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Use a collaborative design process
Access to daylight inside buildings makes for healthier and more comfortable occupants—and is also linked with greater productivity. When designed with proper glare control and minimized solar heat gain, daylighting provides high-quality light while significantly reducing energy use for lighting and for cooling. Increased daylight through increased vision glazing can help projects earn EQc8.2 for access to views. Realizing the benefits of daylighting requires a collaborative design process.
Balance other design goals
Keep in mind that daylighting strategies must balance with other design goals. For example, you will want to provide enough glazing area for daylighting, plan for open spaces that allow for light transfer, but not at the expense of too much heat...
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107 Comments
Anyone tried ID credit for dayligting > than 75% reg occ spaces?
Has anyone applied for and/or received ID credit for dayligting more than 75% of regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building.? We have a building that provides daylight to 67% of all spaces including kitchen, bathroom, maint. workroom, offices and conference rooms. I'm just wondering if a project got denied such a credit what the GBCI's comments were denying such. OR if your project did get the ID credit we'd like to know your approach to documentation.
Thank you!
Debra Lombard, LEED AP, EMIT, EIT
Well 67% will not even meet the minimum level for one point. The 2.2 Reference Guide states that 95% is the minimum for any option used and must follow the requirements of the credit.
Simmulation help..
Hello,
We just recieved our reveiw comments back on one of the school projects that was done using Schools 2007. We did not get the daylight credit and got the suggestion to do simulation in addtion to clarifying the calculation method. We currently have the drawings in Autodesk Building Systems 2004, does anyone know of a program we might be able to make use of that will work with our current plans? Or has anyone had luck doing metering to off set the calculations method?
Thank you
Well you can use Ecotect which is an Autodesk product which you can import to radiance. Depending on the complexity of the design and the shape of the space, you could use SPOT. 3d Studio Max will also do simulations which is an autodesk product.
Todd, Thanks for your reply. I am looking to figure out some rooms that have borrowed lights. which seems to be a problem for this school. I will take a look at these programs though.
We have had luck with the measurement option. Not sure what you mean by offsetting the calculations. As you know, 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 cannot be used for borrowed light.
I will be curious to know what you decide on. Please post back when you do! Thanks
Tyler,
I see your issue now. So you attempted the credit using the glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. calculation, in which borrowed light scenarios can not be used. Depending on the number of spaces that have this scenario and if the project is already built, the measurement option might be more feasible. I'm assuming the learning curve on doing simulations and the time in which you need to re-submit.
Did you adjust your glazing factor calculations for compliant and no-compliant square footage to see if you earn the credit that way?
Tyler,
If the simulation you need is just a lighting simulation, I believe Autodesk Building Systems 2004 has a simple version of Autodesk VIZ that comes with the product. As long as your model is in 3D you should be able to do a daylight simulation and export it to an avi file.
Todd- Yes we did adjust the compliant and non compliant square footages and it still does not work. we are looking into some simulation programs but measurements seem a much easier way to go with the time we have. I will pass along the out come. Thank you for your information!
Tyler and Philip,
Unfortunately, Autodesk VIZ is not a valid software for LEED daylighting calculations, although I hear it does produce nice renderings. The only product from Autodesk that can produce these calculations directly is 3DS Max Design. Autodesk's Ecotect can export to Radiance (included) for these calculations as well. It's best if you know something about Radiance in order to produce the required LEED documetation. And I think you can use Autodesk's Green Building Studio service with Revit for export to Radiance too. Personally, I use AGi32 for LEED daylighting calculations.
See these links for some discussion on lighting calculation software.
http://www.leeduser.com/credit/CI-2009/IEQc8.1
http://www.leeduser.com/credit/NC-2009/iEQc8.1?page=3
Daylighting for Nurseries
We are working on a project that has 'Crib Rooms' which are meant to be sound and light isolated as they are meant for sleeping babies only. We are looking at this as a non-regularly occupied space becase it is essentially serving as 'baby storage,' and daylighting/views would not be beneficial in any way. Again, these spaces are only for sleeping babies, not for awake children. Please help.
Your argument is this. Describe what the space is for and how and why daylight is detrimental to the activity of the space. Technically that should be sufficient, but if this space has a bunch of windows and you are not considering it in the calcs, then that may be questioned as to why it was designed with lots of windows. If it is in the core, then it makes sense.
Church
Should the meeting room for weekend use by a church be considered a regular occupied space? Yelena
Yes, a meeting room is like a conference room and must be included, even though it is only once a week. Occupants should still benefit from daylight and views regardless of the current frequency of use. This space may only be used once a week by the church, but what's to day that they do not rent it out to local groups on a more regularly basis.
