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.
Compliance paths for IEQc8.1 have some key differences between v2.2 and v2009. In LEED-NC v2.2, Option 1: Calcualation allows you to show compliance with EQc8.1 by demonstrating over 75% of the regularly occupied areas have a glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. of at least 2%. These glazing factor calculations consider window, wall, ceiling and floor areas, glazing type and VLT values.
In LEED-NC v2009, the glazing factor calculations option has been removed. In v2009, however, the Option 2: Prescriptive method provides a new approach to demonstrate achievement of the credit that considers many of the same factors as the glazing factor calculations from v2.2.
Another significant difference between v2009 and v2.2 is that v2009 allows for a combination of compliance path options to achieve the credit, via Option 4.
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.
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.
Simulation is the only way to account during the design phase for daylight designs that have many variables such as the use of lightshelves and light-colored interior finishes. The Glazing Factor Calculation path (Option 1) takes into account only walls, windows, floor and ceiling areas, and the measurement path (Option 3) will not help inform design as much.
Simulation is the only way to account during the design phase for daylight designs that have many variables such as the use of lightshelves and light-colored interior finishes. The Glazing Factor Calculation path (Option 1) takes into account only walls, windows, floor and ceiling areas, and the measurement path (Option 3) will not help inform design as much.
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 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.
Through 1 of the 4 options, achieve daylighting in at least the following spaces1:
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.
Use a combination of sidelighting and/or toplighting to achieve a total daylighting zone (the floor area meeting
the following requirements) that is at least 75% of all the regularly occupied spaces.
For sidelighting zones:
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; ly, additionally, automatic photocell-based controls can help to reduce energy use. Predict daylight factors via manual calculations or model daylighting strategies with a physical or computer model to assess footcandle levels and daylight factors achieved.
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 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 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 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 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.
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 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 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.
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.
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.
The following links take you to the public, informational versions of the dynamic LEED Online forms for each NC-2009 IEQ credit. You'll need to fill out the live versions of these forms on LEED Online for each credit you hope to earn.
Version 4 forms (newest):
Version 3 forms:
These links are posted by LEEDuser with USGBC's permission. USGBC has certain usage restrictions for these forms; for more information, visit LEED Online and click "Sample Forms Download."
Documentation for this credit can be part of a Design Phase submittal.
When working on leedonline for this credit, we are told to Download, complete and upload the Supplemental Daylight and
Views Calculation Spreadsheet (found under "Credit Resources").
The problem is, we cannot locate where the Credir Resource is or where to download the spreadsheet. Anybody can help?
We found it already, thanks.
I abhor this new layout. I could not find it either and after hours, discovered it here: http://www.usgbc.org/node/2614118?view=resources
I realize you have already found it but others may be struggling with the same issue so I thought we could help them.
I am documenting this credit using the simulation method. For many of the regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building., the rooms are above the 10fc requirement except for a small corner of the room. Based on reading this thread, my understanding is that the % of the room that is daylit can be counted towards the total required daylit SF. Is that correct?
Or if a room has an area that is below 10fc, then is that entire room disqualified? Thanks for your help!
With the simulation method, what ever area in a room that is above 10fc and below 500 fc at both 9am and 3pm, that is your compliant square footage.
For example, a 200 sq ft room has 190 sq ft within the range at 9am and 180 sq ft within the range at 3pm, then your compliant square footage for the space to be entered into the calculator would be 180 sq.
If some of the area of a room is below or above any limit, it does not disqualify the entire space, only the sq footage.
Hope that clarifies your issue.
Thanks for your fast response!
Are rolling shades mandatory when doing the prescriptive method?
Some type of glare control is required for all methods. Rolling shades are one type.
Although the October 2013 Matrix, does not allow any patient rooms to be without daylighting/ views, I believe these rooms could be eliminated due to the nature of their process. Has anyone dealt with these rooms before in a medical center setting?
Because of the required shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow. for a MRI room and what occurs during the scanning, of both MRI and CT, you can exclude these rooms from the calculations.
We have incorporated daylighting into CT rooms in the past. Check on the distance/elevation of required shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow.. You could potentially just use top lighting or if adequate distance is provided, side lighting. Daylight in these rooms is highly desirable for the staff and patients.
Should an area designated for hot desking be included as a regularly occupied area? No single user will spend more than one hour per day at these workstations.
Yes, its still considered a workstation, and why wouldn't you want these spaces to have daylight.
Todd, it is a workstation, but why would it be considered regularly occupied if it doesn't fulfill the one hour requirement?
I agree that I personally would want these spaces to have daylight.
Paul, these are very hot hot stations!
