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

  • CI IEQc8.1 actions steps and doc 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.

  • 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.


  • Installing photosensitive lighting controls and occupancy sensors can help Commercial Interiors projects achieve EAc1.2: Lighting Controls.


  • 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.


  • 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 Commercial Interiors

    IEQ Credit 8.1: Daylight and views - daylight

    1–2 Points

    Intent

    To provide occupants with a connection between indoor spaces and the outdoors through the introduction of daylight and views into the regularly occupied areas of the tenant spaceTenant space is the area within the LEED project boundary. For more information on what can and must be in the LEED project boundary see the Minimum Program Requirements (MPRs) and LEED 2009 MPR Supplemental Guidance. Note: tenant space is the same as project space..

    Requirements

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

    Regularly Occupied SpacesEnclosed space intended for human activities, excluding those spaces that are intended primarily for other purposes, such as storage rooms and equipment rooms, and that are only occupied occasionally and for short periods of time. Occupied spaces are further classified as regularly occupied or nonregularly occupied spaces based on the duration of the occupancy, individual or multioccupant based on the quantity of occupants, and densely or nondensely occupied spaces based on the concentration of occupants in the space. Points
    75% 1
    90% 2



    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

    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.) 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 tenant spaceTenant space is the area within the LEED project boundary. For more information on what can and must be in the LEED project boundary see the Minimum Program Requirements (MPRs) and LEED 2009 MPR Supplemental Guidance. Note: tenant space is the same as project space. to maximize interior daylighting. Strategies to consider include lower partition heights, interior shading devices, interior glazing and high ceiling reflectance values; additionally, automatic photocell-based controls can help reduce energy use. Predict daylight factors via manual calculations or model daylighting strategies with a physical or computer model to assess foot-candle 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.


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.


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.     


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

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.  


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.


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.

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.

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.

LEED Online Forms: CI-2009 IEQ

Sample LEED Online forms for all rating systems and versions are available on the USGBC website.

Design Submittal

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

147 Comments

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SAMY Chamy Enginneer T&T Green
Jan 05 2017
Guest
813 Thumbs Up

Minimum Daylight Level

Dear Sir:-

what is a minimum daylight requirement for LEED CI

1.270 LuxMeasurement of lumens per square meter. (25 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.)
2.110 Lux (10 FC)

in LEED CI reference guide it is 25 FC so please clarify is there any addenda

Post a Reply
0
0
SAMY Chamy Enginneer T&T Green
Jan 05 2017
Guest
813 Thumbs Up

Minimum Daylight Level

Dear Sir:-

what is a minimum daylight requirement for LEED CI

1.270 LuxMeasurement of lumens per square meter. (25 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.)
2.110 Lux (10 FC)

in LEED CI reference guide it is 25 FC so please clarify is there any addenda

Post a Reply
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Rustem Saitov
Jun 24 2016
Guest
53 Thumbs Up

Distance from windows to area

Project Location: Russian Federation

Hi,

We are taking 3rd option, measurement to show compliance with the credit requirements.
The text of the credit does not postulate when a regularly occupied area can be considered daylit (for instance, distance from window to the room is given as 15 feet in Lighting Controls credit EAc.1.2).
Does anyone have an idea what is the threshold?
Many thanks.

Update: actually, I have found the answer.
http://lightingcontrolsassociation.org/content/whitepapers/daylight-zone...
this link contains info on how ASHRAE/IES 90.1-2010 defines daylit spaces.

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Todd Reed Daylight Designer, 7group Jun 27 2016 LEEDuser Expert 15358 Thumbs Up

For this credit, the entire square footage of any space designated as regularly occupied must have measurements taken on at least a 10 foot grid. So if you have a space that is 100 feet deep, you will need at least 10 measurement points from the window wall. You cannot use the argument of what is considered a daylit zone.

Post a Reply
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Haoyang Li
Apr 06 2016
Guest
17 Thumbs Up

Question about terrace without roof

Project Location: United States

Hi all,
I am working on a commercial interior university restaurant project. There is a non-roof terrace at 3rd floor. This terrace is located at the west side of the main building which east side is wall and glazing windows of main structure, west side is surrounded by 14' high curved glass wall. This area is designed to be used as seating or outdoor lunch area. I am wondering how to deal with this area to achieve the LEED requirement. Thanks.

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Todd Reed Daylight Designer, 7group Apr 07 2016 LEEDuser Expert 15358 Thumbs Up

Since the space is not enclosed, has no roof, then it would be considered an outside space. Therefore, it does not need to be included in the daylight calculations or considered regularly occupied.

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Haoyang Li Apr 07 2016 Guest 17 Thumbs Up

Hi Todd,
Thanks for help! And Does it have anyway to exclude from calculation but still count in the regularly occupied?

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Todd Reed Daylight Designer, 7group Apr 07 2016 LEEDuser Expert 15358 Thumbs Up

It's an outside space, so it does not fit the definition of regularly occupied in regards to LEED. In Table PIF3-1, it would be included under the gross floor areaGross floor area (based on ASHRAE definition) is the sum of the floor areas of the spaces within the building, including basements, mezzanine and intermediate‐floored tiers, and penthouses wi th headroom height of 7.5 ft (2.2 meters) or greater. Measurements m ust be taken from the exterior 39 faces of exterior walls OR from the centerline of walls separating buildings, OR (for LEED CI certifying spaces) from the centerline of walls separating spaces. Excludes non‐en closed (or non‐enclosable) roofed‐over areas such as exterior covered walkways, porches, terraces or steps, roof overhangs, and similar features. Excludes air shafts, pipe trenches, and chimneys. Excludes floor area dedicated to the parking and circulation of motor vehicles. ( Note that while excluded features may not be part of the gross floor area, and therefore technically not a part of the LEED project building, they may still be required to be a part of the overall LEED project and subject to MPRs, prerequisites, and credits.) column, but would not be included in the regularly occupied spaceAn area 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. The one-hour timeframe is continuous and should be based on the time a typical occupant uses the space. For spaces that are not used daily, the one-hour timeframe should be based on the time a typical occupant spends in the space when it is in use. column. That column is linked to both EQc8.1 and 8.2.

