NC 2009 IEQc8.1: Daylight and Views—Daylight

I'd would look at areas that are identical to reduce the amount of measurements first. I would say an approach of grouping similar areas would be acceptable. If its a flat roof and there are not any exterior objects that would block the skydome from any one skylight this could be simple. If its not a flat roof, then the distance from the floor to skylight and the angle and orientation of the skylight would require more work to show similarities to the reviewer.

700k sf at a 10-foot spacing is actually only (!) 7,000 so I just saved you 700 measurements right there...

Are all 700k sf considered regularly occupied space? Most warehouse space is not. If you have an office space that is daylit within the warehouse, you can get the credit by just showing that the office space is the only regularly occupied space and that 75% of it complies.

If it is considered regularly occupied, I could see an argument for something more like a 20' spacing. The addenda hint at using a spacing that is appropriate for the scale of your building. Might be worth a try. If you do, I would explain the repetitive nature of the building layout and assuming you have a high-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. ceiling, would explain that this type of ceiling produces a better max/min layout requiring less frequent measurement spacing.

yes

Matthew, It's actually a simple measurement. There is no requirement who should conduct the measurement in LEED. Thus, anyone who knows can do the measurement.

Thank you Eddy. One other question: When attempting Option 3, does the same rule from Option 2 apply where if 75% or more of the space complies then 100% of the area may be calculated? For example: If there are 4 readings in a room, 3 are compliant and one is below 10fc, then does the entire space 'pass'? If not, then how does one calculate the portion of the area that does pass?

No. And actually, I believe the 75/100 rule only applies to the Views calculation?

If there are 4 readings in a room and 3 of them are compliant, 75% of the area of the room gets added to the compliant area. You don't pass/fail based on rooms, you pass/fail based on % of compliant area to total are of ROS.

The last addenda issued by USGBC changed the minimum requirement to 10fc. This is only noted in the addenda so Reference Guides will not show this . I assume the 25fc minimum you have seen in the forums and the threads were prior to this addenda.

Where did you hear this from? I've never heard of this or read about any issues on this.

Several places, but here is one example: http://biggreenboulder.com/tag/leed/

Thanks,

I think the statement that LEED buildings have create poor cell phone reception is not relevant or accurate. There are alot of buildings, that are not LEED that have poor reception. I think the most accurate statement would be buildings with heavy mass (reinforced concrete, masonry) and high performance glazing tend to have weaker cell phone signals.

I would like to see a study that actual compares different low e coatings and how it reduces reception before i would consider such statements relevant.

As in the article you had linked, it clearly states that the reception was already poor in the area. So i think there are too many variables to just link LEED buildings.

I heard the low e coating may impact the signal strength because the low-eLow-E or Low-Emissivity Coating: Very thin metallic coating on glass or plastic window glazing that reduces heat loss and heat gain through the window; the coating emits less radiant energy (heat radiation), which makes it, in effect, reflective to that heat. In that way it boosts a window's R-value and reduces its U-factor. is metal oxide coating. However, I suspect it shouldn't be the solely factor in the problem.

Our office is a LEED building and uses low-e glass (air filled) and I never experience any issue with my cell phone in any location or weak cell phone signal. I guess the layout of the interior may be a factor as well, because our building is mostly open space areaOpen space area is usually defined by local zoning requirements. If local zoning requirements do not clearly define open space, it is defined for the purposes of LEED calculations as the property area minus the development footprint; it must be vegetated and pervious, with exceptions only as noted in the credit requirements section. Only ground areas are calculated as open space. For projects located in urban areas that earn a Development Density and Community Connectivity credit, open space also includes nonvehicular, pedestrian-oriented hardscape spaces. with low partition between the cubicle.

I believe you may be confusing Low E glazing with RF (radio frequency) shieldingShielding is a nontechnical term that describes devices or techniques that are used as part of a luminaire or lamp to limit glare, light trespass, or sky glow. film? This type of glazing film is used in high security situations to block cell phone and other communications from entering a secure space. This is an entirely different product than the typical Low E coatings used in the industry.

