouse house gas emissions (GHG), energy efficiency and a significant decline in the energy use is one of the most important measures to limit the rise in temperatures. In this scenario, architecture can plan an important role: Buildings and building construction sectors combined are responsible for over one-third of energy use and 40% of total direct and indirect CO2 emissions [3], and in recent years the emissions have risen2. Energy reduction in the building sector is, nowadays, crucial.

This work has two main objectives. The first is to discuss and clarify a new concept of architecture that takes greenhouse gas emissions into account in the design and construction process (Zero Emission Buildings or ZEB). In 2016, the European Commission developed guidelines to ensure that, by 2020, all new buildings would be “nearly zero energy buildings” [4]. However, the definition of “nearly” is not clear, and it is up to national and sometimes private sectors to interpret it. This lack of unanimity and the variety of terminology leads to projects that sell a false and utopian idea of sustainability, sometimes with the aim of financial gain. The ambition of each project and the type of building to be realized must be clear from the very design stages.

Therefore, the first purpose of this work is to investigate and develop in depth the definition of what “zero” architecture means, and the difference between Zero Net Energy (ZNE) and ZEB buildings. For this aim, the system of the Norwegian Research Centre for Zero Emission Buildings (ZEB Centre) will be used, which is based on research from 2009 to 2017.

1 - IPCC or Intergovernmental Panel on Climate Change is an organization that prepares Assessment Reports about the scientific state and impact of Climate Change.

2 - According to the IEA (International Energy Agency): “Energy-related CO2 emissions from buildings have risen in recent years after flattening between 2013 and 2016. Direct and indirect emissions from electricity and commercial heat used in buildings rose to 10 GtCO2 in 2019, the highest level ever recorded. Several factors have contributed to this rise, including growing energy demand for heating and cooling with rising air-conditioner ownership and extreme weather events.” Due to COVID-19, predictions about the emissions in 2020 are still in consideration.

The second objective is to provide a study case of a Zero Net Energy architectural project, showing a working methodology. To this end, the work includes my participation in the competition “ARCHITECTURE

AT ZERO 2020”, based on the design of a public library in the city of Hollister, California. The proposed hypothesis is that solar radiation and climatic conditions of a particular site, can contribute to the morphology of the building, integrating photovoltaic (PV) panels that cover the energy demand of the building’s operating cost. Computer-assisted simulations have been used in the development of the scenario. The environmental analysis tools chosen have been Ladybug and DIVA, both plugins for Rhinoceros and Grasshopper which provide interactive 2D and 3D graphics and show different climate analyses, such as solar radiation among others, to support the decision-making process during the initial stages of the design.

The final results will show the floorplans of the proposed architecture for the competition, with a construction detail of the roof and the building envelope. It will also show an estimation of the total generation of the PV panels over a year, and analyse if it is balanced with the demand and operational energy of the public library.

This work is not intended to be a definitive solution to the project, but an exploration of an interdisciplinary approach and of the values of sustainability within the discipline of architecture.

1. ZERO EMISSION BUILDINGS

1.1. Definitions within Zero: a matter of ambition

Conceptually, “zero” architecture can be paradoxical: How is it possible to build in a negative way, one that does not exert any influence on its surroundings, when precisely in the creation of any building it is necessary to exploit the resources in it? In terms of sustainability, vernacular architecture is that which best responds to an intrinsic relationship with the nature and climate of the place. One of the best architectural examples that have minimal environmental impact with maximum passive energy gain would be the igloo, which uses snow as a building and insulating material, along with the thermodynamic principles of convection and heat radiation.

In our current societies and cities, our buildings are not ephemeral or seasonal like traditional Inuit architecture. Nor do buildings today necessarily respond to climatic parameters or the context of the place, but are often works independent of the site where they are erected, with a high carbon footprint. Among that, we need to consider the emissions related to our western lifestyle. Wealth is one of the strongest indicators of our carbon footprint, because we gain access to electricity, heating, air conditioning, lighting, modern cooking, smartphones, computers….

We understand by zero architecture the one which takes into account all of these environmental costs and tries to compensate for it, aiming for a net zero balance over the lifetime of a building. Normally, this idea was referring to a zero net energy building (or ZNE buildings), which are the ones with a greatly reduced energy demand, such that this energy demand can be balanced by an equivalent generation of electricity (or other energy carriers) from renewable sources [5]. The main difference between a ZNE architecture and a ZEB architecture is that the last proposes to consider GHG emissions (kg CO2eq/m2) instead of only calculating the electricity expense in operational use. The radical thinking inside this approach is to consider from the initial design phase the embodied emissions of the particular architecture, among the emissions from operation and demolition.

Figure 1: Cross-section and floorplan of a Netsilingmiut igloo. External source.

Figure 2: The Beddington Zero Energy Housing Development, located in Hackbridge, London, England. Architect: Bill Dunster. External source

from operation of the building.

• ZEB – O ÷ EQ: The building’s renewable energy production compensate for GHG emissions from operation of the building minus the energy use for equipment (plug loads).

• ZEB – OM: The building’s renewable energy production compensate for GHG emissions from operation and production of its building materials.

• ZEB – COM: The building’s renewable energy production compensate for GHG emissions from construction, operation and production of building materials.

• ZEB – COME/COMPLETE: The building’s renewable energy production compensate for GHG emissions from the entire lifespan of the building. Building materials – construction – operation and demolition/recycling. (see figure 5)

This approach in design is focus on developing solutions for individual buildings that are self-sufficient on renewables. On the contrary, a NET building is grid connected, and balances its total annual energy needs with the electrical grid, allowing for the natural fluctuations of renewable energy production without the need for on-site energy storage. New studies about “smart cities” or zero emission neighbourhoods are considering connected ZEB buildings groups to achieve synergies between energy use and generation. However, in this study I will focus solemnly in the design and solutions for individual buildings, since zero emission neighbourhoods (ZENs) are beyond this topic.

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Weight supply Weight demand (kWh, kBtu, CO2) PRODUCED BY AN AUTODESK STUDENT VERSION

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Figure 5: Graph showing different ZEB ambition levels from the Norwegian ZEB centre. External source.

1.2. A common design process

“We are ecologically interdependent with the whole of the natural environment; we are socially, culturally, and economically interdependent with all of humanity; Sustainability in the context of this interdependence, requires partnership, equity, and balance among all parties.”

―UIA/AIA World Congress of Architects, Declaration of Interdependence for a Sustainable Future, Chicago, 18-21 June 1993

“What is good architecture? (…) Every project has a context, and you have to understand many different variables and make your own processes and research to make the design. That is why architecture is complex, it’s a whole.”