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Haoyang Li Apr 07 2016 Guest 17 Thumbs Up

Thanks, I think i can get this credit for sure>

Post a Reply
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Alain Brierley Mr WSP Canada Inc.
Nov 30 2015
LEEDuser Member
14 Thumbs Up

System Furniture Include or Excluude?

Project Location: Canada

I am working on a large 12 story office building that has a 12 story toplite open atrium requiring the credit be documented using option 1. A number of the floors have large open office areas with systems furnitureSystems furniture includes panel-based workstations comprising modular interconnecting panels, hang-on components, and drawer and filing components or a free-standing grouping of furniture items designed to work in concert.. I am having a hard time figuring out if I need to include the system furniture in the simulation or if it can be excluded. Could any one direct me to where it outlines if system furniture needs to be included for IEQc8.1 for LEED CI?

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Todd Reed Daylight Designer, 7group Nov 30 2015 LEEDuser Expert 15358 Thumbs Up

As long as the systems furnitureSystems furniture includes panel-based workstations comprising modular interconnecting panels, hang-on components, and drawer and filing components or a free-standing grouping of furniture items designed to work in concert. meets the definition of movable partitions, it does not need to be included in your simulations.

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Maria Jose nuñez Vargas Apr 18 2017 Guest

For commercial interiors v3-2009. For the daylight simulation,
Do I need to model the entire floor with each of the interior spaces like office cubicles, printing rooms etc.?

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Todd Reed Daylight Designer, 7group Apr 19 2017 LEEDuser Expert 15358 Thumbs Up

Only regularly occupied spacesEnclosed space intended for human activities, excluding those spaces that are intended primarily for other purposes, such as storage rooms and equipment rooms, and that are only occupied occasionally and for short periods of time. Occupied spaces are further classified as regularly occupied or nonregularly occupied spaces based on the duration of the occupancy, individual or multioccupant based on the quantity of occupants, and densely or nondensely occupied spaces based on the concentration of occupants in the space. need to be included. Refer to the Regularly Occupied Space Matrix. For areas that include cubicles, the cubicles would be considered movable partitions, so they would not need to be included in the sims, but the area they inhabit would be be. Printing rooms, such as copy rooms are not considered regularly occupied and would not be included.

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Maria Jose nuñez Vargas Apr 19 2017 Guest

Thank you for your reply. For calculations I´m aware i only have to include regularly occupied spacesEnclosed space intended for human activities, excluding those spaces that are intended primarily for other purposes, such as storage rooms and equipment rooms, and that are only occupied occasionally and for short periods of time. Occupied spaces are further classified as regularly occupied or nonregularly occupied spaces based on the duration of the occupancy, individual or multioccupant based on the quantity of occupants, and densely or nondensely occupied spaces based on the concentration of occupants in the space., but for building my model for the simulation, Do i need to model every regularly space, partitions with walls, or i only need to make de perimeter of my floor?

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Todd Reed Daylight Designer, 7group Apr 19 2017 LEEDuser Expert 15358 Thumbs Up

Your model does not need to include every space.

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Ian McCall Environmental Engineer
Jun 03 2015
Guest
1613 Thumbs Up

Confirmation - perforated sticker sign

Project Location: France

Hello,
Can someone confirm that an temporary (3 months) publicity perforated window decal installed by the future tenant on the glazed facade is out of the scope of the LEED NC or CS certification and hence is NOT to be modeled on the day-lighting calculation.
Thank-you,
Ian

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Todd Reed Daylight Designer, 7group Jun 03 2015 LEEDuser Expert 15358 Thumbs Up

Anything temporary, such as the perforated decal, does not need to be modeled.

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Ryan Favier
Feb 05 2015
LEEDuser Member
33 Thumbs Up

Option 2 - Glazing Area

Per 2009 CI you cannot count any glazing area below 30". Is it safe to assume that if a 42" file cabinet is placed in front of the window (not my design) that you can only include the area above 42"? As a side bar; the glazing is full height at 9' with a 2" frame...do I start my 63 degree angle from the 9' mark or from the 8'10"? Also, when calculating the glazing area do I subtract any other vertical or horizontal mullions?

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Todd Reed Daylight Designer, 7group Feb 06 2015 LEEDuser Expert 15358 Thumbs Up

Ryan,
If the file cabinet is just a piece of furniture that can be moved, then it does not have to be considered in the calculations. So you could use the 30". I would recommend not putting furniture in front of windows plus why would you design a façade like that only to cover it up.

Moving on, you would only use the 63 degree angle if there is some sort of overhang on the exterior or there is soffit near the window wall. In your case, you can use 2H starting at 8'-10".

When calculating glazing area, you only calculate the area of the glazing, all framework and large mullions should be excluded. Now if you have small mullions that you might find on a residential type window, you could just measure the glass within the frame, it would not really effect anything.

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Ryan Favier Feb 06 2015 LEEDuser Member 33 Thumbs Up

I appreciate the reply but the design commentary is not necessary; it's an interior fit-out of a 30 year old building that may or may not have fit the storage needs of the client.

Moving on...
The reality is, the file cabinets nor will any of the workstations up against the window will ever be moved without the use of special tools or assistance from multiple people. That said, can they still be used in the calculations?

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Todd Reed Daylight Designer, 7group Feb 06 2015 LEEDuser Expert 15358 Thumbs Up

Being new to LEEDuser, people are here to help one another with their experience and knowledge and sometimes may make suggestions. We are professionals, at least I hope we all are, therefore we take suggestions and sometimes comments professionally, especially in threads where all of the information is not given. When we are wrong we admit and graciously accept the corrections, because its about providing the correct answer to all users.

