7.0 Daylighting Results and Reports

The Daylighting Results screen presents the Design Day workplane illuminance throughout the year and various annual daylighting metrics. By this point in the program, SPOT has calculated a sampling of climate calibrated ‘Design Day’ sky conditions (the days and times of which are specified on the Advanced Options pages) and has performed annual climate-based daylighting simulations using the TMY2 file or other climate data selected. Note, that while the design day conditions and annual average estimates with this method will be fairly accurate and represent typical conditions for the given climate, they may never exactly represent a future partly cloudy sky condition.

The Design Day and Annual Metric Table and associated plots and spatial binning can be used to inform the user of the range of potential daylight distributions in the space throughout the year. Both illuminance plots and perspective renderings can be generated for the range of design conditions. With this information the user can start making decisions regarding the quality and quantity of daylight and inform any refinements in the luminaire zoning.

The Interactive View button can be selected at any time and will launch an interactive viewing (rview) window for the current daylight condition selected in the table, except when an the annual average, maximum or an annual metric is selected. For any clear or cloudy sky design condition selected, this will generate a rendering showing the distribution of light under daylighting only (no electric lighting). This can be a good way to understand how the space will look under extreme conditions and how the luminous environment will vary throughout the year. If a large maximum number exists for a certain condition, the rendering can help illustrate why this is happening, where it is coming from and whether it is a problematic glare incident.

Selecting the View Report button will activate the Daylighting Reports screen which allows for a variety of annual daylight metric reports to be reviewed and copied or printed.

Selecting the View Climate Days button will activate the Detailed Climate Specific results page. This page will display the simulated daylight illuminance, based on the given weather data, for any occupied day and time throughout the year.

The Copy Table button can be used to make a copy of the entire Annual Daylight Workplane Illuminance table. This puts an image of the table onto the clipboard which can then be directly pasted into any other MS Office document such as Word or Powerpoint. To get the image into another format, it can be first be pasted into any excel cell as a picture and then copied from there.

At this point, if the daylighting results do not correspond well with the defined luminaire zones or there are other errors or changes needed to the model, the user can click the Back buttons. However, depending on the changes made, certain calculations may have to be recalculated. When pressed, the Next button will initiate sectional renderings of the space (if selected on the Advanced Options screen) and will activate the Photosensor Generator page only if Electric Lighting has been input into the model.

7.1 Design Day and Annual Metric Table

The Design Day and Annual Metric table reports averages, maximums, minimums and a variety of annual metrics for each luminaire zone. For each of the representative clear or cloudy sky design day times, and an annual average and maximum, the table reports the workplane illuminance. For the various annual metrics the table reports that given metric’s average, maximum and minimum values. The radio buttons to the left of the table can be used to select a condition or annual metric. The selected metric value for each point on the workplane grid will then be displayed in the plot and the isometric chart and summarized in the spatial binning table at the top of the page. The Interactive View button can be used to generate a rendering of any design day selected (note that it cannot render the annual average, annual maximum or annual metric selections).

The bottom rows of the daylight results table display a number of annual daylighting performance metrics. The metrics displayed and their definitions are as follows:

Annual Average – When selected, the grid and plot will display average illuminance for each point throughout the year. The annual illuminance is not just an average of the “Design Day” conditions that have been simulated and shown in the table but derived from an annual climate based simulation (using the selected weather file), hence giving a more accurate annual picture.

Annual Maximum – When selected, the grid and plot will display maximum illuminance recieved at each point throughout the year. The maximum illuminance is not just taken from the “Design Day” conditions that have been simulated and shown in the table but derived from an annual climate based simulation (using the selected weather file), hence giving a more accurate annual picture.

