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.
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.
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.
The USGBC's IEQ Space Matrix has detailed guidance that is helpful for any spaces you aren't sure about.
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.
On LEED Online, in the credit, under credit resources.
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.
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.
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).
No. The only option in any of these cases will be the simulation or the measurement methods.
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.
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.
A Chartwell schools classroom with abundant daylight and electric light controlled by a photo sensor. Photo – EHDDLocate classrooms and other regularly occupied spaces near perimeter glazing, courtyards, or other daylight sources. Support areas such as restrooms, storage, and areas that do not require or would be hindered by windows, such as restrooms, storage areas, and transitions can be located near the building core.
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.
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.
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.
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.
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.
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.
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.
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.
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.
Excerpted from LEED 2009 for Schools New Construction and Major Renovations
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.
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.
For sidelighting zones:
For toplighting zones:
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.
Any of the above calculation methods may be combined to document the minimum daylight illumination in the applicable spaces.
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; 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.
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.
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.
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.
This is a database of window brands, VLT and U-values for different glazing manufacturers. The program provides a versatile heat transfer analysis method.
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.
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.
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.
This is a comprehensive list of modeling tools compiled by the U.S. Department of Energy.
This daylight modeling tool is widely accepted in the lighting industry.
SketchUp is used to create 3-D graphic models that can help in your daylighting analysis and documentation.
This is a lighting group that has published research on the effects of daylighting.
This is the organization that sets lighting standards. The IES also works directly with ASHRAE to develop energy standards.
This is a case study for the effects of daylighting on productivity in schools. Prepared by Heschong Mahone Group for the California Energy Commission.
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.
This is a case study for the effects of daylighting on productivity in schools. Prepared by Heschong Mahone Group.
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.
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.
Sample LEED Online forms for all rating systems and versions are available on the USGBC website.
Documentation for this credit can be part of a Design Phase submittal.
I am assuming the daylight modeling must utilize daylight savings time. Is this correct?
It doesn't say so in the text and since they chose two times of day that are equally offset from noon, I have always assumed it was standard time.
As Jill has noted, it does not state that it does nor will a reviewer ask whether daylight savings was used or not. I just use standard time, but you may find that when it comes to direct penetration issues that will put you over the 500fc level, your exterior shading my be off due to the time you used to calculate the length of the overhang. This depends on what you have used to calculate the suns positions, be it manual calcs or one of the many modeling programs out there.
The printed material states that the simulation threshold is 25fc but LEEDuser states there is a 10fc threshhold. Has this been revised?
Yes, it was revised.
Does LEED's "window area" take into account framing or is "window area" the actual glass area (excluding framing)?
Its the actual amount of glass, minus frames.
I'm working on a Auditorium and classroom addition for a High School. I have to use Option 3 and want to get clarification on the theater space. On page 559 it states "Dedicated theater spaces (not multipurpose rooms) must meet an illuminance of 10 footcandles, as recommended in the IESNA Lighting Handbook Reference and Application". I'm assuming the "Auditorium" in this case would be classified as a "theater", does that seem appropriate? I've been in a number of school theaters and I cannot think of one that had windows. For this project, it appears the "Auditorium" will eliminate this credit. Any thoughts?
If you download the IEQ space matrix from the USGBC website it says that auditoriums and theaters may be excluded from EQc8 credit calculations. There is a note similar to the one you posted but it says "Dedicated theater space can qualify as a daylit space in credit calculations if the daylight design meets the recommended illuminance of 10 footcandles as noted in the IESNA Lighting Handbook Reference & Application. Dedicated theater space may be excluded from EQc8.2 calculations for access to views." You will not have to eliminate the credit from your project!
Lauren is correct.
I am hoping LEED removes this reference to the IESNA Handbook from the credit, as it is taken out of context. If you read further you will understand that the recommended illuminance is for the seating area of the auditorium and only while people are being seated, not during performances.