Jill, there are numerous spaces listed in the regularly occupied space matrix that you could easily say, will be occupied for less than one hour and therefore are not considered regularly occupied. But to avoid the continuous argument as to what is and is not regularly occupied, they listed a bunch of spaces. Well, they haven't listed every single type of space out there. So you take these spaces that are not specifically listed in the matrix and then group them with what type of activity occurs in this space. Hot desk, people getting together to discuss items, review documents etc. etc. You could say the same for a conference room. You could argue they are different and that a hot desk is only meant for "quick" get togethers, where as conference rooms are not. But I could argue that you could meet at a Hot desk for more than an hour. Where are hot desks typically located? Within an open office plan off to one side where teams can gather. How can you not list that as regularly occupied, its not circulation.
So it is best to place the space based on activity rather than argue that it is "meant" to be used for less than one hour, even though it could be used for more than hour.
You can make
Thanks. Also, it was good to remind myself that the one hour per person isn't a requirement as much as a guideline.
Paull, I think Todd is right and if you're going to try to exclude these spaces you're going to have to provide a very strong case as to why no one would want to use them for more than an hour. When I think of non-regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building. based on the time guideline, I think of a corridor, as he mentions, or a small copier station for example.
Great. Thanks so much for your help.
DIVA Day is a full-day event focused on the use of DIVA and associated simulation tools to improve and enhance design through performance-based, especially daylight, workflows including presentations by practitioners and researchers at leading architectural, consulting, and engineering firms and universities.
I have a large conference room with a folding partition to create two smaller conference rooms. Do I run the simulation with the partition open (one large room) or closed (two small rooms)?
Run without the partition. Movable partitions are not to be considered.
We are proposing to carry out the Option-3 daylight measurement in our project to demonstrate compliance. I would like to know if the measurements could be taken before the furniture have been installed or should it be done after the complete fit out with the furnitures installed ?Please advice.
The measurements can be taken prior to the furniture being installed to document the credit.
I would also say that you take measurements after the furniture is installed. It can show you the effect furniture has on the daylight conditions of the space. Spaces are designed to provide the best daylight, then ignore the furniture layout and color. This can result in the wrong color of furniture or layout negating on the daylight design put into the space.
Thank you Todd.
We are documenting this credit and ran up against an issue. While we have exhibit spaces currently listed under regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building. under Plf2. We are attempting to exclude them for IEQc8.1 and 8.2 calculations as they are spaces that we typically like to control the lighting. Have others tried this in a narrative approach and been denied the point? Is this another futile argument like auditorium spaces?
Even though general gallery spaces are considered regularly occupied as noted in the space matrix, you can provide a narrative to exclude them. An exhibit, such as art, which cannot have direct sun could be excluded. A natural or living exhibit which requires certain types of daylight could be excluded.
But this exclusion is based on how well your narrative is written for the exclusion. A narrative that says, "some exhibits can't have daylight" and that's it, will be challenged. Be specific and use real examples and state how daylight is a detrement to the exhibit. If it's nothing more than you want to control the lighting levels, that will not be accepted either.
Is it mandatory to run the model on Radiance when the model has been built up on Ecotect?
I have been facing issues on installing Radiance because of my computer windowns version.
The reason is that Ecotect only can run under uniform or overcast sky. You can install desktop radiance version.
Whats your issue with Radiance, can you not get installed or can;t you get it to run with Ecotect? If you could expand your issue i may be able to help. I'm running the latest of everything and have had no issue with installing Radaince. Linking them all together was tricky.
Thanks for your responses.
Radiance is not installed properly for an unknow reason. Radiance doesnt find rview and falsecolour.exe files. When I run the simulation and try to import the results, it says: invalid file format - no data found.
Ahh yes, i had that problem. You need to install desktop radiance and link those files. When you setting up the simulation in Ecotect, do you get all green checks on your links?If so, where are you saving the sim file. It should have a very short path name. I save it to my C drive to get results then move it to the server.
Todd, the link you sent below is of help! Thanks very much for this! Now the green checks are all OK and the simulation is running properly!
If the software can't find the file, it is usually caused by newer version radiance that you installed. You can try older version of radiance. I believe the newer one is no longer use falsecolor.exe, but,as i remember, it uses falsecolor2. Check your radiance folder whether you have the file that the error mentioned.
I have a couple of questions:
We have a hotel project with 80 villas that are grouped into building blocks of 4 and 6. Would we have to take measurements for each individual villa or could we use the measurements for one villa and duplicate it over the other ones in it's block?
Would a butler pantry count as a regularly occupied space? The butler would be in there only part of the time for housecleaning and to prepare simple meals.