Building is Europe and particularly in Germany have been using low-eLow-E or Low-Emissivity Coating: Very thin metallic coating on glass or plastic window glazing that reduces heat loss and heat gain through the window; the coating emits less radiant energy (heat radiation), which makes it, in effect, reflective to that heat. In that way it boosts a window's R-value and reduces its U-factor. glazing for a long time. I have works and many project and really it's not the glass. Todd is write there is no correlation. The reinforcement in the concrete or radiant ceilings, so lots of metal cause the problem for the most part. This is a common and pretty know problem in Europe, which is why they use systems in the building which boost reception. I was just working on a project over there. During construction with the system not working yet, you had no reception, get close to the window and you are fine. After the system was up and running, you couldn't tell the difference form been outside.

So no it's not LEED causing bad reception.

Option three only has the minimum requirement and with lower sun angles at this time of year you should not even have any issues on even partly cloudy days, dependent on your VLT of the glazing.

I don;t believe taking measurements to determine the daylight levels of your building is a waste of time, whether its for a credit or not. The information can help in making future decisions on energy saving strategies or address occupant issues.

Being that there are no specific requirements as to when the measurements have to occur, and even if they have to occur on the same day, i would take them.

I agree that you should continue with taking measurements but I disagree that lower sun angles aren't going to cause issues.

Summer sun IS brighter, generally than winter sun. For example, here in Denver we get an average of 1.5 times the lumens from the sun at noon in June than in December. The farther north you go, the greater discrepancy there is going to be from summer to winter.

I say wait until a nice sunny day in June and try for the credit again, if you have the time to wait! Good luck and if you remember, come back here and let us know how it went!

One more thing, you can look up the difference in your location's summer and winter lumen1. A lumen is a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of 1 candle intensity. 2. A measurement of light output. values through weather files. One easy way to access these are from Solatube. They publish these for use with their IES files. You don't need the IES files to see the difference, just letting you know why they have them.

Unfortunately, we're submitting LEED documentation in late winter. I couldn't find the lumen1. A lumen is a unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of 1 candle intensity. 2. A measurement of light output. values from Solatube - do you have a link? Thanks!

I stand corrected, based on the most recent addenda, you must meet at least 10fc and no more than 500 fc, So depending on when this was registered and if the addenda is applicable, then low winter sun angles may be a problem depending on the time. If the addenda is applicable to your project then the minimum will help you.

Sorry, they don't have them available online. They like to give them out personally so that they can explain how their IES files work. If you don't have a local rep, I'll bet you could just call them directly.

I could probably dig up a weather file for you when I clear a few things off my desk. Where is your project located and do you happen to know its nearest airport?

The project is in Concord, New Hampshire. We have a tiny airport here (CON) but the nearest substantial airport is in Manchester, NH (MHT); after that it's Boston-Logan (BOS). Thank you!

Hi Maura,
Just my 2 cents, if I were you, I would just try to measure the daylight. I don't think you need to spend a lot of time to ensure the credit achievement if you can strategize measurement correctly. You can take some measurements in certain rooms that may represent the floor plan first. Then you can do quick analysis on how deep the daylight can be brought to the building. If you think based on the measurement, you can get the credit, then you can continue to measure the daylight in the rest of the building. Approximately, the initial assessment is about 1 hour.

Additionally, I wouldn't worry so much about low angle sun except most of the rooms have windows on the south side only. If you can fulfill the requirement in the north part of your building, then you may need only 25% additional in the south part to get 75%. I concern more on the north part that only gets the daylight from the north sky which is less bright that the sky on the south. Moreover, you can adjust the time of the measurement if you get the problem with low angle direct sun.

Hope it helps..