― Architect Xi Zhang, What’s good architecture and why the world doesn’t need more star architects, TEDx Zurich, 2019

To achieve the goals of ZEBs, architects and designers need to carry out the design process differently, and also involves to study and make different decisions from the early stages of design. As Johanna Sands analyse, “Architects are coming back to an ideological middle ground between advanced technology and traditional systems. For many years, architects have relied on mechanical systems to solve the indoor environmental and energy use problems that their aesthetically centered designs created” [7]. So it is not that we have invented new solutions inside the field of sustainability. The challenge of building with minimal impact on resources and the use of passive solutions from nature it has always been there. What is different nowadays is the complexity of the integration of all the parts in the overall concept, to think every system inside the whole of the design, and not only based on isolated performance criteria.

1.2.1. Main goals and design choices in Zero Emission Buildings

As described above, they are many ambition levels developed by the ZEB Centre’s pilot buildings. However the main goal behind every project, renovation or new construction, has to be on the fact that to reduce, (apart from the functionality and the comfort and experience of the users) is one of the most important premises. In every truly green project, passive energy design should be included since the beginning, as is crucial in the aim of reducing the energy demand and related GHG emissions. This reasoning is well illustrated through the Trias Energetica pyramid31(see figure 6). The Trias Energetica model contains three levels ordered according to their priority, with the objective of creating an energy-efficient design. These basic rules are as follows:

3 - The Trias Energética strategy was first developed in 1979 by the Urban Design and Environment (SOM-1) study group at the Delft University of Technology (TU-DELFT), and was published in BOUW

1. The first level is to reduce the energy demand (and therefore the related GHG emissions) by using energy reducing measures in the architecture itself and passive design, such as compact building form, orientation, plan, façade layout, good thermal insulation, heat recovery…In a ZEB process, this step also includes designing for low emission from construction and use of materials [5 p. 36] (Also connected with the actuation at level 3).

2. Make maximum use of energy from renewable sources such as wind, water and solar energy, for example by installing on-site a solar thermal systems, photovoltaics (PV), biomass, heat pumps etc.

3. If necessary, use the least polluting fossil fuels in the most efficient way as possible.

Following the Tria Energetica pyramid, we can summarize the design choices for an overall sustainable design into 9 main issues:

• Location, orientation and building form

• Daylight and sun

• Material choices

• The building envelope – insulation and airtightness

• Energy efficient lights and appliances

• Efficient heating, ventilation and cooling systems (using passive instruments as possible)

• Renewable thermal energy

• Renewable electricity

• Measurement and control

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Figure 7: Illustration of the Trias Energetica pyramide. Own production.

All of these design measures should not be interpreted as a linear checklist, but as a highly integrated process, where each measure has a direct or indirect impact on energy optimisation and architecture of the building. The interconnected methodology is shown below in figure 8:

The complexity of highly-performance building is, therefore, the multiple parameters and interrelated concepts that have to be taken into account. A way to increase the probabilities of elaborate environmentally responsive design decisions is to start answering meaningful questions, such a identify the main characteristics of the site and any environmental issues or factors that can influence the followed architecture.

To bring the designer closer to interdisciplinary knowledge, the use of parametric programs provide architects an integrative design platform where they can make environmental analyse and see the respond of the building according to its geometry form, materials and surroundings. In the present paper, analyse tools for Rhinoceros, such as Ladybug and DIVA 4.0 have been used in the definition of the proposed case study (see chapter 3). The principal design choices used from the overall 9 main issues have been the location, orientation and building form, daylight and sun and finally, renewable electricity

Figure 8: Diagram showing the interrelation between the design choices, and how they affect the resultant carbon dioxide emissions. Own production

The calculation for the emission balance in a building differs by countries and locations due to different energy supply systems, climates, and the accesibility to materials and land. As described above, in the theoretical case of a strictly ZEB methodology connected to the general grid, you should take into consideration the emissions from:

• The product stage: Where you count all emissions from the raw production, transportation and manufacturing of the materials. Here you should also account for the embodied emissions of renewables systems.

• Construction proccess stage: The emissions of carbon dioxide related to the construction process depends on the preparation of the ground, the erection of the building and the amount of waste generated and treated.

• Use stage of the building: The operational phase, where emissions are related to the users that occupy a building and its behaviour. Normally, it carries the biggest amount of energy demand of all phases; more or less all building Life Cycle Assessments (LCAs)41have concluded that the operational phase of a building has the largest environmental impact of all the different stages [8]. However, since in ZEBs or ZNE buildings projects, the operational phase is also the state where emissions are “paid “ back”, the embodied emissions are actually the largest contributors in kg CO2. [5 p. 72].

• End of life: The emissions related to the renovation or demolition of the building. The end of the use stage of a building is not easy to estimate, and there are serveral uncertainties regarding how you should account for carbon dioxide emissions. At the Norwegian ZEB Centre they estimate a 60-year time period of service, which is the periodical time that it has been used in Section 4.2.1.

The formula that applies when you include all possible energy carriers is as follows [5 p. 73]:

∆CO2 = CO2p + CO2mo + CO2e* (Qd- Qe) (1)

Where:

- CO2p is the product stage emissions in a year [kg CO2 eq/m2 per year]

- CO2mo is the material emissions during operation in a year, referring to the product stage replacements within the building) [kg CO2 eq/m2 per year]

- Qd refers to the annual electricity delivered to the building [kWh/m2 per year]

- Qe refers to the annual electricity exported to the grid from the building, and produced by renewables on-site. [kWh/m2 per year]

- CO2e averaged CO2 eq emission factor for electricity. [kg CO2 eq/kWh]

4 - A Life Cycle Assessment (LCA) measures the environmental impact associated with all the stages of a product’s life, which refers from the extraction of the raw material through its production, manufacture, distribution, use and end of life. Taking into consideration LCAs would make it possible to create better environmental design solutions.

1.3. The emission balance

2. CASE STUDY: A NEW PUBLIC LIBRARY FOR HOLLISTER (CA)

2.1. Context

2.1.1. “Architecture at Zero” 2020 competition

This competition started in 2011, when the Pacific Gas & Electric (PG&E) along with key partners formed the ARCHITECTURE AT ZERO challenge, which is a ZNE design challenge for a pre-selected site in California. In 2020 the task has being the design of a new library for San Benito County Free Library in Hollister, CA, replacing the existing structure. While accommodating the program, the main goals of the competition were to reduce building loads as much as possible to lower the renewable energy required to balance energy consumption and production.

