Schools 2009 IEQc8.1: Daylight and Views—Daylight

Sounds like a download issue, or an error in the script. Down load it again and save it some where else. I personally create my own spreadsheets that do the same thing as the one's available. This way it can be modified and i can correct any issues.

Lauren, if you can send me the spreadsheet, I can take a look on that.

Todd is correct that it may be the macros from the excel. I didn't have any problem using their spreadsheet last time but there was a formula error last time in one of them. I agree with Todd, if you can make your own, it's much better.

Thanks, Eddy. I figured out what is going on with the template. I am trying to get the toplighting percentage between 3 and 6 to comply, and am reducing the zone floor area to reach that number. The calculator is using the actual floor area, but I think that it should be using the zone floor area to calculate the toplighted area. Someone from GBCI has been helping me, but it's still not working! At least I know what is wrong now. Thank you!

It's good, Lauren.. You may need to double check though.. as I remember, the new amendment define that the zone floor area is the daylit area.

Felix you are correct with the ZFA. The reason for the difference between sidelighting and the toplighting calculations is because there is a big difference between how sidelighting and toplighting actually works. If such a method were to have the same means of calculating sidelighting and toplighting, it would be invalid. The view, or access to the sky vault is completely different between the two scenarios.

I do not know of any tutorials that show you how the areas are calculated. I suggest you personally consult with someone who knows how to correctly document this credit.

Thanks Todd. After I posted that I signed up as a LEEDuser member and the resource materials posted here helped me quite a bit. I ended up calculating each room in its entirety.

Felix,
The "Sample Prescriptive Compliance Calculation and Path" file in the Documentation Toolkit tab above may help answer some of your questions.

The graphics show how the floor area zones are set up and then adjusted to first determine how much daylight coverage you get from side lighting. You may want to do all the side lighting calcs first for all the rooms to see how close you are to 75% of your 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..

Then, look at any areas in a room that don't have enough daylight and assess whether you have toplighting over those areas. If you do, analyze the additional daylight provided by skylights for those top-lit areas that are below the skylight as defined by the footnote #5 (using ceiling height, distance to next skylight or partition, etc.)

Since it would be possible to over-estimate daylight provided if you add the lighting provided by sidelight and toplight for the same floor area, there's a note at the top saying "only one daylight method may be selected for a space." I think most users assume that Prescriptive section in columns M-Z is one "method," but my understanding is that this spreadsheet can only analyze the light hitting an area of the floor from one source - either all from the side or all from the top.

This might be clear as mud... if you're confused, look at the graphic for Step 6 in the LEEDUser sample above. This example doesn't use the 2009 spreadsheet - it uses a simpler scenario to manually calculate the areas being day lit. Notice in the example how an area that has both side light and top light doesn't get double counted since they are looking at the % of the space that is not-day lit - 550 sf. But in the spreadsheet, I don't think there's a way to distinguish in one space (one row of the spreadsheet) the areas that are have only top light, only sidelight, or a mixture of the two.

The work around might be to define smaller spaces or zones based on what kind of day lighting they receive- say, a perimeter zone of a class room that only gets sidelight, and an interior area that's all top lit.

This prescriptive method has used different calculation methods in several different LEED versions, and has always been an imperfect tool. To make it more accurate would make it even more complicated... so for some situations it just won't give an accurate assessment of the daylight. If that's the case, you'll have to use either the Simulation path or the Measurement path.
Hope that helps,

The prescriptive method is a means to provide projects some type of guidelines that will get them some daylighting scenarios that would be better if they had not even considered daylight. It is method of formulas and rules. It is not a method that can effectively or accurately provide projects teams information about the performance of their daylighting scenarios.It is not meant for anything other than punched openings in a building envelope.

Your not going to get the actual performance of the solartube using the prescriptive method. You will need to use a combination of methods as Solar tube had mentioned. When simulating soar tubes you will actually simulate them as electric lights. You can get the IES file from Solar Tube to do this.

Dana,

I'm working on a project which will also attempt to earn the daylighting credit with the prescriptive approach, and is also using Solatube skylights. I would be interested in what your outcome was if you have had your project reviewed- and how you chose to document the Solatubes.

We have an approach we used during design - allowing us to decide how many we needed, how to space them, and we expected it to comply with the LEED requirements, but it hasn't been submitted yet. I don't want to post our idea on the forum in-case it's incorrect- (then it will just confusion), but we can compare notes if you haven't submitted yet. Here is my contact mnolan (at) BelayArchitecture (dot) com -thanks!

Susan,
What you need to simulate is footcandles to meet the credit requirements. Daysim provides daylight autonomy ratios, which are based upon a whole year worth of sky conditions and not just one time step. Radiance does not simulate daylight autonomy like Daysim, but Daysim does use a Radiance engine.