I would like to direct you to the following page;http://www.usgbc.org/glossary/39#letterm

There you will find USGBC's definitions of furniture and furnishings, modular and moveable casework, and movable furniture and partitionsMovable furniture and partitions are those that can be moved to provide access to the view by the user without the need for tools or assistance from special trades and facilities management.. Cubicles, even ones that require a few bolts to be removed to move it is considered non-permanent. Filing cabinets, eventhough you are saying they will never ever be moved once placed does not mean that they are permanent.

Based on what you have described and to the best of my understanding of how the space is used, you can use the 30" as your starting height for the glazing. I'm saying this because the furniture and the workstations do not meet the definition of permanent.

I hope that has answered you question.

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Library Resources Librarian Lord, Aeck & Sargent
Oct 02 2014
LEEDuser Member
163 Thumbs Up

Option 3 - Measurement

Project Location: United States

Is the minimum foot candles for CI 10 or 25? The credit language here says a range of minimum daylight illumination level 10 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) but the reference guide says minimum daylight illumination level 25fc?

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Todd Reed Daylight Designer, 7group Oct 02 2014 LEEDuser Expert 15358 Thumbs Up

Its 10, the last addenda changed it from 25 to 10.

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Yasuhito Koike LEED AP, Green Building Consultant Izumi System Planning
May 01 2014
LEEDuser Member
184 Thumbs Up

net area vs gross area (simulation)

Hello,

I got a simple question and read most comments here and in NC, but it seems I cannot find a similar question.
In my understanding, the regularly occupied areas in IEQ 8.1 and 8.2 must be consistent to each other, and that should be net floor areas.
Also, to fill out the supplemental spreadsheet, you'll need to know the floor area, not only the ratio of daylight area between 10-500fc.

Now, if you use simulation method for 8.1, do you model a building with thick walls to get the result in net area? i.e. modelling the rooms and extra wall spaces? Or is it OK to model the building with single lines and run simulation (wall thickness = 0: gross area), then estimate the result in net area in any ways like; 1) multiplying the each area's result daylit ratio to its net area or 2) counting the calculation points within the net area space (excluding the points within walls/furniture/shelves) and re-calculate the daylit area? Is there any established method for that?

Alternatively, is calculating the gross areas for both credits in this case all right? - that may affect the result in negative way though.

I haven't submitted any project using IEQ8.1 simulation method yet and I appreciate to hear any thought about that.

Thank you.

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Todd Reed Daylight Designer, 7group May 01 2014 LEEDuser Expert 15358 Thumbs Up

The coordination that needs to occur is between the credits and PIF 3.In PIF 3 you have a gross area and the regularly occupied area. The regularly occupied area is the area used in your simulations. That area is not the net, do not consider the thickness of the wall, its the space between the walls that is modeled, the actual space that someone can stand in. Disregard your thoughts of estimating results vs. net. One last time, the regularly occupied column in PIF 3 in table PIF3-1 is the only area you need to worry about with 8.1 and 8.2. That area must be the same as that which is modeled.

As modeling goes, the thickness of wall should be considered when you have an opening, such as the exterior wall. Walls between adjacent spaces can be just one plain, and that is typical modeling protocol. The more surfaces, the more errors, the longer run times.

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Yasuhito Koike LEED AP, Green Building Consultant, Izumi System Planning May 01 2014 LEEDuser Member 184 Thumbs Up

Thank you for your prompt answer, Todd.

I thought the thickness of wall are not considered in simulation. Thank you for your clear explanation, that's really helpful for me. Thinking about that, it's really time consuming to model and calculate a building...

In the credit forms, there are "Total regularly occupied area" where figure is linked to Pif3 and "Total regularly occupied area documented in Upload L-8" that you fill in manually. I thought the former is a gross area and the latter is a net area (excluding space between the walls and other objects occupants do not stand in), and when I did so in my previous project, that was accepted by the reviewer.
The other areas we fill in in PIF forms are gorss, so it is little uncomfortable to use net area only for regularly occupied area in PIF3. I think it is not a problem if we use gross area in PIF3 and net area in 8.1 and 8.2, if you can show the suggested spaces correspond to each other. But of course it's easier to use net area in PIF3 than explaining precisely about the different areas if the reviewer asked.
Has anyone ever had problem when using gross area in PIF3 and net area in 8.1/8.2?

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Anna Bak Ove Arup & Partners Int. Ltd Sp. z o.o. Oddzial w Polsce
Apr 23 2014
LEEDuser Member
256 Thumbs Up

Minimum daylight illuminance levels

Dear all,
Could you please clarify what is the minimum daylight illuminance level to be achieved using option 1 - computer simulation? The credit language sais 10fc. In the "Checklist" , last point under "schematic desig" it sais 25 fc. In the LEED referece Guide in "Calculations" section under "Option 1" it sais again 25fc as a minimum illumiannace level. Am I reading it wrong? Many thanks in advance.

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Todd Reed Daylight Designer, 7group Apr 23 2014 LEEDuser Expert 15358 Thumbs Up

The addenda posted in 2010 changed the minimum illuminance value to 10fc. So if you read the online version of the credit language you'll see 10fc, but an older version of the paper Reference Guide will not have the addenda in it.

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Anna Bak Ove Arup & Partners Int. Ltd Sp. z o.o. Oddzial w Polsce Apr 23 2014 LEEDuser Member 256 Thumbs Up

Great! Thanks for the quick reply:-) Regards!

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Mike Stopka Director of Sustainability Solomon Cordwell Buenz
Aug 16 2013
Guest
752 Thumbs Up

Older existing building - no VLT available

Has anyone else experienced this?

We are doing a Commercial Interiors project in a building that was constructed in the 1950s. The Building Manager/Engineer has no clue what the glass type/vlt is.

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Todd Reed Daylight Designer, 7group Aug 16 2013 LEEDuser Expert 15358 Thumbs Up

Two ways to go about this; 1.If the windows can be opened, then use a light meter with the window open to get your base, close it and take a reading on the inside of the glass. Should get a rough idea of the VLT. Taking a reading inside and then walking outside will be less effective since the sky illuminance changes frequently. That is if its a long walk to the outside.