While the latest (October 2013) IEQ Space Matrix lists auditoriums as regularly occupied, they are NOT under the subheading of Educational Facilities but are standalone. Yet the Reference Guide (page 404 of the first edition) says that Auditoriums are Spaces Not Regularly Occupied. Does anyone have a definitive answer on whether auditoriums in a schools are regularly occupied or not? (What takes precedence the Reference Guide or the IEQ Space Matrix when there is a conflict?) If I just went by the Reference Guide, I would say auditoriums are not regularly occupied and hence the requirements for daylight do not apply. What am I missing?
Space Matrix takes precedent over the Reference Guide since the space matrix was developed to specifically define what is and is not regularly occupied per credit. The matrix is also used and referenced by reviewers as the definitive answer to what is and is not required to be included. Exclusion of spaces is reviewed on a case by case basis. This is not coming from anyone one official or documentation from USGBC so I can;t say that is the final "Official" word.
They must be included, Y means yes. As noted with note 7 that dedicated theater spaces can achieve the minimum 10fc. Most high school auditoriums could be considered a dedicated theater space. Jill points out the issue with this reference that i agree with.
They are not considered core learning spacesCore learning spaces are spaces for educational activities where the primary functions are teaching and learning and where good speech communication is critical to a student's academic achievement. These spaces include, but are not limited to, classrooms, enclosed or open plan), instructional pods or activity areas, group instruction rooms, conference rooms, libraries, offices, speech clinics, offices used for educational purposes and music rooms for instruction, practice and performance. or classrooms, so when trying to achieve either 8.1, they fall under other spaces. So typically the square footage of this space does not hurt you with at least two points.
The space matrix is a good idea, but when the remove a space in one version and then include it in the next, it does cause problems. ie gymnaisums. Personally auditoriums are about acoustics and vision lines and should not have to be included as regularly occupied.
Todd - Thanks for your response. The issue of conflicting and problematic changes and updates is an ongoing obstacle to getting projects certified expediently.
Forgive my confusion; but Is the consensus: (a) that an auditorium is not considered regularly occupied and my be excluded or (b) that auditorium is considered a regularly occupied non-core learning space and must be included in that point's calculation or (c) it is the designer's discretion since reference note 7 in the Space Matrix says "can" not "must".
Also is there a difference between a theater and an auditorium for the purpose of this credit?
The answer is b. Auditoriums are considered regularly occupied. Dedicated theater spaces are not. The note is for reference to project team, kind of like an educational note that theatres can also have daylight.
For the purpose of LEED what is the difference between a theater and an auditorium? If we have a proscenium, theater lighting and effects and the necessity of blacking out the space but may also use the space for an assembly or concert; can I still classify it a theater?
What you have is an auditorium, a space that serves a multitude of services and what is typically found in schools. I have seen larger schools that have both a auditorium and also a theatre black box. Auditoriums can have shades or black out curtains to provide the necessary environment.
To name a space theatre or classify it as one, its sole use would have to be just theatrics, plays, and other performances that require complete control of the environment.
We received Construction Review comments that the areas reported in PIf3 do not correspond to the areas in IEQc8. We used the definition for 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.) (see http://www.leeduser.com/glossary) in PIf3, which measures the size of a room from exterior walls. As the middle of a wall can obviously not receive natural daylighting, our calculations for IEQc8 used the area of rooms based on their floor area measured from the internal walls. Has anyone ever come across this issue or received a similar comment? Would you recommend an explanatory note or recalculating IEQc8, so that the floor areas presented are in line with those of PIf3?
In PIF3 there is the occupied area table. One column is 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.), the other is regularly occupied area. The regularly occupied area is what is linked to EQc8.1&8.2. Regularly occupied is different than gross. So did the reviewer specifically state which areas? Are the regularly occupied areas within your calculations not adding up what is claimed in PIF3? If the only comment provided is what you have stated, i would definitely ask for specific clarification on this issue.