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The design solutions needed to have a reasonable expectation of approaching the ZNE goal. The technical demands for this competition were:

- Energy was measured in “site” units [kWh/m2 or kBtu/sf]

- All buildings designed as part of the competition were grid-tied

- Renewable resources are provided on the project site, without counting on off-site ener

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- The ambition level in this competition was ZEB – O (only operational ener

- The energy demand target as a starting point for the competition was 24 kBtu/sf-yr, as the Energy Use Intensity (EUI)51

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The city of Hollister is located in the agricultural county of San Benito, part of the Monterey Bay Area and close to Santa Clara (also known as Silicon Valley). Regardless, the character of the region is mostly rural, with a composite landscape of oak woodlands and canyon bottoms among suburban communities.

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EUI or Energy Use Intensity, is a metric that divides the total energy consumption of buildings in one year by the total gross floor area or Conditioned Floor Area (CFA) of the building. Is normally express in kBtu/sf-yr units.

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Figure 9: Illustrations showing the state, county and region of the new library Own production

The foundations of the city had a perpendicular grid configuration, which is still mantaiend today. The historic Monterey Street, which crosses the city vertically in its cen ter, contains the majority of architecture richness and buil dings from this period and beyond. Like in many american cities, boundaries within districts depending on the character of the neighbourhoud are well stablished. The city centre is formed by malls, supermarkets, american-food restaurants and recreative entertainments. The north and south borders marked respectively the administrative and educacional part of town. In this context, the existing library is a hub for the community, hosting english and literacy classes, computer faccilities , free movie nights and even a “bookmobile” that delivers library services to the surrounding communities.

The town of Hollister in particular is most important of the region, containing two thirds of the county’s population. (The total population in San Benito was estimated in 2019 to be 62.808 where 40.740 of its population resides in Hollister). The city was founded in 1869 by William Welles Hollister, an american rancher and entrepenaur.

Figure 11: Floorplan showing the grid structure of Hollister, with the location of the library marked in red. Own production

Figure 10: Google Earth view of the town of Hollister and its urbanistic plan. The site of the library is marked in red. Own production

Last year, the Library hosted 892 programs with over 21,000 attendees. The intense use of the library urged for new installations; it requires a bigger square footage and more space to host programs, as well as more computers and IT facilities, since some residents can not afford to purchase a laptop. For Community Programs Librarian Erin Baxter, it needs to be “a place where people can meet and develop themeselves”.

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Figure 13: Site context and project area, showing the current historic bulding which will be removed, and the current library from 1960. Own production

Figure 12: Google street view images; first one shows the existing library entrance and the historical society building below (which will be relocated and should not be included in the design), while the second image shows the backyard with the parking lot. Own production

3. SOLAR ENERGY AND THE BUILDING FORM

3.1. Climate analysis

A good orientation and location of the building in accordance to the climatic and site conditions is the most efficient way in passive energy design¸ It creates the basis for the utilization of renewable energy. The state of California is divided in various climate zones, and the city of Hollister is in California Climate 4. Due to the lack of environmental data of the city of Hollister itself, for the competition we were using as reference the climate information of San José, another city in zone 4, around 74 km from Hollister. Weather files from San Jose Reidhill-Airport, for 3d simulations using Grasshopper and Rhinoceros, were obtained from “EnergyPlus Weather Data” [9].

Both cities are inside the Central Coastal Range, inland from the coast but with some ocean influence. Seasons are sharply defined. Summers are hot and dry, with a large daily temperature swing, making cooling a necessity. Winters are cold, but not severe, and normally the days are with clear skies, because the coastal range blocks much of the fog and high winds of the area. After interpreting the basic climate conditions6, the bioclimatic design priorities established for a good functioning of the library were:

• During winter:

o Insulation

o Reduce Infiltration

o Passive Solar heating

• During Summer:

o Shading

o Natural ventilation

o Distribute Thermal Mass

o Use plants of the area or evaporative cooling

The following chapters describe the decision making of the orientation and shape of the library by studying the position and radiation of the sun.

Figure 14: California climate zone 4, with Hollister and the reference city of San Jose. Own production.

Figure 15: The diverse climate zones of California External source.

3.2. The concept

“In terms of orientation, it can be said that sunshine is decisive in both cases, positively (in cold periods) and negatively (in hot periods). (...) A graph of the sun’s path, in addition to geometric and radiation calculations, can show us the effectiveness of the elements designed to control the sunshine.”

―Victor Olgyay, Design with climate

The hypothesis proposed is that solar radiation with active and passive strategies regarding daylight and the sun can define the orientation and the form of a Zero building. Solar radiation that hits the Earth’s surface is a combination of both direct solar radiation and diffuse daylight71. The irradiation at one surface in our planet depends of the incidence angle, the local climate (clouds and seasons) and since the industrial revolution, air pollution. The method followed during the design of the San Benito County Free Library was to first study the annual radiation and the monthly radiation levels for four different surface orientations82:

External source

Maximum annual solar radiation generally falls onto a surface that faces within ±25º true South9, with a tilt angle corresponding to their latitude plus 15º in winter or minus 15º during the summer. From figure 11, we can see the distribution of radiation from San José; as starters, maximum annual radiation comes from surfaces with a tilt around 42º facing true South. Figure 12 give us more information on practical architecture matters, such as the irradiation on north-south oriented facades (with a tilt of 90º) during the different months and seasons in a year, along with the horizontal radiation that could receive, for example, a flat roof of a building.

6 - Charts and detailed climatic information about temperature, wind speed, relative humidity and a bioclimatic chart are shown at the end of this paper, in the Annex section.

7 - A considerable sunlight that enters the Earth’s atmosphere is reflected off by clouds, air vapour, air molecules. We called this part “diffuse radiation” when after been scattered still reaches the Earth’s surface. It is also responsible of the blue sky and the visible part of the electromagnetic spectrum.

8 - The following data was obtained using “climaplus”, where you can access environmental data from United States. Available at: <http://web.mit.edu/sustainabledesignlab/projects/climaplus/index.html>

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Figure 16: False colour map of annual solar radiation (kWh/m2) onto different surface orientations for San Jose¬-Reid-Hillview (CA, USA).

Figure 17: Study of the monthly radiation onto a surface depending of its orientation. Data collected from San Jose-Reid-Hillview (CA, USA) Own production

From the graph we can see and deduce different facts that can be implement in architecture strategies of passive design; during the hot season, between May and end of July, south and north orientation are actually better than surfaces that looks direct west or east. The reason to this phenomena is shown in the 3d sun-path of figure 13, where we can see that the altitude of the sun during those months is very high at the main hours of the day (which will explain the higher levels of solar radiation on the horizontal plane). Passive solutions could be to implement shading devices within the architecture for protecting the interior spaces from the overheating rays from the east/west orientation. Also, to use the south façade as a heat collector during the cold months and the use of natural ventilation to balance the interior temperature of the building.