My suggestion to you, and this is if you have Sketchup Pro, export the model into a dxf or other compatible format. Import into Ecotec, and then run the lighting analysis with the export to Radiance. You can then import the Radiance file back into Ecotec. The numbers will be in LuxMeasurement of lumens per square meter., so in the import data table, you will have to revise the equation to convert the incoming lux to footcandles. You can also leave it at lux and explain to the reviewer in narrative the lux levels which meet the requirement.

Hope that helps

Caroline,
What is your step set to in Daysim? In Daysim you can set the time step to have the program look at the weather from every 5 minutes up to every 60 minutes. By setting it to 60 minutes you'll decrease your simulation time and you may get results that are closer to clear sky conditions.

You may need to really explain your methodology to the reviewer on this. Just stating that you got better results on those days will not cut it. The reviewer may not be as familair with how Daysim works as you so you will need to justify the results. I would dig in the weather file and look for those 3 days, pull out the sky illuminance for those days. Use that information to show the reviewer that clear sky conditions for the projects location has an illuminance of ( ) and typical cloudy conditions have an illuminance of ( ). Based on the average illuminance of those days, the date you use is closer to clear sky conditions for the site. You may have to add some fcs to your calcs since how daysim is looking at weather conditions and there are times in there which are cloudy. State that those days are closer to clear sky conditions than the 21st.

For this version of LEED it requires clear sky conditions to demonstrate compliance, this is because it requires projects to consider direct solar impacts. If the 2012 daylight credit were a pilot credit, you would have an easier time. The reviewer could deny it because the calculations where not done under true clear sky conditions.

I have only played with Daysim plugin for Sketchup and not sure if it allows you to run radiance and import the radiance results. This would be better for this version of LEED.

Tyler,
Not sure as to exactly what you are asking. So you are saying that the rooms you are simulating will only meet the credit requirements if the amount of glazing is changed? What program are you using? Is your VLT correct? Are all your input parameters correct? Is it only meeting at one time and not the other?

Lots of unknowns to your question so if you could be more specific it would help in providing you an answer that will help.

Sorry for the lack of info.
I am using IES ve with a sketch up model.
I am working with a 5000 sf cafeteria that has just under 2000 sf of glazing..
the room is meeting the 9am simulation but not the 3pm.
I have my parameters in to the best of my knowledge with the IES ve Program.
It seems that we have a few rooms with large amounts of glass that go over the maximum threshold for this credit. Does anyone know how to work around this?
Thank you!

There is no work around for this. There have been complaints about the 500fc limit at these times in trying to meet the requirements. I think the next addenda may be addressing this issue.
If you have this submit this soon, this is what i would do. Run a simulation with binds half way down the window and all the way down. You can do this two ways to simulate blinds. Actually create a blind in the model and give it an opacity of 10%. Or you can take half the window area and make it translucent with a 10% VLT. Assuming then that you meet the requirement, make the argument that blinds will be in all those spaces and they will be used. People use blinds to reduce direct sun, especially in schools and an assumption that occupants would not lower the blinds is not accurate. DAYSIM, which is yearly daylight simulation program and calculates daylight autonomy uses blinds in the calculations. The reason that the blind option is there is that we know people use blinds. The trick is figuring out at what level of illuminance do people pull the blinds down. Anyway, state the argument that it is not possible for space with easterly or westerly facing spaces to meet the 500 limit. Automated shades are costly, and again, shades will be installed and used.

Have you modeled all exterior buildings and other natural features? There is no barren sight. So if you have buildings or terrain that would help use it. I would on a project that was located very close to the north side of a very large mountain. The sun never impacted the east elevation till late in the morning in the summer time. Without actually modelling the terrain, the project would have issues meeting the 500fc limit even with exterior shading.

Good luck

Do you know when the next addenda may be coming out?

This is a school in Falmouth, Maine. there are no other buildings around just lots of trees along the outside of the site.

Thank you!

Tyler,
the new addenda may help you. It said "Identify the area of the room that has daylight illumination between 10 footcandles and 500 footcandles at both times (9:00 am and 3:00 pm).Spaces that do not meet the daylight illumination levels at both times do not qualify."

Diana,
The manufacturers data will provide the VLT of the Window. Depending on how the unit is built, such as thickness of glass one, location of any films or coatings, and the thickness of glass two, will determine the center of glass VLTs.

Diana,
you can also use Window6 software to calculate by inputting each glass type and the thickness of the gap.

There is a LEED interpretation Inquiry number 5748 from 4/18/05 that states that areas with movable furniture cannot be excluded but storage areas can. I could see this being used to justify exclusion of built-in cabinetry. That space, obviously, cannot be occupied so it stands to reason it cannot be regularly occupied.