We have tested this with a known VLT piece of glass and a good meter and have been within 5% of the actual VLT.

2.Use table A8.2 in 90.1 as a default value for your VLTs. Its a valid methodology.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Aug 19 2013 LEEDuser Expert 6663 Thumbs Up

This is pretty common actually. You could try putting the engineer on the spot and asking them what they would do if they had to replace a broken window. Depends on your relationship with them. Of course, this might not work because they might have a different answer if they have a broken piece of window to work with.

Todd lists some good methods for estimating.

Todd, do you think that ASHRAE 90.1 is a good source for default VLT in this case? Are you suggesting using the current version of 90.1 or the version for when the building was built? I believe the first version didn't come out until 1975.

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Todd Reed Daylight Designer, 7group Aug 19 2013 LEEDuser Expert 15358 Thumbs Up

Jill,
I personally would not use the ASHRAE values, but would attempt the measurement option; especially with older buildings and especially if I'm doing daylight analysis. But, using the ASHRAE method is acceptable in EAp2, so there would not be any question in regards to using these values for the daylighting calculations. If you are just documenting the credit and not trying to change the daylighting performance of the space, then this might be an easy option.

The more recent version of ASHRAE is probably more reflectant of values of the glass we currently run across in windows from the past decade or two. Not sure whether there is a table like that in the older ASHRAE versions. But, for LEED purposes, i can;t see an argument to not using the most recent version.

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Stantec Inc. Stantec, Inc.
Aug 07 2013
LEEDuser Member
532 Thumbs Up

Open office - do I count the inner offices & meeting rooms?

I am doing the calculations for 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. method" for Daylight and Views credit. It is an office floorplate that is roughly 150'x150' with an inner core. The perimeter is all open workstations and hugging the core are private offices and meeting rooms.

Can I include the inner meeting rooms/offices in the calculations given that they have glass demountable paritions? Referencing an earlier comment: "A good rule of thumb for daylighting and the LEED daylighting credit is that usable daylighting reaches back into a space about 1.5 - 2 times the head height of the window." from Jill makes me think that they would have a daylit area of 0 and a daylight factor of 0% considering daylight would never reach this deep into the floor plate.

Please advise if I presume these areas never receive daylight and score them a 0, or do I calculate based on the amount of glass that receivs views and maybe some daylighting from the exterior glazing.

Thanks!

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Todd Reed Daylight Designer, 7group Aug 07 2013 LEEDuser Expert 15358 Thumbs Up

You mean the prescriptive method? This is CI 2009 which does not have the DF option.

If the glass partitions require the use of tools and staff, then the spaces they enclose would need to be included in your calculations. But you cannot use the prescriptive of 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. method when a borrowed light scenario comes into play. You did not mention your window head height, so its hard to say as to whether those spaces would be impacted. by daylight or not. I doubt they would fall within the depth of the daylight zone, so that would be considered as having 0, their square footage would still be considered in the overall regularly occupied square footage.

The rule of thumb mentioned by Jill is a design rule of thumb. Its to give designers a basis when determining head heights to space depth. In general a south facing space will have an area, 1.5 - 2 times the window head height that may receive a level of daylight illuminance that would be enough for some tasks. Many more factors come into play. It is is just a starting point.

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John Steingraeber Designer James Dayton Design, Ltd.
Jun 07 2013
Guest
69 Thumbs Up

translucent privacy glazing & EQc8.1 / 8.2

We are pursuing LEED CI certification for a client who has requested the application of translucent window film in some spaces for security concerns. You can see through the film, but the result is quite blurry. Will this affect our ability to pursue view-related credits?

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Todd Reed Daylight Designer, 7group Jun 10 2013 LEEDuser Expert 15358 Thumbs Up

Yes, views need to be through clear glass. Views through fritted or translucent glass is not acceptable since the view would be obscured.

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Petr Vogel Specialist Consultant EkoWATT CZ
Apr 13 2013
Guest
491 Thumbs Up

Tenant Lease Agreement - Interior glare protection

Dear all,
when assuming interior blinds to allow glare control in tenant spaces. Does the condition of installing blinds have to be included in the Tenant and Lease Agreement? Credit IEQc8.1 is not listed in Appendix 4 of the Reference Guide.
Thanks for any kind of help.

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Todd Reed Daylight Designer, 7group Apr 15 2013 LEEDuser Expert 15358 Thumbs Up

If the owner is not providing them, then the requirement would fall to the tenant and have to be noted in the lease agreement to ensure the daylighting requirements are still met.

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Marco Abdallah
Feb 15 2013
Guest
978 Thumbs Up

window-to-floor-area: including frame?

Does the window area consider the whole assembly including the frame or just the non-opaque area (glass)?

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Todd Reed Daylight Designer, 7group Feb 15 2013 LEEDuser Expert 15358 Thumbs Up

Just the area of the transparent glazing.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 15 2013 LEEDuser Expert 6663 Thumbs Up

I have always done just the overall window rough-in dimensions.

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Marco Abdallah Feb 15 2013 Guest 978 Thumbs Up

"I have always done just the overall window rough-in dimensions." That means for me also opaque elements, which is in my opinion against the intent of the credit. But I can not find a official statement to this issue...

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Todd Reed Daylight Designer, 7group Feb 15 2013 LEEDuser Expert 15358 Thumbs Up

The reason you cannot find any official statement on this is because why would you take credit for opaque area which does not provide daylight to a space? You can say its against the intent of the credit. Is there anyway in which a reviewer could determine whether you are doing this or not?, No, unless you provide CAD files that can be measured.