The intense radiation and the high temperatures values, with an average daily high temperature above 79°F (26ºC) during the warm season, makes the typology of “house-patio” the most appropriate typology for the environmental conditions of the area. In this case, nocturnal heat emission is the best tool to refresh the library in a passive way. During the cold period, a rational use of the solar radiation shall satisfy the rest of the calorific requirements of the public building1

9 - It is important not to confuse True South with magnetic south. In the Northern Hemisphere, PV arrays and the long side of passive-solar designed homes are oriented south to maximize solar gain. But using your compass to find south will only give you an indication of magnetic south—not true south. In that case, you need to correct for the magnetic declination difference, which varies from place to place. The magnetic declination for our site in Hollister, CA, is of + 13º 1’ due East.

Figure 18: Annual sun path with an initial simple 3d model of the library and its surroundings in its centre. Latitude and longitude used of the pre-existing library (N36º51’, W121º24’). Created with Ladybug + Rhinoceros. Own production

Figure 19: Illustration showing a cross section of the thermal concept of a “house-patio”. Sketch of the Toujereng bungalows, by VIRAI Architects. External source.

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Program volume of the library:

Maximum building footprint, 1400 m2

Maximum height: Four floors

Project area

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The definition of all these parameters among the program neccesities of the library and the urban surroundings are mixed resulting in the definition of three volumes oriented according the needs of the programme and the necessary solar radiation. The bioclimatic courtyard serves as a central axis of circulation between the main public access to the library, and the staff entrance which is locaated in the eastern part of the project area. Not only that, but fulfils to unify the diverse services and functions of the three volumes, with the goal of creating a community for the people of Hollister and St. Benito County. The next design diagrams show the process and criteria previously mentioned:

Building height of the urban surroundings

Net assignable square footage: 4173,762 m2

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Main entrance

Green courtyard as a passive strategy for refreshing the building during the night and promote California native plants. Among that,has a social aspect, connecting diverse spaces of the library.

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The south facade will be open to their surroundings, in the aim to open the library to the community, and improving the public and urban space.

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Main entrance open to the public: Is protected from the west rays during the summer by enclosure it between the two wood blocks

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VERSION

Figure 20: Program volume concept. Own production Figure 21: Courtyard and surroundings influence. Own production.

Figure 22: Division into 3 compact volumes and circulation. Own production.

Figure 23: Solar radiation influence and definition of the best incidence angle. Own production.

3.3. PV panels design and energy harvesting

3.3.1. Ladybug in the initial radiation analysis

To test the hypothesis, the solar harvesting roofs of the library have been tilt with the optimal angle towards the south. This method considerates solar radiation as a design parameter and uses Ladybug as a finding tool for the best annual possible orientation. Ladybug is an environmental plugin for Grasshopper that allows designers to perform simulations dinamically at the conceptual design stage [10].

Ladybug imports standard EnergyPlus Weather files (.EPW) in Grasshopper. An .epw file contains climate data collected over decades by diverse observatories at different locations all over the world. Weather files used in the following building simulations come from what is called a Typical Meteorological Year, also known as TMY. TMYs are defined as a set of real measured hourly values for global, diffuse, and direct normal solar radiation, dry temperature and wind velocity of a region. In the United States, there is a new set of collected weather data every 12 years. We are currently using TMY3, which registers the period between 1976 to 2005.101

Grasshopper is a “graphical algorithm editor” for Rhinoceros, a 3d modeling tool very popular among architets, designers and students in recent years. Once the .epw file is uploaded in the platform, you can “run” different codes using both components of Grasshopper and Ladybug to perform a variety of simulations. The following pages show an explanation of the factors used in the radiation study, and the resulting code (figure 25 and 27)

10 - There are some studies that claims the simplification in the algorithms and limitations of simulations tools [11]. As a note to take, weather data will change due to climate change, and maybe the information summarized in TMY3 is not stringent enough.

Figure 24: Interface of Ladybug with all the components and parametric tools. Own production

Figure 25: Components used in the radiation study to find the optimal roof angle. Own production

This component carries all of Ladybug’s main classes. Other components refer to these classes to run the studies. Therefore, when you want to start using Ladybug, running this component is the first step before uploading any .epw file. After that all the classes will be copied to

This component allow you to import lists of weather data into Grasshopper from a Gen Cumulative Sky Matrix: This component uses Radiance’s gendaymtx11 function to calculate the sky’s radiation for each hour of the year. The component takes the weather file as input (with the direct and diffuse radiation data), and generates an annual matrix of sky patch values using the Perez all-weather model122 [12]. This is a necessary pre-step before doing radiation analysis with Rhino geometry or generating a radiation rose. The first time you use this component, you will need to be connected to the internet so that the component can download the “gendaymtx.exe” function to your system. [13]

After running the “Gen Cumulative Sky Mtx” component, you need to establish a time period in which you select a simulation of a specific sky matrix. Therefore, the totals levels of radiation will vary depending on the hour of the day or the analysis period you choose.

This component calculate the radiation falling on an input geometry of your choice, using the sky matrix predefined with the “Select Sky Mtx” component. The output is the total amount of radiation shown as a colored mesh to be able to visualize the results. The advantage of using Ladybug is that the results are obtained over the actual input geometry, or brep geometry, that is your case study. This type of radiation study is useful for building surfaces such as windows, where you might be interested in solar heat gain, outdoor spaces or solar panels, where you might be interested in the energy that can be collected. You can also add a context geometry (other buildings, chimneys, trees etc.) to see if there is any partial shading that might be of any concern.

No reflection of sunlight is included in the radiation analysis with this component and it should therefore be used neither for interior daylight studies nor for complex geometries nor for surfaces with high a reflectivity. [13]

11 - Gendaymtx or also called Gen Day Matrix is written by Ian Ashdown and Greg Ward.

12 - The Perez All-Weather Sky Model is a mathematical model used to describe the continious and discontinious luminance distribution of the sky dome, parameterising the magnitude and spatial distribution of discontinuous features based on indices for the sky clearness and brightness. It has become the standard model for daylighting simulations, as it uses real data gathered from weather stations all over the world.

