NC-2009 IEQc8.1: Daylight and Views—Daylight

  • NC&CS EQ8.1 Type3 Daylighting Diagram
  • Use a collaborative design process

    Access to daylight inside buildings makes for healthier and more comfortable occupants—and is also linked with greater productivity. When designed with proper glare control and minimized solar heat gain, daylighting provides high-quality light while reducing energy use for lighting and for cooling. Increased daylight through increased vision glazing can help projects earn IEQc8.2 for access to views. Realizing the benefits of daylighting requires a collaborative design process.

    Balance other design goals

    Keep in mind that daylighting strategies must balance with other design goals. For example, you will want to provide enough glazing area for lighting, and plan for open spaces that allow for light transfer, but not at the expense of too much heat gain, glare, or loss of privacy. Incorporating daylighting goals into the early planning stages will help project teams avoid design conflicts at more advanced stages. Daylighting goals should be laid out explicitly in the Owners Project Requirements document required for EAp1: Fundamental Commissioning.

    Documentation can be cumbersome

    This credit is easy to achieve for projects with large windows, open floor plates, and most occupied areas near the perimeter, but the documentation may be cumbersome for some large projects, depending on the chosen compliance path.

  • Changes in LEED-NC v2009 versus v2.2

    Compliance paths for IEQc8.1 have some key differences between v2.2 and v2009. In LEED-NC v2.2, Option 1: Calcualation allows you to show compliance with EQc8.1 by demonstrating over 75% of the regularly occupied areas have a glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. of at least 2%. These glazing factor calculations consider window, wall, ceiling and floor areas, glazing type and VLT values.

    In LEED-NC v2009, the glazing factor calculations option has been removed. In v2009, however, the Option 2: Prescriptive method provides a new approach to demonstrate achievement of the credit that considers many of the same factors as the glazing factor calculations from v2.2.

    Another significant difference between v2009 and v2.2 is that v2009 allows for a combination of compliance path options to achieve the credit, via  Option 4.

  • FAQs for IEQc8.1

    What spaces are considered regularly occupied and must be included in the calculations?

    The USGBC's IEQ Space Matrix has detailed guidance that is helpful for any spaces you aren't sure about.

    When should daylight measurements be taken?

    LEED does not prescribe the date or time, but it is recommended that they be taken close to noon under clear sky conditions, and, if possible, on or near one of the two equinoxes.

    Do I need to have glare control devices?

    Yes.

    Where can I find the Supplemental Views and Daylight Calculator?

    On LEED Online, in the credit, under credit resources.

    Do I need to submit the Supplemental Views and Daylight Calculator?

    You must submit a spreadsheet which contains all the information required on the calculator, and submitting the LEED Online calculator is recommended, but some teams have preferred to create their own, and have had them accepted.

    Can I average the compliant square footage between 9 a.m. and 3 p.m. for a space and use the average as the compliant square footage?

    No, the compliant square footage would be the worst-case scenario between the two times. For example, a 900 ft2 space located on the western side of a building is 100% compliant at 9 a.m. but only 50% compliant at 3 p.m. The compliant square footage in this case is 450 ft2.

    What daylight simulation software can I use for LEED compliance?

    LEED doesn’t require certain software to run the compliance calculation. However, the simulation should be able to run under “clear sky” conditions and calculate illuminance levels at 2’-6” above finished floor (AFF).

    Can I use Option 2: Prescriptive method if I have:

    • Windows with different Tvis values within the same wall width?

    • Windows with different head heights within the same wall width?

    • Windows with different sill heights (and above 30”) within the same wall width?

    • Windows with permanent shading devices?

    • Skylights with different Tvis values within the same ceiling area?

    • Clear skylights?

    • Light that is transferred between one room to the next through an interior wall opening—glazed or unglazed?

    • A Tvis/WFR value above 0.180?

    • Rooms that borrow light from an atrium?

    • Roof monitors?

    • Tubular daylighting devices such as Solatube?

    • Roof overhangs?

    • Shared daylighting scenarios?

    No. The only option in any of these cases will be the simulation or the measurement methods.

Legend

  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip

Pre-Design

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  • Focus on optimizing building orientation. Look for opportunities to optimize the glazing on each orientation to account for varying heat gain and lighting angles. When selecting a site, look for potential obstacles to daylight such as neighboring buildings, vegetation, and topography.


  • To reduce heating loads, use daylighting strategies in tandem with passive solar heating strategies, such as using materials with greater thermal mass and orienting the building for maximum solar gain.


  • To reduce cooling loads, use overhangs, lightshelves or fins, courtyards, and lightwells to block high-angle summer sun and low-angle morning and afternoon sun. These strategies also reduce glare and can improve daylighting by reflecting it deeper into the building.


  • Glare can become a problem if you have too much glass, or east- and west-facing glass. Using shading devices can allow projects to combat glare and still have large expanses of glazing. Daylighting from the north is consistent and high quality, while daylighting from the south is abundant and comparatively easy to control.


  • Large areas of glazing may cause unwanted heat gain and compromise energy efficiency. However, daylighting may require less glazing than you think—about 40% window-to-wall ratio may be more than you need. Glazing closer to the ceiling will have a greater daylight benefit than glazing near the floor—anything below 30 inches is considered to have no daylight benefit.


  • When programming, identify occupant lighting needs that could be met with daylight. The Illuminating Engineering Society of North America (IES) has prescribed footcandle levels for project types, occupant types, and tasks.


  • Set daylighting goals at the initial goal-setting workshop and incorporate them into the Owners Project Requirements document required for EAc1: Fundamental Commissioning.


  • Having two different sources of daylight in a space will help minimize contrast and shadows.

Schematic Design

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  • Identify regularly occupied spaces that need to be included in the LEED daylight calculation. Locate these spaces near perimeter glazing, courtyards, or other daylight sources.


  • Your project's regularly occupied spaces should be defined consistently across other LEED credits, especially IEQc8.2: Daylight and Views—Views.


  • Some applicable spaces may be exempt from the daylighting calculation if their uses are daylight-sensitive. Examples include museum or gallery spaces, auditoriums and high-security areas. If you have daylight-sensitive spaces in your project that you would like to exempt from the calculation, you must provide a detailed narrative explanation and exemption request along with the credit documentation. This requests are scrutinized carefully, however, and may not be successful.


  • Find out the Visual Light Transmittance (VLT) value of the glazing and enter it on the LEED credit form for each occupied space. The VLT is usually included with the glazing specifications.


  • Take the VLT of the whole window, not just the glazing, to account for shading from mullions.


