Bachelor of Architectural Technology and Construction Management

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1 F 7.1 7th Semester Dissertation Bachelor of Architectural Technology and Construction Management Daylight Factor and BIM Peter Nicholas Pringle Consultant: Poul Børison Hansen, Underviser/Associate Professor VIA University College Horsens Denmark March 2014 VIA UNIVERSITY COLLEGE, HORSENS, DENMARK

2 HORSENS CAMPUS, DENMARK 7.2 TITLE PAGE ELECTIVE TITLE: Daylight Factor and BIM CONSULTANT: Poul Børison Hansen, Underviser/Associate Professor AUTHOR: Peter Nicholas Pringle DATE/SIGNATURE: 02/04/2014 STUDENT IDENTITY NUMBER: NUMBER OF COPIES: 2 NUMBER OF PAGES: 30 pages, introduction to end of conclusion. CHARACTERS FONT STYLE Total number of pages is 43. : Main section with spaces characters per page. : Times New Roman size 12 for main text. All rights reserved no part of this publication may be reproduced without the prior permission of the author. NOTE: This dissertation was completed as part of a Bachelor of Architectural Technology and Construction Management degree course no responsibility is accepted for any advice, instruction or conclusion given within! 2

3 7.3.1 Preface This report was written as a 7 th semester dissertation assignment as a part of the final examination for the Bachelor of Architectural Technology and Construction Management education. Report heading: Daylight Factor and BIM All the illustrations and pictures used in this report unless specified were constructed during the writing of this report, using the software mentioned Acknowledgements My sincere thanks and gratitude go to the following people, Associate Professor, Poul Børison Hansen for being my consultant. The library staff for helping me find research material. Brian M.Wendin, architect Cand. Arch/VELUX Aalborg technological institute Autodesk green building team. 3

4 7.4 Abstract This report focuses on: Ways in which we can calculate the daylight factor in buildings, either manually or by using Building Information modeling (BIM) simulation software, and what we can do with the results. My problem statement is: As constructing architects, we barely touch on the subject of daylight analysis using BIM analysis software. In future, with higher demands from the government and clients there is a strong possibility that this will change. As leaders in computer technology in the field of architecture, we may be best suited to the task of analysis, using these programs. But we need programs that function with one another, that can give us more results than stress. The daylight factor in a room should be important. Could analyzing, window dimensions, light transmittance and ambient nature help us to design buildings that optimize natural lighting, possibly saving on artificial light consumption, Or can we just put windows wherever we want? My research questions are: 1. Are there any building regulations that we need to comply with? 2. What is important to gain from a daylight analysis? 3. Can we calculate the correct window dimensions needed using BIM software? 4. How do BIM tools compare with traditional forms of daylight analysis? Theory is gained from SBI s, Building regulations, 2010, European regulations, CIE skies, software guides, reports, videos and interviews and most importantly hands on physical analysis. Brief conclusion I successfully examined how the constructing architect could analyze the daylight factor by hand, and more preferably with the use of functional simulation software, aided by rule of thumb calculations. Early design considerations for window sizing, shape and placement are useful. These considerations effect the project costs and building running costs. There are a number of suitable programs for this task. Some of them are easy to use and mentioned here. Calculating the daylight factor for a building according to BR 2010, does not need to be difficult. This has been an interesting subject to begin looking at other areas of building simulation analysis. Key words BIM, Solstice, Azimuth, Daylight protractor, LUX, Equinox, Daylight Factor, Daylight zone. 4

5 Transition to BIM lighting analysis Figure 1; from left to right, Slaughter house Egypt 3000BC showing the importance of information modeling five thousands years, George Beals Heliodon invention 1953, Vincent Van Gochs use of light in sunflowers painting, Modern Bim analysis showing luminance levels, Modern Heliodon for teaching purposes. 5

6 7.5 Table of Contents 7.1 7th Semester Dissertation TITLE PAGE Preface Acknowledgements Abstract... 4 Key words... 4 Transition to BIM lighting analysis Table of Contents INTRODUCTION/PROBLEM FORMULATION Background information Reason for choice of subject and profession relevance a Problem formulation b Research questions Delimitation Choice of theoretical basis and sources of empirical data Choice of research methodology Choice of working method Main Section Are there any building regulations that we need to comply with? Section 1 summary What is important to gain from a daylight analysis? Design methods and tools CIE skies (Commission Internationale de l Éclairage) Calculate the daylight factor (DF) Obstructions Completion and 1-5 year inspections Section 2 summary Can we calculate the correct window dimensions needed using BIM software? Daylight - Sky component - Build 82 (CEI sky 1) BIM Light analysis software Velux daylight visualizer

7 Reflection Surface transmittance Window to wall comparison Section 3 summary How do BIM tools compare with traditional forms of daylight analysis? The Daylight Protractor A brief introduction to Ecotect Revit to Ecotect Export Import Velux Daylight Visualizer Corruption of data Calculation of the savings Section 4 summary Conclusion References List of Illustrations List of Tables Annex A. System and programs used Annex B. Daylight protractor Annex C. SBI Results

