Sustainable Building Design with Autodesk Ecotect

Ecole des Mines de Nantes La Chantrerie 4, rue Alfred Kastler B.P. 20722 - F-44307 NANTES Cedex 3 KTH Valhallavägen 79, Stockholm Kungl Tekniska Högs...
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Ecole des Mines de Nantes La Chantrerie 4, rue Alfred Kastler B.P. 20722 - F-44307 NANTES Cedex 3

KTH Valhallavägen 79, Stockholm Kungl Tekniska Högskolan, SE-100 44 STOCKHOLM

Master Thesis Report

Sustainable Building Design with Autodesk Ecotect

Le Sommer Environment 5 bis rue des Haudriettes 75003 PARIS

Date: 11/12/10

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Summary Abstract.............................................................................................................................4 Introduction.......................................................................................................................5 Context....................................................................................................................................5 Climate change....................................................................................................................................5 The HQE Scheme...............................................................................................................................5

Le SOMMER Environment.............................................................................................7 The company........................................................................................................................................7 Internship Objectives...........................................................................................................................7 Typical day.............................................................................................................................................7

Case Study......................................................................................................................8 Description.............................................................................................................................8 Visualization Conventions..............................................................................................10

Relationship between the building and its environment..............................11 Climatic interactions.........................................................................................................11 Heliodon..................................................................................................................................................11 Solar potential.....................................................................................................................................15 Impact of nearby buildings............................................................................................................18 Solar protection..................................................................................................................................21 Visual conditions................................................................................................................................24

Energy Management................................................................................................26 Dynamic Thermal Simulation......................................................................................26 Thermal Response...........................................................................................................................26

Hygrothermal comfort...............................................................................................31 Summer overheating .....................................................................................................31 Direct Beam Radiation....................................................................................................................31

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Visual comfort..............................................................................................................34 Natural light .......................................................................................................................34 Daylight access.................................................................................................................................34 Daylight factor....................................................................................................................................36

Discussion and Conclusions.................................................................................39 Capabilities..........................................................................................................................39 Limitations............................................................................................................................40 Conclusion..........................................................................................................................40

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Abstract In 2002, an environmental assessment scheme was released in France in order to measure and improve the environmental performances of new and existing buildings: the High Environmental Quality Scheme (HQE). Similar to the LEED or BREEAM assessment methods, the HQE Scheme focuses on 14 different environmental themes, such as energy consumption, daylight availability, acoustic comfort, etc. with objectives such as limitation in energy consumption, minimum daylight levels, adequate reverberation time, etc. Due to the complexity of the many scientific phenomena involved, advanced calculation procedures are required to measure most environmental performances. For instance, the study of heat transfer through building fabric to determine internal temperature variations and heating/cooling loads or the computation of daylight levels in a room when a building is overshadowed by surrounding obstructions is a complicated task that necessitates the use of computer simulation. However, if various analysis software are today available, they rarely often the possibility to study all these effects at once. As a consequence, the most time consuming process of drawing the geometry of the building and making the right assignments, often needs to be repeated. This not only leads to a waste of time. It also favors local optimization by considering sequentially each environmental quantity in spite of strong interactions between them. Thus, it was highly desirable to develop a user-friendly and comprehensive software that could optimize a building's environmental performances at once. Within the frame of a six months internship at Le SOMMER Environment - a small Parisian consultancy specialized in building environmental certification - a presentation of the possibilities offered by one such software: Autodesk Ecotect is given through a simple housing project case study.

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Introduction Context Climate change In order to tackle the worldwide issue of climate change, the European Union committed to reduce greenhouse gases emissions through the signature of the Kyoto protocol and the adoption in December 2008 of a “climate energy package» aiming at setting a common energy policy and fight climate change. It should enable to reach by the year 2020 the goal of the « three 20’s » : a reduction by 20% of greenhouse gases emissions, an improvement of 20% in energy efficiency and a share of 20% renewable energy sources in the European energy consumption. For France, the objectives are in agreement with the Kyoto protocol and the climate energy package aims at dividing by a factor of 4 its greenhouse gases by the end of 2050.