Figure 26: Radiation Analysis of different PV modules orientated due south, with different tilt angles. Own production

Figure 27: Graphical algorithm code with the inputs used for the orientation study. The resulting output is a colored mesh shown at figure 23. Own production

Table 1: Annually radiation results, in kWh/m2, for inclinations between 0º to 90º. The numbers show a predicted statement: that the best orientations for a photovoltaic system in Hollister (CA) are between south and west. Own production

3.3.2. PV System design and final form

The design of an active solar energy system has to provide enough electricity and heating to meet the net zero energy or emission balanced of a building. In this case study, solar photovoltaics will be the primary source of renewable energy for the library. PV panels are made up of smaller units called solar cells, each composed of a semiconductor material, making it possible to convert sunlight into electricity thanks to the photovoltaic effect13. Nowadays, the most most common solar cells are made from crystalline silicon for being a robust product and have an efficient fabrication cost.

A photovoltaic panel is normally formed by 36 cells in 4 parallel rows connected in series. For the integration of the PV panels on the roof we will have an installation with several modules connected in series to the string inverter14 2. The dimensions of each PV panel used in the study will be 1 x 1.5 meters. Depending of the type of PV cell used, the percentage of power converted into electrical energy from the total sunlight absorbed by a panel will vary. Figure 26 shows different η153efficiencies with the maximum recorded figures reached in laboratory tests. Since mono-crystalline silicon (Si-mono) and polycrystalline silicon (Si-poly) PV modules have efficiencies of commercially available modules between 11-22% [14 p. 3], being both the most popular PV technologies of the market, a mono-crystalline module with an average efficiency of 20% was used for the study.

After the radiation studies of table 1, it is decided to orient the roof towards the south, with a slope angle between 15º and 30º. To test the architectural expression and see the amount of kWh/m2 generated, two 3d models of the library, both incorporating within the architecture the maximum amount of PV modules as possible, have been created in Rhinoceros. By using the software DIVA onto the 3D models, we can create a code that simulates the solar radiant exposure towards the PV panels and see the total electricity per square meter produced by them.

13 - The photovoltaic effect is the generation of voltage and electric current in a material upon exposure to light. It is a physical and chemical phenomenon, causing the excitation of an electron to a higher energy state.

14 - Its mission is to convert the direct current produced by the panels into alternating current of 230 V, which is the normal tension at which our red system works.

15 - η is the Greek small letter “eta”, and refers to the efficiency of an electrical system. Is defined as the division between the usefull power output divided by the total power input or consumed.

Figure 29: Efficiency comparison of different types of PV technologies with maximum recorded data. External source.

Figure 28: Graphical explanation of the solar cell, module, panels, string and photovoltaic generator External source

The original design configuration of the library proposed three separated volumes around a common courtyard. Each volume responds to a different program, having the main volume containing the library, second volume the children library, services and staff spaces, and the third volume being of a more public function, with the auditorium and the library museum. The intention is to use the first and second volume’s roof surface as a renewable power source. The roof angle at the first 3D model has an inclination over 15º in both volumes while the second 3D model shows an inclination of 30º (the most optimal angle) with some horizontal areas. Both results will be compared and it will be decided which solution is the most optimal both in architectural quality and structural roadway along with the energy contribution to the building.

DIVA, which stands for Design Iterate Validate Adapt, is an environmental analysis plugin for the Rhinoceros 3D Nurbs modeling program initially developed by the School of Design at Harvard University, and later distributed by Solemma LLC. It runs thermal, solar radiation, daylight and glare simulations onto individual buildings and urban landscapes using two simulation engines: EnergyPlus and Radiance.

In both examples the aim is to embed a building integrated photovoltaic (BIPV) system, which is advantageous from budgetary, environmental, and aesthetic standpoints. This also avoids self-shading, unlike panels on a flat surface with a predetermined angle of inclination After having modelled the two concepts in Rhinoceros, PV panels of 1 x 1,5 meters are sistematically collocated onto the roof surfaces of the library as previously described. Figure 28 and 29 shows visually how the panels are integrated in each 3d model aswell as the building form of the complex.

The choice to use DIVA over Ladybug in this case has been motivated by the fact that DIVA also includes the plugin Archsim. Archsim allows you to create complex multi-zone energy models, and has a specialized area dedicated to photovoltaics. The work methodology using DIVA is shown in Figure 30. The algorithim created has two parts: First, the code estimates the solar radiation exposure onto all the PV panels surfaces during one year using the solar irradiance data from the epw. file; second, a PV simulation is made taking into account the panel efficiency and effective area (both numbers are expressed as a fraction) to finally convert solar energy into electricity (kWh/m2). Contextual shading referring to neighboring buildings along with the library’s own volumes are included in both studies as another input. Results are shown in the following pages.

Figure 30: DIVA 4 Rhino components. Marked in red are the ones used in the PV system design of above. Own production

Figure 31: First 3D model (3D model 1) created with Rhinoceros wih a roof inclination over 15º. Own production

Figure 32: Second 3D model (3D model 2) created with Rhinoceros wih a roof inclination over 30º among some flat areas. Own production

[1] Solar radiation exposure onto the PV panels surfaces

a. Both PV panels from 3D models 1 & 2 are collected in two Brep parameters. Brep stands for “Boundary Representation”. All surfaces and polysurfaces in Rhino are Breps.

b. This component opens an .epw weather file from a location on your computer. Same as the environmental studies with Ladybug, we use the same .epw file provided by ARCHITECTURE AT ZERO contest.

c. DIVA component that creates a daylighting analysis grid Inputs needed are a reference geometry/G (brep, surfaces or mesh) and a number/S referring to the grid spacing. The default grid spacing is 0.8.

d. DIVA component that creates a Radiation map. In other words, it computes time-integrated solar irradiance on a surface. The inputs used in this study have been: the daylighting grid/Grid, contextual objects/Obj (in our case, the external buildings among the library’s volume of each model, in case of any shadow) and the location/Loc and time period of the study, which have been over 1 year, with an hour range/Hrs from 0 to 24 hours. After runing the component it gives you four possible Outputs parameters, which are:

- Out (Text): Any possible messages

- SE (Number): Total solar energy received by analysis surface over a run period [kWh]

- SED (Number): Solar energy density received by analysis surface over run period [kWh/m2]

- Grid (Daylighting Grid): Analysis surface as grid, which is the one we used in the study.

e. DIVA component called Grid viewer that displays a 2d graphical representation of the SED onto the studied surfaces inside the Rhino interface. It creates a falsecolor gradient scale, where you can modified it lower and upper limit to obtain better graphical results.

f. The results can also be displayed as a numerical list. We used the DIVA component Bounds/Bnd to create a numeric domain which encompasses a list of numbers between the lowest and highest numbers in {N}. The output is a list showing the minimum and maximum kWh/m2 for each panel.

g. DIVA tool that creates a sun path diagram displayed in the Rhino interface, reveling also the shadows depending the position of the sun and the chosen time period.