8 7.6. INTRODUCTION/PROBLEM FORMULATION Peter Nicholas Pringle - 7 th semester Bachelor thesis Background information This report was written as a 7 th semester dissertation assignment as a part of the final examination for the Bachelor of Architectural Technology and Construction Management education. The introduction of the Heliodon (figure 1), and CIE sky standard calculations, really influenced the way in which people looked at daylight analysis and the way this affected buildings. Through these inventions and others, it has been possible to change the way that we look at building design in general. The reasoning is simple, energy efficiency through better daylight factors. Gradually these systems have been incorporated into complementary BIM analysis software. This report intends to analyze some of the problems associated with choosing, and using software that can effectively analyze conceptual models for problems associated with natural lighting from the perspective of the constructing architect Reason for choice of subject and profession relevance. Increases in energy regulation mean that we look more and more at what analysis programs can do to help us. Light is so simple that we often forget how important it is to us. During a project, you may be asked to review areas where you can save money for the client. Window dimensioning could be one area. We may reduce window dimensions because we over dimensioned in the early design phase, or increase dimensions if it makes economic sense when weighed up against using artificial light such as in school classrooms, where we could save on artificial lighting. The projects could benefit and the future occupants of the building, from a thorough lighting analysis. I have seen tools like Ecotect used before, but never had the time to examine their capabilities. I think that understanding light and BIM tools, will help me understand the building better and give me the tools to calculate quantifiable results that can assist in quality control during the design phase. We are involved in the project from the conception, and that is what these tools are all about. Understanding daylight analysis may also improve skills such as rendering a Problem formulation The world is facing tough challenges in tackling global warming. Reducing the amount of CO2 emissions and other poisonous gases is a serious matter. The USA s Energy and Information Administration (EIA), estimated that in 2011, about 461 billion kilowatt-hours (kwh) of electricity were used for lighting by the residential and commercial sectors in the USA. Converted to UK prices, with cheap power at about pence per (kwh) this is = to 70,6 Billion pounds. The 21 st century has seen an explosion in computer technology. BIM is a system that is designed to control the information flow through a project. BIM support tools, such as 8

9 daylight simulation software helps us in the process. The estimate is that BIM will cut expenditure by 8%, or 5.6 or Billion pounds or 37 billion kilowatt-hours of poisonous gases in the previous scenario. Saving money can allows more money to be set aside for new innovation projects. As constructing architects, we barely touch on the subject of daylight analysis using BIM analysis software. In future, with higher demands from the government and clients there is a strong possibility that this will change. As leaders in computer technology in the field of architecture, we may be best suited to the task of analysis, using these programs. But we need programs that function with one another, that can give us more results than stress. The daylight factor in a room should be important. Could analyzing, window dimensions, light transmittance and ambient nature help us to design buildings that optimize natural lighting, possibly saving on artificial light consumption, Or can we just put windows wherever we want? 7.6.3b Research questions 1. Are there any building regulations that we need to comply with? 2. What is important to gain from a daylight analysis? 3. Can we calculate the correct window dimensions needed using BIM software? 4. How do BIM tools compare with traditional forms of daylight analysis Delimitation The test area is Copenhagen for weather data. All regulations apply to current Building Regulations 2010 for Denmark. European standards, green building agencies and the American energy environmental agency are mentioned briefly, but not elaborated on. The main focus of this report is how the daylight factor can be calculated and used for designing the size of windows needed in modern buildings constructions in Denmark. Reference may be made to the energy framework but the main focus is on what natural lighting levels are required. Only windows in facades will be analyzed. Sloping roof lights and skylight may be mentioned but are not being analyzed in this report. It is assumed that with slight adjustments to calculations, then a similar process can be adopted for them. Shading and glare are mentioned briefly, but these can be whole topics in their own right. The main emphasis is on how to establish the daylight factor levels in rooms. 9

10 7.6.5 Choice of theoretical basis and sources of empirical data. The research methods used in this report are based around information and guidelines from: Aalborg technological institute, BR 2010, SBI 219, Daylight in rooms and buildings, SBI 203, Calculation of daylight in a building. (EN15193) Energy performance of buildings - Energy requirements for lighting, The Autodesk energy design forum and video guidelines. I also looked at a number of research papers. And followed guidelines and setups with the software mentioned in annex A. Using, my standard Lenovo laptop, which runs on windows Choice of research methodology After thoroughly examining the building regulations and guidelines, I have chosen as a main feature to conduct primary research based on small experiments and to manually test the capability of some analysis programs. This produced some quantitative data that I compared with secondary data, available in reports and SBI guidelines. I was also able to use this empirical data to carry out quality checks to test the validity of the guidelines in BR 2010 (theory in use) and other sources. Other information was obtained from research papers and validation testing results of software. I compared using some software with what I found on videos. I also interviewed a member of the Velux design team, this gave me some qualitative date which more or less confirmed my own findings and had no bearing on my research analysis results or personal choice of software. My consultant advised me through the whole process. I have developed new skills in light analysis using BIM tools and also in the fundamental use of daylight analysis where choice and design of windows may become an important factor Choice of working method This report has a 3-part structure. 1. An introduction with problem formulation and questions. 2. The main section examines 4 research questions, explaining regulations, daylight analysis, window calculations and methods to calculate the daylight factor in buildings with part conclusions. 3. A final conclusion answering the questions from the problem statement. I made mind maps and from there planned which areas of the report I would concentrate on each week, with evenly space consultation sessions to balance my progress. 10

11 7.7 Main Section Are there any building regulations that we need to comply with? This report is aimed at the constructing architects, and deals with daylight factor calculations, which are a necessary part of the building regulation demands when applying for planning permission. The following section highlights these regulations translated from the Danish version. Danish Building Regulations updates from January Daylight (1) Workrooms, occupiable rooms in institutions, teaching rooms, dining areas, Herein after called workrooms etc., and habitable rooms and kitchen must have sufficient daylight for the rooms to be well lit. Windows must be made, Located and, where appropriate, screened such that sunlight through them does not cause overheating in the rooms, and such that nuisance from direct Solar heat gain is avoided. Guideline: (6.5.2 (1)) In workrooms etc., habitable rooms and kitchen the daylight can usually be taken to be sufficient if the glazed area of side lights corresponds to a minimum of 10% of the room floor area or, in the case of roof lights, no less than 7% of the room floor area, assuming that the light transmittance of the glazing is no less than The 10% and 7% are guidelines assuming a normal location of the building and a normal layout and fitting out of the rooms. If the type of window is not known at the time of design, the frame clear area can be converted to the glazed area by multiplying the clear frame area by a factor of 0.7. The glazed area must be increased in proportion to any reduction in light transmittance (for example solar control glazing) or reduced light ingress to the windows (for example nearby buildings). Daylight may similarly be deemed to be adequate in habitable rooms and kitchen when calculation can demonstrate that there is a daylight factor of 2% in half of the room area. In workrooms, daylight may also be deemed to be adequate when calculation can demonstrate that there is a daylight factor of 2% in the work zone. This can be calculated by means of a calculation grid (figure 2) that covers the room or the work zone. The grid has an off set of 0.5m from the walls and contains evenly distributed grid points with a maximum distance of 0.5m. Daylight may similarly be deemed to be adequate when calculation or measurements can demonstrate that there is a daylight factor of 2% at the workplaces. When determining the daylight factor, account must be taken of actual conditions, including the design of the windows, the light transmittance of the pane and the nature of the room and of the surroundings. See By og Byg (SBi) Guidelines 203, Beregning af dagslys i bygninger [Calculation of daylight in buildings] and SBi Guidelines 219, Dagslys i rum og bygninger [Daylight in rooms and buildings]. (BR, 2010). Change of use and extensions 7.3.2(2) The area of windows and external doors must be in accordance with the rules specified in DS 418. Calculation of heat loss from buildings. Max size of windows no more than 22% of heated floor are, change of use, extensions. 11

