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.
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.
For dayligting simulations, there is usually a 0.5m margin applied around the perimeter of the room, excluding the area from the assessment. In our understanding, this is because of potentially misleading illuminance values so close to the wall (i.e. influence of vertical surface reflections) and also because of the assumption that there are usually no work spaces that close to the wall.
However, in our project (office building), there are workstations adjacent directly to the glased facade. If we apply the 0.5m margin, a great part of these workstations within the ROA would be excluded from the assessment.
Would that be acceptable to set the margin to 0m while providing an explanation in a narrative?
Run both and compare. I'm betting it does not effect credit achievement. Personally i run my calc points right up to the wall and have submitted multiple daylighting reports like that and have never been questioned.
Thank you Todd for the quick reply. I agree that to do a comparative study would be ideal, but unfortunately we are pressed by time and the simulations are quite time consuming. But I understand that you haven't had a problem with no margin at all, so will use this option.
Next to the original question, I would also like to confirm my understanding (sorry if that would be better to start a new thread, I can re-post if you would prefer so) - following the LEED guidance, the maximum allowable grid spacing is 5ft. In our software (IES VE) the default spacing is 0.5m. I am thinking about increasing this value as I assume that the simulation will be faster.
I guess that this will be acceptable, even if the reviewer may know that the software can simulate at higher resolution. But ideally, I would like to avoid any questions later on. Can I ask - what resolution do you usually simulate with (office buildings with open, as well as separate offices)?. Is this something I should be concerned about?
Set it at 5 feet and run it, this will be fine for LEED documentation. If you were doing this during the design phase, i would set it a little tighter, but that is my own preference and situation dependent.
When you submit, you will include a narrative that states all your simulation parameters, reflectances, grid height and spacing, times of day, etc. A reviewer is not going to try and determine whether you are at 5 feet or 4 feet. If you include the illuminance levels on the sim output image, you'll need the spacing to allow the clarity of the text, program dependent. A reviewer would probably question a space that is 20x30 and only has four calc points shown.
Fewer calc points do tend to lead to quicker calc times, of course many other factors can make sims slow, but with everything right, it should be quicker.
The biggest thing you should focus on is consistency. Ensure whatever information you have submitted is consistent between all other documentation in other LEED credits. Make sure the room names and numbers are the same between sim reports, floor plans, and daylight calculator, Make sure the areas are the same. Make sure the numbers in the calculator much the numbers in the credit form. Make sure your ROA matches the number in PIF2. Provide a narrative as to what you did, make sure it can be read, and you should be fine.
A reviewer is not there to find fault, even though some believe that is what they do, they are there to ensure that "you" have demonstrated that your project has met the requirements. You'll get the benefit of the doubt if you are honest, consistent, and demonstrated that you a general concern for the submission process. Being sloppy, inconsistent, and not providing the minimum will tend to sway a reviewer away from the benefit of doubt.
Thanks a lot for this detailed answer Todd, this is really great. This is our first dayligting project taking the simulation route, so your support is really appreciated. Thumbs up!! :)
Hi , I wonder what happens when you have more windows than is required and the index exceeds the recommended?
What light and views index or standard are you referencing? There is no requirement within LEED that references or uses an index.
Hello, is there a filled out sample of the Daylight/Views calculator Spreadsheet anywhere? I'm using the prescriptive method to conduct the Daylight calcs. I want to make sure I'm doing this correctly. Thank you in advance!
If you understand how the prescriptive method works and how to do it, then the calculator is not hard fill out since you will have what you need from the prescriptive calculations. If you do not know how it works, then a filled out calculator will do you know good without knowing where the numbers came from.
1. Identify all spaces that must be included in the calcs.
2.List them and their regularly occupied area in the spreadsheet.
3.Determine the daylight zone for each space, list it in the calculator.
4.Determine the area of glass for each space, list it in the calculator.
5. Insert the VLT of the glass into the calculator.
The rest is pretty much self calculating.
LEED's definition of a regularly occupied space is one where individuals normally spend more that one hour per person per day on average. Regarding a hotel with a small fitness room, the typical person is not expected to spend more than an hour per day, and thus would not be considered regularly occupied. Will this logic be accepted by the USGBC/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). reviewer?