Documentation
Our project was denied this point for being just under the threshold (74.98%). We were not going to change the design of the windows, but the owner has had to increase the width of a hand full of windows by 3" in order to meet code. The increase gets us to well above 75% and we are going to appeal, but are unsure of what exact documentation we should submit to prove that the windows are indeed going to be larger. I have a floor plan that outlines all of the windows which will be modified, and plan on getting a letter from the owner and architect explaining the situation. Would this typically be enough evidence to support our new design and new daylighting percentage?
Prudence,
The additional info you mention sounds like it would be enough to support the new percentage and not look like you were "cooking the books." It might also help to include any documentation of the code issue that triggered the width change such as plan check comments if available.
Change orders and invoices and contracts are also helpful to verify that the change has or will be occurring. The reviewer needs to take professionals or owners signature as the truth, but the other helps eliminate the doubt.
Do not remove previously submitted documentation. i suggest that you upload a copy of the original calculations. Provide a narrative explaining the reason for the appeal and what was done to earn the credit.
My suggestion is: Please don't forget your elevation drawings (before and after) and provide narrative that explains why you appeal the credit.
template
if i have a project with 14 floors that are typical do i have to submit space by space for each floor in the (supporting calculator) for documentation purposes?
No, do just one floor completely. Then in just the total for the other floors to be placed in calculations. Supply a narrative explaining your method along with floor plans that verify the floors are the same.
Gross Floor Area for calculating "regularly occupied gross area"
Does the thickness of the exterior wall get included when calculating the "regularly occupied gross area" on PI Form 3, Occupant and Usage Data? I did at first, as gross to me always usually does.
The inconsistency right now in my calc's is that I excluded the exterior wall area in the "supplemental daylight and views calculation spreadsheet" which I am using for IEQ 8.2. I am going for the prescriptive method. The problem is that I have 2' of strawbale wall on the exterior, which is significant amount of area not being carried over to the spreadsheet.
It doesn't seem like you should be including the exterior wall area when figuring daylighting, but I either I need to go back and exclude the exterior wall area from the PI form or add the exterior wall into the daylight zone area so that I get an accurate calculation.
Yes, regularly occupied area should really be Net, not Gross, so don't include wall thickness. This has confused a lot of people. Are you using certifying under version 2.2 or version 3 (2009)? The forms behave quite differently, and in version 3 you'll want to check via the "Feedback" link if there is an updated credit form and PI Form 3.
Thanks! That makes sense. I will just have to back out the gross area for walls, etc. and show under unconditioned gross area.
We are on Version 3. I'll have to check on the most current forms.
Daylight into interior space
I have a daycare center with a few occupied rooms falling in the center "core" surrounded by support space or classrooms. We have interior windows in the core room that allow you to see all the way out and plenty of windows on exterior walls. Some daylight is being provided but through the interior window. Are you able to count daylight into a core space through one window, as you are allowed to do with views?
Yes, you can count by using daylight simulation or measurement but you can't use the prescriptive as your calculation method.
By prescriptive method, do you mean calculations?
Our project is LEED Canada NC V-1. We have a MURB where the kitchen is in the core of the room. It has a doorway into a dining room with a large window, and a pass-though window into a living room with a window and a patio door. How can we show there is daylight in the kitchen? Could the openings be counted as vision glazing with 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. of 1.0 since it is just an opening with no glass?
No, prescriptive method and calculations are not synonymous. I don't know about LEED Canada but for the US LEED, the prescriptive method is also Option 2 in the credit and it is not possible to show that you have daylighting in your kitchen using it. The only way is through a daylighting computer simulation (Option 1), measurement (Option 3) or both (Option 4). It doesn't matter what the TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing. is of your interior window. The fact that there is a any kind of opaque wall or divider makes the prescriptive method invalid.
Thank you Jill. We will run the calculation with the kitchen having no daylighting, and because it's a small area we may still make the 75%.
Regularly Occupied Spaces
Would conference rooms in Institutional buildings such as a Medical Office Building or a Research/Lab building be considered a regularly occupied space?
in my opinion, they will be considered as 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..
Tvis for 2 windows
I am trying to determine the TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing. with the use of 2 windows for an interior space. I have an office with an exterior window with a Tvis of 0.52. That office has an interior wall with windows with a Tvis of 0.89. I am trying to determine the combined Tvis for the windows for a cubicle area beyond the interior office wall with windows for this credit. Do I multiply the 2 together (0.52 * 0.89) to get a Tvis of 0.46?