  • More natural light is transmitted through glazing with higher VLT values, but higher VLT values tend to correlate with higher solar heat gain coefficients (SHGC). Assess the optimal balance of these values, along with U-value, based on the project’s climate and heating and cooling needs. These values are available on manufacturers’ specifications.


  • Hold an integrated design meeting with the architect, interior designers, mechanical engineer, lighting designer and the end users to discuss daylighting-related tradeoffs.   Optimize glazing area while preventing excessive heat gain and glare; and use open space planning that allows for greater light transfer while preserving privacy.


  • Consider designing spaces with narrow floor plates so that most spaces are near windows and have access to daylight.


  • Prescriptive compliance paths for EAc1 (other than energy modeling) do not allow window-to-wall ratios greater than the relevant reference standard. Projects using these compliance paths are limited in the amount of allowable glazing area.


  • Designing for daylighting will allow you to reduce the number of ambient light fixtures and their frequency of use, reducing the cost of electric lighting both upfront and in operations.


  • Retailers may see increased sales linked with daylighting, according to studies showing a correlation between sales and natural lighting. Additional savings may be seen by employers through increased employee retention/satisfaction as well as productivity and reduced absenteeism.


  • Choose a LEED compliance path to verify that the daylighting meets the footcandle requirements of 25–500 footcandles for 75%–90% of regularly occupied spaces.

    • Option 1:  Computer daylight simulations can be the most effective design tool, but hiring a modeler will be an upfront cost.
    • Option 2: Prescriptive LEED calculations can help inform design, but not as accurately as a daylight simulation. The calculations can be time-consuming for large buildings, but do not require expert help.  The prescriptive calculations will only take window, wall, ceiling and floor areas, and glazing type into account, so other methods that help daylighting such as lightshelves and light-colored finishes won’t be factored in.
    • Option 3: Daylight metering can be an inexpensive way to measure actual footcandles, but won’t be accurate until construction is complete, when the results cannot help to inform design.

Design Development

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  • Explore a combination of daylight strategies such as space planning techniques, glazing selection, lightshelves and more.


  • Interior finishes can enhance or hinder daylight levels. Specify light-colored ceiling and wall paint to bounce light further into the room.


  • A common misconception is that a design needs to have more glass for effective daylighting. But effective daylighting can also be achieved with smaller apertures and glazing designed for specific indirect light, located high in a space to bounce light on to a ceiling.


  • Daylight sensors that adjust lamp brightness based on the presence of natural light can greatly reduce lighting energy loads. On average, commercial buildings use 25% of their energy for lighting. Dimming ballasts are more expensive and complicated to specify than stepped ballasts. Stepped lighting is considered less attractive because the dimming is not gradual  but can do an excellent job reducing energy use.


  • Daylight controls, sensors, integrated blinds, and lighting controls come with moderate first costs but will bring energy savings over the long run.


  • Integrate glare control into the design.


  • Identify designs that combine glazing and building elements for optimum daylighting, such as window frames with integrated overhangs or light shelves. However, make sure that there is a thermal break (insulation) between the interior and the lightshelves, or these could become large-scale radiators of interior heat.


  • Glare can hinder the use of a space and be unpleasant for occupants. Daylight modeling can help project teams anticipate problem areas due to sun angles as they interact with the architecture. Exterior and interior shading along with associated controls can greatly reduce the effects of glare.


  • Fill out the LEED credit form with the names of the regularly occupied spaces and their square footage.


  • Simulation is the only way to account during the design phase for daylight designs that have many variables such as the use of lightshelves and light-colored interior finishes. The Glazing Factor Calculation path (Option 1) takes into account only walls, windows, floor and ceiling areas, and the measurement path (Option 3) will not help inform design as much.


  • Option 1:  Computer Simulation


  • Use daylight simulation software to adjust daylight design as needed before it is finalized.


  • Coupling daylight modeling with energy modeling can help project teams make effective decisions about daylighting as it relates to other strategies like thermal massing, window area, window efficiency, and shading.


  • Simulation makes documentation easy by clearly indicating compliant areas.


  • Simulation is the only way to account during the design phase for daylight designs that have many variables such as the use of lightshelves and light-colored interior finishes. The prescriptive  compliance path (Option 2) takes into account only walls, windows, floor and ceiling areas, and the measurement path (Option 3) will not help inform design


  • Daylight simulations may add an upfront cost but they offer fast payback in the form of effective daylighting strategy selection resulting in reduced energy costs.


  • Option 2:  Prescriptive Design


  • Run prescriptive design calculations to verify that the required percentage of floor area meets the required levels.


  • This compliance path does not require modeling and can still help inform decisions during the design phase. However, the documentation and calculations can be complicated and time-consuming.


  • Option 3:  Measurement


  • Measuring daylighting with handheld light meters can be time-consuming for large areas. Also, you are likely to need to defer this credit to the construction phase LEED submittal so that accurate light readings can be taken with interior walls in place.


  • Measurement can account for complex daylight designs but does not help inform the design process. It can only confirm compliance once the space has already been constructed.  At that late phase, it may be too costly to make design changes to bring more floor area into compliance.


  • Measurement is a low-cost compliance method but may not help to optimize daylight during the design phase. An optimized daylight design can cut down substantially on lighting costs over the long run.


  • Option 4: Combination


  • A hybrid compliance path may be the best solution for some projects. For example, if most of the regularly occupied spaces pass the calculation criteria in the prescriptive path, and a portion of the spaces fall short very narrowly or use strategies like lightshelves not accounted for by the prescriptive path, measurement of those spaces after finishes are complete could demonstrate that they are sufficiently daylit after finishes are complete.

Construction Documents

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  • For Options 1 and 2, enter square footage for the portions of the regularly occupied areas that meet the daylight requirements in the LEED credit form and upload all required documents to LEED Online.


  • Incorporate daylight-related items such as lightshelves, daylight sensors, and light-colored paint into specifications.


  • During the value engineering process, ensure that components critical to the daylight design, such as high-performance glazing and internal shading devices, are not removed from the project.

Construction

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  • For Option 3, take daylight measurements with a hand-held light meter and record the values on a 10x10 grid plan. Enter square footage for the portions of the regularly occupied areas that meet the daylight requirement in the LEED credit form and upload all required documents to LEED Online.


  • Measuring daylight levels can be a time-consuming process in large buildings. Measurements are taken on a 10-foot by 10-foot grid, with four measurement points for each 10 ft2 section. Taking and recording each measurement takes about 30 seconds—not including setting up the grid—for a total of about two minutes per grid section.


  • Daylight sensors and other daylight controls should be added to commissioned systems for lighting for EAp1: Fundamental Commissioning.