The regularly occupied space matrix does not specifically list fitness rooms, but these would fall under gymnasiums, which must be included for daylight, but not views. The only way you might be able to argue against daylight would be to have information from the owner showing that the majority of the guests do not use the room for more than an hour. Otherwise, your going to have to include them.
I have not seen an argument for a fitness room to be excluded that has been successful.
Are there any areas that can be exempt from dayligting calculations, while still being part of ROA? More specifically, we have a project with laboratories / incubators, which form part of the ROA, but have no windows due to the nature of the work carried out within (i.e. they were deliberately designed with no windows). Can these rooms be exempt from the ROA for dayligting purposes if properly explained in a narrative, or does it still have to be included?
Yes, if daylight is detrimental to the activity, such as ruining experiments which there are many cases with labs and daylight, then they can be excluded. So just note in the narrative as to why daylight cannot be allowed into the space.
Its pretty common to have labs excluded for the very reason you have stated and i have not ever seen it denied.
Thank you for the quick response Todd, it has been helpful
A corner room in our project has windows on two sides (North + West). Currently, the project is designed to include view-preserving automated shades for just the west wall. These windows make up approximately 75% of the window-area of the room. When we do our analysis for this credit, the space is considered overlit before any accounting for the automated shades is considered.
Are we allowed to answer "Yes" to the "View Preserving Automated Shades" question (Column S) as the majority of the windows have shades (and the more-critical daylight-intensive direction has them)? Do we have to answer "No" as not all windows have the shades? Any guidance for this sort of a situation?
You will need to divide the room in two separate lines in the calculator to properly document the credit. One line for the west wall and daylight zone, and one line for the north wall and daylight zone. You can check automated shades for only the west wall.
we have done daylight analysis for factory building.
we get daylight of 85% in 9 AM and 73 % in 3AM (Date -21 - September)
In this case which value we take to enter in V2009 Spread sheet
1.Worst value (74%)
Worst case compliant area is what you use. So 73%.
why we can't use Average value instead of worst case
Because the reference guide states, the area that meets the minimum illuminance requirement at both 9am and 3pm. This requirement was discussed within the TAGLEED Technical Advisory Group (TAG): Subcommittees that consist of industry experts who assist in developing credit interpretations and technical improvements to the LEED system. and working groups, and then voted on by the public, so it is the requirement.
Allowing projects to use the average would allow some projects which have poor daylighting condition at certain times of the day to earn the credit. The intent of the credit is to ensure the occupants are provided adequate illuminance values and good daylighting throughout the occupied times of the day.
If you are going to use daylight in your project, then you set your daylighting performance goals at the beginning of the design and then you ensure that the design meets that goal.
could you please clarify, as I have read mixed messages on this. I understand that the worse case between 9AM and 3PM applies. But is it:
a) worse case for the building as a whole (i.e. 73% at 3PM < 85% at 9AM - figures for the whole building)
b) worse case (between 9PM and 3AM) for specific rooms in the building, which then then make up the total percentage? (e.g. ROOM_01 69% at 9AM < 76% at 3PM = ROOM_01 worst case is at 9AM, but ROOM_02 83% at 9AM > 72% at 3PM = ROOM_02 worst case is at 3PM --> total daylighted area = ROOM_01 at 9AM + ROOM_02 at 3PM)?
It is b. So, as fill in the daylight and views calculator to document the credit. You will list the individual spaces and include the worst case value for each space, be it 9am or 3pm. The only way you should group anything is when you have similar floors. Then you can extrapolate the results of one floor for the other similar ones. Do not group spaces. Even if the same room is side by side, you need to list them individually.
Thank you Todd, it is clear now. Is it possible to develop / submit my own version of the calculator sheet that would automatically take care of the selecting worst case between 9AM and 3PM for each space (i.e. after loading with the data from software from both simulations) and then report the final figure? Or should I perform the comparison else where and then report just the final column in the dayligth calculator? I am asking as my colleagues commented that if the reviewer sees a tool he/she is not familiar with, it may actually work to my disadvantage. Or can I submit both? Thank you for any comments / thoughts on this
The answer is yes. I have submitted my own spreadsheet many times because i do not like the new one not having either of the times listed as in previous versions. Just ensure you include the same things like room names, SF, etc. etc. Make sure your calculations are right. I also include a narrative stating that i am including my own calc. Also, i make sure that i upload it as xls format so that the reviewer can check the formulas and see that I'm not playing around with the numbers.