Hi Mark,
Your question indicates that you are trying to use the prescriptive method to calculate the daylighting contribution of a borrow light, which you cannot do. You must you the simulation option for this type of set up. One reason is that the opening size of the both windows has a big effect on the amount of light that reaches the cubicle area. Does that make sense? The prescriptive method is meant only for very straight-forward calculations.
Thanks for your response Jill. I understand what you are saying.
option 1 calculation strategy
Hello everyone,
i'm working on my first leed project and as we are getting closer to final submittal date (in3 weeks), we are now starting to put these submittals together. i need some help.
we are working on a 2 story office project that's placed east and west direction. we have very large curtain wall facing south and north with very open floor plates using low parition walls/cubicules. most occupied areas are right next to those windows. however, some spaces are 15'-20' away from the perimeter. i'm sure we will get some daylight from 12' tall curtainwall windows. however, in order to calculate each space 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., i have to input glazing areas. if those spaces are 15'-20' away from windows, what should i put the glazing area?
do i have to go with option 3?,
i have 3-4 rooms will have full height partition, so i know i have to do them individually, however, most of the spaces(low partition/cubicles) are in one big area. can i treat them as one big space and do the calcualtion once?
Also, i have huge conference room with big windows on the north side. with option 1 calcualtions the room won't meet the minimum 2%. can i divide room into 2 spaces and made half of the room meets the min. 2% requirement? i'm not clear if this strategy allow with option 1 calculation.
Thank you very much,
Jin
Thanks, Jin
Hi Jim,
For each space, enter the actual glazing area. Draw lines across your elevations at 2'-6" and 7'-6" above the floor level. Calculate the glazing area between these lines and enter them in as view windows. Enter the area above 7'-6" as daylight glazingA vertical window area located 7'6" above the floor. Glazing at this height is the most effective at distributing daylight deep into the interior space. area.
If you do not reach 2%, scale back the floor area in your calculations until you do. This is the square footage that complies. This area must be 75% or more of all 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. in order to get the point.
How low are your low partitions? I would say if they are at or below desk height, they are okay. Otherwise, you will need to use the other options (you can combine options.)
Good luck!
Hi Jill,
Thanks for your response. We have couple big open spaces with cubicles which divided by low partitions. They are really 50"-62" height. I was going to combine each cubicle spaces into one huge area. And calculate 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. using option 1 since they are movable partitions and furniture. Or should I completely take those spaces out of my calculation because of the height of movable partitions (being over 42" tall) even if they are 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.?
Jin, Sorry I mistook your name at first.
I'm not sure what you're asking about taking out the spaces - do you mean from the total regularly occupied space (ROS) or do you mean you will not calculate them? I don't see an exception here that would allow you to remove them from the total ROS.
Since your cubicle height is so tall, you cannot use the glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. method for calculation of the areas behind them. You must use either the simulation or measurement methods. It does not matter if they are moveable or not.
One more thing to note, depending on your building's climate, very large southern and northern curtain walls are not usually the best approach for energy use or daylighting and require careful glazing selection and shading design.
Jill,
Jin/Jim that's close enough. It's okay.
I got confused with "EQc8.2 Daylight and Views" about not counting areas with movable partition/furniture.
We have 5-6 regularly occupied rooms that are not located adjacent to the windows. We did not want to use simulation or measurement methods. By giving those 5-6 spaces 0% 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., we are at 91%, which comply with credit requirement. I was hoping to get an exemplary performanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements. point from meeting over 95%. I’m guessing, in order to calculate those 5-6 spaces, we must use measurement methods.
I'm debating weather I should do that or not for a possible point.
Anyways, thank for your comments.
Vehicle Maintainance Facility
We are certifying a 10,00 sf vehicle maintenance facility (for trucks) - basically a large repair garage with a 3,600 sf 2-storey office facility tucked in the building. A portion of the office is directly exposed to the outside while the other part is inside the facility. On the interior side, there are windows that are overlooking the maintenance area. I guess the question is, can we treat those windows as exposed to daylight even if its inside the structure? Hence, the vehicle maintenance facility has 6 -16' X 28' high roll-up doors that is always open during work hours. Thanks.
To consider whether those interior spaces with windows overlooking the maintenance 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. receives any daylight, the maintenance doors would have to be down. So the only light would be coming through the windows in the doors if they had any. To document this you would need to use either simulations or measurements.