The only way i see being able to measure one and use it for all others is if they are all orientated the same way and there is nothing surrounding them such as trees or buildings. You would have to have a clear narrative on using this method and clearly demonstrate that there is nothing effecting the daylight distribution of any of the villas.
If it were just a pantry, just storage, then it could be excluded. However, you state that the preparation of meals will occur in the pantry. As noted in the regularly occupied space matrix dated October 2013, residential kitchens must be included as regularly occupied. Hotel guest rooms fall under the residential category. I'm not exactly clear as to what is in this pantry. If there is a stove and refrigerator then there is no getting around this. However, if the preparation of meals in this space is just the butler making a sandwich on a counter and there are no food preparation appliances in the space. Then you could argue that it is not a true kitchen and could be excluded.
To whom it may concern,
We are involving a project going to be built in Uppsala, Sweden. Its aim is to get the LEED 2009 certification for this building.
So to get a point of IEQ Credit 8.1 (Daylight), we saw that if in its manual, page 549, says that “However, designs that incorporate view-preserving automated shades for glare control may demonstrate compliance for the minimum 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. illuminance level). Moreover, in page 554, it says that:
“To control glare, use any of the following common strategies:
• Fixed exterior shading devices,
• Exterior light shelves,
• Interior light shelves,
• Interior blinds and louvers,
• Operable draperies and blinds
• Fritted glazing
• Electric blackout glazing”
Now the question is if we used one of the above systems to control glare, can we skip to exclude all values above 500 fc? And also, is it possible to use a screen printed glass to prevent glare and then again skip to exclude all luxMeasurement of lumens per square meter. level above 500 fc?
Screen printed glazing is equal to fritted glazing, so it can be used to control glare.
The only thing that allows you to take the exemption on page 549 is view-preserving automated shades that are controlled with a photocell. They want to make sure that the shades are opened when the glare condition is not present.
If you are running into a lot of cases with values 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., you have a lot of glare. Glare is the biggest design concern with daylighting. In reality, you don't need a high quantity of daylight in the interior of a building because eyes will adjust to the level available (to a point.) Even, high quality illumination is better.
I'm now working on a project (office building, new construction) under LEED NC v2009 Certification.
Can you confirm that the non-permanent forniture (not used as functional distribution, e.g. internal walls) is excluded from the model (e.g. cabinets, desks,..)?
I've not found any specific note about that into the reference guide.
Thank you so much.
There are no specific mentions of furniture in the credit. It is generally agreed that it is optional. However, you might be surprised at the difference it makes in your calculations and should include it for a more complete analysis. At the very least, you need to know what the typical desk height is in order to set the vertical level of your calculation plane. If it is a child's classroom or a maintenance shop, adjust accordingly.
I understand that if view–preserving automated shades are incorporated, that the project need not comply with the 500fc requirement. Can someone please help clarify for me the logic that for exemption from this threshold that the shades must be automated?
For energy calculations, I understand the logic behind the practice having solar shading automated for their effect to be included. A building user when thermally uncomfortable is likely to adjust the thermostat before the solar shading. However, I do not think that this is not the case for daylight/glare. A building user who is subject to glare is very likely to make adjustments to the curtains, drapes or blinds on an as needed basis. Whereas with, an automated system, the shades are often triggered regardless of whether or not a building user is subject to glare.
Do other group members agree with the above or is it do they feel that it is an advantage to have automated shades for glare?
The problem is that if you have a bad design with constant glare problems, the user will endup just leaving the shading in place with the lights on...even if the conditions improve and the shading is no longer required, he won't make the adjustment to open the shading because he does not experience discomfort in his current state. However, he is (perhaps subconciously) robbed of his views and no daylighting happens and the lights don't turn off. This defeats the intent of the credit.
Not only what Jean said, but also with automated shades, they will come down at a certain level, so its assumed that the space will never reach an illuminance level that will be uncomfortable. Although, people are more acceptable to high daylight levels, including levels well 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.. Without automated shades, it is not known whether someone would actually get up and pull the shades, therefore the daylight scenario must be designed to not exceed that level.
I have no problem with this option in LEED. The hardest element to design for in a building is the occupant. However, i believe that with proper occupant education, we don;t need all these automated controls. All to often we design these high tech automated controls and never tell the occupants anything. Then facilities is doing nothing but answering questions as to why this is doing this or that. One thing we neglect is to educate those who will use these spaces. I see way too much during an occupancy walk through of project where teachers have never been told anything about the lighting controls, thermostats, or why there are these "thingys" hanging from the outside of the buildings. To me it means failure and thats why you see sensors taped and all kinds of methods to override or disconnect those expensive control systems. I could go on about this topic but i believe there is word limit in posts.