In regards to the reviewer, any reviewer who would not understand a spreadsheet that is almost exactly like the calculator probably should not be reviewing the technical aspect of the daylighting credit. Like i noted, i have never had an issue with my own since it includes everything the calculator does along with some extras. But upload it as a xls format so that the reviewer can confirm your formulas. If you upload as PDF and they see something fishy they will question it.
Thanks Todd. This has been very helpful
For the majority of our project we are using intelligent, electrochromic windows that automatically tint to maximize natural light. How should we go about calculating and documenting daylighting for this? Thanks
You have three options, simulations, prescriptive, and measurements.
Simulations; if you used sims during design then you should stick with them if they were done correctly. What I mean by correctly is that you used a program which had a script which actually tinted the glass as the illuminance levels increased. Or, you used the lowest VLT the window will produce as the value for all your simulations.
Prescriptive; you would need to use the lowest VLT produced by the window in the calculations.
Measurement; since there is no specific guidelines as when and under what conditions measurement should be taken, to be truthful, I would do it under clear skies around noon.
Hopefully this helps.
Does the intelligent glazing meet the criteria for "automated shades?"
Technically no, blinds should be able to block the majority of direct light entering a space. But if the glazing were able to dim to say about 10% VLT which is the same as some shades, then you have an argument that it would be.
Todd, is it mentioned in the reference that we need to use lowest VLT?
If I were the daylight consultant, I would use highest VLT and treat electrochromic capability as "blinds" for single point approach or prescriptive.
Eddy, there is nothing in v3 that I have seen or read in regards to how to handle automatic glazing. But, throughout LEED, and take the MR credits for example, when given a range of performance or recycled content, you always use the lowest value, the worst case scenario.
So is the reason you are saying to use the highest VLT is because if the electronic side fails, you will only have the properties of the glass. Or, because of the potential for over daylighting and glare/
The reason I say the lowest VLT is not only what I mentioned above, but also because if the glazing goes too dark, like mirrored glass low (.3 or lower VLT) then your daylighting zone is smaller. I use the lowest levels as worst case scenario, kind of like the worst case scenario sky conditions. If you can meet it under those conditions then you are good. Blinds will always help with glare over daylit situations.
I just assumed it looks like a regular glass with blind. We usually simulate the best case scenario without blind pulled down. Using similar assumption, I will use highest VLT and make electrochromic capability as "blinds". This approach is only for single point time.
LEED usually uses best case scenario in daylight such as sunny clear sky for single point time of time approach. In my opinion, the idea of using best case scenario is related to energy impact. Definitely, climate based approach is better such as shown in LEED v4.
This is definitely an interesting topic. I may have to dig around and see If there ever was a discussion with this. Might propose this as a question to the TAGLEED Technical Advisory Group (TAG): Subcommittees that consist of industry experts who assist in developing credit interpretations and technical improvements to the LEED system..
Peter, one suggestion might be to propose a question to 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). in regards to this issue. What would be the accepted methodology and documentation. I hate for you to submit a credit based on what is posted here to then have it rejected during the review. LEEDuser comments do no override GBCI requirements.
Todd, I will try to propose the question to 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)..
Thanks for all the help!
For our project we are using View glass which has 4 tinting stages which are controlled as desired:
Tint state 1: 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. 58
Tint State 2: Tvis 40
Tint State 3: Tvis 10
Tint State 4: Tvis 1
The issues is, if we are supposed to use the lowest Tvis value, we ironically are at an extremely high disadvantage because of the extremely low Tvis. What do you advise?
Did you propose a question to 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). to see if this can be pushed to the TAGLEED Technical Advisory Group (TAG): Subcommittees that consist of industry experts who assist in developing credit interpretations and technical improvements to the LEED system. to provide direction in regards to this?
As Eddy had mentioned in one of the earlier posts, the VLTs of 10 and 1 could be considered your glare control. I did not know previously that your glazing could basically black out. Again, I would propose this to ensure this methodology is allowable. In my opinion, I say that since you can drop the glass that low, then it would meet the requirements of glare control. But I'm not GBCI nor your reviewer and LEEDuser comments do not set ruling precedents for LEED.
So that leaves the other two VLTs. Because the occupant can control the VLT, then I would say that the highest VLT can be used. It is the same as providing regular glass at x VLT and then having blinds that occupant can lower or adjust. There is no control over the occupants, so using 58% would be what I would use.