Non-built-in Furniture and Equip't: Include in Simulation Model?
For NC 2.2 EQ 8.1 Option 2, we are using the "3DS Max Design version 2011" software to create the simulation model.
Should the simulation model be run with or without the furniture (e.g., office cube partitions)? The "Figure 2: Sample Daylight Simulation Model Output" on page 378 of the Reference Guide does not show any furniture included in the floorplan.
If the furniture is to be included, will the GBCI reviewers accept areas where the average of the readings on the 2 ft x 2 ft grid at 30" above the floor is at least 25 horizontal footcandlesHorizontal footcandles occur on a horizontal surface. They can be added together arithmetically when more than 1 source provides light to the same surface.?
If the average of the readings would not be accepted, would you suggest creating multiple, separate segmented grids that lie within the horizontal spaces between the vertical partitions and walls -- and do not fall within the vertical solids?
As would be expected, if the furniture is included and a single grid with points at every 2 ft x 2 ft is applied, a few of the points do not reach the 25 footcandle minimum because the grid points either fall inside a cube's vertical partition or fall very close to a corner of vertical partitions (even though the vast majority of the grid points on the work surfaces are well above the 25 footcandle level and so is the average for the entire area -- even including the points imbedded in and very close to the vertical partitions).
If the overall average figures are not acceptable, should we proceed according to Note 1 on page 378 of the Reference Guide and separate regularly-occupied space into conforming versus non-conforming areas?
If so, is there a minimum number of square feet (or any other required criteria) necessary to qualify as a non-conforming area? For example, would the GBCI reviewers allow us to consider even a 4 ft x 4 ft area that has a single point below 25 footcandles as its own area?
Thank you.
Hi Doug,
I cannot speak on the behalf of the reviewer. However, here is my opinion:
- If the partition is high and showed in the construction drawing, you may need to include in the calculation. Otherwise, for 2.2, it is usually OK for not including the low partition. However, it will be the best practice to include in your simulation.
- Typically, the average readings would not be acceptable.
- You may need to adjust your grid so it won’t be in the inside the partition. I think the small adjustment (6-12”) should be OK since the guide said the grid is approximately set 2 foot interval.
- You can proceed according “Note 1”, please see the point 5 of the option 2.
Hope it will help.
Moveable partitions, such as modular cubicle systems do not need to be part of the simulation for NCv2.2. I would have the furniture on a separate layer for the furniture and turn it off before running the simulation.
Yes you can submit your simulation results with the furniture in it and it will be reviewed. You may receive the comment that it appears furniture has been included in the calculations and since the credit is not earned, the furniture should be removed. If earned, then you are fine.
Circulation paths can be excluded but should highlighted and a narrative explaining the spaces not included.
With the simulation option, you will just provide the area of compliant regularly occupied in relation overall regularly occupied. Separating the compliant vs. the non-compliant regularly occupied is a method used in 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.
Your grid for spaces under 1000 sq ft, should be on a 2x2 grid. This will give you a are more accurate result as to exactly how the daylight distribution is in the space.
In general, i would include all furniture in my daylight simulations. This is how the space is going to be used, so yo need to see what will happen as it is used. Cubicles can be notorious light sponges if the color chosen is dark. This is why you need to run it with the furniture. You find out very quickly that your daylight penetration and distribution is quite different form just an open floor plate.
Option 3 - Meter reading height
We are wondering at what height the light readings should be taken at. We don't find anywhere in the credit where it says what height the 25 foot candles is required - is that at floor level, seated height, or ???? It's possible it doesn't matter but we want to take the readings at the required level if there is a requirement. Thanks for your help.
Great that your doing the meter readings - ideally they will confirm the daylight analysis done during design development!
Take your readings at the work surface height - typically 30" above the finished floor. 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. on a 10 foot grid.
Glass vs Window?
I have some glass cut sheets that give the "Visible Light Transmittance" as 75% and the window cut sheets (the window contains the glass from above) that give a "Visible Transmittance Total Window" of 0.549. Which one should we be using as the Actual 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. in the Daylight FactorThe ratio of exterior illumination to interior illumination, expressed as a percentage. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis), and window height. Calculation? Thanks!
You need to use the glass VLT and not the TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing. for the window unit. The glazing factorThe ratio of interior illuminance at a given point on a given plane (usually the work plane) to the exterior illuminance under known overcast sky conditions. LEED uses a simplified approach for its credit compliance calculations. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis) and window height. calculation uses the area of glass and does not consider total window unit area.