We are now trying to achieve this point by the measurement option.
There is no mention in the book at what time the daylight measurement should be taken.
Would someone be familiar as to what time the measurement needs to be taken, or can it be taken at any time?
Also, for this credit do all the windows require glare controls? And if so, do they need to be manually operated...such as roll down curtains?
There is not specific time to take the measurements. However, to get the most out of the measurements it is suggested that the measurements be taken under clear sky conditions as close to noon as possible.
All windows in all spaces being included in the calculations require some form glare control device such as roller shades. These need to be controlled either manually or automatically.
Todd on the Supplemental Daylight and Views Calculation Spreadsheet provided by USGBC, for Option 3 Measurement the "Glare Control Type" column is under "For spaces with illuminance levels above 500fc". For Option 2 Prescriptive the "Glare Control Type" column is under "For spaces with VLT x 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. > 0.18". In both options it looks like "Glare Control Type" information is only provided for spaces that have too much daylight and are too bright. Do we enter glare control for all spaces? I would think there would be some situations where glare control is not needed (small windows on the north side of the building or windows with a very low VLT eg: 0.4). Also, we cannot include spaces over 0.18 or 500fc so I do not understand what these columns are included for.
I'm currently trying to get clarification on this exact issue. I should have a solid answer within two weeks.
The daylight calculator is not consistent with the Reference Guide or the addenda from 5/09/11. Nowhere in any of the requirements does is state that "automated shades are required for spaces above the limits in all three options. This is what i have been trying to get consistent.
If you scroll over the the box it states " View preserving automated shares are required for 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. with daylight illuminance values above 500fc". It says automated, it says required. So based on that and how it is noted, you would have to provide automated shades. Automated, not manual.
Now what i have not confirmed yet is whether the average illuminance has to be over 500fc or whether just some calc points over 500fc would require shades to be installed. This is unclear and needs to be specific. This is one of my questions. If its just one point then you will need to install in almost all spaces. Spaces on the west, south , and east facades, even with exterior shading will always have a point or two over 500fc because of using both 9am and 3pm. Measurement option not likely.
With the prescriptive path, well, if your over 0.18 you need automated shades.
Now if you read the reference guide and the addenda, it states that glare control devices should be installed for high contrast scenarios. Well what type of glare, what level of glare, and what is considered high contrast? Do i reference IESNA and the definitions and contrast ratios? This is the issue i have, without specifically defining these values, one could argue whether or not shades are needed.
What we do, and this is based on own work, is have some form of shade installed in all spaces. Glare comes in all forms, natural and unnatural. Even though your space may look norht, what about reflections from cars, buildings, and even off of snow. What would the occupants be able to do then. Even though a space is facing north, and depending on the atmosphere condition, could cause discomfort. Occupant, every occupant is different as to what they believe is comfortable viewing. So by providing shades in all spaces, you cover all scenarios and occupant needs.
As 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). as to what to do with the shades as far as documentation, i say that the reference guide and addendas override any credit form or calculator. The credit form and calculator are just tools to help document.
Hope this helps.
From my experience, you only have to include glare control devices for spaces that surpass the 0.18 threshold. You can include these spaces as long as you have automated view-preserving shades. In the columns for glare control devices you would just write the type of shades and select "yes" for the view-preserving shades column.
I think only the spaces that go beyond 500fc have to have the shades, not every space based on an average. Is this what you're asking?
The issue is that the calculator is not clear on the issue as whether its based on an average of each space or whether its based on either individual calculation or measurement points. Its not clear. So if i have a space using simulations, and i have some area in the space that has over 500 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., do i need shades, or does the overall average.
Its all a little fuzzy with room for assumptions, which should not be. It needs to be clearly defined to be consistent.