Well if you are using the opaque elements of the window such as mullions and frames, then you should be reducing the VLT you are using because you are taking credit for an area which is not providing daylight to the space. Modeling protocol would be:

 the area of the sills, jambs, and mullions can be calculated and summed into an ‘occlusion area’. Then the net window area can be calculated and the ratio of the occluded area relative to the rough opening determined (occlusion area/gross window area = reduction factor). Then, the gross window area can be simulated with the reduction factor applied to the VLT of the specified glass. (E.G., If the gross window area or rough opening is equal to 100 square feet and the occlusion area is 5 square feet; a 5% reduction factor is applied to the VLT of the glass. Therefore glass with 70% VLT X 95% = 66.5% VLT.)
 When window framing details are not known, a 20% reduction factor should be assumed relative to the rough opening. For skylights, a 10% reduction factor should be assumed relative to the rough opening.

Would a typical mullion of like 1 inch make a difference, probably not, but larger frames of store fronts and curtain walls it would be.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 15 2013 LEEDuser Expert 6663 Thumbs Up

Not to worry. No one is trying to "take credit for opaque area which does not provide daylight to a space."

If we can all agree that: 1. LEED is not the authority on daylighting, 2. the prescriptive method is intended as an easy, cheap way to determine credit compliance and not daylighting aptitude (an important distinction), and 3. the prescriptive method is crude, then I submit that it is not the intent of the prescriptive method that the design team spend their time calculating the area of every window pane, but that it is assumed by the creators of the prescriptive method that all windows have frames and mullions.

This forum is for LEED users. My statement is intended to help users use LEED. Reviewers have always had the option to review my calculations with drawings or to ask for more drawings to do so.

This is similar to the confusion over the simulation option and what it means to meet the minimum footcandle level at 3pm and 9pm. Even though it seems to me that the 75% should be met only with points that meet at both times, reviewers haven't been responding that way. It is all in the interpretation. I'm letting people know that reviewers have been responding to my interpretation that a certain amount of occlusion is already included in the prescriptive method.

I'm not sure where the 20% for windows or 10% for skylights comes from? Can you enlighten me?

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Todd Reed Daylight Designer, 7group Feb 15 2013 LEEDuser Expert 15358 Thumbs Up

I don;t worry whether people take credit or not. Much of the information provided must be accepted because we are all professionals who put our names on the results. Just like no one ever manipulates simulation parameters or other tweeks which cannot be asked for by the reviewer unless there is an unquestionable issue that has been submitted. It must be assumed that everyone is doing it the right way and are honest. There are a number of projects that have earned the daylight credit over the many versions that are very farFloor-area ratio is the density of nonresidential land use, exclusive of parking, measured as the total nonresidential building floor area divided by the total buildable land area available for nonresidential structures. For example, on a site with 10,000 square feet (930 square meters) of buildable land area, an FAR of 1.0 would be 10,000 square feet (930 square meters) of building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet (1395 square meters), an FAR of 2.0 would be 20,000 square feet (1860 square meters), and an FAR of 0.5 would be 5,000 square feet (465 square meters). from what many of us in the industry would consider well. if even daylit. But their case studies spout that their building is daylit and has earned the credit.

I agree with all you said, x4.

Reviewers don;t really have that option anymore of just calling out items that look questionable and asking for documentation that is not required. The days of credits being audited, just to be audited are in the past and to get documentation that is not required submitted needs to have pretty definitive case presented to get it.

Jill, the info i submitted is from a draft of a document that will probably be published here within a few months and has been the work of many daylight industry practitioners to create consistency across the board. I can;t specifically say how the 20 and 10% was established since i was not one of the contributors. But i'll try to find out.

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Adam Targowski Owner ATsec
Jan 17 2013
Guest
2440 Thumbs Up

option 3 requirements

Are there any requirements regarding the time of the day when the daylight measurements have to be taken?

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Todd Reed Daylight Designer, 7group Jan 17 2013 LEEDuser Expert 15358 Thumbs Up

There are no requirements as to when you should take the measurements. I would suggest that you take in under clear skies as close to solar noon as possible and near one of the equinoxes.

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Jeremy Theodore Senior Project Architect SHW Group
Jan 03 2013
Guest
175 Thumbs Up

Measurement Method - Submittal Semantics

From anything I have read, Credit IEc8.1 is a design credit, which would obviously suggest it be submitted with the "design" submittal in a split submittal.

It however offers the option to measure daylight in the space, which for a new or renovated space (like ours) would have to occur after construction is complete, suggesting it will not be done in the normal timeline for submitting the "design" credits.

In short, how is this handled in the current submittal system, assuming we have a split design/construction submittal?

Do you submit the form with the measurement option checked as part of the design submittal package, but add an uploaded narrative that states the credit is 'deferred' to the construction submittal? then resubmit with the construction package?

Or is there a way to designate it rather as part of the "construction" package, and just submit it then?

Another semantic method?

Will the selection of the measurement option hold up the design submittal review in any way? Which then might hold up the construction submittal, since it can't be submitted until the design submittal results have been accepted by the design team?

We are trying to avoid any reasons for delay in our process, thanks for any thoughts.

.

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Todd Reed Daylight Designer, 7group Jan 03 2013 LEEDuser Expert 15358 Thumbs Up

Under the Timeline Tab, Submittal Review, you will select credits which are complete for review. So to defer EQc8.1, do not select it to be submitted for review for the design review. When time to submit the construction review, select it for submission along with the other credit.

This also explained if you select help in the quick links when in the credit information tab.

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cecilia uri architect ffkr Architects
Jan 26 2012
Guest
56 Thumbs Up

WFR question

I am working on a project wehre the offices are bout 140 sq ft, the window is 5'x5' and the VLT is .70... I am not achieving the credit 8.1 with the prescriptive method...Do I use the full 100% of the 140 sqft or only 75% of the 140 sq ft? LEED NC 2009
Thank you!