We are doing an addition to a classroom building on a college campus. A ~100 seat auditorium style classroom makes up about 25% of the regularly occupied space of the building. Has there been any precedent for auditoriums and/or classrooms being allowed to be excluded from calculations? The space will be used heavily for AV and distance learning presentations which will require specific lighting conditions.
Since its a classroom, it cannot be excluded. Also, even if it were an Auditorium by use, the Regularly Occupied Space Matrix dated October 2013 states that they must be considered regularly occupied.
Our current daylight simulation shows hotspots along a window wall that is shaded by existing trees and topography. We did not model the topography as part of the simulation. How can we account for trees and topography in the simulation
I guess I don't understand why you can't include the trees and topography in the simulation?
As Jill stated, why can;t you?
You can definitely include topography into your simulation and it should be to determine actual levels. How its modeled depends on your program. Use simple geometries for items in the near vicinity. I have modeled a mountain, (what we call mountains in PA) for a project that was located on the north slope of the mountain and for one located in the valley in the Pittsburgh. Morning and evening low sun angles were non- existent because of the terrain.
Vegetation can be tricky,especially if its deciduous trees, and what values of transparency do you use based on tree type and depth of the woodline. Vegetation is a great element to use to help with direct solar issues.
I use simple planes for trees and make my best judgement on transparency of the canopy. You can sometimes get this information about the canopy density from arborist books to help determine the transparency.
Isn't it usually calculated & completed by electrical engineer ?
Are you asking who fills out the daylighting LEED form? I would say that most of the time the architect fills out the form.
If a firm is contracted to perform daylighting simulations, it can be a wide variety of disciplines such as a lighting designer, daylighting designer, LEED specialist, or electrical engineer. In this case, it is usually the person who does the simulation who fills out the LEED form.
If the credit is achieved by the measurement option, it can be anyone who knows how to use a light meter. I guess in this case it is most likely the electrical engineer or architect, but could also be the building engineerA qualified engineering professional with relevant and sufficient expertise who oversees and is responsible for the operation and maintenance of mechanical, electrical and plumbing systems in the project building., facilities manager, LEED specialist, or the lighting or daylighting designer.
We have a project that is relying on quite a bit of borrowed light for their interior spaces. I was told by a colleague that in NCv2.2, borrowed light was allowed but we cannot find any information saying it is or is not allowed with version 2009 (aside from LEED user's exclamation above.) Are we sure as a community this is not an acceptable route and can someone prove it to me via a comment by a reviewer etc?
Borrowed light scenarios are only accepted to demonstrate credit compliance when using either simulation or measurements. It has never been accepted in either version when using either the prescriptive method or the glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. calculations.
The prescriptive method in v3 and the glazing factor calculation in v2.2 is a simple geometry and there is no means with those calculations where you can consider the daylight illuminance levels with borrowed light levels.
The LEED v2.2 Reference Guide states that when analyzing complex geometries, simulation or measurements should be used. You may see a comment from a reviewer that says this,"However, the provided drawings indicate that some of the project's interior spaces are receiving daylight using borrowed light strategies (i.e. sidelights, glazed transoms, etc.) The glazing factor calculation is designed for simple geometries and provides default data to support a simplified analysis. As described in the LEED-NC v2.2 Reference Guide, when analyzing more complex geometries, it is necessary to use daylight simulation or light measurements to demonstrate meeting the credit's requirements."
Same with the prescriptive method in v3, where you may see a comment like this,"However, the provided drawings indicate that some of the interior spaces of this LEED-NC project are receiving daylight using borrowed light strategies (i.e. sidelights, glazed transoms, etc.). The prescriptive calculation is designed for simple geometries and provides default data to support a simplified analysis. For a more detailed analysis, a daylight simulation or light measurements are appropriate means to demonstrate meeting the requirements of this credit. To document compliance using a simulation model or light measurements, projects must document that a minimum of 75% (90% for two points) of the occupied space achieves a minimum 25 footcandleis at 30 inches above the floor.
At one time in the interpretation database, there was a LI that indicated that hand calcs cannot be used for borrowed light scenarios, i looked for it and it appears to be gone, or maybe I'm not putting the right parameters into the search column. It really is no longer an easy to use database.
Thanks for the clarification!
I am currently running daylight calculations using the prescriptive method on a project with an open plan with large expanses of glazing all around. In most areas, the glazing is floor to ceiling. With this, the window area and the floor area are very close, causing the building to be well above the .180 max compliance. However, we have automatic roller shades throughout. Am I correct to assume that this is acceptable because of the shades? Also, if so, how do you document this for submission? Do we still run the calcs and show our values that are too high, but mention the roller shades?