Daylight Saturation (DS) – is the fraction of a given location’s ‘annual daytime lighting load’ that is met with daylight. It defines the maximum lighting savings that could be obtained while ensuring the target illuminance is always met at a given point. The ‘annual lighting load’ for a space or point is considered to be how much light is required to maintain a target illuminance annually during a set period: all daytime hours or occupied daytime hours. It is similar to DA, but gives credit to hours where there is partial daylight saturation meeting a portion of the target illuminance (E) in addition to the hours where the target illuminance has been exceeded (100% saturated). This is an annual daylight quantity metric useful for determining the daylight “potential” of a space, especially for spaces with continuous dimming daylight responsive electric lighting control. The target illuminance can vary and is a function of the space and design goals (in SPOT it is set to be the design illuminance) and is written as a subscript when reporting DS (ie. DS_30fc_). DS is used in the SPOT performance reports as well as the Collaborative for High Performance School (CHPS) reports.

Daylight Excess (DE) – a measure of excessive daylight in a space and reports the fraction of annual daytime or occupied daytime hours that exceed a certain threshold. The maximum acceptable illuminance threshold for a space is considered to be some multiplier of the target illuminance, typically 10x. For example, if a space has a target illuminance of 430 lux (40fc), then DE430×10 would be a measure of how many hours an analysis point exceeds 430×10 lux = 4300 lux (400 fc) throughout the year. While potential daylight glare in a space is a function of view angle and the viewed luminance, excessive illuminance can be a good indicator of daylight glare potential, excessive solar heat gains and just excessive daylight in general. Illuminance calculations can be a good proxy for luminance based glare potential for a range of viewing angles. The high illuminance threshold can vary and is a function of the space and design goals (in SPOT it is set to be the design illuminance x10) and is written as a subscript when reporting DE (ie. DE_300fc_ or DE_30×10fc_). DE is used in the SPOT performance reports as well as the Collaborative for High Performance School (CHPS) reports.

Daylight Autonomy (DA) – a measure of the fraction of annual hours that a given target illuminance (E), often 215-430 lux (20–40 fc), is exceeded by daylight. This is a common metric used for evaluating the quantity of daylight available for a given space particularly when evaluating on/off daylight responsive electric lighting control systems. The target illuminance can vary and is a function of the space and design goals (in SPOT it is set to be the design illuminance) and is written as a subscript when reporting DA (ie. DA_30fc_).

Useful Daylight Illuminance Combined (UDIa+s or UDIc) – a measure of the amount of useful daylight illuminance throughout the year. UDI combined is the summation of UDI autonomous (UDIa), defined as the fraction of the year where the daylight illuminance is between 300 and 3000 lux (~30-300 fc), and UDI supplementary (UDIs) defined as the fraction of the year where the daylight illuminance is between 100 and 300 lux (~10-30fc). The UDIs calculation is binary, reporting the number of hours the daylight falls into the 100-300lux bin rather than giving “partial credit” like the Daylight Saturation metric. The resulting UDIc value is a good measure of the amount of useful daylight throughout the year for a space targeting around a 300lux (30fc) ambient lighting level and is used as the primary metric in the UK’s Priority Schools Building Programme (PSBP).

Useful Daylight Illuminance Exceeded (UDIe) – a measure of excessive daylight illuminance in a space throughout the year. UDIe is defined as the fraction of the year where the daylight illuminance is above 3000 lux (~300fc). This is a measure of excessive daylight that has a high glare potential in the space, similar to the DE metric.

Daylight Factor (DF) – a historic metric used to estimate the quantity of daylight in a space. It is simply the ratio of interior illuminance at a point to the exterior global illuminance at the same time under a standard CIE overcast sky. It is a static metric in that rather than looking at multiple climatic conditions throughout the year it is based on the one cloudy sky distribution. However, given this rather large simplification, it can still be useful metric in comparing the relative daylight quantity between designs and for climates where cloudy conditions truly dominate.