Operations & Maintenance

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  • Cleaning plans need to integrate the maintenance of interior and exterior shading and control dust so that reflectivity is not compromised.


  • Daylighting controls can be set and tailored for each space. The facility manager or another designated person should be in charge of adjusting the settings to meet the needs of occupants.


  •  Educate staff and occupants on daylight-related and glare-control technologies. Some daylighting controls such as shades or blinds may require occupant operation, and without instruction, may not be used properly, resulting in the building not operating as designed.

  • USGBC

    Excerpted from LEED 2009 for New Construction and Major Renovations

    IEQ Credit 8.1: Daylight and views - daylight

    1 Point

    Intent

    To provide building occupants with a connection between indoor spaces and the outdoors through the introduction of daylight and views into the regularly occupied areas of the building.

    Requirements

    Through 1 of the 4 options, achieve daylighting in at least the following spaces1:

    Regularly Occupied SpacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building. Points
    75% 1


    Option 1. Simulation

    Demonstrate through computer simulation that the applicable spaces achieve daylight illuminance levels of a minimum of 10 footcandles (fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter. 2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter.) (108 luxMeasurement of lumens per square meter.) and a maximum of 500 fc (5,400 lux) in a clear sky condition on September 21 at 9 a.m. and 3 p.m.

    Provide glare control devices to avoid high-contrast situations that could impede visual tasks. However, designs that incorporate view-preserving automated shades for glare control may demonstrate compliance for only the minimum 10 fc (108 lux) illuminance level.

    OPTION 2. Prescriptive

    Use a combination of sidelighting and/or toplighting to achieve a total daylighting zone (the floor area meeting

    the following requirements) that is at least 75% of all the regularly occupied spaces.

    For sidelighting zones:

    • Achieve a value, calculated as the product of the visible light transmittance (VLT) and window-to-floor area

      ratio (WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area.) of daylight zone between 0.150 and 0.180.

    • 0.150 < VLT x WFR < 0.180


    • The window area included in the calculation must be at least 30 inches (0.8 meters) above the floor.
    • In section, the ceiling must not obstruct a line that extends from the window-head to a point on the floor that is located twice the height of the window-head from the exterior wall as measured perpendicular to the glass (see diagram on the next page).



    • Provide glare control devices to avoid high-contrast situations that could impede visual tasks. However, designs that incorporate view-preserving automated shades for glare control may demonstrate compliance for only the minimum 0.150 value.

    For toplighting zones:

    • The toplighting zone under a skylight is the outline of the opening beneath the skylight, plus in each direction

      the lesser of (see diagram below):

      • 70% of the ceiling height,
      • 1/2 the distance to the edge of the nearest skylight
      • The distance to any permanent partition that is closer than 70% of the distance between the top of the partition and the ceiling.



    • Achieve skylight coverage for the applicable space (containing the toplighting zone) between 3% and 6% of the total floor area.
    • The skylight must have a minimum 0.5 VLT.
    • A skylight diffuser, if used, must have a measured haze value of greater than 90% when tested according to ASTMVoluntary standards development organization which creates source technical standards for materials, products, systems, and services D1003.
    Option 3. Measurement

    Demonstrate through records of indoor light measurements that a minimum daylight illumination level of 10 fc (108 lux) and a maximum of 500 fc (5,400 lux) has been achieved in the applicable spaces. Measurements must be taken on a 10-foot (3-meter) grid and shall be recorded on building floor plans.

    Provide glare control devices to avoid high-contrast situations that could impede visual tasks. However, designs that incorporate view-preserving automated shades for glare control may demonstrate compliance for only the minimum 10 fc (108 lux) illuminance level.

    Option 4. Combination

    Any of the above calculation methods may be combined to document the minimum daylight illumination in the applicable spaces.

    Potential Technologies & Strategies

    Design the building to maximize interior daylighting. Strategies to consider include building orientation, shallow floor plates, increased building perimeter, exterior and interior permanent shading devices, high-performance glazing, and high-ceiling reflectance values; ly, additionally, automatic photocell-based controls can help to reduce energy use. Predict daylight factors via manual calculations or model daylighting strategies with a physical or computer model to assess footcandle levels and daylight factors achieved.

Technical Guides

IEQ Space Matrix - 2nd Edition

This updated version of the spreadsheet categories dozens of specific space types according to how they should be applied under various IEQ credits. This document is essential if you have questions about how various unique space types should be treated. Up to date, 2nd Edition.


IESNA Recommended Practice of Daylighting—Daylight Design Guidance

This is the American industry authority on lighting levels and energy use.  The Illumination Engineering Society of North America (IESNA) publishes several design guides for recommended lighting levels, daylighting and much more.


Window 5.2 computer program—The Lawrence Berkeley National Laboratory

This is a database of window brands, VLT and U-values for different glazing manufacturers.  The program provides a versatile heat transfer analysis method.     


Whole Building Design Guide—Guidance for Daylight Design

This is an excellent resource for researching how to apply different daylight strategies and the implications the design strategies may have.  Includes information on materials and methods of construction as well as calculation tools and software resources.


IEQ Space Matrix - 1st Ed.

This spreadsheet categories dozens of specific space types according to how they should be applied under various IEQ credits. This document is essential if you have questions about how various unique space types should be treated.  This is the 1st edition.

Software Tools

Building Lighting System Software Tools Directory

This is a comprehensive list of modeling tools compiled by the U.S. Department of Energy.


Radiance—Lighting Design Software

This daylight modeling tool is widely accepted in the lighting industry.


Virtual Environment Apache Thermal Analysis Software

A simple modeling tool for preliminary light and energy analysis.  Virtual Environment software, or VE-Ware, gives you instant feedback on a building's energy consumption and carbon emissions, as well as benchmarking it against the Architecture 2030 Challenge if it is located in the US.  You can access the carbon and energy calculator through the Revit and SketchUp plug-ins.  


AGi32—Lighting Design Software

This is one of the most frequently used daylight modeling computer simulation programs.  AGi32 offers lighting analysis software for calculations and renderings of electric lighting and daylighting systems.


SketchUp

SketchUp is used to create 3-D graphic models that can help in your daylighting analysis and documentation.

Organizations

Heschong-Mahone Group

This is a lighting group that has published research on the effects of daylighting.


IES—Illumination Engineering Society of North America

This is the organization that sets lighting standards.  The IES also works directly with ASHRAE to develop energy standards.

Publications

Daylighting in Schools: Reanalysis Report

This is a case study for the effects of daylighting on productivity in schools.  Prepared by Heschong Mahone Group for the California Energy Commission.