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Todd Reed Daylight Designer, 7group Jan 27 2012 LEEDuser Expert 15358 Thumbs Up

You use the area in your daylight zone which is either determined by 2x the window height for the depth, or if there is an obstruction, i believe it is then a 63 degree angle. This is the area that is used in the calculations.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Jan 27 2012 LEEDuser Expert 6663 Thumbs Up

Cecillia,

See this guide by LEEDuser. http://www.leeduser.com/credit/NC-2009/IEQc8.1#doc-tab

And page 400 of this "Addendum Details". https://www.usgbc.org/ShowFile.aspx?DocumentID=9377

You use the floor area that makes the result come out between 0.150 and 0.180. If your initial result using the 140 sf comes out above 0.180, none of the area complies. If it comes out below 0.150, adjust the depth of your floor area down until the result is above 0.150. This is the area of the room that complies that you enter into the spreadsheet. You can break up the space how you like as long as each one is connected to a perimeter zone with a window.

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Adam Barker Feb 08 2012 Guest 168 Thumbs Up

Jill Dalglish wrote: "You use the floor area that makes the result come out between 0.150 and 0.180. If your initial result using the 140 sf comes out above 0.180, none of the area complies. If it comes out below 0.150, adjust the depth of your floor area down until the result is above 0.150."

Jill, just to clarify, are you saying that we are allowed to adjust 'bayA bay is a component of a standard, rectilinear building design. It is the open area defined by a building element such as columns or a window. Typically, there are multiple identical bays in succession. depth to core' as much as we want until we get a value between 0.15 and 0.18? Can you please clarify a bit if you don't mind, as this has not been my interpretation in the past - rather it has been that the depth is 2 x the wall height, or less based on a 63 deg angle if there is a dropped ceiling or other obstruction. This has always produced wildly different values for each zone, often out of the 0.15-0.18 range. As a result we have basically given up on the prescriptive path as it is farFloor-area ratio is the density of nonresidential land use, exclusive of parking, measured as the total nonresidential building floor area divided by the total buildable land area available for nonresidential structures. For example, on a site with 10,000 square feet (930 square meters) of buildable land area, an FAR of 1.0 would be 10,000 square feet (930 square meters) of building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet (1395 square meters), an FAR of 2.0 would be 20,000 square feet (1860 square meters), and an FAR of 0.5 would be 5,000 square feet (465 square meters). too rigid. If we have no control over the bay area or window area, we would basically need a different TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380–780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing. for each zone, which is unrealistic. We have instead tried to learn Ecotect / Radiance to show compliance (which I think is more accurate / fun, but much more time consuming, and a big disappointment if you put in several hours of work just to see that you don't meet). In fact I have considered the rigidness of the prescriptive path is the US/CAGBCs way of saying "sure you can do it this way..but don't waste your time, it wont work unless you have a square box). If you are saying otherwise this may change a lot of our approach!

FYI, I am in Canada and using the LEED Canada Reference Guide, which is even more vague than the US version on this credit, proving to be very frustrating. As far as I can tell, our Ref Guide gives no indication to being able to adjust the bay area.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 09 2012 LEEDuser Expert 6663 Thumbs Up

As much as I would rather be encouraging use of simulation instead because it is much more informative, I do understand that it is more costly than the prescriptive method.

So, the answer is Yes, and I finally found the link to the document again from LEED where I had originally seen it. Click here: https://www.usgbc.org/ShowFile.aspx?DocumentID=9377 then go to page 400. A little more than half way down the page, it says "If the result is between 0.150 and 0.180 the space counts as a daylight zone. If the result is between 0.000 and 0.150, a portion of the space is [compliant]. Calculate the [compliant] floor area as follows: Divide the calculated result by 0.150 and multiply by the floor area of the space. This fractional result represents the floor area to be counted as qualifying daylight area." This math is basically shrinking the area of the bayA bay is a component of a standard, rectilinear building design. It is the open area defined by a building element such as columns or a window. Typically, there are multiple identical bays in succession. to the point where it just meets 0.150.

There is no calculation solution for if you are over 0.180. You will need to modify your design to get it under the 0.180. And, I would say that if you are over the 0.180, you are *definitely* over-lighting with daylight and the project would benefit greatly from a re-design.

You still need to do the 63 degree calculation to determine your eligible head height.

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Todd Reed Daylight Designer, 7group Feb 09 2012 LEEDuser Expert 15358 Thumbs Up

What is your backing for saying that a space is definitely over-lighted when only using the prescriptive path? This is not to start any issues, (just a professional discussion) but since this method considers nothing in relation to climate, location, orientation, etc. and you have found a study or have yourself some examples that would make the number 0.180 a daylighting benchmark, i would like to know.

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Adam Barker Feb 10 2012 Guest 168 Thumbs Up

Jill,

Thanks a lot for the clarification ,that really hopes. Now to determine whether or not the CAGBC will accept this method.

We re-ran our prescriptive calcs for a MURB building using this method and are finding that the TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380–780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing. which gives us the most compliant area is 0.31. This seems really low to me. In fact, I rarely see below 0.65 or so with a reasonable SC we like to see. Is this is a Tvis you would expect?

It seems to me that by allowing this method when you are below 0.15, and not when you are above 0.18, they are placing a real emphasis on glare reduction. I can't understand why glare is such an issue in these calculations, especially when they mandate glare control anyways. Anyone have any insight into this?

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 10 2012 LEEDuser Expert 6663 Thumbs Up

Todd, I am basing it on Cecilia's original question regarding a 140sf office with 0.7 TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380–780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing.. It is my professional opinion based on experience that in most climates, locations and orientations, this office does not NEED 36 sf of 0.7 VLT glazing for adequate daylight. In fact, I'm surprised that the original design with a 25 sf window doesn't comply. I can see an argument based on certain climates, locations, orientations, window and ceiling layouts where it might not be overlit. Again, the prescriptive method is a very poor method for evaluating daylighting, which I know you agree with. But, I do think that, just based on experience, if you achieve the 0.180 in the calculation, in most situations, you can do with reducing window size or VLT. Going the other direction is not as easy as I can see a lot of cases where a good daylighting design will come under the 0.150. What is your experience?