Per the weather files, Boston-Logan will be about 1.5 times brighter at noon on March 15th than today. How low are your measurements? I believe you have the choice to apply the addenda that Todd mentions no matter when you registered the project. So you should just have to meet the minimum of 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.. Is the trouble meeting the minimum or the maximum?

I am not familiar with DB but as I heard it uses the radiance engine as well. The different between two tools may occur because the translation process from the input to the radiance file. If you can take a look the radiance file generated by two software, you can compare both and see whether they are same.

Hi Green,

Though I do not have experience with residential projects, in commercail projects it is not the walls that define which spaces are regularly occupuied. For example, in an open office plan the "corridors" between the cubicals may be excluded since they are not regularly occupied, even though they are not contained by walls. 

However, the definition 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. for commercial projects is basically if work occurs in that area. I am not sure what the definition is for residential projects. Anyone else?

Kitchens must be included in your calculations for residential units.

Regularly occupied is not so much as the time spent in the space, but if the occupants and the activity of the space benefit from daylight.

We've typically included kitchen areas of our residential projects as regularly occupied space. Often these are open to other living spaces, and do see a lot of use. Although I can't find a 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 interpretation to verify this, I seem to recall guidance that said residential kitchens were considered regualrly occupied space.

If it hasn't amended, please see the ruling dated on 1/2/2002. The ruling includes the kitchens in residential facility as a regurlarly occupied space.

Generally, yes, it is possible to have too much daylighting. However, without knowing more about your project and calculations I can't say for sure.

Are you excluding all non-regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building.? Is your VTL correct?

Alternatively, assuming your calculations are correct here's what the credit language says: "designs that incorporate view-preserving automated shades for glare control may demonstrate complianc efor only the minimum 0.150 value"

Your going to have to incorporate all of the floor sales area, looked at options for you in LEED for retail and could not find any. One strategy is to break up the space into zones. So determine 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. depth based on window height, and then seperate the space. If the space has bilaterally daylit, such as form three sides, seperate your zones that way. The language does say the length of the zone is wall to wall. So to argue this you need have a either a change in glass properties or size. For example, along your one wall that is 40 ft long, you have have the length with glass that runs from sill height to 10ft, then then other half is floor to ceiling. It would be justifiable to argue that these are two separate zones based on the change in glass. Will it get you in between .15 and .18, i don;t know.

I ask you this, was the daylight credit a before or after thought with this project? If you want to incorporate daylight, then it needs to be in the DNA of the design. If you are attempting this credit as an after thought, then the prescriptive path is doing what it is kind of meant to do, that is set a standard for projects that have not incorporated daylight into the design to ensure spaces are not over lit and that the amount of glazing is reasonable as far as handling solar heat gain and loss.

If the project is a glass box then i would suggest the other options.

Emily,
My VLT is correct and I have excluded all regularly non-occupied areas. I do, however, have electric shades along the west facing windows. Where can I find your reference on automated shades?

Francisco,

Just click the "credit language" tab above. You can also find it in the addenda to the reference guide. I believe it was in the May 2011 addenda.

There are no specific times to take measurements for LEED.

If taking measurements to determine daylight performance, i would look at multiple times of the year, different sky conditions, and times of day. I would also take exterior readings during the interior readings.

Mohamed, I think the floor area is the daylit area, you can check the latest addenda. As I remember, there is still a problem in the new definition. The problem in the revised calculation is that it only defines the distance to behind as the projection of the height of the window, but the calculation does not define the side distance of the daylit area from each side of the window.

I suggest you break it up into 3 zones, one for each glazing wall. Technically, if 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. is not met this way, then you could use one big zone to meet the requirements.

Not knowing if this is enclosed or not would make it easier to answer. I would consider the restaurant, VIP lounges and press boxes as regular occupied. Here is the thing, eventhough a sporting event does not happen everyday, what about all the other events that occur. Secondly, a football game and most other events are more then an hour. So these spaces are occupied for a decent amount of time. Look at the intent of the credit.

