Today, the typical industry tolerances around fabric solar performance properties is large and can cause reduced visual comfort and energy savings. If fabric performance properties are not tightly controlled, your building design intent will not be achieved.
Find THEIA™ compliant fabrics in the Performance Shading Solutions binder
Spec Grade Solar Screens
THEIA™ Fabric Performance Data THEIA™ Performance Specification Summary THEIA™ Performance Specification White Paper
In the Fabric Wizard, select "Display only THEIA™ Compliant Fabrics" to filter the results for those that meet the Performance Specification.
Glare is the visual discomfort or disability from an intense light source or surface. The most common glare sources for daylight include:
Daylight glare can cause extreme detriment to occupants' visibility and long term comfort. Therefore, occupant productivity can be greatly decreased if glare is not properly controlled. *(Heschong Mahone group). In commercial buildings, the cost of occupants' salary and benefits is often 100x more expensive than total building energy cost.
Diffuse Glare - the perception of uncomfortable brightness caused by too much light in the field of view. When daylighting, diffuse glare is most commonly experienced when the sky is bright and the shades are open, or when a shade fabric has too high of a visible light transmittance (Tv) for the application.
Direct Glare - the perception of uncomfortable brightness caused by high contrast from a light source, such as the sun. When daylighting, direct glare is most commonly experienced when there is direct view of the sun orb and the fabric's openness factor is too high for the application.
Daylight Glare Probability (DGP) - estimates the likelihood that an average occupant would begin to experience glare from large diffuse daylight sources, like windows. This metric is the best means for estimating daylight glare, as it accounts for brightness, high contrast, light level, as well as the size and position of glare source in the field of view. The following table provides typical perceived glare values based on DGP scores.
| DGP Value | Functional Area | Transitional/ Social Areas | Description |
| 50% | Critical | High | Many occupants will perceive significant discomfort |
| 45% | High | Medium | Some occupants will perceive significant discomfot |
| 40% | Medium | Low | Some occupants perceive moderate discomfort |
| 35% | Low | Low | Most occupants will perceive minimum to no discomfort |
Photo © Halkin PhotographyDaylight Autonomy describes the percentage of work hours during which all or part of a building's lightings needs can be met through daylighting alone. It maximizes the amount of useful daylight, thereby minimizing the need for supplemental electric light.
What are the benefits?
Learn how Lutron automated shades save energy from daylight harvesting.
Spatial Daylight Autonomy (sDA) - the area of the space that receives the required illuminance (30 fc, 300 lux) for atleast 50% of the work hours. This, however, does not account for partial daylight received in the space, i.e. anything less than 30 fc (300 lux) but greater than 0 fc (0 lux).
Useful Daylight Zone - is the area of space that receives 30FC (300 lux, the typical ambient light level for offices) from daylight alone for at least 50% of annual work hours. Essentially, this defines the area that gets enough daylight to make use of switched daylight harvesting. However, the area where dimmed daylight harvesting is typically much larger (1.5 times or more).
Lutron Hyperion® Automated Shades have been shown to double the useful daylight zone in commercial offices.
View preservation is the ability to maintain exterior views to provide occupants with a connection to the outdoors. Views are maintained in two ways:
Why is it important?
Typical Shade Position - indicates the average annual position of the shade hembar in inches above the finished floor. For example, a value of 48 inches (1.2m) indicates that on average the shade hembar is positioned 4 feet (1.2m) from the floor. This indicates how much un-obstructed view is expected on average.
View Clarity (VCI)* - describes the ability to see the exterior environment through a closed shade. A value of 100 means the fabric causes no interference with exterior views, and a value of 0 means that there will be no view through the fabric. This metric does not account for the effect of the glass on view clarity.
In general, darker fabrics with higher openness factors provide greater view clarity. Use the table below to better understand typical VCI scores based on fabric openness factor and color.
Sources: *Link to whitepaper on View Clarity Index
In the Fabric Wizard, the star rating for a fabric (0 to 5 stars) is determined by three performance factors – glare reduction, daylight autonomy, and view preservation. The following table gives a summary of each star rating:
| Star Rating | Glare | Combined Daylight & View Performance |
 | Low | High |
| Low | Medium |
| Low | Low |
| Medium | High | |
| Medium | Medium |
| High | High | |
| Medium | Low |
| High | Medium | |
| 0 Stars | Critical | Any |
Glare is based on the Glare Reduction score in the results carousel. This score is computed by comparing the predicted direct and diffuse glare metrics against what is typically considered acceptable for each space type. For example, the acceptable glare potential for Functional spaces is less than for Social and Transition spaces.
Combined Daylight and View Performance is a weighted average of the Daylight Autonomy score and the View Preservation score in the results carousel. The relative weighting is based on space type.
An example result from the Fabric Wizard with a 5 star rating (best balance of priorities) is shown below:
In some applications, the priorities used to generate the star ratings in the Fabric Wizard may not align with your project priorities. Examples of different priorities are shown below.
Note: regardless of what your alternate priorities are, we do not ever recommend fabrics with a 0 star rating, as this indicates that the Glare Reduction performance is in the Critical range.
Thermal management is a primary concern on façades that receive direct sun and do not have window glass that is designed to minimize solar heat gain.
How is thermal comfort affected by shades?
Solar Reflectance (Rs) - the solar reflectance of a shade fabric is the percentage of total radiation that is reflected off the exterior face of the fabric. Although the glass may reflect some of the radiation back into the space, shades are able to reflect solar heat back out of the building.
Design Considerations:
A Lutron commissioned study by Purdue (2010) showed the cooling energy savings benefit of adding automated shades with high solar reflectance to a building without shades.
Specifically, the savings shown is based on an open/closed automated shading system designed to eliminate periods of intense light level. Neither the baseline (no shades) nor the new systems (automated shades with high solar reflectance fabric) utilized lighting controls for daylight harvesting. The ranges of energy savings shown occurs based on variation due to window to wall ratio (WWR) and glass solar heat gain coefficient (SHGC). The highest energy savings occurs with large windows (WWR = 75%) and clear glass (SHGC = 0.47). The lowest energy savings occurs with smaller windows (WWR = 45%) and slightly tinted glass (SHGC = 0.4). Similar results were found for peak cooling demand reduction. Lower savings are likely for glass with greater solar control.
Using Thermal Comfort in the Fabric Wizard:
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