[2] Detailed electricity production (kWh/m2)

h. This component generates PV simulations by taking as an input a brep or collection of brep surfaces/Surf among the PV module efficiency/Eff and the effective area covered with PV cells/Area. As mentioned in page 25 of this paper, the efficiency of each PV panel is 20% (or 0.2 as a fraction). The default effective area is 0.8. That means the 80% of the total area of the photovoltaic system will convert solar radiation into electricty.

i. Now that we have simulated our PV system, we need to run the PV simulation/PV. Again we add as inputs the Panels contextual shading/Shade, EnergyPlus weather file/Epw Run button and a text if we want to give the project a name.

In the settings button we can especify the run period, whether we want the results hourly, daily, monthly etc., the resolution and the output variables. We set an annual run period, with monthly results and an output of Generator Produced Direct Current Electric Energy, which means the data generated will be in Joules.

j. Load result file/LoadCSV is a component that loads the information given as a model in the PV simulation component and filter the columns by tags, interpreting the results. To lunch the component we use a boolean toggle and set it “true”, like when you are programing an algorithim.

k. If we connect a panel to the LoadCSV results, we will have the energy in joules (work) generated by each panel per month, from january to december.

l. Since we have many photovoltaic panels, to calculate the total sum of the kWh produced by them during a year, we must add up the joules generated by each panel every month and then perform the conv ersion to kWh. To this end, the component Mass Addition/MA can perform a sumatory of a list of items.

m. One joule (J) is equal to 2.777778 x 10-7 kilowatt-hours, or (1/3600000) kWh. So the energy in kilowatt-hour E(kWh) is equal to the energy in joules E(J) divided by 3600000. Dividing the results from the mass addition component will give the total kWh produced by the PV system from model 1 or model 2.

n. Besides the annual kWh, it’s possible to know the total kWh per month. We can manipulate the data by placing a Flip Matrix component. It flips a matrix-like data tree by swapping rows and columns. Now, if we were to connect a panel as an output, instead of a branch for each panel amd a list of the 12 months, we will have a branch for each month with all the results. Repeating the above process, using a Mass Addition component and flattening that to make it one list and dividing the output with the conversion factor for kWh gives the total kWh each month.

o. The grasshopper component Quick Graph displays a set of y-values as a graph. This gives us a quick sense of how the monthly graph looks like. Logically, we can see that the maximum of the energy production comes from the months of spring and summer.

p. In terms of electricity, it is more common to measure the kWh per square meter. Grasshopper component Area solve area properties for breps, meshes and planar closed curves. In this case we plug as an input the Brep Geometry of our PV system in each case.

q. As previously described, we have considered the effective area as a 0.8 from the actual area. Having the area of each panel (m2) as a list we can multiply each number by the factor 0.8 contain in a numerical slider. Grasshopper has a slide containing 107 different components that runs mathematical operations, including division and multiplication. The generic data obtained is the effective area of each PV panel. Results by ising again the Mass Addition component gives as an output of the total effective area (m2) of the chosen PV system.

r. Finally, the division component uses as inputs the total kWh and the total effective area in m2. The output will be the total DC electric energy produced by the photovoltaic system in kWh/ m2

b.

c.

d.

e. f.

g.

Figure 33: DIVA methodology and code with grasshopper. Each algorithim has been used for both samples, naming them as Model 1 and Model 2 Own production 29

Table 2 shows how you can visualize the data and algorithim in grasshopper into the Rhino interface and, further more, on your own 3D model. This helps the architect making a quicker understanding of the environmental data results. Same simulations have been runned in both models to compare the results; The first row of the table shows the 3D display of the results on model one, where the angle of the cover is about 15º, and the second row the results from the second building form, with a roof angle of 30º,

Table 2: Graphical results from the DIVA simulations and the elements used in the analysis. Own production

4. ZERO NET ENERGY

4.1. Results

Table 3 compares the numerical results of both models. It is important to note that the previous simulation from figure 30 takes into account neither conversion losses for alternating current energy (AC energy) or other types of performance losses, like the influence of temperature on the panels production or residues. Also, the number of PV panels has been maximized in both examples, trying to cover the maximum surface of the roof, understanding it as a first theoretical study before choosing a model and submitting it to further testing and refinement. Results are shown below:

Analyzing the results from table 2 and table 3, we can reach a series of conclusions. First of all, 3D model 1 has a greater useful surface to integrate more PV panels than 3D model 2; because of that the total kWh generated by it is 1.5 times bigger than at model 2. However, the solar radiation received throughout the year at this tilt angle is less than that received from a tilt angle of 30º. Among that, although in this study we do not integrate the embodied emissions from renewable energy inside the carbon emissions diagnose, the energy needed for produced around 700 PV panels is way bigger than the emissions from producing around 450 PV panels. As for architectural expression, model 2 allows the design of skylights that provide the library with direct light from the north-northeast, while maintaining the aesthetics of the gable-roofed neighborhood. In terms of construction, the structure of model 1 is more simple to managed than model 2, with more space for installations.

The technical challenge energy demand targets for the ARCHITECTURE AT ZERO 2020 contest was to use a site EUI target of 24 kBtu/CFA as a starting point for the competition. To compare both the on-site generation and the energy consumption of the library, we need to convert our kWh/m2 to kBtu/CFA. The proccess is described in formula (2):

1 btu = 2.93 · 10-4 kWh;

1 kBtu = 0.293 kWh (rounded to 3 significant figures (s.f)) and

1 sf = 0.093 m2 (rounded to 3 s.f)

Table 3. Numerical results. Own production

Then:

Therefore, formula (2) expresses that:

Where �������� refers to on-site energy produced over a year by our PV panels but expressed in kBtu/sf- yr while EM is expressed in kWh/m2- yr. -

Applying formula (2) to the results obtained by DIVA and grasshopper:

Both ��������1 and ��������2 are bigger than the demand of 24 kBtu/sf-yr. The government -back company ENERGY STAR® has a study of median EUI for different building types in the United States. For libraries, the site EUI or in other words, the amount of heat and electricity consumed by a building, is of 71.6 kBtu/sf-yr [15].

This average EUI energy consumption corresponds more to the volume, characteristics and program of our library. Both 3D models together with its photovoltaic system would meet the energy demands, being feasible the balance between the renewable energy production and its consumption

Having all these variables in consideration, the final building envelope chosen is the one proposed by the 3D Model 2, as its form is optimized for solar collection through surface area, orientation and tilt angle. Among that, as previously mentioned in page 30, it needs less PV panels to produce as much as 130 kBtu/sf-yr.