Psychosocial Value of Space—Whole Building Design Guide

This is a study exploring the relationship of daylighting and other design features on human psychological well being.  By Judith Heerwagen -
J.H. Heerwagen & Associates, Inc.


Windows and Classrooms: A Study of Student Performance and the Indoor Environment

This is a case study for the effects of daylighting on productivity in schools.  Prepared by Heschong Mahone Group.

Prescriptive Compliance

Option 2

To use the prescriptive compliance path, follow a process like the one in this example, which achieves the credit using a combination of side and top lighting.

Daylight Measurement

Option 3

Take daylight measurements with a handheld light meter and record the values on a 10x10 grid. Enter square footage for the portions of the regularly occupied areas that meet the daylight requirement in LEED Online.

LEED Online Forms: NC-2009 IEQ

The following links take you to the public, informational versions of the dynamic LEED Online forms for each NC-2009 IEQ credit. You'll need to fill out the live versions of these forms on LEED Online for each credit you hope to earn.

Version 4 forms (newest):

Version 3 forms:

These links are posted by LEEDuser with USGBC's permission. USGBC has certain usage restrictions for these forms; for more information, visit LEED Online and click "Sample Forms Download."

Design Submittal

PencilDocumentation for this credit can be part of a Design Phase submittal.

586 Comments

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ADRIENN GELESZ LEED AP ABUD Engineering Ltd.
Apr 15 2014
LEEDuser Member
706 Thumbs Up

Skylight coverage

Hi, in case of a not meeting the skylight coverage ratio of 3-6% for the total room space, e.g. having only 1.5%, is it possible to devide the space into two zones and include half or the room in the compliant areas, which on it's own meets the 3% skylight coverage?

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Kristina Abrams AIA, LEED AP BD&C Ayers Saint Gross, Inc.
Apr 14 2014
LEEDuser Member

Glare Control - Glazing film

Can a film be installed as a form of glare control for spaces with illuminance levels above 500fc?

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Todd Reed Daylight Designer, 7group Apr 14 2014 LEEDuser Expert 6673 Thumbs Up

No; glare control devises must be able to be controlled by the occupants unless automated shades are controlled.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Apr 15 2014 LEEDuser Expert 4171 Thumbs Up

For the situation you are describing, no. But if you install the film and your simulation can show that you are still meeting the minimum footcandle requirement, not going above the 500 maximum, and you can prove you are still providing a view, then maybe. As you can see this could be tricky, because you need the optical properties of the film from the manufacturer and simulation software that knows what to do with it. You would also need to either prove to the reviewer somehow that the film doesn't obscure the view and/or install the film in the upper portion of the glazing and provide shading or glare control for the lower portion of the glazing to preserve the view.

I think the new redirecting films have potential, and want to make sure designers and reviewers don't dismiss them outright.

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Eddy Santosa Lead Building Performance Analyst, Callison Apr 15 2014 LEEDuser Expert 2792 Thumbs Up

View compliance is not required in daylight credit. As long as the illuminance levels are between the required range after adding the film, the project will comply.

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Amanda Johnson Penicaud Green Building
Apr 10 2014
Guest
45 Thumbs Up

Regularly Occupied Spaces - Hotels

Hello,
I was wondering if the bathroom area of a hotel guestroom would be considered a regularly occupied space? Dito entry closet area...
Thanks for any feedback on this,

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Todd Reed Daylight Designer, 7group Apr 10 2014 LEEDuser Expert 6673 Thumbs Up

Both would not be considered regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building..

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Amanda Johnson Penicaud Green Building Apr 10 2014 Guest 45 Thumbs Up

Thank you!!

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Shenhao Li Atkins
Mar 10 2014
LEEDuser Member
190 Thumbs Up

how to execute calculation if balcony exist?

Hi, Guys
I have a residential project, each housing unit has a balcony in front of side window of the living room, should i need to consider shading impact of balcony when using OPTION 2. Prescriptive, if so, how to do it?

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Todd Reed Daylight Designer, 7group Mar 10 2014 LEEDuser Expert 6673 Thumbs Up

If there residential units are stacked, then the balcony of the unit of above would be considered an overhang. You would need to use the 63 degree angle from the outer edge of the balcony above to determine the depth of the daylight zone for the space that is effected by this in the lower unit.

Its all about access to the skyvault so the balcony for the space would not need to be considered, even if it were a concrete balcony.

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Annalise Reichert LEED Project Coordinator Environmental Building Strategies
Feb 26 2014
LEEDuser Member
39 Thumbs Up

Option 2: Prescriptive Method Skylight Inclusion

I am working on a project using the prescriptive daylighting method for achieving IEQc8.1 The project has both sidelighting and toplighting. If the skylights are excluded, the project's regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building. meeting the requirement ( 0.15 < WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area. x VLT < 0.18) will be less than 75%, and they will not achieve the credit. If I include the skylights in the calculation, the WFR x VLT will be greater than 0.18 for most regularly occupied spaces (over-daylighting in terms of this method) and the project will still not achieve the credit.

My question: can we pick and choose what skylights we use to comply with this credit via prescriptive method, or do we need to include all of them?

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 26 2014 LEEDuser Expert 4171 Thumbs Up

No.

Also, skylights don't use the WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area. formula. See an excellent example of the Prescriptive Method calculation on this web page at the top under Documentation Toolkit.

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S S
Jan 09 2014
Guest
36 Thumbs Up

Min lux level for Project which has registered 5 months before

Hi Every one,

Currently we are working for factory building project which has registered five months before under USGBC Rating system LEED 2009. We would like to get Daylighting credit and it is natural ventilated building.
We would like to know the required minimum luxMeasurement of lumens per square meter. level & maximum lux level. As per the reference guide, the min lux is 270 lux. Whether it is reduced to 110 lux after that? Please let me as soon as possible. Also let me know how to check with addenda.

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Todd Reed Daylight Designer, 7group Jan 09 2014 LEEDuser Expert 6673 Thumbs Up

The minimum luxMeasurement of lumens per square meter. level is 107 and the maximum level is 5381. The addenda was posted in April of 2010.

You can see these levels in the online credit language and here in LEEDusers.

Searching the LEED addenda and interpretation database is painful.

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Jean Marais b.i.g. Bechtold DesignBuilder Expert Jan 13 2014 LEEDuser Member 7143 Thumbs Up

Wow. That is a massive difference. I just tested it on a project that simulated 42% compliant area on the old requirement and 82% with the new. At the time I was completely dissapointed that the design appeared not to be good enough and couldn't understand why.