12 For detached single-family homes, two-family houses with a horizontal boundaries and duplexes with vertical party walls local authority may not refuse to approve building height and distance relationship when the conditions in points 1 and 2 are met. 1). Maximum height: 1.4 x distance to the boundary and path. 2). Minimum distance to adjoining properties, roads and paths: 2.5 m Danish Working Environment Authority In their guideline A1.11, the Danish Working Environment Authority outline requirements to daylight in workrooms and permanent workplaces (June2007): Daylight levels in workrooms should be adequate. Daylight can usually be taken to be sufficient if the glazed area of side lights corresponds to a minimum of 10% of the room floor area or, in the case of roof lights, no less than 7% of the room floor area. Another configuration may similarly be deemed to be adequate. The 10% and 7% is a guideline that will usually give adequate daylight with a normal layout of the rooms. However, situations may occur, where daylight access is not adequate. Daylight may similarly be deemed to be adequate when calculation or measurements can demonstrate that there is a daylight factor of 2% at the workplaces The green building type certification systems comprises U.S. LEED, the British bream and German DGNB, Cradle to Cradle and Passive house design model. These systems are all subscription certification services. So there is limited access to information. But they all use a form of scoring system which gives points for better daylight factor levels in rooms than the min levels found in the building regulations. Some are self-certifying so open to scrutiny. EN Energy performances of buildings - Energy requirements for lighting, stipulates how calculations should be made from member states with regard to lighting levels. This is a very specific technical document about how calculations are made. But for natural lighting, there are correction values stipulated for obstructions, overhangs, vertical fins, atriums, and glazed double facades. What is interesting is the following extract. For simplicity the obstruction can be evaluated for a window in the middle of a façade. Obstruction influences should be averaged. (EN15193, 2007) Guide to DIN EN The following grid size p should not be exceeded: p = 0.2 x 5 log10 d Figure 2; Light analysis grid shown in sketchup model. where: p is the grid size and d the relevant dimension of the reference surface. The number of points is then given by the next whole number of the ratio d to p. Rectangular reference surfaces are subdivided into smaller, roughly square rectangles with the calculation points at their centre. The arithmetic mean of all the calculation points is the average illuminance. Where the reference surface has a length-to-width ratio between 0.5 and 2.0, the grid size p and therefore the number of points can be determined on the basis of the longer dimension d of the reference area. 12

13 Table 1; recommended grid size for rooms Peter Nicholas Pringle - 7 th semester Bachelor thesis 2014 Size of grid recommended for room and areas Type Longest dimension Grid size of area of room Task area Approx. 1m 0,5m (Min) Small rooms/zone rooms Approx. 5m 0,6m Medium sized rooms Approx. 10m 1m Large rooms Approx. 50m 3m In all other cases, the shorter dimension needs to be taken as the basis for establishing the spacing between grid points. A 0.5m wide strip along the walls is excluded from the calculation area. This is unless task areas are located within the strip or extend into it. (Licht, 2011). The EU directives are slightly different to the Danish building regulations which states max 0,5m spacing. Section 1 summary There are a number of regulations regarding daylight in buildings, BR2010 basically says the min daylight factor required is 2% in ½ the work zone in living areas, and 2% in the work zone in working areas. We don t want unnecessary glare, which can be a nuisance in office buildings, cover picture, and there should be adequate screening to stop overheating. The height of buildings is also important to know for shadow casting. The Guide to DIN EN gives information about grid dimensions. In here it does not say that the 0,5m strip running round the walls should not be calculated if that area is going to be used, eg. a kitchen bench and cooker and the grid spacing calculation is different to BR EN Energy performance of buildings, gives more detailed information on complex calculation methods but is much more difficult to understand. Certification schemes on subscription, can give guidance on attaining higher levels of daylight factor in a building, but fall outside the demands according to building regulations. As a general rule, for min levels of daylight factor, we can calculate 10% of the heated floor area for glazing. At the other extreme, we could go up to 22% for change of use or extensions, before we start worrying about excessive heat loss. Some of the guidelines to building regulations are looked at in the following sections What is important to gain from a daylight analysis? Our whole existence depends on natural light from the sun. The sun gives us free light and energy. Free natural light can reduce the overall running costs of a building if used in the correct setting. Especially for buildings that are generally occupied during daylight hours. Offices, work-shops schools etc. At a day to day scale, we may not be able to appreciate that, but over years, this could run into thousands of Kroner. Not to mention the extra burden placed on artificial lighting and the extra discharge of CO 2 and other damaging gases into the atmosphere. A natural lighting analysis will help us examine the full potential of the building in relation to the location, orientation, obstructions and effects on surrounding buildings. Using analysis software should not be complicated at the level which the constructing architect will be involved. We perceive light in different ways. If we have different eye color, our eyes can react differently to light. Age wears the eyes, so older people generally need better light quality. We can 13