The HQE Scheme In line with the principles of sustainable development, the French building sector agreed upon a High Environmental Quality Scheme (HQE). Born in 1996, the HQE Association entrusted in 2002 to the « Centre Scientifique et Technique du Bâtiment »1 the mission of establishing a reference guide for the HQE Scheme certification of tertiary buildings. According to this guide, environmental performances are assessed via fourteen different environmental themes, grouped in four families presented page 6. For each theme is assigned a level of performance among three possibilities:   

1

Base Performing Very Performing.

The French Building Scientific Centre

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The 14 environmental themes of the HQE Scheme:

Site and Construction

  

Theme n°1: Relationship between the building and its environment Theme n°2: Materials environmental impacts Theme n°3: Construction site management

Eco managmement

   

Theme Theme Theme Theme

n°4: n°5: n°6: n°7:

Energy management Water management Wastes management Maintenance of environmental performances

Theme Theme Theme Theme

n°8: Hygrothermal comfort n°9: Acoustic comfort n°10: Visual comfort n°11 : Odour comfort

Comfort

   

Health

  

Theme n°12: Spaces health watch Theme n°13: Air quality Theme n°14: Water quality

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Le SOMMER Environment The company Founded in 2002 by Michel Le SOMMER, Le SOMMER Environment is a small Parisian consultancy whose main activity deals with building environmental certification (HQE Scheme, BREEAM and LEED). Since its creation the turnover steadily increases by more than 50% each year (700 000 euros in 2008). The company has 9 employees comprising 8 engineers and a secretary.

Internship Objectives The objective that I was assigned consisted in assessing the software Autodesk Ecotect on a simple case study while focusing on a certain number of environmental themes of the HQE Scheme. Four themes among the 14 presented page 6 were studied:    

Theme Theme Theme Theme

n°1: Relationship between the building and its environment n°4: Energy Management n°8: Hygrothermal comfort n°10: Visual comfort

Typical day During my internship, my work mainly consisted in learning how to use properly the software. Apart from the case study presented in the report, many other simple examples were thus designed and tested during the first four months to understand clearly the functionning of Autodesk Ecotect. The typical work hours were from 9am to 6pm with a 1 hour lunch break, from Monday till Friday. I was most of the time working in an open space on a desktop computer in coordination with a team of engineers, except when I had the opportunity to visit construction sites.

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Case Study Description The following case study serves as an example for the illustration of the environmental objectives addressed by the High Environmental Scheme (llustration 1) and was specifically developed to test the possibilities of Autodesk Ecotect (Illustration 2). The project itself is a three people family housing oriented south, composed of a bedroom, living, kitchen, bathroom, toilets, storage room and a balcony, located in Paris (48.7°N,2.4°E).

Balcony

Kitchen

Living

Corridor

Storage

Bathroom

WC

Bedoom

llustration 1: Top View of the project

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Illustration 2: 3D Modeling of the project (Autodesk Ecotect)

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Visualization Conventions In the remainder of this text, the apartment studied is located on the 3rd floor of a fictitious building (it is colored in blue in Illustration 5 and 6). For simplicity, it is assumed that the 1 st, 2nd and 4th floor apartments are exactly the same, ie they have exactly the same shape and dimensions (as can be seen in Illustration 3 and 5).

Illustration 3: Apartments arrangement

For better visualisation purposes, the 3rd floor apartement is sometimes visually isolated from the other apartments so that it might appear as not having a balcony over itself (as in the upper picture in Illustration 4 below) though in reality it is always overshadowed by 4th floor apartment balcony.

Illustration 4: Though not alwoays drawn (as in the upper picture), the balcony of the 4 th floor apartement is always active and taken into consideration in any calculation.

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Relationship between the building and its environment Climatic interactions Heliodon By inserting the project within a building (Illustration 5), and inserting that building in an urban environment (Illustration 6), exterior climatic conditions relatively to the Sun can be studied via the help of a heliodon. A heliodon is a set of pictures taken at certain key dates of the year enabling one to measure the overshadowing mpacts of nearby buildings. It thus enables one to assess qualitatively the solar potential of the site.

Illustration 5: 3D Modeling of the building within which the project fits in (Autodesk Ecotect)

Illustration 6: 3D Modeling of the urban environment (Autodesk Ecotect)

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Illustration 7: Heliodon on summer solstice (21 june) for 10h00, 14h00 and 17h00 legal time.

Master Thesis report Sustainable building design with Autodesk Ecotect

Illustration 8: Same as Illustration 7.