If you had automatically dimming glass without any occupant override, then it would be more complicated.
Hope this helps you better. I still suggest that this is run past GBCI. I have not found any rulings on this issue. An since the LI database is so small anymore, and individual project LIs don't get posted, its hard to determine how to handle some of these unique circumstances.
Thank you, Todd.
How do i contact 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). with this issue?
I am biginner in LEED, for the first time I am meeting with some things. I met first difficulty in Credit 8.2 Daylight and Views...If someone have to give me pdf of the concrete project with SPIDER facade how to solve angles of light and views ? I read instruction but I am not sure how to apply it on spider.
Not sure what exactly your SPIDER façade looks like, so if you can send me a pic I could probably help you a little better.
Whenever you have a complex or unique façade, the simulation or measurement option is your best way to go. The prescriptive method is meant for simple geometries.
I made mistake, I wrote comment below R2M solution srl instead mine
Your link has my security software blocking. I suggest you contact me through LEEDuser and send me a snap shot of what you have.
Do you have some official mail to send you there snap shot?
I not managing good here.:))
Click on my name, you will then see my profile where you can hit contact, this is how you can contact me from there we can follow up.
So I reviewed your plan with your proposed view lines. It is not correct. The space you are showing looks to be a typical curtain wall construction. You can pretty much ignore the frames. I'm replying with an attached drawing show how to do the view lines. This space would be 100% compliant. Also, refer to page 570 of the reference guide for how to do view lines.
In DesignBuilder for the daylight simulation you have to impose a value for the parameter "margin", which is defined in the following way:
Enter the margin (in m or ft) around the zone boundaries where illuminance data is not to be calculated or included in summary results. This option can be used to help avoid inclusion of potentially misleading illuminance data close to walls and windows. A typical margin recommended by CIBSE is 0.5m.
What value is more appropriate for LEED?
There is no value that should be used or is referenced in LEED. Just a calc point grid of no more that 5 feet should be used. You can refer to LM 83-12 that is used for LEED v4, IES Lighting Measurements LM 83-12 Approved Methods.
Having your calc points pulled away from the wall is good practice, I use at least a foot but 0.5 m would be fine also.
Thanks for your answer.
I am giving you link where you can see one space which has spider...Just told mi is the angle good ( drowned angle) and how to solve shadows of the columns.
We submitted for this credit using the results from the REVIT 2016 daylight analysis tool. Both the Lighting Analysis plans and the Room Schedule Threshold results were submitted as part of the documentation.
The credit was denied. The reasons given included one, that some of the spaces had simulated illuminance levels of less than 10 fc1. A footcandle (fc) is a measure of light falling on a given surface. One footcandle is defined as the quantity of light falling on a 1-square-foot area from a 1 candela light source at a distance of 1 foot (which equals 1 lumen per square foot). Footcandles can be measured both horizontally and vertically by a footcandle meter or light meter.
2. The non-metric measurement of lumens per square foot, one footcandle is the amount of light that is received one foot from a light source called a candela, which is based on the light output of a standardized candle. A common range for interior lighting is 10 to 100 footcandles, while exterior daytime levels can range from 100 to over 10,000 footcandles. Footcandles decrease with distance from the light source. The metric equivalent of a foot candle is 10.76 lux, or lumens per square meter.. Our submitted documents include lighting analysis plans that clearly showed NONE of the spaces mentioned in the Review comments had illumination levels below 10 fc. Another reason for denial of the credit was that the interior renderings did not show shading devices. Well, the renderings were created showing the shading devices concealed in the pockets. If the intention is to indicate shading devices, we could have included the drawing sections that call them out.
We are mystified.
How do we question this? We don't think it falls under an appeal, as we are not requesting a different interpretation. We think the ruling is incorrect.
Thanks in advance for any helpful suggestions!
I would suggest you email them this question through the contact us form, stating the evidences you provided. I have had some review comments where it also seemed that there was a mistake and have always received a clarifying response on what they are looking for.
If this was just a preliminary review, provide a review response and outline each issue and be very specific with your response. If this was a final review, then submit a project team inquiry outlining the issues.