Eamon, you need to be more specific. What option of the credit have you attempted and what option of the credit are looking for? My other question is this, are the projects that you have worked truly attempted to daylight the spaces? What i mean by this is that daylight was in the DNA of the design, not an after thought during CD. To be successful with daylight, it has to be designed into the spaces.

I agree with Todd. Daylight design shall be incorporated into early design to get this credit. Building massing and interior layout strategy will be important to achieve this credit.

Take a light meter, take a measurement in the inside of the window and on the outside. The ratio would be as close as you can get to the VLT and may be better accepted since it is actual measurements.

But i would say that you can use the ASHRAE tables because in EAc 1 when the glazing is unknown you can use the tables. I would find the method acceptable. But say measurement would be more accurate.

Emily,
Have you considered the measurement option? You may comply the requirement by using measurement option.

Have you accurately modeled the terrain and surrounding buildings? This will sometimes help. Models in flat planes are not true representations of the majority of all buildings. Plantings, such as coniferous trees can be used to reduce the direct solar aspect.

What you mean by mechanical is automatic?

When did you register your project? Which option are you using? Automated shades only applies to over lighting in the simulation option for projects registered before 8/1/11.

Window 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 an easy and cheap way to lower daylight values. What Tvis are you at now?

An interior shading device, such as light shelf or even a baffle would effect the window height. An interior light shelf is an interruption in the window head height, You would have to actually do tow zones for a space, one for the view window and and one for the daylight window. You would actually have a dead area in the zone if correctly using the formula, There is nothing that states that exterior shading devices must be considered with the prescriptive method.

Simulation would be easier.

I'm going to say no. However, previous CIRs that state borrowed light is not accepted has not been validated for 2009 projects. I would not argue that case to a reviewer. Since the prescriptive method is a formula which is only attended for one layer of glazing, then borrowed light would not work. Even if you were to do a weighted average of the two glazings, the formula does not consider the effects of reflection and refraction of light as it travels through the layers of glass.

The prescriptive method should not be used to determine whether you have good daylight or not. What if that space is north facing in a northern climate that has alot of overcast days? You may have to provide more glazing with a higher VLT to meet the daylight needs year round.

Since the prescriptive method is a general formula, the formula is what it is. You can try and break up the space into multiple daylight zones, but that may make it worse.

I would recommend simulation, there are some free downloads of daylight simulation programs such as SPOT that can help you. I would not change a design based on meeting the requirements of the prescriptive method.

The 63 degree is used when the ceiling height is below the window head height. I would have to say that you cannot use interior windows through vestibules since there are multiple layers of glazing. This is what on considers a borrowed light scenario which was not accepted 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, which was a formula. I would also say that using a weighted average between the two glazing areas would also not be acceptable. The area behind the vestibule would have to day lighted from other glazings. If it is not that large, consider the area behind the vestibule as a non-daylight zone. Combine this area into your calculations. If the intent and design of the space was to receive daylight through the vestibule, then use simulation.

Do you have a daylight consultant in your project? If you don't, I would suggest you to hire one. The daylight consultant can advise the correct sizing for your skylight and solatubes. 3%-6% is optimal skylight design to get sufficient daylight and energy reduction. If you put higher than that, you will not gain the benefit of the daylight because your energy consumption is higher. Additonally, there are many good readings in "resources" tab above.

We do not currently have one but I will definitely pass this along to my boss. Thank you for the response.

I second Eddy's recommendation of getting an expert's help. However I have to add that the prescriptive guide of 3-6% of floor-to-skylight ratio doesn't work well in some climate zones. Although the light level from the 3-6% might be proper, in many cases, the heat gain becomes too much that it negates one of the big advantages of daylighting - energy saving. Also the daylighting level depends on many other elements such as ceiling cavity depth, color of the light well, etc. I strongly recommend not rely on the prescriptive method. This is why LEED 2012 proposed to remove it if you look at the LEED 2012 2nd public comment version available now.