Using Atrium space to account for Daylight
We are working on a two-storey building with a central atrium space having large clerestory windowsPronounced and sometimes spelled "clear-story," these are vertical, or close-to-vertical, windows high in the wall of a building that bring daylight deeply into the building and, if operable, can help ventilate the space. on the roof. The spaces surrounding the atrium well on the first and second floors have clear glass from floor ro ceiling to take advantage of the daylight.
We are using the Daylight FactorThe ratio of exterior illumination to interior illumination, expressed as a percentage. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis), and window height. approach to document this credit. How do we account account for the clerestory windows for both first and second floors?
Jim,
You using 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. method, which is the formula method, which cannot be used with shared daylighting scenarios as you describe. The reason being is that the formula only accounts for one glazing component and there are multiple window geometry factors which cannot be weighted into an average in the formula. If you are trying to show credit compliance for EQc 8.1, you should use the simulation method.
IEQ 8.1 Daylight and Views- Option 2. Prescriptive Method
Has anyone use the scorecard for option 2? It's very confusing in terms of what they meant by daylighting zone, 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. width, bay depth etc. Does anyone have a good example of how to do the prescriptive calculations?
You may refer to Kathleen Burke Jun 02 2010 discussion in IEQc8.1 forum for LEED 2009 rating system.
Daylight factor or daylight simulation model
I would like to clarify regarding Option-1daylight factor & Option-2 daylight simulation. I have completed office & factory building daylight calculation with both options and option 1 is complying with 85% and option 2 is not complying . How can we determine the daylight is meeting the requirments moreover simulation is more reality than daylight factor. Can anyone help me?
Good question. I don't know why the expence has been made to do both options. I aggree the simulation (if properly done) is more likely to reflect reality and will be more stringent, but as to your question...that is something the USGBC would have to decide on. If your option 1 complies, then you have proven that good design practice is employed to ensure healthy daylighting. I would say that that is the most important, not that the exact daylighting levels are less than expected after the design. Here, I believe one should "get points for trying".
Technically, you could submit the complying option and out of good practice submit the results of the simulation as a sublimental to option 1, explaining why the expected daylighting is not being achieved dispite the good design.
In order to ensure that I will get daylight in building, I usually do more simulations beyond what LEED requests in option 2.
However, sometimes, I do a minimum effort to just get the point including using option 1. The good practice is always by using simulation and you may even try to simulate daylight beyond what LEED requests.
The Option 1 calculation of daylight factorThe ratio of exterior illumination to interior illumination, expressed as a percentage. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis), and window height. is less reliable than a computer simulation, and has been offered under version 2.2 as a simpler path to demonstrate credit compliance for some project types. Since it cannot account for important design parameters such as wall color, reflectance, exterior obstructions, or room geometry, it is a fairly rough approximation of daylight performance. Depending on the specific design, the Option 1 method may come close to actual or simulated performance, in some cases, but in others could be as different as you found. It's more of a "rule-of-thumb" estimate based on glazing to floor area ratios that works best for very regular building geometry.
Note that under the proposed 2012 requirements for this credit, this calculation option may no longer be offered, and only computer simulation or measurements of actual illuminance may be used to comply.
As professionals, we've probably all seen cases where it is possible to meet a technical or regulatory requirement, especially an older one, in a way that might not provide the best results for a client. Since it is acceptable to the GBCI to document credit compliance with the Option 1 calculation since you are registered under version 2.2, it might be simplest to submit just that result. And it sounds like you're already looking at the simulation results to decide if the design is providing the lighting performance that would meet the intent of the client.
The question is what is you daylighting goal? Are you looking to just earn the daylight credit, or are your wanting to provide the appropriate daylight levels for your client? If you are looking to provide the proper daylight levels then simulation is the method of choice.
Daylight FactorThe ratio of exterior illumination to interior illumination, expressed as a percentage. The variables used to determine the daylight factor include the floor area, window area, window geometry, visible transmittance (Tvis), and window height. is actually the percentage of exterior illuminance impacting a point on the interior. 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 are just a formula, and as previously noted, it is like following the rules of thumb.
We have done buildings where they will not meet the LEED requirements using the glazing factor calcs. The reason being is that the window to floor ratio was too low for the VLT in the window. Yet, simulation, both illuminance calcs and DAR (daylight autonomy ratio, and actually measurements have the space not only earning the credit but providing the proper quantity and quality of daylight.