I will say that the comment in regards to the light levels is a mistake. I can see where the reviewer may have some justification to question the shading devices with a rendering but to me it shows that the reviewer may not have a working knowledge of renderings and the simulation program. Shading devices are not required for daylight sims in v3, so why would you expect to see them in the daylight rendering. Now if you submit an actual image and don't see any, that is a legit question.
For a warehouse, can I deduct the permanently fixed high racking coverage area from the gross floor areaGross floor area (based on ASHRAE definition) is the sum of the floor areas of the spaces within the building, including basements, mezzanine and intermediate‐floored tiers, and penthouses wi th headroom height of 7.5 ft (2.2 meters) or greater. Measurements m ust be taken from the exterior 39 faces of exterior walls OR from the centerline of walls separating buildings, OR (for LEED CI certifying spaces) from the centerline of walls separating spaces. Excludes non‐en closed (or non‐enclosable) roofed‐over areas such as exterior covered walkways, porches, terraces or steps, roof overhangs, and similar features. Excludes air shafts, pipe trenches, and chimneys. Excludes floor area dedicated to the parking and circulation of motor vehicles. ( Note that while excluded features may not be part of the gross floor area, and therefore technically not a part of the LEED project building, they may still be required to be a part of the overall LEED project and subject to MPRs, prerequisites, and credits.), and focus my 75% daylight coverage on the aisles and landing spaces only? I say yes. Right?
using TDD's & simulation.
( I can't believe I don't know this answer, forgive me if this is a regularly asked question, and I missed it in a search result. I have read several posts and I am not sure I am clear.)
Permanently mounted rack system that cannot be occupied by a person can be excluded from your regularly occupied floor area calcs. An yes, you will need to show the illuminance levels in the aisle.
Also, as noted in the regularly occupied space matrix dated April 2015, an inactive warehouse/storage does not have to be included in the credit. So you could exclude the whole area if it is not considered active.
First off I have a slight confusion about whether library stacks should be considered non regularly occupied area or a regularly occupied area with movable furnitureMovable furniture and partitions are those that can be moved to provide access to the view by the user without the need for tools or assistance from special trades and facilities management..
If the stacks are not bolted down but would still require staff to move them would they be considered movable furniture. Also would the area under them then be regularly occupied because the use of that area is thus flexible. The concern being that the library will eventually move away from books on shelves and utilize the space differently. So would this area then be regularly occupied with movable furniture that is not modeled and does not impact the simulation. I suppose the situation is similar to an open plan office with system furniture that could be reconfigured by building staff over time.
On the other hand if we are concerned only with the current appearance of the space this would be unoccupied given the category space matrix. But should the geometry of the stacks be included in the simulation in order to influence the daylight penetration into the rest of the space. Similarly would they be present for 8.2 views calculations.
I would imagine that this is a judgement call on using the prescribed usage or constructing a narrative to describe the design intentions. If anyone has had experience with this any advice would be much appreciated.
It really is a judgement call, but best practice would be to include them. We include the stacks in our daylight simulations. We also include as much of the movable and fixed furniture in our sims. It is how the space is going to be used, so that's what we want to see. Interior designers can be helpful or detrimental to your daylighting strategies. It is best to have them part of the early discussions in regards to furniture layout and material and color selections. I have seen on more than one occasion where a space was designed to be well daylit, that did not consider any furniture or colors, get ruined by color and furniture selection that basically negated all the daylighting strategies.
All the projects that we have submitted that included a library, we have kept the stacks in the calculations and kept them included in the overall regularly occupied area. The main reason is that we design the space so that the stack area would also be daylighted. The key is that you design the space to meet your required performance. So if you want it to be daylit, you design it to be daylit. If you design and then see how it works, then you become reactive instead of proactive and then you begin to look at how you exlcude things. .
Technically, if they are not permanently fixed, then they can be excluded, but the area they would occupy is considered regularly occupied and would have to meet the daylight requirements.
With EQc8.2, we orientate the stacks so that they are perpendicular to the window wall. This helps with daylight penetration and views.
First off, I have had a very hard time finding information to help complete this Credit's documentation. There are terms that are undefined or have one meaning in regards to this Credit but other meanings in the Architectural realm. Are there any examples that a first time documenter could look at to reverse engineer the process that is required to correctly document this credit?