Ciaran, all of this information can be dug up from the usgbc.org web site. The link actually refers to the 5 May 11 addendum, not the full reference guide.

Adam, the glare control they require is for direct glare. I think what they are trying to accomplish with the restriction on going over the recommended VLT*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. is more of a "quantity" glare avoidance meaning that glare can come from high contrast but also purely high quantity of light. Here in Colorado, I only recommend VLT above about 40% for north facades, but I can see in Canada why you might want a higher corresponding SC value. I have seen VLT installed here at 18% facing south that almost looked too bright. It is all relative once you get inside the building and your eyes have adjusted to ambient levels (to a point.)

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Todd Reed Daylight Designer, 7group Feb 10 2012 LEEDuser Expert 15358 Thumbs Up

Thanks Jill,
I have found and have data from our own projects, both simulations and actual measurements, that many of the spaces would not earn the credit using the prescriptive path, yet are exemplary in simulations. We have gone back and done measurements in a few of our projects to verify our simulation methods and these spaces are meeting the requirements in overcast skies (measured) for about 50% of the space. Which was the design strategy in which we implemented.

Ciaran,
The prescriptive method is really meant for projects that are not truly integrating daylight into the design. You are correct that to meet it, you have to have these very low VLTs. Understand this prescriptive path is somewhat based on ASHRAEs' method of establishing the percentage window to wall ratio to reduce solar heat. (I believe it was ASHRAE) So a project not really considering the multiple factors of the impact of the sun on the building are somewhat forced into these low VLT type glazings.

Jill,
18% VLT and it was too bright? I know the air is thinner there, but that is like wearing sunglasses.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 15 2012 LEEDuser Expert 6663 Thumbs Up

I did say "almost" too bright. Can you say that you've never had your sunglasses on and still had more than enough light? The view windows on this EnergySmart high school have a VLT of 18%. http://www.psd.k12.co.us/school/fossil-ridge-high-school

The windows on this fairly new high rise alternate between 20% and 8% (eight percent) VLT. When I was there and before I knew what the VLT's were, I guessed that the 8% glazing was 30%. http://www.xcelenergy.com/staticfiles/xe/Marketing/Files/CO-Bus-EDA-1800...

IT ALL DEPENDS ON HOW YOUR EYES ARE ADJUSTED. On an average day, if there are 5,000 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. outside, 8% of that is 400 fc, right? Now, that is right inside the glass, but to look through it, it doesn't look dark.

Don't be afraid to lower your VLT and correspondingly your SHGCSolar heat gain coefficient (SHGC): The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. and save on cooling load. Prove it to yourself first by visiting buildings with low VLT and low SHGC.

Todd, what I was asking was, in your experience have you seen a space that was over the 0.180 by a prescriptive calc, and would be hurt lighting level-wise by cutting back on window area or lowering VLT?

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Todd Reed Daylight Designer, 7group Feb 16 2012 LEEDuser Expert 15358 Thumbs Up

Jill I have yet to use the prescriptive method in any of our projects so i cannot say that a space that is over 0.18 would be hurt by lowering the VLTs. I know many of our spaces would not meet the 0.15, yet are well daylit spaces from many aspects. So based on that i can see where a space over 0.18 would not be effected in providing adequate daylight by reducing one or both factors. Its worse to be over daylit then under daylit.

I;m not convinced on those very low VLT glazings. So you get a SHGCSolar heat gain coefficient (SHGC): The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. of below 0.20 with such low VLT. I can use a VLT of between 60 and 70 and get a SHGC of between 0.25 and 0.30. In our experience and how we do things is that we bounce between the daylight sims and energy models on this matter to find the correct glazing that meets both the energy and daylight goals. What we have found is that once you get below a certain SHGC, the difference is negligible (weighing in other factors). The big difference is the savings from daylighting, and those low VLTs will not get you them. Everyone forgets about the frame and when you have a high performance glass in a cheap conductive frame you are not helping yourseld at all. There are so many variables and that is why cookie cutter buildings don;t work.

I have been in many buildings with these super low VLT glazings and i have yet to be in one where the lights where not on when the sun was out. Secondly the actual quality of view is dramatically decreased. Occupants in those spaces experience a dramatic difference between interior and exterior lighting levels. There have been studies on this and the next version of LEED is proposing a VLT lower limit to even earn the views credit.

I will say that is really dependent on the location and what the target daylight levels are. So if you are meeting what you targeted and have provided a good daylit environment for your occupants, then you have done the right thing.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 16 2012 LEEDuser Expert 6663 Thumbs Up

A lower SHGCSolar heat gain coefficient (SHGC): The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. is only one reason for a using a lower VLT. The other is to not overpower the electric lighting design. It is very difficult to daylight most spaces 100% of the occupied hours. Therefore, you will be using some electric lighting to augment the daylighting. However, if you have 400 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. on the wall next to the window and 100 fc on the wall away from the windows, the wall with 100 fc will appear dark and most occupants will want to turn on the lights in this situation. For this reason, lower VLT can result in higher daylight harvesting.

I'm not saying that low VLT's are appropriate in all cases. I'm just saying that they should be considered.

I'm not sure why you brought the frame into the conversation. Are you saying this affects the VLT somehow?

I have been in these buildings in many cases where the lights are off and the daylighting is nicely balanced across the space. I invite you to come out and experience them. Come up to the 20th floor of the Xcel Energy building and I will show you the beautiful view of the Rocky Mountains through the 8% and 20% VLT glazing. The view is not diminished.

I would like to read the studies you are referring to. Can you tell me where I can find them? Of course there is a dramatic difference between interior and exterior lighting, there usually is. What is the harm in this?

Thanks for the discussion! This is fun!

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Todd Reed Daylight Designer, 7group Feb 16 2012 LEEDuser Expert 15358 Thumbs Up

Jill I will glady take you up on coming out to Colorado to experience the scenery and the buildings so when i get the chance i shall.