Jill,

Thanks for the advice. I looked a little closer at this 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 and one statement makes me a little nervous - 2) The areas to be categorized as "regularly occupied" should include all spaces that an occupant would utilize in the course of their daily work. Though I can't apply this CIR to my project I will use it if challenged by the reviewer but I'm not expecting it to carry much weight with the new LEED Interpretations process.

Thanks again & best of luck,

John Drigot

I agree with you. The calculation method is not a robust method. I will suggest to use simulation method. I think if there is no direct light in the room, the room will comply easily.

Do you have any program suggestions for the simulation method? I have been trying to figure out a couple different ones but would like some input from others that have done this before.
Thank you!

Tyler,

At our company we have used two software packages, Autodesk's 3d Studio Max and AGI. It seems like AGI has less of a learning curve than 3d Studio Max. What we haven't found yet is a daylighting simulation software that takes the results from 9am and 3pm and gives you the net percentage which is compliant. Any ideas anyone?

Tyler, I use Ecotect as GUI and run the calculation in Radiance engine. Additionally, I heard AGI is a good tool as well.

Carol,
To address your initial question of too much window area: from your description it does sound like you have too much window area and quite a high VLT.

In what way do you think that reducing your window area does not follow the purpose of the credit? A lot more information about your project is needed to assess this, for example, what is the use of the room (a classroom) ? What are the hours of the room? Is the building heating load or cooling load dominant? Are the windows on the same wall or two different walls with two different orientations? What is the height of the window head height? What is the height of the ceiling?

Glare and over-glazing are the two main enemies of good daylighting. What type of shading devices are being provided?

To answer the software question, first a question in reply: What kind of resources do you have to commit to purchasing, learning and using daylighting software? If you do not have roughly $1,000/2 years, at least 40-80 training hours and roughly 4-8 hours per room simulation, you are probably better off hiring a daylighting consultant or simulationist on an as-needed basis. Daylighting simulations are like any other computer software, garbage in-garbage out, so you need someone who is experienced with the output to make sure that it is accurate.

I have a similar situation. My project has a large overhang external shading, but with big windows. Simulation results show all the perimeter rooms with almost no light at Sep 21 09:00 and 15:00. However, when I attempt with the prescriptive method, my WTF ratios are too large for compliance! My TvisVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380–780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing. is 0.83.

Something is wrong here. And also is the "Daylit zone" deturmined from the 62º rule (or is that only for internally dropped ceilings), or is it 2H where H is the allowable window height for calculations, OR is it the bayA bay is a component of a standard, rectilinear building design. It is the open area defined by a building element such as columns or a window. Typically, there are multiple identical bays in succession. depth to the back wall of the zone?

Jean,
What simulation program are you running? Something appears to be wrong if simulation is showing nothing with a TVISVisible light transmittance (VLT) (Tvis) is the ratio of total transmitted light to total incident light (i.e., the amount of visible spectrum, 380–780 nanometers of light passing through a glazing surface divided by the amount of light striking the glazing surface). The higher the Tvis value, the more incident light passes through the glazing. of 0.83 (This TVIS is typical for interior glazing or single glazing. Seems high for an exterior glazing component) and your WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area. is too big. I would say you have an input error or you modeled something incorrectly. I have done projects were the WFR was too small to meet compliance, yet, both simulation and actual measurements show the project meeting the daylight requirements with a 63% VLT in north facing glazing.

It is actually 63 degrees, and is used to determine your daylight zone if there is a drop ceiling that would intersect the glazing if continued across the space. If there is no ceiling that would interfere with the glazing then the depth of your daylight zone is twice the window head height.

Thanks for the reply,
Actually, in my prescriptive method, I discovered a meter to foot conversion error. I just, just get 75%, but I've not limited it to 2H (we don't have any dropped ceilings under the top of the window height). That means if I recalculate with 2H...it's dead. Also, at the moment I am using a 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. area that starts on the interior side of a glass vestibule (on x2 occasions)...which makes it even more dead, if this is not accepted.

As for the simulation, I have simulated with energy plus using fullexterior reflections (and am rerunning with fullinterior and exterior reflections to see if it improves things), and got the same result when running the model in the new DesignBuilder v3 Daylighting simulation which uses Radiance.

There are public picture up of the building here: http://www.schloss-geister.de/nachricht/items/baufortschritt-28-juni-2011/

The funny thing is, is when you look at the model and try to tell someone that it doesn't have "good enough" daylighting, they will laugh in your face.

It looks like I used the 62º Rule on the lighting through the glass vestibules which gave 0ft² conforming square meter. So I'm still in there with a chance.