With that said, I have a question regarding the Floor Area. At first I assumed that it would be the actual floor area but after calculating many of my rooms, I found that most of them were not meeting the requirements that determine if those rooms would apply to the Regularly Occupied Daylighted room area. So I read further into the other options for documenting this credit and I found that the Simulation Option requires that you record the light levels at 30" AFF. So my question is just that, Can we/ should we determine the Floor area at a certain height AFF, or does this number need to come from the Floor Level. If I take the area at 30" AFF, Most of my rooms are applicable.
Thank you in advance for your time and attention to this matter.
Lets go in reverse, by answering your second question first. Why, because you need to have your regularly occupied area established before starting any of the options with the credit.
Make sure your regularly occupied space is established. This is different than your gross area. It is determined at the floor, not 30", and is the floor area between the walls. the 30" is for where the one should set their calculation grid or take their hand measurements from. Circulation areas, or areas within a space where permanently mounted equipment may be placed does not count. Refer to the Regularly Occupied Space Matrix which can be found in the resource tab of the credit in the credit library on the USGBC website.
Now that you have the regularly occupied area established, you need to establish the daylight zone. The daylight zone is the distance from the window wall which will or may receive adequate daylight levels. If there are no exterior overhangs or interior surfaces that are below the head height of the window, then you use times the window head height to establish the daylight zone depth. You should show this is in a section and on a plan. Note the daylight zone in the calculator. Then complete, the rest of the calculations.
Daylight zones should be established in a room when the window size or properties changes. In a space with more than one window wall, a daylight zone needs to be established for each wall.
I do not know of any publicly available examples for you to review.
So, back again to ask another one. We are ever so close to reaching 75% threshold and without having the engineers run daylight models or measure the space I'm trying to pick up any space we can. As I was reviewing the plans again, I realized that we did not count 3 reception areas in the main building lobby that will be staffed full time. The lobby is a massive circulation space and the desks sit in the space. How would we go about calculating the reception area space? would we just calculate the adjacent desk area? or would we split it into a "zone" that is basically the entire column 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. at that location? Any advice would be a great help! I have a diagram of what I mean if that would be beneficial. Thank you!
You would have to show that the reception desks fall within the daylight zone, 2H, from the window wall, then as you noted, apply the amount of glazing from that bayA bay is a component of a standard, rectilinear building design. It is the open area defined by a building element such as columns or a window. Typically, there are multiple identical bays in succession. to the reception desk area. Include where the person sits.
It may make the space over daylit since you are not including the lobby. Now lobbies are not considered regularly occupied in the space matrix, but that does not mean that may not have spaces within them that are used for certain things. YOu could include the lobby in the calculations and then just group the reception desk with the lobby space.
Again, the prescriptive method is just for simple spaces and you begin to really muddy up the waters when you try and push it.
The LEED reference guide does not indicate that the occupied space (the reception desk in this case) needs to be within the 2H zone as you stated. The guide only mentions that a ceiling cannot impede on the angled connection between H and 2H.
If the reception desk is not within the established daylight zone, which is determined by either 2 times the window head height, or using the 63 degree angle, then you cannot say that the reception desk will receive adequate daylight using the prescriptive method. It is just like any other space, any area out of the daylight zone cannot be considered daylit and therefore will go against achievement.
What is the distance from the window wall to the reception desk and what is the window head height?
We just received our design credit responses and used method 2 - Prescriptive. We have a 3 story cafeteria space within a 30 story office building.
The lowest level butts up to the 3 story glass wall on the exterior and the 2 levels above are held back from the 3 story glass wall by 20'-0"-ish. We are getting a comment saying that these upper cafeteria levels do not count. I know that above in the explanations, it mentions borrowed light from an atrium is not allowed, but these spaces are open to the adjacent glass, just not touching the glass exterior wall.
Is there no way for us to respond to this comment with a narrative explanation that the spaces are daylit, showing a section with light hitting the surfaces of the mezzanine levels? These levels are open and only separated by a railing, not another glass wall falling under the borrowed light definition.
thanks for any comments you might have.
I will agree that the upper spaces do not fall under the specific definition of borrowed light but I can see why the reviewer may have used this language.
The prescriptive method is meant for simple geometries and daylighting scenarios because it is all based on formulas. Your situation is not one that would be considered simple. I think the reviewer should have provided a specific reason for saying why they cannot be included or given you a possible method to demonstrate how. Your situation is one that would require more than a narrative to show compliance with the option 2.