Spatial Daylight Autonomy (sDA) – a new approach for reporting Daylight Autonomy for a given area or space as a single number representing the area that exceeds a certain DA threshold, such as 50%. This idea of a single ‘spatial’ number can be used to report all the daylighting metrics and various spatial bins are reported for each metric in the spatial bin summary table at the top of the page. When reporting sDA (or any spatial metric), the DA threshold is written as a second subscript behind the illuminance target used for the DA calculations (ie. sDA_30fc_,50% would be the % of an analysis area that exceeds 30fc for 50% of the time). The term ‘sDA’ and the form adopted by LEED v4 does not use variable targets but includes specific details explained in the IESNA LM-83 document created by the Daylighting Metrics Committee. For example, it sets 300lux and 50% as hard thresholds, and defines the analysis period to always be 8am-6pm annually. SPOT calculates sDA to conform to the LM-83 definition and hence sDA is listed separately and may differ from the normal DA calculations. Note: When sDA is shown on a workplane plot, the plotted numbers are actually DA values calculated according to the sDA standards and not sDA values as there is a single sDA number for an entire space.

Annual Sunlight Exposure – a new metric developed in conjunction to the sDA to attempt to detect incidences of too much direct sunlight and high glare potential. This metric calculates the number of hours a year in which a point exceeds 1000lux from direct sunlight alone and with no window treatments on any windows. It is reported as a single ‘spatial’ number similar to the sDA metric and uses 250 hours a year as the time threshold. This metric can be a good indicator of how dependant a given daylighting design is on the window treatments. If ASE is low, then it may be a good ‘passive’ daylighting design, not reliant on active interior control elements for its performance. If ASE is high and the other metrics show good performance, than it may be good design but it is highly dependant on the proper functioning of the window treatments. High ASE might be a good argument for more automated shade controls so that the daylighting performance of the space is not dependant on user behavior. Note: When ASE is shown on a workplane plot, the plotted numbers are actually Annual Sunlight Fraction (ASF) values calculated according to the ASE standards and not final ASE values as there is a single ASE number for an entire space.

At any time, the View Zone Diagram button can be used to pull up the zoning diagram for the space. This is useful in analyzing the various zone averages in the table and where they occur in the space.

Daylight Glare Probability (DGP) – an upcoming glare metric that is beginning to be able to predict the probability of glare given a view angle and accurate luminance calculations in the view direction for specific office settings. However, DGP is still being heavily researched, the results are not yet repeatable even in laboratory settings, and it is not ready to be used for reliable glare predictions. Softwares claiming to provide accurate glare calculations or annual glare calculations using DGP are jumping the gun and may be giving mis-leading information. More field and laboratory research is needed to continue to develop the DGP approach making it more robust and a reliable predictor of glare probability in a wider range of scenarios. Having said that, DGP calculations are still possible in a SPOT project behind the scenes. All the renderings generated by SPOT are High-Dynamic Range (HDR) images that include accurate luminance information. A DGP calculation can be done on any of these images using a command prompt in your projects “/images/” directory or wherever else you saved your renderings. See that Radiance online documentation for information on how to perfrom this calculation using the Radiance tool Evalglare.

The workplane plot on the right of the page is color-coded according to different spatial binning of the points. A small Spatial Binning summary table sits above the workplane plot and reports the area fractions for each spatial bin. As discussed in the sDA section above, these values are termed “spatial” metrics and are refered to as spatial Daylight Saturation (sDS), spatial Daylight Autonomy (sDA) and so forth. The bin ranges used for the different daylight results are as follows:

  • When one of the Design Day or Annual illuminance rows are selected, the spatial bins report the fraction of the workplane that partially meet or exceed the design illuminance using bins of <33%, 33%-66%, 66%-100%, and >100%. Portions of the workplane that are >66% of the design illuminance (color coded orange) are likely the best zones to control with a photosensor system.

  • When one of the annual sufficiency daylight metrics (DS, DA, UDI) are selected, the spatial bins report the fraction of the workplane that exceed certain metric thresholds. The bins used are 0-40%, >40%, >60%, and >80%. The >40% bin will inform the fraction of space with minimally sufficient daylight contribution. The >60% bin represents the fraction of space with good daylight contribution and the >80% represents the fraction of the space with great daylight contribution.