Actually, it turned out to be a moot point, because it was a kindergarten (School) project without "classrooms" in the typical sense and therefore I'm not allowed to apply for the credit.

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Kathryn West LEED AP BD+C, O+M, Guiding Principles Compliance Professional, Energy Ace Jan 13 2014 LEEDuser Member 1423 Thumbs Up

What is the ID# for the Addendum? I can't find it when I search through the posts from April 2010. Thanks!

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Todd Reed Daylight Designer, 7group Jan 13 2014 LEEDuser Expert 6673 Thumbs Up

Use this link to read it, it was 2011 not 2010. Anymore it easier to go through the specific credit information rather than the LI and addenda database.

http://www.usgbc.org/resources/daylight-and-views-daylight-addenda-05092011

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Candice Rogers Paladin, Inc
Nov 14 2013
LEEDuser Member
190 Thumbs Up

Daylight and Views - Simulation Documentation

Hello -

This is my first time using the Simulation option for documenting Daylighting. For the Supplemental Daylight and Views Calculation Worksheet, do we represent our 5 ft. grid in the "Regularly Occupied Space ID" column? Or, can we input the whole room as unique ID's and submit the total sq. ft. daylit and not daylit?

Many thanks -
Candice

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Nov 14 2013 LEEDuser Expert 4171 Thumbs Up

I'm not understanding what you mean by "represent our 5 ft grid" in column. Are you asking if you have to enter your fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter. 2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter. values into the spreadsheet? No. Just the square footages go into the spreadsheet.

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Marian Keeler Senior Associate Thornton Tomasetti / Sustainability
Oct 18 2013
LEEDuser Member
3073 Thumbs Up

What controls are required so autoshades can comply with credit?

We note that the prescriptive method for IEQc8.1 allows view preserving automated shades to be used as a glare control device, and that in the sidelighting section of theTable IEQ-1 spreadsheet, answering “yes” in the view preserving automated shade column allows the zone floor area to count toward the credit even if VLTxWFR > 0.18. For this and other reasons, we are considering electrically operated shades for our high-rise multi-family residential project. However, in attempting to specify a control system, we note that “automated” can be interpreted in different ways and we see that there are few specifics in the LEED Reference Guide relating to this part of the credit. Are there any established precedents or minimum criteria governing the operation and control of the shades?

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Todd Reed Daylight Designer, 7group Oct 21 2013 LEEDuser Expert 6673 Thumbs Up

Automated shades must have a sensor that recognizes a certain level of illuminance and then automatically lowers the shades. There should be a manual override.

When submitting, ensure you provide a floor plan indicating the location of the automatic shades, the sensors. Provide a sequence of operation for shades, cut sheets, and a brief narrative.

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Rick Alfandre Principal Alfandre Architecture
Oct 04 2013
LEEDuser Member
115 Thumbs Up

Daylight measurement requirements...

I am not finding any parameters for the daylight measurement option as far as times of day or other issues.

The project is a bank branch, and I imagine we will need to have electric lights turned off to provide an accurate measurement of the daylighting. Where can I find procedural guidance for this option?

Thank you.

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Todd Reed Daylight Designer, 7group Oct 07 2013 LEEDuser Expert 6673 Thumbs Up

There is no specific date or time of day in regards to when to take the measurements. Take the measurements on a clear day around noon. Create your grid on a floor plan prior to taking the measurements. Hold the meter at 30 inches. Pretty simple for this version.

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oleg petryuchenko lighting designer
Sep 30 2013
LEEDuser Member
45 Thumbs Up

equipment

if we have manufacturing equipment on the floor and all area is daylit through skylights, providing even lighting level across the space do we need to exclude sq. footage of equipment from complied area?
Thank you

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Todd Reed Daylight Designer, 7group Sep 30 2013 LEEDuser Expert 6673 Thumbs Up

If you have large pieces of permanently mounted equipment, you may exclude the area it occupies from the total regularly occupied space. However, you must include it in your calculations. So if using simulation, it must be included in the simulation model in some form. This would also be true with the views credit, these pieces of equipment basically are large partitions and need to be included in your sight line drawings.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Sep 30 2013 LEEDuser Expert 4171 Thumbs Up

Exactly how large? If they are large enough that people can work inside of them, or that people lean over them, or that people need to look at them to work, then I would say include them. If they obstruct space from being occupied and there is no need to look at them (monitor gauges or meters, for example), then I think it would be fair to exclude them.

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oleg petryuchenko lighting designer Sep 30 2013 LEEDuser Member 45 Thumbs Up

It is manufacturing equipment that 3-8’ high with people working on this equipment all day. the whole area under skylight (diffuse) with even lighting level of 45-50fc across entire space (with manufacturing equipment included in calculation model)
If we include the area that covered with equipment to qualified area it will increase our qualified % for 8.1 credit. In some way it similar to office equipment such as desks, partitions, standard file cabinets, etc. but may be slightly larger in scale. I’m really appreciate your advise.
Thank you

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Eddy Santosa Lead Building Performance Analyst, Callison Nov 13 2013 LEEDuser Expert 2792 Thumbs Up

I believe you need to include if the workers work on the horizontal surface of the equipment (3'-8"). You can also use 3'-8" grid high.

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oleg petryuchenko lighting designer Feb 19 2014 LEEDuser Member 45 Thumbs Up

I have another question for the same project..Part of the same building is active warehouse with large storage racks going from floor to ceiling. Racks take about 50% of floor space. We have skylights in between the racks providing required lighting levels. In simulation model whether we include or exclude sq. footage of racks, we have required % to meet LEED requirements. The other energy models (credits) do not exclude sq. footage of racks from total sq. footage of regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building. which kind of predefines the total regularly occupied area for daylight credit to follow.
Will it be correct to include racks area in total calculated area, or these areas need to be excluded? And what would be the best way to handle the situation when we need to exclude the racks?

Appreciate your advice.. Thanks

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Jean Marais b.i.g. Bechtold DesignBuilder Expert Feb 19 2014 LEEDuser Member 7143 Thumbs Up

One of the things reviewers are sticky about is consistancy across credits. This is a picky point for the energy simulations which are modelled in thermal blocks and the regularly occupied space has more to do with when an assigned lighting power density will switch on or off for that block and other such simulation stuff. This means that "regularly occupied space" for the EAp2 credit is bound to deviate. It does not set the president for the LEED submission as a whole! Quite the contrary in fact. Sometimes, you need to do some extra explaining unfortunately. Personally, I (and not only I) think that the regularly occupied space part of the online forms for EAp2 can be scrapped without effecting anything.