I don't enter anything in the Glare Control Type or the "View Preserving Automated Shades?" question columns unless I have a space that reaches the upper thresholds (0.180 or 500 at any point in the space). It is assumed that if your calculations come in below these numbers that you don't have glare (a very bad assumption, but that is the way the credit is written.) You will notice that only an answer of Yes to the "View Preserving Automated Shades?" question transfers the sf that you have entered that is over the thresholds under "Floor Area with Daylight Illuminance Levels Above 500 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. (sf)" to the column "Total Daylighted Area, Measurement (sf)."
This means that you CAN include this space in your daylighted area if you have these shades and you cannot if you don't. This is also written directly into the credit.
I agree the wording of the credit needs clarification, that most everything trumps the spreadsheet tool, and that there needs to be greater consistency between them.
I don't see anything that would suggest an average value to me. The spreadsheet has two clear columns asking for floor area between 10-500 or over 500. I guess the words "for spaces with illuminance levels above 500" could be confusing, but because the Yes and No under "View Preserving Automated Shades?" act only on the "floor area above 500" column, this cannot mean average.
The words assume and assumption appear quite often in this discussion. When we are assuming one thing, and USGBC is assuming another, the outcome is only good if the assumption is the same. The issue is that no one should have to assume anything and this issue can be easily addressed. The original version of the calculator was quite clear, when they revised it in June 12, it got fuzzy.
Todd, Lauren and Jill,
Thank you for your timely responses and discussion on the topic. We do not have any automated shades, we only have interior manual shades and fixed exterior sunshades for glare control. What I understand from the discussion is if none of our spaces are over 0.18 or 500fc we do not have to complete the "Glare Control Type" column.
Todd when I scroll over the box on the spreadsheet I do not get message "View preserving automated shares are required for 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. with daylight luminance values above 500fc". As Jill points out SF over 0.18 and 500fc is included as daylighted area if you check yes to view preserving automated shades, but it is not included if you provide a description for glare control type (eg; exterior fixed sunshades) and check no or N/A to view preserving automated shades. The reference guide lists fixed exterior shading devices, exterior light shelves, interior light shelves, louvers, manual view preserving shades or operable draperies as common glare control devices. Does anyone know why the SF that utilizes these types of glare control does not count? By asking that question it occurred to me I should ask the next question, if you are pursuing the measurement option do you take measurements with the interior manual shades up or down? I had assumed you would measure with the shades up so the space would be the brightest.
I downloaded the latest version of the calculator in one of project that has just been recently registered. I get that note. Anyway, the reason you cannot include the square footage with the use of those glare control devices is because they are manual or fixed shading devices. Since you can;t trust the occupants to pull the blinds at a certain time, it doesn;t count.
Measure with the blinds up.
My whole issue is the wording which, with just clarification statements and some rewording would eliminate assumptions. When people are allowed to assume, there is no correct answer or the answer that is wanted is never obtained.
In addition to Tod's comment, the prescriptive method has many limitations. Does the exterior shading device help to reduce the glare? It is possible but the prescriptive method doesn't recognize that.
My suggestion is if you have fixed shading devices, you can use simple sketchup modelling to assess whether there is direct light that penetrates to the rooms. If there is none, the simulation method can be used. If there is direct light, it is highly likely the rooms won't comply even we run the simulation.
It is always recommended to bring a daylight expert in early design to assist the design process so he/she can provide design inputs and adjust the design. If it's too late in the design process, it is sometimes harder to make a justification because the architect and client will start questioning whether the point can be achieved without changing the design after they hire a daylight expert or run the simulations in the end of the design.
If the intent is to provide a good daylight design and go beyond LEED, the luminance study and glare index calculation can be used during the design.
Can someone please confirm the following.
If my window has a head height of 10 feet, then my zone floor area would be:
Twice the head height (20) times the length of the 60 degree line?
In this case if the 60 degree line was 20 feet long.....would the zone floor area be:
20x20=400 square feet?????