When you complete the Supplemental Daylight and Views Calculator, in the column that is labeled automated shades, mark yes. This will automatically ignore the exceeded 0.180 limit.
To document, provide floor plans indicated the location of the automated shades, the sensors, submit a sequence of operation, and manufacturer info. You still need to complete the calculator and submit everything else.
Also, make sure that your shades are view-preserving. This is a somewhat subjective call but I would say that as long as you can still see the general outline and color of objects outside, and people moving around, for example, it is view-preserving. They are not hard to find and even shades with low transmittance (or low openness factor) can be surprisingly view-preserving. An example would be a fabric roller shade with perforations.
Hi, in case of a not meeting the skylight coverage ratio of 3-6% for the total room space, e.g. having only 1.5%, is it possible to devide the space into two zones and include half or the room in the compliant areas, which on it's own meets the 3% skylight coverage?
If toplighting is the only source of daylight, then no. You are not meeting the requirements of the credit by possibly providing adequate daylight to the space.( I say possibly because the prescriptive method is not a determinant of adequate daylight levels or good dyalighting in general) Use simulation or measurements to document possible credit compliance.
If the room also has sidelighting, then you may be able to break up the space into multiple daylight zones, dependent on the perimeter glazing, and then separate the skylights between zones.
Can a film be installed as a form of glare control for spaces with illuminance levels above 500fc?
No; glare control devises must be able to be controlled by the occupants unless automated shades are controlled.
For the situation you are describing, no. But if you install the film and your simulation can show that you are still meeting the minimum footcandle requirement, not going above the 500 maximum, and you can prove you are still providing a view, then maybe. As you can see this could be tricky, because you need the optical properties of the film from the manufacturer and simulation software that knows what to do with it. You would also need to either prove to the reviewer somehow that the film doesn't obscure the view and/or install the film in the upper portion of the glazing and provide shading or glare control for the lower portion of the glazing to preserve the view.
I think the new redirecting films have potential, and want to make sure designers and reviewers don't dismiss them outright.
View compliance is not required in daylight credit. As long as the illuminance levels are between the required range after adding the film, the project will comply.
I was wondering if the bathroom area of a hotel guestroom would be considered a regularly occupied space? Dito entry closet area...
Thanks for any feedback on this,
Both would not be considered regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building..
I have a residential project, each housing unit has a balcony in front of side window of the living room, should i need to consider shading impact of balcony when using OPTION 2. Prescriptive, if so, how to do it?
If there residential units are stacked, then the balcony of the unit of above would be considered an overhang. You would need to use the 63 degree angle from the outer edge of the balcony above to determine the depth of the daylight zone for the space that is effected by this in the lower unit.
Its all about access to the skyvault so the balcony for the space would not need to be considered, even if it were a concrete balcony.
I am working on a project using the prescriptive daylighting method for achieving IEQc8.1 The project has both sidelighting and toplighting. If the skylights are excluded, the project's regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building. meeting the requirement ( 0.15 < WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area. x VLT < 0.18) will be less than 75%, and they will not achieve the credit. If I include the skylights in the calculation, the WFR x VLT will be greater than 0.18 for most regularly occupied spaces (over-daylighting in terms of this method) and the project will still not achieve the credit.
My question: can we pick and choose what skylights we use to comply with this credit via prescriptive method, or do we need to include all of them?
Also, skylights don't use the WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area. formula. See an excellent example of the Prescriptive Method calculation on this web page at the top under Documentation Toolkit.
Hi Every one,
Currently we are working for factory building project which has registered five months before under USGBC Rating system LEED 2009. We would like to get Daylighting credit and it is natural ventilated building.
We would like to know the required minimum luxMeasurement of lumens per square meter. level & maximum lux level. As per the reference guide, the min lux is 270 lux. Whether it is reduced to 110 lux after that? Please let me as soon as possible. Also let me know how to check with addenda.
The minimum luxMeasurement of lumens per square meter. level is 107 and the maximum level is 5381. The addenda was posted in April of 2010.
You can see these levels in the online credit language and here in LEEDusers.
Searching the LEED addenda and interpretation database is painful.
Wow. That is a massive difference. I just tested it on a project that simulated 42% compliant area on the old requirement and 82% with the new. At the time I was completely dissapointed that the design appeared not to be good enough and couldn't understand why.
Actually, it turned out to be a moot point, because it was a kindergarten (School) project without "classrooms" in the typical sense and therefore I'm not allowed to apply for the credit.
Lead Building Performance Analyst
Glazing provided for daylighting may also be vision glazing providing views.
This rectangular building’s long axis runs north–south, rather...
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