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Results Interpretation: On summer solstice, the heliodon reveals that the building inside which is integrated the project is impacted by nearby buildings at 10h00. However, it is not impacted nor at 14h00 neither at 17h00. At 10h00, the ground floor to 3 rd floor housings are totally overshadowed by nearby buildings. Only the 4th floor housing benefits from direct beam solar radiation, in spite of the overshadowing of a small part of the balcony. At 14h00 and 17h00, housings from ground floor to 3 rd floor appear shaded, but that is due to overshadowing by the building itself due to the balconies. The nearby buildings play no role in this effect. Reciprocally, the nearby buildings are impacted by the project and the building inside which it integrates at 10h00 and 17h00. The impact is however negligible as only a part of the ground floor of these is affected.

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Solar potential Whereas a heliodon is a precious tool to determine the impacts of shadows of nearby buildings or obstructions on the project, it does not yield a quantitative result about the site solar potential. That is why, in addition to the visualisation of shadows, it is possible with Autodesk Ecotect to quantify sunlight hours and exposure of the project surfaces and those of nearby obstructions By mapping the results directly on the digital model (Illustration 9 and 10), the site solar potential can be clearly seen.

Illustration 9: Site solar potential: percentage solar exposure on summer solstice cumulated from 10h00 to 20h00 legal time.

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Illustration 10: Same as Illustration 9. Project close - up.

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Results Interpretation: The results reveal non uniform solare exposure for the different façades. The western façade is much more exposed than the eastern façade. It is thus beneficial to place the living and the bedroom along the western side and keep the kitchen and sevice rooms on the eastern side. It can also be noticed that the southern façade is well protected from direct beam solar radiation, at least on summer solstice, but that the balcony still receives direct solar radiation and is thus not completely overshadowed to offer a pleasant place to enjoy in summer.

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Impact of nearby buildings Urban environment can have a detrimental effect on the development of a project. Nearby buildings may overshadow surfaces, prevents windows from receiving sunlight, diminishing solar loads in winter when needed. Autodesk Ecotect is able to measure the overshadowing effect by calculating the solar exposure with and without nearby buildings. The difference between the two, expressed as a percentage reveals the overshadowing effect (Illustration 11 and 12).

Illustration 11: Impacts due to nearby buildings on summer solstice cumulated from 10h00 to 20h00 legal time.

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Illustration 12: Same as Illustration 11. Project close - up

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Results Interpretation: The overshadowing caused by nearby buildings from 10h00 to 20h00 on summer solstice is different for each façade of the project. For the eastern façade, the kitchen and the bathroom are impacted relatively similarly with a 11% to 22% cut in cumulated solar exposure which represents a loss of 1 to 2 hours of sunlight. For the western façade, the corridor and the bedroom are impacted with a cut between 8% and 17% in cumulated solar exposure which represents a loss of 1 to 2 hours of sulight For the northern façade, a cut between 14% and 29% in cumulated solar exposure can be noticed which represents a loss of 1 to 2 hours of sunlight. Lastly, for the southern façade, solare exposure is lowered for the kitchen due to nearby buildings. The decrease in solar exposure is comprised between 14% and 25%, which represents a loss of 1 to 2 hours of sunlight. It can be noted that the overshadowing effect due to nearby buildings is beneficial in summer since it lowers direct beam solar radiation and mitigates overheating.

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Solar protection The problem of overheating due to direct beam solar radiation through windows can be avoided by means of either fixed or moveable solar shading devices. In the case of fixed solar shadings, Autodesk Ecotect offers different analysis tools to determine the optimal shape to intercept direct beam solar radiation over the requested period of the year. The profile shown in Illustration 13 et 14 was obtained by means of ray-tracing techniques.

Illustration 13: Solar shading profile of the southern façade.

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Illustration 14: Ray tracing techniques for the determination of the optimal solar shading profile.

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Results Interpretation: Colours reflects the importance of direct beam solar radiation on summer solstice. The yellow dots represent the spots exposed the longest time during the day while the blue dots represent spots that are less exposed.

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Visual conditions The location of windows being defined, Autodesk Ecotect offers the possibility to map the spots of the site that can be seen through them (Illustration 15). The result, expressed as the total visible window area illustrates the spots on which landscaping is important. Indeed, these spots are those that have the greatest chance to be seen when the users will look through the windows.