The depth of your zone is established by either twice the window height or if you have an overhang or interior obstruction then you must use the 60 degree angle which would intersect the lowest point of the overhang or interior obstruction. The length of the zone, side to side would be from wall to wall.
Gabriela, Are you the same Gabriela who posted a similar question under the NC board? If not, please see that board for a good discussion of this question. http://www.leeduser.com/credit/NC-2009/IEQc8.1
For the "glare control type"....can it be an overhang of a second floor, or a canopy that is used for glare control?
No, a glare control device must be able to be manually operated by the occupants or automatically controlled. If you have implemented exterior shading or other architectural elements to help control glare and provide good daylighting, i would suggest that you use the simulation option.
I disagree. I don't see any reason why you can't used fixed features for glare control. However, these features must shield the window from all direct glare for all occupied hours. Technically, even an extremely low TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380780 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. (usually accomplished with window obscuration) could block glare altogether.
I have had some long discussions about what is considered glare and glare control devices. I agree that overhangs or exterior shading devices can control some forms of glare, but in regards to someone using the prescriptive method, which is not orientation or climate based, how can it be proven that said devices do what it does. It can't. Therefore, with the prescriptive method, and even the other options, glare control devices are basically manual or automatic shades. The other reason GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC). consider shading devices shades is that many project probably do not take into account the effects of reflections, such as off facades of neighboring buildings and even windshields off cars in the parking lots. So a building may have exterior sun shades designed based on the sun path, but what do the occupants do when the sun is reflecting off a neighboring building or even off snow and they can;t block it?
I haven;t bought into the whole extreme low VLT solution to solve issues like these. The relation of the quality of view and the spectrum of light that the eye receives is very much connected to ones circadian rhythms and health. I will have to look for the study that i read awhile ago about the effects of the quantity of light that young adults are exposed to and its effects upon sleep. There is a part of the light spectrum which effects this. So if you were to use an extremely low VLT or obscure the view, this spectrum could be removed.
I'm a firm believer in providing as clear of glass and highest VLT possible. Make the inside as connected to the exterior as possible.
I didn't see "prescriptive option" listed in the question. True, you should not be using the prescriptive option if you are using fixed glare control.
Daylighting for quality and daylighting for LEED are two different discussions as much as you and I would like that it wasn't. I agree for quality daylighting that visual spectrum should be preserved as much as possible, but there are quality low VLT glazings that will do this. Personally, I would not recommend this for a majority of windows in a buliding, but if you can't locate blinds on, for example, a window in an overhead door, a low VLT could be an option and an energy-efficient one.
Applying a "highest VLT as possible" policy in all situations ignores the complexity of the human visual system especially in different space types and reduces options for energy-efficient glazing.
Having a view is addressed in the Views credit. An option such as low VLT glazing should not be eliminated in the daylighting credit when daylighting for LEED, especially if the views credit is not being attempted.
Gabriel G has been the one asking all about the prescriptive path, therefore the response was towards that option.
I agree on areas such as doors and other areas like that where harvesting views and daylight through is not critical, one needs to look more at the thermal performance. ie, glass stair towers.
To clarify, i wouldn;t recommend a VLT of 70% on a glass box in Dallas and also recommend that they not install blinds. But if by some chance they wanted a glass box and no blinds, then yes, i would say to balance the energy side and the daylighting side, that you have to go dark. But there are now some really good high VLT low U value and SHGCSolar heat gain coefficient (SHGC): The fraction of solar gain admitted through a window, expressed as a number between 0 and 1. glazings on the market.
Yes in LEED the views and daylight are separated, and if you design a to scorecard, well then you;ll look at them as separate elements and not as a whole as they should be. You can use a low VLT if you want but i won;t say that a certain level of VLT takes the place of a glare control device. By glare control device, i mean one that has the ability for all types of glare. I also think that there is a certain level of VLT where the view is not what is considered a quality view (the discussion of quality is a long one and has many opinions) I look at this way, the view you get wearing sunglasses is not the same you get without them. Same with the amount and quality of daylight.