I have found that if you have at least a window to floor area ratioFloor Area Ratio (FAR) is the measure of the density of non-residential land use. It is the total non-residential building floor area divided by the total buildable land area available for non-residential uses. For example, on a site with 10,000 square feet of buildable land area, an FAR of 1.0 would be 10,000 square feet of built building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet of built floor area; an FAR of 2.0 would be 20,000 built square feet and an FAR of 0.5 would be 5,000 built square feet. of at least 14% with a VLT of at least 60, you will earn the daylight credit. This has nothing to do with quality, which is one of the reasons that the glazing factor and prescriptive option has been removed in LEED 2012
What program are you using? I'm experimenting with IES plugin for Revit, has anyone had experience with this, especially how USGBC has responded to the results?
Daylight calculations for future tenant spaces-HELP!
Question: I am tasked with determining the daylight calculations for a 2-story office and retail building. The building is currently under construction and it includes future tenant spaces that have not been designed with interior space plans. How is it possible to determine the amount of regularly occupied areas within future tenant spaces for compliance with the daylight credit?
Peter, the answer here is the same as the similar discussion on EQc8.2.
Regularly occupied spaces within a dining facility
Has anyone had experience with determining "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." within a dining facility? Would the kitchen, food prep, dish wash areas, be included? I am thinking, yes since they are spaces in which people will be standing while they work, but am not finding any CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide's that specificallly state which spaces should be included for a dining facility.
Yes, those spaces would need to be included, since they are work spaces requiring good illuminance.
EQc8.1 - Room Splitting
We have numerous projects that are so close to getting 75% daylighting but are just a little short. In these cases we usually split the rooms, meaining decreasing the floor sf to increase the Window to Floor Area ratioFloor Area Ratio (FAR) is the measure of the density of non-residential land use. It is the total non-residential building floor area divided by the total buildable land area available for non-residential uses. For example, on a site with 10,000 square feet of buildable land area, an FAR of 1.0 would be 10,000 square feet of built building floor area. On the same site, an FAR of 1.5 would be 15,000 square feet of built floor area; an FAR of 2.0 would be 20,000 built square feet and an FAR of 0.5 would be 5,000 built square feet., therefore increasing 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.. Does anyone else do this? We show on the drawing plans areas that are not receiving daylight and consider these areas that aren't hindered by not having any daylight. By exluding these small portions of the floor area (essentially along the walls and corners where cabinets or printers might be located) we are able to achieve EQc8.1.
GBCI has been picky lately asking to clarify these methods and even denied the credit once although we have been doing it this way for a while.
Does anyone have tips or know more about this loophole?
Thanks
You may try to use page 378 in the LEED reference.
For cabinet and printer, in my opinion, you may need include those ones since those areas are actually where the tasks will be conducted, except the cabinet is a full height cabinet.
Does anyone know if this can be used with LEED for Schools 2007 as well? I have found that it is in v2.2 and LEED for Schools 2009 but it is not spelled out in the 2007 version.
Thanks!
Tyler, I think it can be used.
Option 3 - Measurement Timeframe?
What is the timeframe during the day that is recommended/required for manual indoor light measurement of a space? Must an average be calculated from various times throughout the course of the day?
Adolfo - based on what I understand you don't have to take an average over the course of the day. I recommend you take the measurements during the time of the day that the most people will experience the space.
How to calculate Open Space workstations and circulation areas.
We have a corporate headquarters renovation with major shell modifications to introduce daylighting to the interior. There are a few open plan workstation spaces distributed through out and I can not locate the complete ruling on how much floor area to include around these spaces in the "Regularly Occupied Space" category. RealLifeLEED refers to a ruling on Circulation paths within open office environments in offices (LEED-NCv2.0 and 2.1 - EQc6.1 - 06.26.01), but I can't find the teexet of the full ruling. Can anyone point me to the consensus method for determination of ROS in an office environment? Do I include or exclude corridors. Can I an exclude and existing Lecture Hall, Kitchen and Servery that are internal and not adaptable to natural light?
Gary,
http://www.usgbc.org/LEED/Credit/CIRDetails.aspx?RequirementID=61
You may check in above link if you want to see the full ruling. If you have a future interior of the space, you can use the layout to determine the circulation path. For corridors, you can exclude the space. For other rooms, you can check "Exclusion of Space Requiring No Light Intrusion" discussion.
Eddy,
Thanks, that helps a great deal. I couldn't find these under Public Rulings, didn't think to dig beyond. I am not finding the "Exclusion of space.." discussion, moist likely because I am new to the site. Is there a better way to search than entering the text string?
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