14 function in areas lit between bright sunlight ( lux) and Moonlight (1,0 lux) Or : 1. In buildings, we are comfortable above 200 Lux. The eyes take around 15 min s to adjust between ratios of 100:1 ie, coming in from an CEI 1, overcast day lux, to a standard lit room. Different tasks also require different luminance levels to be effective. The daylight supply factor is valid between 08:00hrs and 1700hrs between latitudes 38 º to 60 º North. Copenhagen is in 55º46 North. (EN15193, 2007). Between the working hours of 0.900hrs 17.00hrs, we can find around 70% to 80% of daylight factor that will light rooms above 3%. The rest of the time is below 1,5%. (Energy Research Group, 1994) Daylight and views makes us feel better. As constructing architects, we have experimented with placing the building on a plot, either in a 2D or 3D program such as Autocad, Revit or sketchup. In 2D, sun path protractors enable us to estimate where the shadows are going to fall. In 3d, this becomes much easier to see. We can identify places where light can be useful for such things as gardening, drying clothes, play area. There are many rules of thumb for window dimensions and positioning, but for more accurate calculations, we need to make an analysis, either by hand or digitally. This will become more important if people choose to study or adopt a green building certification system, such as U.S. LEED, the British bream and German DGNB. Cradle to Cradle or the Passive house Model. Early decisions can have long term effects on a project. Conceptual BIM light analysis tools, could save us time and money, before planning applications are sent in. In some areas it is a requirement to conduct a Daylight assessment, especially if there is a negative impact risk in such built up areas as London. Using analysis programs needs careful thought. Some programs are still in the early stages of development. They feel half baked, can give you stress and some are also very expensive. But there are also programs that are functional and give us effective results. But we need to know what this software can do for us? Making a risk analysis is a good place to start. We can examine areas Such as: How much time will we spend on analysis? Which software can we afford? Life expectancy? Compatability with other programs? Table 2; Risk analysis Ease of use? Who will use it? How we will use it? When we will use it? The most important question is what information we can get from daylight analysis? Important, you should plan where and how much daylight you want in room zones. The aim here is not to do the lighting engineers job. But we have a responsibility to the client for producing an efficient design. Starting off on the right foot, will make the project run smoothly, and thus eliminate potential threats to the smooth running of the project. 14

15 We are performing conceptual analysis, which will later become construction drawings. At some point the lighting engineer is going to check the design and make calculations for indoor lighting demands. The tools that we use need to be fairly accurate but at the conceptual stage, this may or may not be so critical, depending how you look at it. I have found, some programs have been certified whilst others have failed tests. Some have never been tested at all. Design methods and tools When calculating daylight factors should be used recognized methods or computational tools that can take into account the essential factors. (BR, 2010) 10 manual protractor templates are available for calculating daylight factor (Johnsen. Christoffersen, 2008). As to recognized computational tools, Last year SBI, 2013, 26 tested 10 pieces of software. Most of them fulfill certain criteria for use as computational tools. See annex B. (Byggeforskningsinstitut, 2014) Calculation programs need to be calibrated to be effective (figure 3). WEB-Matriklen - Geodatastyrelsen, for a fee provides cadastral information for the building plot. So GPS location is input. Climate data can be loaded from weather files. For Ecotect, we can download weather files (wea.) from the Department of Energy in the USA. We can also import energy plus weather (epw.) Format files, from the Energy Plus Energy Simulation Software site. The Danish Meteorological Institute (DMI) provides weather data for programs like BSIM in Denmark. This building analysis software package is developed by the Danish Building Research Institute, the climate data is basically the Copenhagen area, although other parts of Europe are available (SBI) More regional weather sources may become available, the DMI is probably the best place to contact for information on weather in Denmark. Remember, All weather is unpredictable. North 55 0, West 12 0, Elevation 25,3m Figure 3; Location and climate settings in Ecotect CIE skies (Commission Internationale de l Éclairage) The Commission Internationale de l Eclairage (CIE) has existed since It is a non-profit organization and recognized under ISO as an international standards authority.- devoted to worldwide cooperation and the exchange of information on all matters relating to the science and art of light and lighting, colour and vision, photobiology and image technology. For analysis, we use certain sky type templates. There are 15 CIE normalized sky types (CIE 2003). Lots of them are used in energy calculation programs. But for daylight factor design, we generally need to use two of them, CIE sky No 1, for standard overcast conditions to use for daylight factor calculations and CIE 15 clear skies, to spot areas where we need to apply shading. (CIE, 2001) (Darula.Kittler, 2008) As an alternative to CIE 1 skies, some people have recommend CIE 6 Skies or uniform sky which we can manually input a uniform 10,000 lux. 15