I have a couple of questions concerning the prescriptive method for achieving LEED credit 8.1. We are doing LEED for schools.
*If my space has two windows, how do I add that to the excel sheet?
When I added a row for the additional window I need to add the square footage of the space again…..which means it doubles the area of the space for the total “total regularly occupied area”….right now its highlighting the cell as “red” because I am not repeating the square footage of the space.
*My VLTxWFR is greater than .18….so now I need to fill out three additional columns, my questions are:
-What is noted on the “glare control type column”
-For the “View preserving automated shades”….what I noticed is that when I mark this category as “yes” it takes into consideration the “zone floor area” under the “sidelighted area subtotal”…..my questions is when should I mark this column as “yes”.
For rooms with multiple windows, I normally just add up the window areas and put the total in just one row. GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC). won't question it when reviewing and it is the easiest way to go about including all windows.
If your VLTxWFR is great than 0.18, LEED 2009 now requires that automated view-preserving shades be installed to control daylight. You can only choose "yes" if the project actually has these. In some cases, daylight modeling helps to show the compliant space vs. non-compliant space, because the prescriptive method does not really allow this.
I only fill out the "glare control type column" if there is a "yes" in the automated shade column, or you can just write in "blinds" or whatever type of shading device the space has.
Hope this helps!
Group all you windows together on an orientation that have the same characteristics, VLTand height. This will give the glazing area. The daylight zone is then established, by either twice the head height or using the 60 degree angle. That gives you the depth of the zone. This will establish your VLTxWFR. Which i bet once you combine all your window together may not be over the 0.18.
Glare control is the type of shading and only check yes for automated shades when you actually have them in your project.
Personally, every space used in the daylight calculations should have some type of glare control, especially if the prescriptive path is being used. The prescriptive path cannot tell you if you have any glare conditions or even when they do happen. The prescriptive path cannot show direct sun penetration. So if you just follow the requirements as noted in the prescriptive path, you won;t put blinds in a space. Not good daylight design. Even spaces on the north side of building may experience a condition where shades are needed. How can you say your space or building is well daylit when only the prescriptive path is used? You can;t.
Lauren, you should group all your windows together if they are same, but if not, that is a different zone and you should not group them together. For example, you have six windows on the south wall. All six have the same head height, but the three on the left have a sill height of 12" and the other three have a sill height of 32". Technically, that is two zones, one for each group of three. Why, because the one half the space has more glazing than the other half, and if the same VLT, could actually be overdaylit, and therefore your VLTxWFR is over the 0.18 and therefore you need shades according to the the spreadsheet, well only for half the windows.
This is the stuff that I believe alot of people don;t do and it is hard for a reviewer to determine whether it has been done properly or not. I would question a space that only had one zone for the south facade and was shown two different types of windows.
My dilema is that I have a room that has two windows one on the north and one on the south (this happens for most of my rooms)....how do I then divide the area for that room if I can group the windows together on the south side.....I wish i could upload PDF's to this website....eeekk!
Technically you would have a zone on the north and a zone on the south. The zones can overlap. If you have alot of these rooms you could just do one and then extrapulate the info. Our do what i do, and just create your own so that you can easily manipulate the spreadsheet.
I'd have to see exactly what you have to help you further.
Thanks, Todd, for the tip. We haven't been questioned on this yet for a review but it is helpful to know for the future. I have been splitting up the zones if the TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380780 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. is different, although for most projects so 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). the windows have been located at the same height, with same area and all, so there wasn't a need to separate them.
In my opinion, twice the head height and/or the 60 or 63 degree line are not used to establish the daylight zone. They are only used to establish the applicable window head height. After that, similar windows dictate where you draw your zone lines. If your results are outside of the 0.150 and 0.180 parameters, a second evaluation needs to be done of the zone area. You can check out the NC board for more detail on this.