  • When one of the annual excessive daylight metrics (DE, UDIe) is selected the spatial bins report the fraction of the workplane that exceed much lower metric thresholds as these metric indicate excessively high and unwanted daylight contribution. The bins used are 0%, >0%, >5% and >10%. Different thresholds will be applicable to different space types. For spaces with very critical tasks, anything greater than 2% may be unacceptable. For other spaces with more leisure tasks and some tolerance to direct sunlight the >10% bin may be more applicable.

  • When the spatial Daylight Autonomy (sDA) row is selected, the spatial bins used are 0-30%, >30%, >50%, and >70%. The 50% threshold represents ‘sufficient’ daylight while the 70% threshold represents ‘good’ daylight.

  • When the Annual Sunlight Exposure (ASE) row is selected, the spatial bins used are 0%, >0%, >6.8% (250hrs of 8am-6pm schedule), >10%. The >6.8% threshold has been adopted by LEED v4 as indicating too much direct sunlight.

7.2 Daylighting Reports

This screen provides a number of standard daylighting performance reports. Choose which report you would like to view by selecting it in the pull-down menu located at the top of the page. The LEED v4 metric will require an additional ASE calculation that will happen automatically upon selecting this report before the results can be displayed.

The Copy Image button can be used to copy whatever report is currently displayed to the clipboard which can then be directly pasted in any other MS Office document such as Word or Powerpoint. To paste into other formats, first paste into the selectable cell to the upper right of the report and then copy from there.

The Print button will initiate a print dialog for the currently displayed report.

The Back button will return the user to the Daylighting Results page.

The View pull-down menu allows the user to choose to view the report for the entire space or for daylighting zones individually. The hourly workplane illuminance plot and performance metric results will update when the viewed zone is changed. The workplane plots remain the same as they show performance results for the entire space anyways, including all zones.

The View Zone Diagram button can be pressed at any time to pull up a diagram of the daylight Zones.

The upper Space Summary and Metric Results section of all the reports,provides general space and facade information, intended to be complete enough to replicate/verify the design. An isometric of the space and orientation compass are shown in the upper left. Adjacent to this are Space Properties that list the general dimensions of the space and the reflectance of the various surfaces in the model. The Fenestration Properties table lists all fenestration for each surface orientation. It summarizes the surface areas, internal window-to-wall ratios (WWR), average glazing transmittance and any window treatments and control strategy for that facade. If more than 3 different window control zones exist for a facade it will be indicated in the final More… column. A total Window-to-floor area ratio (WFR) is also included at the bottom of this table. The Performance Metric Results section list the prerequisites and display the overall metric performance for the report type chosen.

The lower Design Performance section of the reports provides various forms of annual daylighting performance charts and plots. An Hourly Average Workplane Illuminance chart on the lower left of all reports shows the average illuminance for the space (or Zone selected in the View pulldown menu) throughout the day, for sunny and cloudy conditions, and for three representative seasons of the year (winter, fall/spring, summer). The two plots to the right of this chart are different for each report and described in the report sections below. The Design Suggestions at the bottom of the report remain the same for all reports and are based on the SPOT Daylighting Performance assessment methods. There are 5 categories of design suggestions given, these are: Glare, Uniformity, Quantity, Control, and Shades. The suggestions will typically give a good assessment of the design and good guidance but they are not fool proof. Daylighting metrics are currently undergoing much development and research and the metrics and potential design guidance are being refined regularly.

The following metric reports are available:

SPOT Daylight Performance – This report uses a combination of metrics to assess daylighting performance, utilizing Daylight Saturation (DS), Daylight Excess (DE), a 75% spatial uniformity threshold, and Daylight Autonomy (DA).

This report includes several prerequisites: 1) the grid spacing must be 5ft or less and 2) the simulation parameters must be equal to a M, M, H radiance parameter setting (Medium Quality, Medium Detail, High Variability) and lists Months and Times as addition potential prequisites. Depending on the application, certain months and timesteps may be required.