16 Calculate the daylight factor (DF) When we calculate light penetration into a building, we measure the daylight factor (DF). Either DF at a point, Or DF mean, as an average of a room, or half grid. To find the daylight factor, we use the recommended CIE sky No 1. This represents an overcast sky with diffuse daylight, where the light has been scattered all over the atmosphere due to clouds. This provides equal sky luminance reflected at our buildings facades, and produces a general all round light. The average value from direct sky is 10,000 LUX. With an overcast sky, we see almost no shadows cast. So the positioning of the windows on the building should have little effect on the calculation, unless there are significant obstructions in front. 200 Lux lighting any spot in our room produces 2% DF. As a min we need this in half the analysis grid according to the building regulations. This comes from combining direct light from the sky without obstructions, reflected external light and internal reflected light. The standard measure, is a working height of 0,85m, on a grid min 0.5m * 0,5m within the room 0,5 m from the walls. (see regulations) (EN 12193:2007 and EN :2007). (Johnsen. Christoffersen, 2008). ( ) ( ) < 2 Is below building regulations, artificial lighting will be required. 2 > 3,5 Adequately lit but artificial lighting may be in use for part of the time 3,5 > 5 Well lit according the BRE standards artificial lighting not required much 5 > Artificial lighting generally not required except at dawn and dusk but glare and solar gain may cause problems with excessive energy consumption So there is a general range, 2% basic to above 3,5 to 5% for well lit. But some tasks require better light such as drawing offices < 7% and high precision tasks <15%. Be aware of possible glare from a high DF especially on south, east and west faces. A well-positioned building, with good sunlight distribution and penetration, will suffer less effect from Northerly façade mold growth and house mold which come seasonally. Being able to identify potential obstructions of light onto the building will help us to correctly position windows to maximize the available light. Seasonal changes are useful for understanding how the weather cycles affect the building. They fluctuate slightly each year. For 2014 they are (Time and Date A/S, 2014). Phases of the sun for Copenhagen 2014 Phase Month Date Sunlight hrs. Angle of Solar noon comments Spring equinox March 20 th 12hr 10min 34,3 0 Mid point Summer solstice June 21 st 17hr 32min 57,8 0 Longest day Autumn equinox September 23 rd 12hr 09min 34,6 0 Mid point Winter solstice December 22 nd 07hr 01 min 11 0 Shortest day Table 3; phases of the sun BRE recommend that the 21 st March gives the best average time for solar plotting. As a minimum, half of external areas requiring sun should have at least 2hrs of sunlight at this time in order to receive adequate daylighting. Sunrise on this day is 06:10hrs, sunset 18,25hrs. Passive 16

17 solar energy collection on facades should be within 30 0 of due south if we are looking for heat gain, as well as good daylight factor levels. The positioning of a house will affect shading devices, which could also influence daylight factor calculations. (Littlefair, 2011) Obstructions Obstructions affect the light we receive. We can identify obstructions in a number of ways. One method using a conceptual cross section (figure 4) allows us to identify obstructions using the angle of intersection. We use the center of a window as the reference point. This is a rule of thumb guide. It is difficult to make accurate calculations for every building in the neighborhood. But as a rule of thumb, if an obstruction is more than 20 0, we should consider changing the window dimensions or placement, to allow more light penetration. (BR, 2010). Any obstruction above 1,5m high in the near vicinity should be included as they can have an effect on the daylight factor. (Littlefair, 2011) Figure 4; Cross section analysis to identify angle of obstruction from clear skies. Another method is shadow casting (figure 5), helps identify potential problem areas and light movement during the day within the working zones. We can also identify windows that will receive the most direct sun, in order to plan for shading. Here there is a good distance between buildings. In special circumstance, caustics can be used to refract or reflect light into window openings where access to light is a problem. But these solutions can be a costly alternative to good effective positioning of windows. Fiber optic sun collectors are another option. But according to building regulations, working areas should have a view. Figure 5; Shadow analysis of plot. Table 4; solar shadow casting 17

18 I ran a little experiment to check the accuracy of the shadow s using the standard software that I use (table 4). As a control, I used a manual directional light at set angles in Turbocad. 4 set ups produced similar results, including the control. Unfortunately Revit produced a completely different result to the others. I ran the test several times, and made two separate files but I got the same result each time. As shown in (figure 6). The project is set up for Copenhagen, the same as the other drawings, default latitude longitude. 3*3*3m box on a level plane. The view shows 21 st June and a shadow that resembles something much more near to the equator than Copenhagen. This is worrying and a surprising result from Revit. It may be a glitch or an isolated incident. But it shows the need to check from time to time, the accuracy of the software we use. Figure 6; Revit s failure to produce accurate solar shadows. Completion and 1-5 year inspections - At the end of the construction, the engineer can make internal and external natural lighting measurements simultaneously on a table, using light meters to assess the accuracy in DF prediction. (Johnsen. Christoffersen, 2008). Our analysis need not stop when the building is finished. At the 1 and 5 year inspection points, we carry out building function checks with the client. At these points, it may be possible to follow up and see how the lighting is affecting the building in use. Visually, people may have put up extra screening. So just by looking round it may be possible to gain some knowledge that can assist you in using this technology effectively. Smart buildings, have computer controlled systems, that can monitor a buildings performance. This technology could show where weaknesses lie. Section 2 summary Effective daylight analysis will reduce the risk of a negative impact on natural daylight entering our buildings. When calculating the daylight factor in rooms. Plan how much daylight factor (DF) you need in individual rooms then identify obstructions to light. Obstacles may be avoided and correct placement of windows could be achieved early in the project. It should be possible to identify potential areas where we may need to apply shading. But this is a whole subject in itself. By ensuring that the correct DF can be achieved in individual rooms, money is not wasted. Enhancement of the project success is strengthened. We also need tools which are recognized as being functional and useful. Local weather and project data is required as it affects the softwares performance. We can make a risk assessment to establish how we will use the tools and at what stages. Check the accuracy of analysis tools where possible and cross check with similar tools if possible. The shadow cast result from Revit was not good in this case. Natural light saves money 18

19 and is good for the environment. We can gain feedback, at the end of the project and also 1 and 5 year inspections Can we calculate the correct window dimensions needed using BIM software? This section covers window dimensioning. There are some easy analysis programs, which can help us make these decisions. Low energy passive houses have an annual heating demand of under15 kwh/m² per year, it will be almost impossible to achieve this, without doing some detailed analysis. BIM conceptual tools can make dimensioning and placement of windows a much easier task and possibly a more effective one too. As far as the energy simulation programs are concerned, we need to know a basic number of things when trying to determine window dimensions. 1. Can the program simulate CEI 1 overcast sky conditions 10,000 Lux. 2. What are the width, height and depth of the room. 3. Design area of glazing and type of shading if this may have an effect. 4. Transmission rate of glazing from the manufacturer or SBI guidelines (table 5). 5. Reflectance factor of glazing, internal and external materials. 6. Height of analysis grid, usually 0,85m and marked calculation area. 7. Daylight factor required, because we may want better levels than 2% DF. Glass type Factor K 1 1 layer of glass 1,00 2 layers of glass 0,92 3 layers of glass 0,82 2 layers of energy glass 0,80 0,88 3 layers of energy glass 0,73 0,79 Solar reflective glass 0,30 0,70 Table 5; glass reflectance type Usually work in daylight can be performed at a distance from person to window of maximum light transmittance? V multiplied by 2.5 times the pane above the table level (a) plus 1 times the height of any window below the table level (b). (BR, 2010) If an external shading Device is going to be used, we can adjust A to 2* instead of 2 5. We can easily calculate this formula in reverse to find the window size from a given point. Using this rule of thumb guide, we can estimate the effective daylight zone from windows. The following calculations look at 3 common window height configurations. The DF at a point can be estimated at around 2% where the person is positioned. Higher levels can be found towards the window. It should be easy to see in the following examples, that depth of daylight factor can usually only be increased with larger windows, or higher rooms. 19