From a professional side, these spaces cannot technically be included in the prescriptive calculations. You would have to show how much of the 3 story curtain wall glass is allotted to each level. You would then need to establish the depth of the daylighting zone from each allotted area of glass. From the sounds of each, with each level being at 20 feet from the glazing , they might be too far away to have any sizable daylight zone. You cannot use all three floors of glazing for each level, that might actually have too much daylight. What I just described, I have never seen done or attempted with option 2. As you can see, it is complicated and does fit into the simplicity method that option 2 is meant for. You could try it and make a case and see what happens or, do a project team inquiry and ask specifically why the spaces are rejected and what must you show to demonstrate compliance.
Personally, I would have done simulations or at least do measurements. The prescriptive is too simple for the scenario you have.
Please follow up if you decide to do an inquiry and what the reviewer asks for or whatever path you choose.
Thanks for the response - we are the LEED sub-consultant to the LEED consultant and were instructed to use method B. I agree, simulation may have saved time - and after all this, we may have to do some simulation of a few spaces to achieve our 75%. The Leed reviewer indicated that we could supplement the diagrams with a daylight model for those spaces to kick us over the 75. From the beginning though, everyone thought option B would be a slam dunk!
Working on a conference center, we are close to get to Gold Certification by 2 points. Our chance to get closer to it is to get 1 pt for Daylight, and most probably another one for Views.
The project has an underground ballroom which makes almost half of the project area and could or couldn't be considered as a regularly space area since this space type isn't mentioned in the LEED Space Types Matrix. This space is a renovation, has no windows and is meant for projections, seminars, meetings and even reception with no intent to use daylight.
Is this something arguable case so we can exclude the space, minimize our denominator in the calculations and maximize our chances to get a better ratio overall just accounting for daylight in the upper levels designed to be exposed to the exterior environment?
Thank you all for your feedback
Unfortunately, I can't tell you what you hope to hear. I've seen many, many cases where teams have tried to argue that they don't want to use daylight in a space (even a military dark-room simulation space) and it does not fly for this credit. Since credits are optional, it makes sense not to give the daylighting and views credit to a building that is mostly underground (I know yours isn't, but I hope you can see my point.)
How confident are you in all of your other credits? I see teams trying to extend themselves to reach the exact number of credits for the next highest rating, only to have one or two of their credits not come through.
The activities of the ball room; meetings, receptions, seminars fall under space types in the Regularly Occupied Space Matrix that require those spaces to be included in EQc8.1. Spaces with AV and projections cannot be excluded, classrooms have AV. Only rooms whose only activity is video conferencing and labeled as such on the plans can be excluded.
Not every project can earn every credit and renovations make LEED harder to achieve than new construction because it is what it is.
Jill and Todd,
Thanks for your replies, that helps to understand.
We are pretty confident in the other credits so the thought was to push to get the daylight ones since the project is made elsewhere to get as much daylight as possible on perimeter spaces. To that point, perimeter spaces are made of "prefunction areas", "lobby" and "terraces" which are used as an extension of the ballroom during events. One might think they are transient spaces which can be the case, but they have multi purpose functions.
Do you think they would fall under "regurlarly occupied space" per your experience? Our intent is that they should.
Thanks again for your reply in advance.
Professionally we know that these spaces are used for things other than circulation and transitions. An so we should provide these spaces with views and daylights. Where do people go when they get out of the conference room after watching a power point presentation for an hour, to the window wall. Yes, from the professional side.
For LEED, its how the spaces are labeled on the plan. Lobbies are considered or not considered regularly occupied based on the type of the project. The regularly occupied space matrix shows this. Terraces, not listed in the matrix, but will be reviewed by the reviewer based on its location. So if you an area listed as Terrace in a large main corridor, it might be looked at as a break out area or it may not.
There is nothing that states you cannot include a space if it can be excluded as noted in the matrix, for most spaces. Circulation areas will get called out. But if you have provided daylight to the space, then include it. But you need to be consistent with it.
Hope that helps.
Thank you for your in depth explanations, really appreciated. There are so much grey areas sometimes that this is hard to make a best judgment call.
I hope we will find a solution if we are short on getting 75% of daylight overall, otherwise, that might be a lost battle since I don't think we can make it with the ballroom being included. I will get back to this topic if I see hope in it!
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