Next to the prerequisites is a Daylight Excess, Autonomy, and Saturation Coverage plot that summarizes the spatial coverage of the metrics. Vertical lines on this plot indicate recommended thresholds for a typical work (office / class / lab / retail) environment. For Daylight Excess (DE), a recommended goal for critical visual environments is to have <5% of the workplane recieve excessive daylight (10x the target illuminance) for less than 10% of the time. For less critical visual environments, a target of <10% of the workplane recieving excessive daylight for <10% of the time is recommended. For Daylight Saturation (DS), it is recommended that more than 75% of the workplane receive sufficient daylight. If the DS is 40% or greater this is considered 'sufficient' daylight quantity, 60% or higher is considered 'good', 80% or higher is considered 'great' daylight, and if 90% of the space achieves a 90% DS this is a nearly full daylit as possible and is considered an 'excellent' daylight contribution or fully daylit. For Daylight Autonomy (DA), if an >80% DA is achieved for more than 75% of the space, the space can consider on/off lighting controls with only a minimal penalty to energy savings. The grey box on the right of the report gives a general rating for the daylit space that is a function of the glare (DE), uniformity (DS ratios, 75% coverage), quantity (DS), and control (DA and DS) metrics.

The plots on the lower right show the annual Daylight Saturation (DS) and annual Daylight Excess (DE) for the space. The color coding indicates the threshold of DS or DE achieved and match the color in the coverage summary bar chart above. These plots help illustrate distribution of daylight and excess throughout the space and can be seen in the screenshot image above.

LEED v2009 – This report presents the sunny equinox at 9AM and 3PM calculations and the necessary prerequisites for LEED v2009.

There are three prerequisites and a caveat for this report. The prerequisites are: 1) workplane height must be within 10% of 30in (2.5ft, 0.76m) above the finished floor 2) grid spacing must be 5’ (1.52m) or less and 3) Radiance parameters must be set to M,M,H or higher. The caveat is dependant on additional glare measures. Upon selecting this report, the user will be asked if there are additional glare control measures to be used on the windows that were not included in the modeling. If there are, select “yes” and then the metric only requires illuminance to greater than 10fc (~100lux). If not, the illuminance must be between 10fc – 500fc (~100lux – 5000lux).

Next to the prerequisites is an Equinox Illuminance coverage chart that includes a Daylight Excess (DE) report as well simply to warn LEED 2009 users if too much potential glare is detected as the LEED 2009 performance metrics do not account for excessive daylight. The 10fc-500fc illuminance coverage under both a sunny Equinox at 9AM and 3PM must be greater than 75% of the space to achieve 1 LEED point and greater than 90% of the space to achieve 2 LEED points. This will be reported to the user in the Grey report box.

The plots on the lower right show the point-by-point daylight illuminace received on the workplane during the sunny Equinox at 9AM and 3PM requirement. Blue coded cells do not achieve the standard while shades of yellow and orange indicate adequate daylight.

LEED v4.0 – This report presents the spatial Daylighting Autonomy (sDA) and Annual Sunlight Exposure calculations and the necessary prerequisites for LEED v4.0.

There are six prerequisites for this report. The prerequisties are: 1) workplane height must be within 10% of 30in (2.5ft, 0.76m) above the finished floor 2) grid spacing must be 2’ (0.61m) or less 3) the space must contain automated or manual glare control (from pop-up window question) 4) the design-day months must atleast contain the solstices and equinox (12, 3, 6) 5) design day times include sunrise and sunset and have at the most a 3 hour timestep and 6) the Radiance parameters must be set to M,M,H or higher.

Next to the prerequisites is a Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE) coverage chart. The LEED v4.0 standard gives 2 point for >55% sDA coverage and 3 points for >75% sDA coverage. For the LEED Healthcare Standard the daylighting requirement is a bit stricter and 1 point is given for >75% sDa coverage and 2 points for >90% sDA coverage. Additionally, the standard requires the ASE value to be less than 10% for the entire space to pass. The LEED points awarded, or a “Reevaluate Design” message reporting the violating metric will be displayed in the Grey report box

The plots on the lower right show the Daylight Autonomy and the Annual Sunlight Fraction values for a grid of points in the space at workplane height. These are calculated according to the Spatial Daylighting Autonomy and Annual Sunlight Exposure protocols laid out in the IESNA LM-83 document.