20 Example 1. Window = Full height floor to ceiling Working height 0,85m V = 0,79 2.8m high room (as in guidelines BR.2010) - frame 2,8m - (0.08m m) =2.64m glass height b =1 x height of window below table = 0,85 0,08 =0,77B a = Pane above working height = 2,64 0,77 = 1,87m Maks (2,5a +b)*v Maks (4,675 +0,77) * 0,79 Maks = 4.19m Dayligt zone Example 2. Window = 2.2m standard head height Working height 0,85m V = 0,79 - frame 2,2m - (0.08m m) =2.14m glass height b =1 x height of window below table = 0,85 0,08 =0,77B a = Pane above working height = 2,14 0,77 = 1,37m Maks (2,5a +b)*v Maks (3,425 +0,77) * 0,79 Maks = 3.31m Dayligt zone Example 3. Window = 2.2m standard head height no b Working height 0,85m Window sill height is 0,9m V = 0,79 a = (2,2m 0,9m) - frame (0.08m m) =1.14m glass height Maks 2,5a*v Maks 2,85 * 0,79 Maks = 2.25m Dayligt zone Peter Nicholas Pringle - 7 th semester Bachelor thesis 2014 Daylight - Sky component - Build 82 (CEI sky 1) This program is freely available (figure 7). Sky component allows you to make a quick calculation based on a 2d façade and plan to represent a room in your building. The analysis grid can be placed at heights with increments of 0,1 the windows can be dragged from the corners to any size and then placed from the center anywhere quickly. Up to 3 windows can be included with transmission rates (Gov., 2009). Figure 7; Sky component build standard results panel. 20

21 An average daylight factor is given for the room and a daylight distribution graph. In the example, the parameters are set up as follows. Room 3*3*3m. working height of window was set at 0,9m. Grid 0,8m height. Transmission 0,8, and full width of window to wall. The average daylight factor is 0,9% for the whole room (figure 7), which compares with results obtained in Velux daylight visualizer (figure 11, 2). This program is simple to use and effective, but has less features and precision than other software and does not deal with complicated room structures. Standard Lux and daylight factors needed for different zones are shown (table 6). It is probably better to increase the daylight factor in a room which will be occupied all day such as a classroom, than one which may be empty, such as the living room of a single family house. Zone Lux DF Most frequent use hrs Monday - Friday Corridors/toilets Lux 1 1,5% DF 3 or 4 times a day average Living rooms 200 2% Parents and children away Kitchen 200 2% Meal times Restaurant/Canteen 200 2% Lunch time 1-2 hrs approx Library/Classroom % - 5% Working day Monday - Friday General office 500 5% Working day Monday - Friday Workbench 500 5% Working day Monday - Friday Factory 500 5% Working day Monday - Friday Drawing office % Working day Monday - Friday High precision tasks % Working day Monday - Friday Table 6; recommended daylight factor zones in buildings (EN15193, 2007) BIM Light analysis software Velux daylight visualizer 2. The following calculations were made in Veluxe daylight visualizer 2, at a height of 0,85m, with overcast skies,. In reality, in winter, the average Lux externally on an overcast day will be 7,500 Lux, whilst in summer this will be around 30,000Lux on an overcast day (SBI 203 page 11). This calculation uses CEI 1 skies, standard yearly average 10,000 Lux on an overcast day externally, anywhere internally, which has 2% daylight factor, will have min Lux of 200 internally. Using the rule of thumb window calculations, and Velux visualizer 2, and 8m * 5m rooms, we see a very similar pattern (figure 8) to rule of thumb examples on page 20, to find where work can be performed in the 2% > daylight zones. Although average daylight factor is much higher. Figure 8; Daylight to a point in Veluxe Daylight Visualizer 21

22 1. 12,62 m 2 glass to 40 m 2 = 31,55 % glass, DF mean was 4,7%, 5,7% for half grid ,78 m 2 glass to 40 m 2 = 24,42 % glass, DF mean was 3,0%, 3,8% for half grid ,49 m 2 glass to 40 m 2 = 13,73 % glass, DF mean was 2,5%, 2,9% for half grid. Location of the building If a building is positioned so that the surrounding shadows essential for daylight access to the window, the glass area is increased proportionately. In general, it is assumed that if the angle of elevation (line of sight from the lower edge of the window to the top of surrounding buildings ) exceeds 20, it will be necessary to increase the glass area. The limit is not fixed but depends, among other things the room depth. (BR, 2010) Figure 9; Reduction of room depth to increase the daylight factor. In (figure 9) the overall room s daylight factor has increased by closing the rear wall towards the light entry wall thus increasing the reflection rate and condensing the light. But we should also bear in mind, that too much exposure to sunlight, can give us glare and overheating problems. See page 16 and table 6 for DF guide levels. In (figure 10), windows are placed around the room to create a working zone of above 2,0% DF. DF mean is 2,6%. DF mean, is the average daylight factor for half the investigated grid. (BR, 2010) The room has an area 5m * 5m with 4 windows 1.212mm * 1.212mm. So we have around 4m2 of glazing, and 25m2 of heated floor. That s about 16% glazing. Having windows all around the rooms would help in workshops etc. and we can adjust the DF values according to specific requirements. Figure 10; Equal luminance around the building can create a good daylight zone within. In the following examples (figure 11), using the 10% rule of thumb guidelines in BR We can see how DF is affected when we move the size and positioning of the window. We have a room width 2,8m * 2,8m and height 2,8m. Area = 7,84m. 10% glazing area = 0,784m. Glass size = by 0,885m. The window frame dimesions are added to this for the final overal size. Only normal standard window placement is good enough to achieve 2% DF mean on a grid set to 850mm, but this is 22