Illustration 15: Mapping of the visible spots from the windows of the project

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Results Interpretation: The main spots seen from the housing project are represented by means of a volumetric mapping. Spots in blue colour are less seen than those in red colour. The main spots of the site to be landscaped are the southern and western part of the building (this was to be expected as the main openings of the projected are on the southern façade with the kitchen and the living and on the western façade with the living and the bedroom).

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Energy Management Dynamic Thermal Simulation Thermal Response In order to analyse the thermal response of the project, a dynamic thermal simulation is performed by means of the Energy Plus software simulation platform. Indeed, Autodesk Ecotect can export the geometry of a project and other information into an .idf file that can be read by Energy Plus1. The idf file can be further refined in the EnergyPlus Editor if necessary and is finally run by the EnergyPlus Engine to produce information about the variations of temperature, heat load, etc within the different rooms of the projects. The results can then be more easily visualized through Sketchup via the Open Studio plugin which offers the possibility to load an .idf file and visualize by different colours the zones temperature variations along the year and other such output variables () To run a simulation, several input parameters have to be defined. These refer primarily to the: 

Site and location:

This information determine solar position calculation, and hence incidence angles, but also outdoor temperatures, solar radiation, wind speed (used for the external convection coefficient calculation), and other important environmental conditions. The reference weather data file is taken from the Energy Plus weather file ParisOrly.epw available at http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data.cfm. The weather values (outdoor dry bulb, beam and diffuse solar radiation, etc) are considered to reflect that of a typical meteorological year. The outdoor drybulb temperature recordings are obtained in such conditions that the effect of Sunlight is substracted (temperature sensors are placed in a vented shelter at the meteorological 1

Ecotect can also export .gbm files that can be read by the software IES Virtual Environment. However, Energy Plus was prefered to IES for the reason that it is a free software.

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station site). In addition, the given temperature curves exhibit the daily average temperature, not the hourly average, which is why the values appearing in the simulation results graph may seem lower than expected. The site location is 48.73° North and 2.40° East. This location refers to a suburb of Paris where the outdoor temperatures are usually lower than that which would be observed in the city centre of Paris. 

Nearby overshadowing objects

Nearby buildings primarily affect solar loads on the various façades of a project and hence contribute to the thermal response of a project. In the simulation which is run, the effect of nearby buildings is studied. Hence two different temperature curves family are derived, the first one corresponding to a reference case without nearby buildings and the second one including them. Solar absorptivity of nearby buildings is assumed to be 40%. 

Constructing Materials

Constructing materials determine the thermal response of a project. Their thermophysical properties indicate their ability to conduct heat and store it. Materials with a low conductivity such as wood will poorly transfer heat while material with a low volumetric heat capacity will get warm more quickly than those having a high volumetric heat capacity and hence will not serve as good thermal storage materials. Constructing materials also influence thermal comfort. Their inner surface temperature, in conjunction with the indoor air temperature, determine the mean radiant temperature. For a same sensation of 20°C, a decrease in the indoor air temperature can be conterbalanced by an increase of the walls inner surface temperature. In the following simulation, external walls are assumed to be made of brick (20cm width) with external insulation (10cm width) and siding (2cm) of following thermophysical properties: Brick: Thermal conductivity of 0,72 W/(m.K), Specific heat of 835 J/(kg.K), Density 1920 kg/m³. Emissivity of 0,93 (assumed equal to thermal absorptivity), Solar absorptivity of 0,6. Raphaël BARRY

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Insulation: Thermal conductivity of 0,042 W/(m.K), Specific heat of 1670 J/(kg.K), Density 120 kg/m³. Siding: Same thermophysical properties as that of brick. Windows are assumed to be made of 4-16-4 air filled double pane glazing of following properties: g value of 58% and U value of 1,4 W/(mK). Internal walls are assumed to be made of brick only (10cm width). 

Building activity (occupants, etc).

Occupants, lighting and electric equipments release heat to the zone to which they belong. For instance, light energy is partly absorbed and partly reflected by surrounding surfaces which has the effect of increasing their surface temperature. No internal gain is taken into account in the simulation. In addition, heat gains/losses due to infiltration of outdoor air is set to zero, ie the apartment is perfectly air tight. 