Jean,
I did laugh when i saw the pictures. Those spaces have to meet the daylight requirements. A far as the programs that you are using for daylighting, i do not have any experience with any of them. I will say that i probably wouldn;t rely on energy plus to calculate my daylighting.

You might break down each space into multiple daylight zones. Break the spaces down so that the WFRWindow-to-floor ratio (WFR) is the total area of the window (measured vertically from 30 inches above the finished floor to the top of the glass, multiplied by the width of the glass) divided by the floor area. meets the requirements. For documentation, provide a table showing the multiple zones for each space and how they meet the requirement.

One last question: Is H (for the daylit area depth) = window head height (adjusted down with 63° rule if applicable, due to underhang) to FLOOR or to the 30" above finished floor level (as used for the window area calculation)?

It would be to the floor. The 30 inches is the minimum height that can be used to calculate usable glazing. This is the same height that was used for 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. Basically, any glazing under 30" in height does not contribute to usable daylight on the work surface.

Hi Jill,

it is hard to me to determine without drawings whether the approach is suitable. The approach will depend on the location of the clerestory.

You may refer to page 404 and check whether you can classify your room as non-regurlarly occupied. I suggest to add narrative about the room usage if you classify the room as the non-regurlarly occupied space.

Great question. I was wondering the same thing...

In my opinion, typical chairs and desks can be excluded since it may not affect significantly illuminance level. However, you may consult with your daylight consultant or modeler for further discussion. If you can include all furniture, it will be better.

To increase the accuracy, you may even try to adjust your grid position according to the height of typical desk in the classroom, but your reviewer may not accept that since the reference mentions the grid shall be at 2'-6".

A skylight diffuser is a roof device that allows visible light to enter the building, but is not used for providing views to the outdoors. An example is a "solatube."

I understand that haze value is a measure of how much visible light is allowed through a translucent material such as a plastic used in a diffuser.

Hi Nicole,

I don't have school project under 3.0 that I can refer to. However, for 2009 LEED NC, it doesn't require elevation. You may actually refer to view credit which under v3.0, it requires to upload interior elevation or section. For views, the purpose of elevation is to define horizontal direct sight requirement.

Thanks

Hi Gendel,
I am not sure I really understand your question but I would like to try to respond. If the plan clearly mentions and defines the area as a foyer or nook area, it will be easy to be excluded. If not, in my opinion, it will be difficult to be excluded.
Another way is by using daylight simulation which you can provide set back in your grid from the wall which may exclude already the entrance area.

Thank you.

Esmeralda,
page 2 and page 3 are for classroom as well, although the header shows for non classroom. From page 4 to the end is for non-classroom. If you need more, I suggest to use copy from LEED NC Calculator or make your own spread sheet.

Alright - I will ignore the headers and just use those spaces.
Thanks so much for the fast reply!

Check out page 404 in the BD+C reference guide (IEQ Overview section). This page categorizes the spaces for schools' IEQ credits. Spaces like gymnasiums, media centers and labs are all considered classroom spaces since kids are generally in these spaces for educational activities for 1+ hours a day.

George,
In my opinion, Both 1 or 2 shall be OK.

For no 3, I am not really sure what your question is. However, you can assume your 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. is your classroom.

For no 4, it looks like LEED requires glare control for each window. You can check last bullet of option 1 and 3. In option 2, the sample of calculation shows the glare control provided in non-compliance area.

Hope it will help.

Eddy, thanks for your reply.

The idea is that when considering option 1, you require that 75% of the number of classrooms be compliant.
However, option 2 seems to allow for a trade-off between classrooms.
For example, I may have 40 non-compliant classrooms, by which 20 are underexposed to light (ex, Compliant area / Class area = 60%) and 20 are overexposed (ex, Compliant area / Class area = 130%).
It is very possible that when adding the total compliant areas and dividing by the total classroom areas to get a value of 90% for example, by which this indicates "overall compliance".

Many thanks,

Yes, they are regularly occupied and for the majority of their use are not compromised or hindered by the presence of daylight (shades could be used to darken the room when needed). Daylight is quite valuable for these spaces.

This question was just answered over on the NC forum for this credit. Eddy Santosa said:

You cannot use ECOTECT daylight reports for credit compliance.
The reason is that ECOTECT does not have capability to do daylight
calculation under "clear-sky" condition as it is required by IEQ c8.1.
ECOTECT daylight calculation has only "uniform" and "overcast" sky
condition options. However, you can export and do the calculation with
RADIANCE engine by using ECOTECT.

Thank you for posting this helpful resource. Does the Daylighting Collaborative work on LEED projects? If so, do you have any tips about daylighting design in relation to LEED that we haven't covered that you might be willing to share based on your experience?
Thanks,
Seema