23 without furniture or external obstructions, which may in reality absorb some of the light. The 2% DF mean ½ grid area is marked by the box. I found that the 10% figure to be a weak basis for estimating the correct window size if you take these factors into consideration. 1. a. 1800mm High placement b. poor DFmean of 1,2% c. diffused scattered spread 2. a. 900mm normal placement b. 2,0% DF mean ½ grid good c. good concentrated spread 3. a. 0mm low placement b. DF mean 0,1% bad c. Light dark diffused across the floor and lower regions 4. a. 900mm placement to side b. DF mean 2,0% almost half grid. c. Good spread of light to one side of room. 5. a. 900mm narrow to high b. DF mean 2% to ¼ the grid c. Light spread in v. Typically found in old churches. 6. a. 900mm narrow and wide b. DF mean 2% to 1 /5 the grid c. concentrated near opening, maybe useful for lighting benches. Figure 11; Window placement can influence the daylight factor 23

24 An imported model in the Daylight visualizer 2, gave better daylight factor results for the room, with and average for the whole room being 1.1% giving >2% half grid, compared to 0,9% average 2% DF half grid using the internal 3D modeler. Reason, better quality set up. In table 7, I examined ground obstructions (figure 4) and found the following results using an imported model, with a standard set up of 10% window area. The 2% daylight factor fails at 20% obstruction, Which fits with the BRE recommendations in figure 4, Section 2. Strangely, once the daylight factor reaches 0,8% then there was no further changes, regardless of the obstruction height here. The reason for this was unclear. The imported model, gives a more credibility to the guidelines in building regulations and according to Veluxe, it is a more preferable method for accurate results than the internal modeler. <2% DF, we can increase window dimensions. Obstruction DF whole room average Standard DF half grid average 0 1,1% Good >2% 10 degrees 0,9% Ok 2% 20 degrees 0,8% Not Ok <2% 30 degrees 0,8% Not Ok <2% 40 degrees 0,8% Not Ok <2% 50 degrees 0,8% Not Ok <2% Table 7, Ground obstructions Window size affects the daylight factor, In (Figure 12), we can see what happens when we increase glazing area by width, or an upwards direction or a downwards direction from the normal horizontal size and placement. Changing the width or making the window higher is preferable to increasing the glass area under the plane. The second chart shows what happens if we add external shading above a high window in 100mm increments. The room begins with 2,3% daylight factor. Results can be cross checked with a solar glare analysis. Figure 12; Daylight factor trend, with increased glazing, and external shading BREEAM classifies the daylight factor An average daylight illuminance of 200 lux for 2650 hours per year. Actually they say 2.1% for lattitudes 55 0 to (BREEAM English manual 2013). That works out at 7Hrs and 15mins per day average for 365 days. Exemplary natural lighting levels would be DF. 24

25 Reflection Surface reflections are important information and will make a difference to our calculations. In a room, light is reflected repeatedly and standard Light Reflectance values (LRV) (figure 13) can be used from BR2010 for walls 0,4. Floor 0,1. Ceilings 0,7. Energy is lost each time light is reflected and absorbed by the reflected surface. A smooth, brilliant-white wall may reflect 85% of the light that falls upon it; a cream wall perhaps 75%; and a yellow only 65%. Bright colors, such as orange or vermilion, absorb as much as 60% of the light that falls upon them. Lighter colors are preferable to dark. But absorption could also be useful to trap light energy and stop it reflecting out of the window, in certain cases. (Garco, 2014). The other thing that will make a difference and should be accounted for is furniture and shelving. With added furniture, the daylight factor will be reduced due to absorption of the reflected light and shading. The guide to building regulations recommends that you use standard values of reflectance for furniture and include it in the calculation process. More information about daylight reflectance and values can be found in SBI 219, Dagslys I rum og bygninger. table 11. Figure 13; Color light reflection values chart. Surface transmittance. Accurate surface reflectance levels are important for accurate results in all the programs tested. If we do not know the reflectance values, we can add standard values found in SBI 219 and Guidelines to building regulations. (table 8 and 9). The first two methods of calculation are fairly straight forward by hand but time consuming. We can add the sky component to the externally reflected component to find a value for our window size. The latter method is best left to a computer generated program. So to calculate each grid of a plan area in the horizontal and vertical will take us a considerable length of time. This is one reason to learn how to use a more simplified calculation program. Light transmittance Window in facade 0.76 Window in skylight 0.76 Internal glass 0.85 Table 8; standard transmittance values 25