Solar shading devices

As with nearby buildings, solar shading devices influence solar loads on the façades of the projet. They are usally used in front of windows to prevent solar overheating in summer. In the simulation which is run, the effect of solar shading devices is studied. Hence two different temperature curves family are derived, the first one corresponding to a reference case without shading devices and the second one including shading devices. Solar absorptivity of the shading devices is assumed to be 40%. The following results of the simulation present the temperature variations in three different rooms (bedroom, living and kitchen) for a full year.

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Temperature Variations Effect of Nearby Buildings 50

40

Temperature (in °C)

30

20

10

0 02/01 01/01

04/01 03/01

06/01 05/01

08/01 07/01

10/01 09/01

-10

Time

Outdoor Drybulb Bedroom Unshaded

Bedroom w. Buildings Kitchen Unshaded

Kitchen w. Buildings Living Unshaded

Living w. Buildings

Illustration 16: Thermal Response – Shading devices off and nearby buildings on

12/01 11/01

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Results Interpretation: Nearby buildings slightly influence the thermal response of the building. The peak temperature observed in the unshaded situation (solar shading devices off, nearby buildings off) occurs on the 24th of August in the living (42,2°C) for an outdoor temperature of 20°C. The temperature observed the same day in the same zone but with nearby buildings on is reduced to 39,5°C, which represents a 2,7°C decrease. The temperature difference between the unshaded situation and the situation where nearby buildings are present is more pronounced in summer than in winter. For the living, on the 24th of August, it is 2,7°C, while on the 15th of November, it is only 0,5°C. The average temperature difference for the bedroom, kitchen and living are all equal to about 1,5°C.

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Hygrothermal comfort Summer overheating Direct Beam Radiation The temperatures observed within the three different zones analysed show that very high temperatures are achieved in summer, even though the outdoor temperature is not significantly high. This result is essentially due to the penetration of direct beam solar radiation into these zones. Since the apartment is assumed perfectly air tight, no air exchange is possible between the indoor and the outdoor air which is why temperatures as high as 42,2°C on the 24th of August can occur. The use of solar shading devices is thus essential in summer to block direct beam solar radiation. The inclusion of such devices, as modeled in the Solar protection paragraph, page 21, combined with the effect of nearby buildings would produce the results given next page (Illustration 17).

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Temperature Variations Cumulated effect: solar shading devices and nearby buildings 50

40

Temperature (in °C)

30

20

10

0 02/01 01/01

04/01 03/01

06/01 05/01

08/01 07/01

10/01 09/01

-10

Time

Outdoor Drybulb Bedroom Unshaded

Bedroom Shaded Kitchen Unshaded

Kitchen Shaded Living Unshaded

Living Shaded

Illustration 17: Thermal Response – Shading devices on and nearby buildings on

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Results Interpretation: The combined effect of solar shading devices and nearby buildings significantly reduce solar gains and therefore decrease the indoor temperature of the three different zones analysed. As previously observed, the peak temperature observed without any protection occurs on the 24th of August in the living (42,2°C) for an outdoor temperature of 20°C while the temperature observed the same day in the same zone but with shading devices on and nearby buildings on is reduced to 26,5°C, which represents a 15,7°C decrease. The temperature difference between the unshaded situation and the situation with shading devices on and nearby buildings on is again more pronounced in summer than in winter. For the living, on the 24th of August, it is 15,7°C, while on the 15 th of November, it is only 3,2°C, which reflects the fact that solar shading devices were designed to block direct beam solar radiation in summer. The average temperature difference for the bedroom, kitchen an living are equal respectively to 6,2°C, 7,1°C and 7,4°C. These theoretical results would not however reflect the « real world » thermal behaviour of the apartment, given the air-tightness assumption. In reality, the appartment would exchange air with the outdoors through both infiltration and ventilation (opening of windows) and such important temperature differences would therefore probably not be recorded.

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Visual comfort Natural light Daylight access The fraction of spaces having access to daylight can be easily computed via Autodesk Ecotect. In addition, it is possible to determine which spaces have a better access to views on the outside by mapping the area of visible windows (Illustration 18).

Illustration 18: Access to views on the outside, 1m² - isolines

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Results Interpretation: As expected, one can observe that the living benefits from a satisfying access to exterior views. It has an average view on 8.5m² of openings, while the bedroom has only 3,5m² and the kitchen 3m².