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Eddy Santosa Lead Building Performance Analyst, Callison Feb 19 2014 LEEDuser Expert 2792 Thumbs Up

In my opinion, If the racks have no solid door, you should add them. If there are solid doors, you can exclude them. If you want to exclude, you need to provide a separate narrative.

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oleg petryuchenko lighting designer Feb 19 2014 LEEDuser Member 45 Thumbs Up

thank you all!

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oleg petryuchenko lighting designer
Sep 30 2013
LEEDuser Member
45 Thumbs Up

LEED Matrix

we have some spaces that excluded from 8.1 according to matrix such as lobby, brake room.. but they are properly daylit (10-500fc) based on AGI calcs. will it be correct to add these areas to complied areas?
Thank you

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Todd Reed Daylight Designer, 7group Sep 30 2013 LEEDuser Expert 6673 Thumbs Up

You can include a space in your calculations even though the space matrix indicates it does not have to be. You must be consistent with including it across all other credits and ensure that its square footage is included in all other calculations.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Sep 30 2013 LEEDuser Expert 4171 Thumbs Up

Please be careful with break rooms. There is a note [2] that states that this space must be considered as regularly occupied "if one or more individuals normally spend time (more than one hour per person per day on average)" etc.So it is likely that if anyone spends their lunch hour in there, you are required to include it.

I don't necessarily agree that if you include the space into the IEQ 8.1 regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building., that it must be included in all other credits. I think that is what the Space Matrix is for. For example, if you include the break room in the IEQ 8.1 requirements for daylighting, I don't think that you are also required to provide individual controls for that space in creditS IEQ 6.1 and 6.2. (Row 113 of the Space Matrix.)

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oleg petryuchenko lighting designer Sep 30 2013 LEEDuser Member 45 Thumbs Up

thank you. It will be occupied during the day and it is beneficial for our modeling to include those spaces in calculations for 8.1

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Jatuwat Varodompun Dr Green Building Soultion
Sep 28 2013
LEEDuser Member
821 Thumbs Up

Gallery space and daylight

In space matrix april 2013, the gallery must be have daylight and view acess. If my project has such space but the objects and displays are inappropriate for daylight. It might be damaged. Can I write the narrative and get the exemption for gallery space? What is the chance?

thanks

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Todd Reed Daylight Designer, 7group Sep 30 2013 LEEDuser Expert 6673 Thumbs Up

If the displays are permanent and you can provide a descriptive narrative as how daylight can harm the displays, then yes. If the gallery space is used for temporary displays, like one that are there for a few weeks or month, then it would be hard to say that every display will be harmed by daylight and there are design options that can happen to help control direct and diffuse daylight.

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Mark Garber MGA
Sep 17 2013
Guest
4 Thumbs Up

Floor Area for Daylight

Can the floor area under built-in casework composed of base cabinets and overhead cabinets be excluded from the floor area using the prescriptive option for sidelighting daylight calaculations for IEQc8.1? If so, is there documention available?

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Todd Reed Daylight Designer, 7group Sep 30 2013 LEEDuser Expert 6673 Thumbs Up

Permanently mounted casework can be excluded from your regularly occupied floor area.

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Gary Greenshields President Infinity Architecture
Aug 22 2013
LEEDuser Member
19 Thumbs Up

Indoor pool daylighting measurement

We have a Wellness Center project with an indoor pool area of approximately 6,000 SF and a pool surface area of about 4,000 sf within that space. We are using the actual daylight measurement option. The daylight measurements on the pool deck on all four sides meet the fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter. 2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter. requirements. Is the actual pool surface area itself considered part of the regularly occupied space requiring measurement? Treading water with a light meter could be challenging...

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Todd Reed Daylight Designer, 7group Aug 22 2013 LEEDuser Expert 6673 Thumbs Up

A natatorium is considered a regularly occupied space as noted in the Regularly Occupied Space Matrix April 2013, but there is not an indication as to whether or not the actual pool is required. There is no argument that daylight is a determent to the activity of swimming, diving, or any other pool activities. It is the most regularly occupied space in a natatorium. I would suggest a small inflatable boat to get the light levels for credit documentation.

The last two natatoriums we did that we submitted, one with glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. and the other with simulation, the pool was included in our regularly occupied square footage and both times was earned.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Aug 23 2013 LEEDuser Expert 4171 Thumbs Up

I agree that the actual pool area needs to be submitted. I like the small boat idea! You also might want to put markers such as construction cones at your chosen measurement spacing increments (10' min.) around each side of the pool so that you can line yourself up with them once you're in there. I would suggest the "appropriate working height" here would be the pool surface but for convenience sake, would say to just get as close as possible without shading or otherwise affecting the light meter. Good luck!

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Gary Greenshields President, Infinity Architecture Aug 23 2013 LEEDuser Member 19 Thumbs Up

Thanks! Both good ideas, we are going to do the measurements today and if we discover any other helpful hints, we'll post them.

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oleg petryuchenko lighting designer
Aug 21 2013
LEEDuser Member
45 Thumbs Up

green house and daylighti credit

We have large warehouse project that also has a green house as a part of the building. could this area be excluded from daylighting? it's a regularly occupied space but the production process dictates it's own daylighting requirements.

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Todd Reed Daylight Designer, 7group Aug 23 2013 LEEDuser Expert 6673 Thumbs Up

A green house having specific "daylighting" requirements would be a hard one to exempt. So if the growing process means shutting off the sun at certain times, but the plants still get some sun during the day, then it needs to be included.

Now a green house having specific "lighting" requirements could be exempted as long as a narrative clearly explains why. If the plants being grown are mushrooms,well that;s pretty easy one, or if the plants being grown require the use of specific electric lighting. If daylight is a hindrance to the growing process of the plants then it can be exempted.

I'm not a plant guy, but we did do a building in which plants would be growing inside the atrium and the glass needed specific properties to ensure the proper wavelengths of light were admitted to the space. There are glazings out there that can be produced to provide what is needed.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Aug 23 2013 LEEDuser Expert 4171 Thumbs Up

To me, a production that has specific daylight requirements is the perfect exemption. It's the definition of the exemption.

I'm guessing the reason the production doesn't meet the requirements in the first place is because the production's daylighting requirements go above the LEED maximum? In that case, you might include the space but try to get an exemption for the shading or maximum requirements. I could see where a reviewer would dock you on not including the greenhouse if the production daylighting requirements didn't contradict the LEED requirements. I'm also assuming that they are contradictory otherwise you wouldn't ask because including the space in that case would only help you earn the credit.