I brought in the frames because it seems that when the discussion of energy and daylight is brought about they are not discussed as much as they should. It is all part of the system . So it was added topic in this great discussion.

I see, and agree about the contrast levels with the lower VLT used. An interesting concept in balancing out the daylight in spaces where daylight levels cannot be reached at the back of the space. So rather than overpower the occupant within 10 feet of the window wall just to meet 25 fcs near the back of the space. Use the electric light to make up the difference and provide all occupants a comfortable environment.

The Excel building has floor to ceiling glass, so the VLT is going to have to be lower, agree and see where you went this. Again, its about balancing all aspects together to achieve the goals set. I would not have recommended anything in high VLT range. My reference of 60-70 VLT would be for a project with an established sill height with a window to floor ratio of between 10-20% depending on the orientation. This would be to start.

Completely agree that you cannot daylight a space 100% of the time and meet all the other requirements without the aid of electric light. In fact daylight and electric light should work in harmony to achieve the required daylight and contrast levels.

I will dig up those reports that i have read on the quality of views and post them. I have also had discussion with others about the clarity of glass and the effects of visual quality. Its not that the view is obscured or blurred, it is the idea about the amount of light received by the eye and the reduction in the subtleties that occur with daylight as the sky changes and the sun moves. The basic idea is to provide a view to the exterior that is as close as it could be if you were outside. This relates to biophilia.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 20 2012 LEEDuser Expert 6663 Thumbs Up

To be clear, I am not responsible for the Xcel Energy building but I have been in it with the glazing supplier.

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Todd Reed Daylight Designer, 7group Feb 21 2012 LEEDuser Expert 15358 Thumbs Up

Jill,
Two reports and a book,
A room wit a view: A review of the effects of windows on work and well being."

Heschong and Mahone" windows in office 2.6.10, page 120 in the results. However, you have to read alot of the report to come to the their conclusion on this.

Biophilic Design, Chapter 15, and the sections on windows.

There is one i read and of course i did not bookmark it or save it to our library, that really had some specifics on the effects of lower VLT glass and view.

One question with the Excel building, how is the view at night from the interior to the exterior? Sometimes, depending on the actually property of the glass, the reflections at night for one looking from the inside is terrible, its like looking in a mirror.

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Jill Dalglish, PE Senior Engineer, Dalglish Daylighting Feb 23 2012 LEEDuser Expert 6663 Thumbs Up

Thanks for the info.

A side note: "Xcel" is their misspelling, not mine.

I have not been in there at night. There is that potential.

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Denise Santini Principal Red Studio Inc. Architects
Jan 16 2012
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269 Thumbs Up

when to use prescriptive vs simulation

In what kind of space would you use a prescriptive method for calculating daylight. it seems as it only applies to open office spaces in a small floor plate. And daylight simulations are applied too all other layouts with offices? What do you think? Is this too quick of a generalization?

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Todd Reed Daylight Designer, 7group Jan 17 2012 LEEDuser Expert 15358 Thumbs Up

I would not say that the prescriptive method is a means to calculate daylight. It is a method that is used to determined whether a space meets a certain set of criteria that would provide adequate levels of light. Its like the older 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 where the area and property of the the space is used in a set formula to determine a number, nothing is based on any type of illuminance levels.

So if you are truly wanting to know the daylight levels of the space, simulations or actual measurements are the methods to use.

I would not use the prescriptive method if I designed a space which has exterior shading, light shelves, sloped ceilings, or any other implemented daylighting strategies. It, like you said, is just general.

If you have an open office space with just sidelighting, and or toplighting, and you just want to meet the credit requirement, then the precriptive method would be applicable.

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Denise Santini Principal Red Studio Inc. Architects
Jan 03 2012
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269 Thumbs Up

building depth and daylighting.

Hi all,

We have a project where the floor plate is 120'x120' with 12' high windows on 3 sides of floor plate. open offices as fully glazed private offices line the perimeter windows up to 45' into the floor plate. The center of the floor plate are support spaces like copy rooms/storage/etc. The client would like to know whether this type of space is qualified for LEED daylighting. We've never dealt with this depth and proportion of floor plate before for an office. We would suggest putting skylights in to add more daylighting into the deep offices at the back but otherwise it seems okay. I read the reference guide a couple of times though it doesn't mention anything about building depth it's quite intuitive that it should matter and that alternative daylight strategies need to come into play.

Can anyone point me in a direction where I can find information on building depth and daylight in the LEED CI 2009. Also, because this is the very beginnings of the project is there a quick and dirty way of measuring daylighting to ensure that we get the daylight points? I really don't want to go to a daylight simulation route as that can get tedious (unless someone knows how to do this quickly) I've looked into both software Radiance and Daysim and it makes my head spin.

Thanks,
D

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Todd Reed Daylight Designer, 7group Jan 03 2012 LEEDuser Expert 15358 Thumbs Up

I believe the prescriptive path would be what you want to follow to help you determine compliance if you don;t want to go with simulation.You would be using the daylight zone, which would be the depth from the window wall, twice the window height, or at a 63 degree angle.

From what you are saying, I'm assuming perimeter offices about 10 feet in depth, then a corridor with more interior offices. The prescriptive path will not work in shared daylighting scenarios, so only the offices along the perimeter can be looked at. If thats the case, you would probably need a bilateral daylighting scenario, which would be toplighting and sidelighting. Areas under skylights can be analyzed using the prescriptive path.

There are simulation programs which do not have such a large learning curve as those you have mentioned. SPOT is one which can do simply geometries. Not sure what other programs you are using or have. If you have AutoCadd, there is 3D Studio Max or Ecotect. The learning curve is not as large (my opinon) as others.

Since this project is in the earliest stage of design, i would use this opportunity to look at the daylight, not to earn a LEED credit, but to provide the best daylighting scenarios to the occupants and for energy savings. This requires more work in the design phase, and to be done correctly you really need to use simulation.

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