CHPS – Collaborative for High Performance Schools (CHPS) – This report presents the Daylight Saturation and Daylight Excess calculations for the CHPS National daylighting credit standard. This daylighting metric has several prerequisites along with the option of three different performance-based compliance paths. The performance path implemented in SPOT uses the Daylight Saturation (DS) and Daylight Excess (DE) metrics.

There are six prerequisites for this report. The prerequisties are: 1) workplane height must be within 10% of 30in (2.5ft, 0.76m) above the finished floor 2) grid spacing must be 4’ (1.22m) or less 3) the space must contain daylight responsive lighting controls that are either photosensor based or have occupant or education-based strategies 4) the design-day months must atleast contain the solstices and equinox (12, 3, 6) 5) design day times include sunrise and sunset and have at the most a 3 hour timestep and 6) the Radiance parameters must be set to M,M,H or higher.

Next to the prerequisites is a Daylight Excess and Daylight Saturation Coverage plot that summarizes the spatial coverage of the metrics. Vertical lines on this plot indicate recommended thresholds. For Daylight Excess (DE), it is recommended that less than 10% of the workplane recieve excessive daylight, defined as exceeding 10x the target illuminance for more than 10% of the time. For Daylight Saturation (DS) it is recommended that more than 75% of the workplane receive sufficient daylight. If the DS is 40% or greater this is considered ‘sufficient’ daylight quantity and worth 1 point, 60% or higher is considered ‘good’ and worth 2 points, 80% or higher is considered ‘great’ daylight and worth 3 points. The grey box on the right of the plot reports whether the space passes the CHPS metric and how many points it achieves.

The plots on the lower right show the annual Daylight Saturation (DS) and annual Daylight Excess (DE) for the space. The color coding indicates the threshold of DS or DE achieved and match the color in the coverage summary bar chart above. These plots help illustrate distribution of daylight and excess throughout the space and can be seen in the screenshot image above. The View Zone Diagram button can be pressed at any time to pull up a diagram of the daylight Zones.

LEED v2.1 Single point-in-time – This is a report for the Single Point-in-time compliance path currently accepted in LEED v2.2 or older.

There are four prerequisites for this report. The prerequisties are: 1) workplane height must be within 10% of 30in (2.5ft, 0.76m) above the finished floor 2) grid spacing must be 4’ (1.22m) or less 3) the space must contain glare control strategies (it is very vague as to what this is in LEED v2.1) and 4) the Radiance parameters must be set to M,M,H or higher.

The plot on the left shows the illuminance distribution in the space for the required day and time of Equinox at 12:00PM. This compliance path requires an average of 25fc at this time. The plot on the right shows the Daylight Excess which is not a part of LEED v2.1 but good to be aware of as this metric does not have a measure to protect against excessive daylight. The box on the right gives the final status of the daylighting design relative to this metric and whether it would achieve 1 point (>75% coverage) or 2 points (>90% coverage).

LEED v2.1 Daylight Factor – This is a report for the Daylight Factor compliance paths currently accepted in LEED v2.2 or older.

There are five prerequisites for this report. The prerequisties are: 1) workplane height must be within 10% of 30in (2.5ft, 0.76m) above the finished floor 2) grid spacing must be 4’ (1.22m) or less 3) the space must contain glare control strategies (it is very vague as to what this is in LEED v2.1) 4) the space must be located in a cloudy climate (answered in a pop-up window when this report is selected) and 5) the Radiance parameters must be set to M,M,H or higher.

The plot on the left shows the illuminance distribution in the space for the required day and time of Equinox at 12:00PM. This compliance path requires an average of 25fc at this time. The plot on the right shows the Daylight Excess which is not a part of LEED v2.1 but good to be aware of as this metric does not have a measure to protect against excessive daylight. The box on the right gives the final status of the daylighting design relative to this metric and whether it would achieve 1 point (>75% coverage) or 2 points (>90% coverage).