I'm trying to update the LEED daylight spreadsheet but it seems to be protected. I'm resubmitting after design review comments and I only want to make chnages to what I already submitted, not make an all-new spreadhseet. Any ideas?
Have you tried doing a save as to another file name? I have not seen it where it says file protected, but i usually just do my own so i don;t have to deal with issues like this.
I agree with Todd. It is probably because the file is still in read only mode when you downloaded. You need to download and save as with different name to ensure that you can edit.
If I use the daylight measurement method for IEQ 8.1, is there a certain time of day the measurements must be taken?
There is no required or specific time to take measurements to document this option. I would suggest to get the most out of taking the measurements other than for just documentation, that you take measurements under clear sky conditions at noon, as close to an equinox as possible.
Hello all! I do believe my questions have yet to be touched upon but apologize if i just missed a comment in this section.
1. I am currently attempting to use option 2 Prescriptive method and am curious if anyone has been able to submit different "work heights" for their calculations? As our rooms are mostly used by toddlers, infants and teachers working and sitting on the floor, it seems 30" is too high of work height. Has anyone made a similar argument and it has been accepted by LEED?
2. This idea 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. floor area slightly confuses me. Looking at the LEEDuser sample, it seems that through sort of arbitrary denotations of space, one can determine what windows light where and then these areas can be adjusted to have a compliant square footage and an uncompliant square footage. This is better than the all or nothing i was initially using to calculate each room but i'm still not sure this would apply to smaller classrooms that are only 600sq ft? I guess i dont see why not, just that it will be extremely time consuming to do this for each classroom.
3. In our design we use a lot of borrowed light through other spaces with interior windows. How would the VLT be calculated for that?
Thanks so much for any information,
The DW Arthur Team
Here is my opinion on your questions:
1. If you use prescriptive, there is no different in calculation for lower work plane. If you use simulation, it should be OK because that is actually the correct way.
2. In LEED calculation, the width is arbitrary. There is no requirement on that. The depth is actually the projection of your window head.
3. You can't use prescriptive for your case.
1.Where do you find work heights in the prescriptive option? They call out a height for the minimum window area as 30", is this what you mean. In that case, I can see an argument for lowering that to the seated height of your toddlers, but I don't know that it will make a huge difference in your calculations.
2. 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." stuff is confusing but the LEEDuser sample can be used in any type of space and space size.
3. You cannot use the prescriptive method for borrowed light. You do have the option of using the prescriptive method for the other areas and then using simulations for the borrowed light areas under Option 4. Combination.
I am currently using the prescriptive method supporting LEED calculator. Each classrooms have two types of VLT. One side window with 53% VLT that is located at one side of the room and another with 75% VLT located at the other side of the room. Right know since I just put only the windows with 53%, the classrooms doesn't not comply with the 75% daylit. I'm pretty sure if I add the windows that have the 75% VLT the classroom will comply with the requirement. My problem is that I don't know how to put the information in the spreedsheat. I though about taking an average between the VLT and sum all window areas but don't know if that approch will be accepted. My other alternative was to put first the room area, the window area with the correspondent VLT and add another row with the same room but changing the window area and VLT (the issue is that I will be duplicating room area) any thoughts, anyone?
Will appreciate any comment
I haven't run into this problem yet (it was easier to document the different VLTs in v2.2!) but maybe you can put them on separate lines. Instead of putting the same room area on each line, you can divide it based on what percentage of the room will receive daylight from one kind of window, and what percentage will receive daylight from the other kind. You can't know this for sure so it would have to be a good estimate. I wonder if that would work? Otherwise you might just have to do a daylight simulation.
The divide the room in half if you can. If the depth of the daylight zone from both sides is halfway, or even if they overlap, use the midpoint. Separate the classroom on two different lines but only for half the square footage. Label it accordingly and definitely provide a narrative on what you are doing. If the two zones do not touch at midpoint, i believe you can increase the depth of the zone, not decrease, increase the one until the two zones cover the total area.