Either way, I would document very clearly and precisely the production daylighting requirements and the consequences to the production if they are not followed. I doubt many reviewer are knowledgeable enough on the subject to make the call without this information.

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oleg petryuchenko lighting designer Aug 23 2013 LEEDuser Member 45 Thumbs Up

Jill, Todd thank you!
so my understanding from your answers that there is no general rule for greenhouse and it very much depends whether production requirements will meet LEED requirement or not and has to be documented anyways. .. and the lighting level should be in range 10-500fc, is that correct?

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Aug 23 2013 LEEDuser Expert 4171 Thumbs Up

That is my understanding.

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Michael Wironen Ecology and Environment, Inc.
Aug 15 2013
LEEDuser Member
302 Thumbs Up

Room by room versus Apartment calculations

Our project is a 14-floor residential project. We are pursuing the prescriptive pathway for daylighting, which requires us to calculate the floor to window ratios for each room. However, we have already prepared documentation for views on a per-apartment basis. Would it be acceptable to complete two versions of the USGBC-provided Supplemental Daylight and Views Calculation Spreadsheet for documentation of IEQc8.1 on a per-room basis and IEQc8.2 on a per-apartment basis? Does anyone have experience submitting like this?

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Todd Reed Daylight Designer, 7group Aug 15 2013 LEEDuser Expert 6673 Thumbs Up

It would be acceptable to provide two different calculators. I believe you will have an issue because when you upload the calculator in one credit, it is automatically linked to the other. You will have to upload the other calculator in the other document section of the credit, I believe.

I would suggest that you provide a narrative explaining what you are doing so that the reviewer knows that there are two different calculators provided. I would also suggest that for your views credit that you also provide individual apartment view calcs on a room by room basis. So for each different type of apartment, provide a separate sheet showing how the overall apt value is calculated. You can then just upload the by apt calculator.

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Xavier Bigot
Aug 02 2013
Guest
17 Thumbs Up

Simulation on the 21 of september

Hi! I was wondering why does LEED require to run a simulation on the 21st of september?
It also requires to perform the simulation during a clear sky condition. However, with the software I used (AGI32) I can't calculate the daylight factorThe ratio of exterior illumination to interior illumination, expressed as a percentage. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis), and window height. under a clear sky condition. Could someone give me some explanations?
Regarding the overcast sky, I would like to know which is the typical value used? I searched on Google but I got different answers...
Thanking you in advance

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Todd Reed Daylight Designer, 7group Aug 05 2013 LEEDuser Expert 6673 Thumbs Up

Xavier,
The reason simulations are typically run on the equinox is because the sun is at the equator, its neither at its highest or lowest altitude in the sky. You can run on March 21st or September 21st.

Daylight FactorThe ratio of exterior illumination to interior illumination, expressed as a percentage. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis), and window height. calculation is different type of calculation than illuminance calculation. DF is calculation uses the CIE overcast sky value. DF is the percentage of the exterior horizontal illuminance value that reaches a point inside a space. Having a DF of 2% is good. Illuminance calculations is the value, either in luxMeasurement of lumens per square meter. or footcandles, on a point in building under all type of sky conditions.

What you want to do in AGI-32 is calculate the illuminance value.

There are alot of good books on daylighting, "Daylighting in Sustainable Building, Daylight in Buildings, "Sun, Wind, and Light". There are also a lot of good sources on the web that talk about daylighting strategies, the different types of metrics, calculations, etc. The Daylighting Collaborative, and the Whole Building Design Guide, are just few of the many sources that i suggest you may want to read to get a better understanding of daylight and daylight simulations.

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Xavier Bigot Aug 05 2013 Guest 17 Thumbs Up

Thank you so much, I don't have much experience in daylighting... May I ask you another question? What is the typical outdoor illuminance value used by the software for the overcast sky? I searched on Google but I got different answer... If you can help me with this, I'd really appreciate.
Thanks!

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Todd Reed Daylight Designer, 7group Aug 05 2013 LEEDuser Expert 6673 Thumbs Up

Are you asking what the typical illuminance is for a CIE overcast sky or just an overcast sky condition in general?
Off the top of my head i believe CIE overcast is 1000 luxMeasurement of lumens per square meter.. In the program, put a ground plane in, place a sensor at 30" facing up, run the simulation under the specific sky condition at noon, this will tell you what the computer program is using.

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Xavier Bigot Aug 05 2013 Guest 17 Thumbs Up

Yes, it's the CIE overcast sky... I'll try it, thank you Todd ;)

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Xavier Bigot Aug 06 2013 Guest 17 Thumbs Up

So I run the simulation and I got a value of 333 Fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter. 2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter. (around 3500 luxMeasurement of lumens per square meter.) for a overcast sky at noon. So DF= (Inside illuminance/Outside illuminance)*100
Therefore: Inside illuminance= DF(%)*Outside illuminance
For a DF equal to 2%, I got: Inside illuminance= 2/100*3500= 70 lux

From my point of view this is not good, I may don't understand something. I'm a little confused...

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Todd Reed Daylight Designer, 7group Aug 06 2013 LEEDuser Expert 6673 Thumbs Up

Xavier,

First off, this is a v3 forum, so calculating the daylight factorThe ratio of exterior illumination to interior illumination, expressed as a percentage. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis), and window height. is not an option for v3 projects. If yo have a v2.2 or even a schools 2007 project, then you have the option to use the glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. calculation method. If you are going to be using the simulation method in v3, then you should be focusing on illumance calculation in AGI-32.

Ok, so you ran a sim with 333 fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter. 2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter., which to me is pretty low, for a CIE overcast sky. Not sure of of all your inputs etc, but that is low. 2% of 333 is rounded up to 7 fc which is well below any level for a regularly occupied space. Is the sensor facing up?

I would suggest that you look into AGI-32's help forum. I believe they have some video tutorials that can help you set your model for simulations. Make sure you have the task of setting up your model and getting all your input parameters correct. The biggest problem with simulations is incorrect input. This will always give you false reads. If you follow the false reads, you will actually make the incorrect design decisions. Part of knowing simulation is knowing when the outputs are false.

Good Luck.

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Luana Bertoletti Sustentech
Jul 30 2013
Guest
613 Thumbs Up

Daylight analysis - inter-reflection

Hi,

I have a doubt related to the considerations that should be assumed in order to perform the daylight analysis simulation.

Should we consider the inter-reflections of the rooms' surfaces or simply the elements that obstruct light?

Regards,

Luana Eid

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Todd Reed Daylight Designer, 7group Jul 30 2013 LEEDuser Expert 6673 Thumbs Up

Luana,

You need to consider both in regards to daylight simulations. There are alot of items that you should consider when performing daylight simulation to ensure the results are as close as possible to the actual performance.