The next chapter shows how the geometry of the form has been redefined after this point to contain the program necessities of San Benito’s new library, with the floorplans and sections developed for the contest.

Table 4. Median EUIs in the United States

4.1.1. Final floorplans

PRODUCED BY AN AUTODESK STUDENT VERSION

PRODUCED BY AN AUTODESK STUDENT VERSION

PRODUCED BY AN AUTODESK

4.2. Carbon dioxide emissions in operational use and grid emission factors

As described above, there are many ways to calculate a Zero carbon balance, and all of them depend largely on the initial objectives to reduce emissions in each phase of the project, along with the level of ambition in sustainability. Calculation procedures and ZEB objectives should be adjusted to the specific location and reflect the local environmental challenges [5 p.75]. The method of calculation in this paper has been counting only for the emissions produced by the use of the library and the current emission factor grid of California. Equation (3) is a modification of formula (1) that takes into account theses parameters:

∆CO2 = CO2e· (Qd- Qe) (3)

As described on page 31, the library has an estimated energy demand of 71.6 kBtu/sf-yr, which is the same at about 226 kWh/m2 (Qd). On the other hand, the chosen photovoltaic panel system (without counting losses) provided about 410 kWh/m2 per year (Qe). As a premise of the contest, San Benito’s new library will be grid-tied. In a zero-energy theoretical concepction, the grid is seen as a battery; in periods with surplus, energy is exported to the grid while in periods of demand (due to partial shading or to the increase of temperature of the solar cells), the library will require an import of energy from the general grid. The emission factor of the imported power depends on the source of the marginal power, i.e. the power that is used to balance a power system in case of increased demand [14 p. 3]. Therefore, the grid emission factor or CO2e implies the averaged CO2eq emission factor for the generation of electricity produced in a region or country. In California, gas accounts for the 45.2% of the fuel mix [16], while solar accounts for only the 14.9%. This means that the fact of the building achieving a net balance over the year does not guarantee the overall environmental impact.

The United States Environmental Protection Agency’s (EPA) e-Grid database provides 2016 regional emission factors that were published in 2018. For the state of California (CA), the annually generation factor (kgCO2e per kWh) is 0.2060. Substituting this data into equation (3) gives:

∆CO2 = 0.206 kgCO2e/kWh · (226 kWh/m2 - 410 kWh/m2)

∆CO2 = -37.90 kgCO2e/kWh

The resulting net emissions balance (ZEB-O ambition level), E net, for the complete building in a year is of -37.9 kgCO2e/kWh, which means that in terms of electricity and operational use it avoids yearly around 38 kg of equivalent CO2 . However, in this paper we did not count for the embodied emissions in the production, transportation and expected lifetime of the PV panels (among the embodied emissions of the library and its materials). For the PV panels, it will take several years of operation to generate enough renewable energy to offset its own emissions. This time period is measure by the greenhouse gas payback time (GPBT) [14 p. 7], and its calculation is shown in equation (4).

GPBT = EEmbodied PV/Eavoided year (4)

5. CONCLUSIONS

The work offers a description of what is called “zero architecture”, which includes a rigorous account of the carbon dioxide emissions into the atmosphere, the different types of projects that exist depending on the level of ambition desired and the importance of decisions taken in the initial design phase, as they influence the final environmental impact. Although the concept of sustainable architecture is not new, the climate emergency and our current way of life (together with our high consumption habits) make it necessary to rethink a new architecture that is energetically self-sufficient. A“solar” architecture is proposed; the building would respond with its form to the environmental characteristics of the place, and would integrate photovoltaic panels that would generate enough renewable energy to compensate for the building’s greenhouse gas emissions over its life span. To further research, a working hypothesis is proposed.

The hypothesis proposed in this dissertation was to study if solar radiation with active and passive strategies regarding daylight and the sun can define the orientation and building form to achieve a Zero Net Building. A particular case study is presented, the design of a zero net public library in the city of Hollister, California, connected to the general network. The objective was the energy optimization of the building through the study of solar radiation and the integration of photovoltaic panels on the roof of the building. The working methodology used has been first, to find out the best orientation and tilt angle for the PV panels, and second, to test two different 3D models checking which shape guaranteed the highest kWh/m2 capture within one year. For this purpose, two environmental pluggins for Grasshopper, Ladybug and DIVA 4.0 has been used. The use of these programs has favored the interpretation of the environmental data and favored the decision making in the project. Both programs use a graphical interface when representing and analyzing data that facilitates its interpretation and the designing response. To carry out the simulations, we have used the climate information contained in an EnergyPlus Weather file (.epw file) of the city of San José, a city near Hollister with similar climatic and geographic conditions.

Figure 34: Endesa Pavilion, built in 2011. Created and designed by the Institute for Advanced Architecture of Catalonia (IAAC). External source

Figure 35: ZEB House Multikomfort in Larvik (Norway) designed by the firm Snøhetta. Ambition level is of ZEB-OM plus an electric car.The building is designed to accommodate a family of four to five members External source

The results of these analysis shows that the harvesting of solar energy, especially by building integrated PV systems can result in a variety of architectural solutions, with different sloping forms and different uses for the roofs. The final building form chosen for San Benito County Free Library has been the most optimal solution between the two 3D models, having a roof inclination in its three modules of 30º (which is the optimal tilt angle with the highest performance in terms of kWh) while maintaining the aesthetics of the gable-roofed neighborhood. Among that provides the main library with direct light from the north-northeast with the construction of some skylights. The extensive use of cross-laminated-timber and glulam has been a constant in the design of the library to reduced embodied emissions as well as for its material and aesthetical properties. The Zero Net balance and the ZEB-O ambition level were achieved, as the proposed library has a yearly net emissions balance of -38 kg kgCO2e/kWh. However, the carbon dioxide emissions from the materials and its life span. construction process and end of life of the building were not included in this paper. This concludes that, to design buildings with low heat loss, low energy use, and with harvesting solar energy is not new, but to plan them so weel that a complete zero emission balance is reached, including the emission from materials, is a complex and interdisciplnary task. The use of parametric programs like the ones used in this work can help to democratizes environmental analysis tools, fostering the advancement of environmentally-conscious architecture designs.

Finally, I would like to add that this work has made me reflect on sustainability, the energy crisis, limited natural resources and how architecture can be directly related to these issues.

The ZEB typology can be applied to any project, at any latitude of the globe, in public, residential or private buildings. The constant is to always think about trying to reduce first; to reduce the energy demand, to see that the building is not independent of the climate and place of the one that surrounds it, to reduce as maximum as possible the damages to the place or even to improve the existing one, to plan the materials and to try that they have little load of carbon dioxide emissions in their production, transportation and life span, to rehabilitate and use vernacular architecture....