IgCC – This is a report for the daylighting performance standard in the International Green Construction Code (IgCC). This metric report is similar to the LEED v2009 requirement in that it uses daylight illuminance under sunny equinox conditions at 9AM and 3PM to determine the daylit area. However, it requires different illuminance thresholds, a minimum of 28fc (300lux) and a maximum threshold of 418fc (4500lux). It is not a space-by-space metric but rather requires that 50% (25% for buildings > 2 stories) of a buildings net floor area be a daylit area.

There are three prerequisites for this report. The prerequisties are: 1) workplane height must be within 10% of 30in (2.5ft, 0.76m) above the finished floor 2) grid spacing must be ~3’ (1m) or less and 3) the Radiance parameters must be set to M,M,H or higher.

Next to the prerequisites is an Equinox Illuminance coverage chart that includes a Daylight Excess (DE) report simply to warn IgCC users if too much potential glare is detected as the IgCC performance metrics do not account for excessive daylight. The 28fc-418fc illuminance coverage under both a sunny Equinox at 9AM and 3PM must be greater than 50% of the buildings net floor area (greater than 25% for building > 2 stories) to comply with the code. The overall coverage that complies will be reported to the user in the Grey report box.

The plots on the lower right show the point-by-point daylight illuminace received on the workplane during the sunny Equinox at 9AM and 3PM requirement.

UDI PSBP – This is a report for the UK’s Priority Schools Building Programme that requires an 80% UDIc coverage.

There are three prerequisites for this report. The prerequisties are: 1) workplane height must be within 10% of 30in (2.5ft, 0.76m) above the finished floor 2) grid spacing must be ~2’ (.7m) or less and 3) the Radiance parameters must be set to M,M,H or higher.

Next to the prerequisites is an UDI exceeded, autonomous, and combined coverage chart. While the PSBP does not appear to have a caveat for high UDIe values, these should be kept to a minimum to minimize potential glare in the space. UDIa can help inform how well the space is saturated with daylight throughtout the year and whether on/off controls could makes sense. UDI (combined) informs the overall daylight saturation available in the space and has to achieve at least 80% coverage to the meet the metrics requirement. The space compliance with this requirement will be reported to the user in the Grey report box.

The plots on the lower right show the point-by-point UDIc and UDIe received on the workplane throughout the year.

7.3 Detailed Climate Specific Results

This page will display the simulated daylight illuminance, based on the given weather data, for any occupied day and time throughout the year.

Using the Select Specific Time pull-down menus, the user selects a specific month, day and time of interest – only days that were simulated based on the annual and weekly occupancy schedule will be available for viewing. Pressing the Display Results button will display the daylight illuminance for the selected day and time in the workplane grid. The illuminance values will be color-coded according to where they fall compared to the design illuminance for the space.

The Weather Results fields display relevant weather information from the weather file for the specified day and time. The global illuminance, diffuse illuminance, reported percentage of opaque sky cover (SPOT actually uses a more advanced metric to detect sky cover), dry bulb temperature, relative humidity, and snow depth are displayed. Comparing global illuminance and diffuse illuminance can give a good idea of exactly how much sky cover exists and what it does to the illuminance calculations in the space under these conditions. Partly cloudy conditions can be very difficult to model as a broad cloudy haze has to be modeled rather than the specific cloud patterns that actually exist on partly cloudy days.

The Workplane Illuminance Statistics fields display average, maximum, and minimum illuminance information for the various electric lighting zones.

The plot at the bottom shows daylighting illuminance calculated for a given day and time based on TMY2 or other climate data. A Climate-Based annual simulation method is used based on the IESNA recommended CIE Sky Model and uses the direct illuminance (illuminance from a 5° circumsolar region) and diffuse illuminance (sky illuminance) to weight cloudy and sunny conditions. The method provides annual accuracy similar to the daylight coefficient approaches, more accurate in some cases as it is not subject to the low resolution of the Klems sky patch approaches. Again note that while annual averages with this method will be fairly accurate, specific day illuminances (particularly under partly cloudy skies) are close estimates but will never accurately represent a future partly cloudy sky condition.