1.Include adjacent structures, especially ones that will shade a facade or produce reflections. These surfaces should have at least a reflectance. Include the ground and even dense vegetation.

2.Interior surfaces, at minimum, floors, walls, and ceilings should be either have the actual reflectance or a default of 30, 60-70, and 80.

3.Permanently mounted partitions should be inlcuded in your model. Furniture is not required for LEED, but we sometimes include when we know what has been specified. My biggest issue with furniture, especially desks and cubicles is to ensure the specified colors maintain a good contrast ratio.

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Emmanuel Pauwels Owner, Green Living Projects s.l. Apr 11 2014 LEEDuser Member 1497 Thumbs Up

Todd,
Is it correct that in case of an adjacent wall with openings in it, we can not use the prescriptive method. Or could we calculate the % of wall openings and apply that % to window surface?

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Todd Reed Daylight Designer, 7group Apr 11 2014 LEEDuser Expert 6673 Thumbs Up

Emmanuel,
Are you talking about an adjacent exterior wall with openings in it next to the window? Or, are you talking about an adjacent space inside a building, which does not have an exterior wall.

Case 1, I would need to see more. How far away is the wall, height, etc. etc. With the prescriptive method, its about access to the sky vault.

Case 2. The prescriptive method cannot be used for spaces with shared daylighting scenarios. This is only for spaces that are separated by another layer of glass. The prescriptive calculation cannot determine compliant percentage through multiple layers of glass. Now if the space adjacent to the perimeter space is separated by a wall with just openings with no glass, and it falls within daylight zone, then some of that space's square footage could be considered in the calculations. Again, without really seeing more of the situation, i could not reliable say it could or how much could actually be considered.

I hope i answered what you were looking for.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Apr 11 2014 LEEDuser Expert 4171 Thumbs Up

30% reflectance is generally hard to achieve with flooring that doesn't show dirt. Traditionally, 20% has been used as a default reflectance for floors, but I've heard that in actuality, most flooring is in the 10-20% range. 70% for walls is achievable, but for me, I'd rather use a more conservative number of 50% and be surprised in a good way when the actual numbers are known.

I can't think of a situation using the prescriptive method where any adjacent wall, interior or exterior could be used. You'll have to describe your situation more accurately.

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Emmanuel Pauwels Owner, Green Living Projects s.l. Apr 11 2014 LEEDuser Member 1497 Thumbs Up

Todd,
It is an outside wall but it is next to the window. So really, only the openings of the wall let light through and we were thinking to take the openings in the wall as transparent area.

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Todd Reed Daylight Designer, 7group Apr 11 2014 LEEDuser Expert 6673 Thumbs Up

Is it like a brise soleil scenario or is this wall part of another building? If the wall is not part of this building, then it can be ignored with the prescriptive method.

How are you determining the depth of your daylight zone? Are you using the 63 degree angles from the top edge of the opening in the exterior wall?

If the wall is right up against the window and part of the building, and these are larger openings, then their "might" be an argument to using the prescriptive method. But, without really seeing what you got, i can;t say for sure.

If your not wanting to use simulations, might be best to take measurements at the end of construction instead of trying to deal with this type of scenario and have it denied in the review.

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Emmanuel Pauwels Owner, Green Living Projects s.l. Apr 11 2014 LEEDuser Member 1497 Thumbs Up

From what you are saying, it looks like the prescriptive method is going to be a challenge. The wall is part of the building. We have a large window area on the ground floor (floor to ceiling window) and there is a wall at more or less half a meter from that window. But the wall is sort of like a chess board with the white squares open and the black squares closed. We wanted to use the surface of the openings, but since it is a thick wall and if we use the 63 degree angle from the top outside edge, that would reduce the opening substantially. But I get your point and I guess in the end we will simulate ...

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Anne Harney Senior Associate Ayers Saint Gross Architects + Planners
Jul 23 2013
LEEDuser Member
198 Thumbs Up

Daylight in Open Plan Area

We have a large open plan cafeteria with three different ceiling heights that define 3 daylit zones. Each zone is divided into occupiable areas by furniture and millwork however the "rooms" defined are not enclosed and are equally impacted by the daylight provided by the envelope glazing. Instead of inputting square footage of each occupiable area, I am defining the occupiable areas within this open plan by zone, so there are 3 occupiable areas total within the open plan.

Each of these three areas meet the requirements for daylighting. Surrounding the perimeter of the open plan are fast food portals. The service area where a customer orders is open to the daylit open plan, however, the kitchens behind each portal are not open to the daylight. If I break the open plan into 3 zones, that only looks like 3 rooms on the calculator, but it is the majority of the building (and is the space occupied by the majority of the building occupants). Adding the kitchens (which may each have 1 person working full-time), which are rated as commercial kitchen spaces requiring fire separation that do not meet the daylighting requirements will make the 75% of occupiable spaces requirement inachievable - even though the majority of the building is daylit. Can the kitchens be eliminated from the calculation on the basis of code required fire separation?

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Todd Reed Daylight Designer, 7group Jul 23 2013 LEEDuser Expert 6673 Thumbs Up

Not sure if you are using the prescriptive option, but if you are, then the method of how you are breaking apart the zones and then documenting them in the calculator is not valid. The zone is depth from the window wall either determined by 2H or the 63 angle. Anything beyond that is not considered a "daylightable" but is still considered in the calculations. Breaking a zone into rooms is not valid, but you can break a room into different zones. Maybe I'm just misunderstanding your method.

The regularly occupied space matrix dated April 2013 states that kitchens, commercial or residential, are considered regularly occupied and need to be included in the 8.1 calcs. Exclusion based on fire code is not valid. Kitchens can be daylit. You can exclude the area in the kitchen where kitchen equipment is permanently installed. So instead of using the gross area, just use the are in which the people will actually be able to occupy. This may help.

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Anne Harney Senior Associate Ayers Saint Gross Architects + Planners
Jul 23 2013
LEEDuser Member
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One Space - Two Glazing Types (VLT values)

I have a large open plan building with curtainwall at two ends. The glazing within the first 30" - 84" has a higher VLT value, and the glazing from 8'-0" up to the ceiling is a lower VLT value. How do I account for this following the prescriptive path

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Todd Reed Daylight Designer, 7group Jul 23 2013 LEEDuser Expert 6673 Thumbs Up

You cannot you the prescriptive option when you have two different VLTs on the same width of window wall. Simulation or measurement is your only options.

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Apr 20 2014
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