There is not a unique recipe for a ZEB architecture, but there is a set of ingenious decisions that, from the particular, can give us global solutions to existing global problems.

6. REFERENCES

6.1. Bibliography

[1] Ritchie, H. and Roser, M. CO₂ and Greenhouse Gas Emissions [online]. OUR WORLD IN DATA, 2017. Last update: 2020 [Accessed 2 July 2020]. Available at: <https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions#endnotes>

[2] IPCC, 2018: Global Warming of 1.5°C.An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty [Masson-Delmotte, V., P. Zhai, H.-O. Pörtner, D. Roberts, J. Skea, P.R. Shukla, A. Pirani, W. Moufouma-Okia, C. Péan, R. Pidcock, S. Connors, J.B.R. Matthews, Y. Chen, X. Zhou, M.I. Gomis, E. Lonnoy, T. Maycock, M. Tignor, and T. Waterfield (eds.)]. In Press.

[3] IEA, 2015. CO2 emissions statistics [online]. IEA Factsheets. Last update: (n.d.). Available at: <http://www. iea.org/publications/freepublications/publication/CO2-emissions-from-fuel-combustion-for-oecd-countries--2015-preliminary-edition-factsheet-html>

[4] European Commission. Nearly zero-energy buildings [online] EUROPEN UNION, 2014. Last update: 12 March 2020 [Accessed 2 July 2020]. Available at: <https://ec.europa.eu/energy/topics/energy-efficiency/ energy-efficient-buildings/nearly-zero-energy-buildings en#national-plans>

[5] Hestnes, G., Anne, EIK-NES LEA, Nancy. Zero Emission Buildings. Bergen: Fagbokforlaget, 2017. ISBN 978-8245020557.

[6] The Research Centre on Zero Emission Buildings. ZEB Definitions [online]. Trondheim: ZEB 2020 [Accessed 6 July 2020]. Available at <http://www.zeb.no/index.php/en/about-zeb/zeb-definitions>

[7] Sands, Johanna, Sustainable Library Design. Cerritos, CA: Libris Design Project, 2004.

[8] Sartori, I., Hestnes, A. G. Energy use in the life cycle of conventional and low-energy buildings. A review article: Energy and buildings. 2007, no 39, p. 249 - 257. ISNN 0378-7788

[9] EnergyPlus. Weather Data by Region [online]. ENERGY PLUS WEATHER DATA. Last update: (n.d.). [Accessed 8 July 2020]. Available: <https://energyplus.net/weather-region/north_and_central_america_ wmo_region_4/USA/CA>

[10] Roudsari, M. S., Pak, M., Smith, A., Gordon Gill Architecture. Ladybug: A parametric environmental plugin for Grasshopper to help designers create an environmentally-conscious design. 2013, proceedings of BS 2013: 13th Conference of the International Building Performance Simulation Association. 3128-3135.

[11] Sawyer, A. and Weissman, D. Design with Climate: The role of digital tools in computational analysis of site – specific architecture. In: Kara, H. and Georgoulias, A. Interdisciplinary Design: New Lessons from Architecture and Engineering. Harvard, 2012, p. 125 - 131. ISBN 978-8415391081

[12] Rodricks, R. and Heumann, A. (2013, January 19). Gen Cumulative Sky Mtx [online]. LADYBUGCOMPONENT FOR GRASSHOPPER |GRASSHOPPER DOCS. Last update: (n.d.). [Accessed 20 July 2020] Available at: <https://grasshopperdocs.com/components/ladybug/genCumulativeSkyMtx.html>

[13] Rodricks, R. and Heumann, A. (2013, January 19). Radiation Analysis [online]. LADYBUGCOMPONENT FOR GRASSHOPPER |GRASSHOPPER DOCS. Last update: (n.d.). [Accessed 20 July 2020] Available at: < https://grasshopperdocs.com/components/ladybug/radiationAnalysis.html >

[14] Good, C., Kristjnsdottir, T., Wiberg, A. H., Georges, L., & Hestnes, A.G. Influence of PV technology and system design on the emission balance of a net zero emission building concept. Solar Energy [online]. 23 February 2016, vol. 130, p. 89-100. eISSN: 0038-092X, [Accessed 12 July 2020]. Available at <https://www. journals.elsevier.com/solar-energy>

[15] ENERGY STAR. What is energy use intensity (EUI)? [online]. ENERGY STAR Buildings and Plants | ENERGY STAR. (n.d.). [Accessed 12 September 2020]. Available at <https://www.energystar.gov/buildings/facility-owners-and-managers/existing-buildings/use-portfolio-manager/understand-metrics/what-energy>

6.2. Other academic thesis

- Armstrong, L., Gardner, G. U. Y., & James, C. (n.d.). Evolutionary solar architecture-Generative solar design through soft forms and rigid logics. University of Calgary

- Caballero, L. A. U. (2016). Edificio energía cero (zero energy building). Universitat Politècnica de Catalunya.

- Caldas, L. (2008). Generation of energy-efficient architecture solutions applying GENE_ARCH: An evolution-based generative design system. Advanced Engineering Informatics, 22(1), 59–70. Available at: <https:// doi.org/10.1016/j.aei.2007.08.012>

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Figure 31 p. 28

First 3D model (3D model 1) created with Rhinoceros wih a roof inclination over 15º

Figure 32 p. 28

Second 3D model (3D model 2) created with Rhinoceros wih a roof inclination over 30º among some flat areas

Figure 33 p. 29

DIVA methodology and code with grasshopper. Each algorithim has been used for both samples, naming them as Model 1 and Model 2

Figure 34 p. 38

Endesa Pavilion, built in 2011. Created and designed by the Institute for Advanced Architecture of Catalonia (IAAC)

ZEB House Multikomfort in Larvik (Norway) designed by the firm Snøhetta. Ambition level is of ZEB-OM plus an electric car.The building is designed to accommodate a family of four to five members

Figure 35 p. 38

7.2. Tables

Table 1 p. 25

Annually radiation results, in kWh/m2, for inclinations between 0º to 90º

Table 2 p. 30

Graphical results from the DIVA simulations and the elements used in the analysis

Table 3 p. 31

Numerical results for both 3D models

Median EUIs in the United States

Table 4 p. 32

7.3. Plans

Plan 1 p. 34

Floorplan level 1

Scale 1:200

Plan 2 p. 35

Floorplan level 2

Scale 1:200

Plan 3 p. 36

Floorplan with the deck and the PV panels

Scale 1:200