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Daylight factor The daylight factor (Illustration 19 and 20) represents the nondimensional ratio between the quantity of natural light transmitted in a space and the quantity of exterior available light under overcast sky conditions. It gives a measure of the worst case natural lighting levels in a space, and enables one to assess the visual comfort performances of a project. The computation of the daylight factor is executed in the Radiance module 1 based on ray- tracing techniques. It requires material visible reflexion factors (floor/wall/ceiling) as well as windows visible transmissivity2.

Illustration 19: Computation of the daylight factor 1

http://radsite.lbl.gov/deskrad

2 Standard hypothesis for these factors are 15%, 60% and 80% for visible reflexivities of floor, wall and ceiling and 80% visible transmissivity for windows.

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Illustration 20: Computation of the daylight factor with (left) and without (right) shading devices

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Results Interpretation: The average daylight factor without shading devices is 3.33%. Hence, under overcast sky conditions, assuming a design sky illuminance of 5000 lux, the average natural light level in the housing is 167 lux which is quite satisfying. Of course, the natural light level is not uniform in space, and some rooms, such as the living, have higher lighting levels than others. With shading devices on, the average daylight factor diminishes to 1.69%. This represents a significant decrease of about 50% from the previous state and clearly highlights the problem of optimizing daylight levels in summer while preventing overheating. Average daylighting levels are worth 85 lux, which corresponds to a dark atmosphere.

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Discussion and Conclusions Capabilities Throughout a housing case study, three of the 14 environmental themes from the High Environmental Scheme were illustrated through Autodesk Ecotect. Concerning the relationship between the building and its environment, the software offers various possibilities to study solar interactions. It can indeed produce heliodons and map the sunlight hours over any surface directly onto a 3D digital model thus making it possible to study solar potential and overshadowing effects due to nearby buildings. In addition, tools are available to define the optimal shading profile to block direct beam solar radiation for specific periods so as to prevent overheatings in summer. These results can be mapped once again directly onto the model for clarity. Autodesk also offers possibilities to analyse thermal interactions between a building and its environment via the Energy Plus platform. The efficiency of previously designed solar shadings can be assessed through the calculation of transmitted radiation and internal temperature variations. Lastly, the software can analyse access to views to the outside and produce daylight illuminance results by computing the daylight factor through the Radiance module. The daylight factor is of critical importance since it represents the worst case natural light levels scenario giving an indication on the ability of a room to be naturally lit throughout the year. The process of optimizing environmental performances thus become greatly facilitated since only one single digital model of the project needs to be drawn. By mapping calculation results onto it, it becomes very easy to visualise any type of effect, saving a lot of time. In order to optimize simultaneaously environmental performances, sensitivity analysis can be performed by modifying hypothesis and testing different scenarios. In this way, to prevent overheating in summer while keeping sufficient natural light levels, the optical properties of windows and shadings such as visible and solar transmissivities can be

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modified to reach satisfying trade-offs.

Limitations In spite of its many capabilities, Autodesk Ecotect also has limitations. The first limitation is probably due to the conditions under which results are obtained. Indeed, model geometry quickly becomes very complex - thousands of vertices is not uncommon – so that tradeoffs have to be made between speed and accuracy. Though Autodesk Ecotect offers the possibility to favor one to the detriment of the other, results should always be carefully analysed before doing any interpretation and one should clearly understand the assumptions used before doing any calculation. Otherwise, Autodesk Ecotect may give totally erroneous results. Secondly, like most software of its kind, Autodesk Ecotect still suffers from unstability which frequently leads to unwanted program termination. The visualisation panel relying on the Open GL interface may become corrupted from time to time, though the issue was adressed many times to the developpers. Other limitations include the absence of tools to assess water management performances. Though the HQE Scheme adresses issues such as rainwater collection or watertightness, Autodesk Ecotect has today no capability in this field.

Conclusion In spite of such limitations, Autodesk Ecotect is certainly a very powerful tool that can help assess at least three of the HQE Scheme environmental themes. Due to lack of time, themes such as Acoustic comfort or Energy Management could not be treated. However, Autodesk Ecotect also offers adapted analysis tools to treat these issues. In my opinion, the many capabilities of the software associated with its user-friendliness make it an essential tool in sustainaible building design. Though it is hoped that the next versions will integrate new capabilities, and improve stability, it is already a very complete software.

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