26 SBI Reflectance (r) Ground plane 0.1 External walls and obstructions 0.3 Floor 0.1 Wall 0.4 Ceiling 0.7 Window frame 0.8 Side of window opening internal 0.7 Side of window opening external 0.3 Light shelf 0.5 Table 9; standard reflectance values Peter Nicholas Pringle - 7 th semester Bachelor thesis 2014 Window to wall comparison In the V & S price book 2011, a side and bottom hung aluminum window, * 1.188mm cost DKr. to fit. An insulated cavity wall of 108mm brick, 190mm insulation and 100mm light concrete block costs DKr. per m 2. (V & S, 2011) So bearing that in mind, and the fact that going up above the horizontal work plane gives 2,5 * the ratio, and below gives 1*, then it is easy to see that having floor to ceiling windows in a small room may be uneconomical. Whatever windows you choose, needs to be balanced against light gain and heat loss and overall cost as well as the aesthetic value (figure 13). Section 3 summary The easiest program that came close to calculating window size and positioning was sky component build. But its capabilities are limited. Veluxe daylight visualizer 2 can also help calculate dimensions and positioning. There is a script for Ecotect which claims to be able to do this function, but I was unable to find a copy to test it. Although it is possible to calculate window dimensions using BIM analysis programs, a good starting point is the rule of thumb calculations found in the guides to building regulations. We can quickly establish the DF at a given point where we want say 2% or higher values at our working surface or areas. Then we can make reverse calculations to determine window height. Once the height is established, we can use the software to run simulation using different width/height and positioning of windows to find the DF mean or the average daylight factor for the investigated grid. Analysis software will make the task much easier with complex room layouts, The guide of 10% glazing to the area of the room proved to be adequate for rooms without any obstructions using the internal modeler software. Imported models gave slightly better results because the model itself was more accurately constructed and were able to take external obstructions and reflectance into account. Furniture and external reflections make a difference. There was noticeable poor light deep in the room which will result in more use of artificial lighting. Shallower rooms increase the reflectance, which improves DF and will reduce the need for artificial lighting. Using the BIM analysis software can be a time saver, especially in complex rooms. A short time spent on analysis, may save wasted time later re-drawing window positioning and dimensions. 26

27 7.7.4 How do BIM tools compare with traditional forms of daylight analysis? As far back as at least the 11 th Dynasty in Egypt, 2000BC (figure 1), people knew the importance of creating realistic scaled models which in a visual sense could explain some of the buildings performance. Vincent Van Gogh , the famous Dutch painter experimented with color and light to create 6 of his famous still life master works depicting sun flowers. In the 1914, Marks and Woodwell published the book, Planning for daylight and sunlight in buildings. This highlights the problems at the time facing New York, and high rise buildings. They begin to describe ways to calculate light and with similar theories to CIE skies and the Daylight protractor. At a similar time, the daylight protractor was developed and patented by the Building Research Institute, UK. Scientific light analysis was taking a new shape. Rational formulas could now be used to describe how light will affect our buildings. The first CEI non uniformed luminance for an overcast sky condition, was suggested by Moon and Spencer (1942). This has been further developed into the 15 CIE + 1 sky types and certification system that we can find today. In 1953, George Beal demonstrated the Heliodon, a model lighting simulator tool for architects and designers. As we moved into the computing age, 2D CAD modelling began developing in the 1950 s and still has huge uses and followings for programs such as Auotocad. 3D CAD applications for aerospace emerged in the 60 s. The 1980,s produced Excel type programs using algorithms that could now give us fast calculations to make the manual task much easier. The BIM potential was realized when Archicad was launched in Building modeling analysis has expanded since then with programs such as BSIM, Ecotect and radiance. Beta software and direct scripting has enables greater ingenuity as we have seen in the success of programs such as sketchup. These developments can allow us to send information direct to the client for example, in 3D Pdf or using Xml integrated spreadsheets such as green building or IFC format. Newer applications of BIM include cloud technology. The future may produce 3D Holographic projection light simulators (Wiki 2012). What we have seen here is a rapid change within the last 40 years compared with 5000 years of slow development. BIM is information about our model in the easiest and most cost effective form that we can find. Building Information Modeling (BIM) BIM is part of the Digital Byggeri in Denmark. The main difference between BIM and pure 3D modeling is the information which is available in the model. This information is used to produce quantifiable results, which will have an improvement effect on design, and provide useful information through many stages of the buildings lifespan. Light analysis can be used from conception till the 5 year hand over and even during building management, till demolition. The Daylight Protractor: is used for the manual calculation of daylight factor, but also as a basis method in all the daylight analysis software programs, which use various forms of ray tracing algorithms. Note, there are at least 10 Different types of Daylight protractor for different situations as developed by the UK Building Research Establishment LTD, In the 1920 s. 27

28 (Christoffersen, 2002). There are also sunlight availability indicators and sun-path indicators (Littlefair, 2011). The daylight entering the room can consist of 3 components (figure 15). Sky component (SC), externally reflected component (ERC), and Inter reflected component (IRC). These results added together will give us the LUX (luminance) at a given point in the room. 200 Lux provides a comfortable reading level. Daylight protractor number 2 (annex B) is chosen for overcast sky and vertical windows. Other protractors are available for different window situations. (Johnsen. Christoffersen, 2008) LUX = SC + ERC + IRC Sky Component (SC) or direct light (figure 14) has two measurements, horizontal and vertical. VSC. (section view) Vertical skylight component. It begins from a point at the center of window 0,85m off the ground, 0,5m in the room. We measure in the center of each grid square, at max 0,5m intervals till the grid area length is calculated. The base angle is an unobstructed path up into the sky at the lowest level. So this line needs to clear buildings etc. this base aximuth line, never goes below 0 0. And if there is obstruction above 20 0, then we will possibly need to increase window dimensions. Find the first unobstructed line. We then find the unobstructed height at or near the top of the intended window head. The highest angle, minus the lowest angle, gives us the SC %. Manually we can stick to the designated grid. The computer will calculate all of the room in 3D if necessary. HSC (plan view). Horizontal skylight component (Waldram diagram). Is the comparison correction daylight factor (figure 14). The opposite side of the protractor is used. The strange lines follow the azimuth angle shifts of the sun. This is used to find the correction values for lateral light shift in the room from the VSC. Start from the center unobstructed VSC start point. 0 (parallel subtraction), measure left and right every 0,5m, and measure in the center of the designated grid squares. If lines are in opposite sides of the protractor, they are added together, if they are in the same side, then the largest number is subtracted from the smallest. This correction value is multiplied by SC (section view) to give a final corrected value for comparative points on our grid. Angling the window opening will only have a very small effect on this calculation if we include the whole room space as the grid area. Daylight protractors are used for different window situations such as skylights and angled windows. SBI 203 gives guide lines for their use. 4.93% SC section 2.61% SC correction plan Figure 14; The daylight protractor left and Waldram protractor right in use. 28