The depth of the zone is driven by the height of the windows. Except they overlap, we cannot adjust the depth.
If they do not overlap, it will be easier. You can split into two floor area in any middle point in the area outside the zone floor areas. Each floor area has its own zone floor area. Because the zone floor area (a.k.a. daylight zone area) is always smaller or equal than the floor area, there will be no issue to split the rooms into two inputs.
I agreed with Todd for the midpoint if the daylight zones or zone floor areas overlap.
Does your project have a gymnasium that is used only for athletic, auditorium or stage uses? If so, your project may be able to exclude the gym from the credit requirements for IEQc8.1.
The USGBC released new space type classifications, available here: http://www.usgbc.org/DisplayPage.aspx?CMSPageID=220 under the Rating System page. Scroll down to the first item under IEQ, and open the excel spreadsheet. Read the Overview statement, and then click on the second tab at the bottom, "BD+C and ID+C Table". Look under Column X, Rows 48-49.
If the gym is also used as an assembly space, please also see Column X, Rows 10-13 to see if the assembly use would necessitate inclusion in the credit requirements. Gyms used for assembly purposes or social activities must be included in the credit requirements.
This is great news, but has the location changed? When I click on the link above I cannot find any items under IEQ. Do you need to select a Rating System first?
Lauren, try http://www.usgbc.org/resources/eq-space-type-matrix. I think the USGBC moved the location since 2012. If that doesn't work search for "EQ space type matrix" under Resources on the USGBC site.
Thanks. Found it, but this version says that gymnasiums must be included for EQc8.1 (Column R, Row 32 of the BD+C and ID+C MAtrix tab). Has anyone else been successful at excluding a gym from daylight calculations?
The last version of the space matrix, dated July 2012 had gymnasiums as being able to be excluded from the daylight calcs. This version they are back in as being required, as they should be.
What reason would there be to not provide daylight into a gymnasium. There are numerous strategies available that would let you provide adequate daylight into a gymnasium successfully.
This supplemental calculator Excel file only seems to create problems every time I used it! Right now, I'm trying to document the prescriptive method for toplighting, but the floor area isn't registering and summing in the total. I put in the floor area the skylight covers, the area of the skylight, and the TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380780 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. but nothing is happening. The spreadsheet caclulates the skylight coverage percentage, but nothing happens in the "toplighted area subtotal" column. Anyone know what else I need to do for this? I have used the calculator before using the simulation and sidelighitng prescriptive options, so I'm not sure what is wrong this time.
Sounds like a download issue, or an error in the script. Down load it again and save it some where else. I personally create my own spreadsheets that do the same thing as the one's available. This way it can be modified and i can correct any issues.
Lauren, if you can send me the spreadsheet, I can take a look on that.
Todd is correct that it may be the macros from the excel. I didn't have any problem using their spreadsheet last time but there was a formula error last time in one of them. I agree with Todd, if you can make your own, it's much better.
Thanks, Eddy. I figured out what is going on with the template. I am trying to get the toplighting percentage between 3 and 6 to comply, and am reducing the zone floor area to reach that number. The calculator is using the actual floor area, but I think that it should be using the zone floor area to calculate the toplighted area. Someone from GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC). has been helping me, but it's still not working! At least I know what is wrong now. Thank you!
It's good, Lauren.. You may need to double check though.. as I remember, the new amendment define that the zone floor area is the daylit area.
Trying to use Option 2 and I'm confused about Zone Floor Area in the spreadsheet. Isn't the ZFA for sidelighting the same as 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. floor area? And if that's the case, why does the top lighting zone have a different definition, one driven by ceilng height and distance to obstructions?
Is there a tutorial that shows how Option 2 areas are calculated? I'm kinda scratching my head here.
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