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Summary

Daylight Redirecting Window Film

Window Glazing: Daylight Redirecting Film vs. No film

Window film on exterior windowpanes that redirects daylight upward towards the ceiling with minimal glare to occupants, using a diffusing film on the interior pane as needed (3M).

Synopsis:

3M offers a daylight redirecting film and SerraLux offers their SerraGlaze redirecting film. Both involve a thin passive acrylic film that contains micro-structured louvres to re-direct incident daylight arriving on the upper portion of the window toward the ceiling of a room. Daylight is then reflected down to light the room.  The redirecting films can be incorporated into windows for new construction or installed as retrofits.  Electricity savings occur as lighting can be turned off or dimmed.  This technology provides little savings during cloudy, overcast days. 

Daylight redirecting films (DRF) can be installed on south, east, and west facing building windows. Generally, the film is installed above a sill height of 6 feet to keep redirected sunlight out of the eyes of occupants. Performance is a function of angle of incidence of sunlight (depends on latitude, orientation of the building façade, season, time of day) and sky conditions. Outdoor views are not possible through the DRF--the appearance is similar to frosted glass. The building façade must not have deep recessed windows, trees, and nearby buildings that block the sunlight. Windows should not have tinted glass or sun control window films.

The films will work as intended but several modifications must be made can reduce cost-effectiveness and/or technical potential. First, the indoor space must have minimal vertical obstructions (for 20 feet to 25 feet). Windows area must be available above six feet from the floor. Ceilings and walls must be light colored to promote reflectance and a dimmable lighting control system is required for affected lights. Sites with vertical shades may have to install horizontal shades just below the DRF level. HVAC cooling and heating loads may increase or decrease based upon the magnitude of the solar gain versus the reduction in heat rejection from lighting sources. Users have found that a diffusing film must also be used to eliminate introduction of glare problems.

The Department of Defense ESTCP program conducted a cost and performance study for DRFs at six sites nationwide including the Bremerton Naval Hospital.  The simple payback for the northwest application (windows for examining rooms) ranged from 11 to 35 years for south, east, and west-facing windows assuming an electrical energy rate of $0.086/kWh.  Savings were found to be heavily dependent upon successful use of lighting controls, plus building location and orientation.  Savings are also dependent upon the light type (32 W fluorescent versus LED) and the existing light level that is maintained in the affected space.   

Energy Savings: 16%
Energy Savings Rating: Limited Assessment  What's this?
LevelStatusDescription
1Concept not validatedClaims of energy savings may not be credible due to lack of documentation or validation by unbiased experts.
2Concept validated:An unbiased expert has validated efficiency concepts through technical review and calculations based on engineering principles.
3Limited assessmentAn unbiased expert has measured technology characteristics and factors of energy use through one or more tests in typical applications with a clear baseline.
4Extensive assessmentAdditional testing in relevant applications and environments has increased knowledge of performance across a broad range of products, applications, and system conditions.
5Comprehensive analysisResults of lab and field tests have been used to develop methods for reliable prediction of performance across the range of intended applications.
6Approved measureProtocols for technology application are established and approved.
Simple Payback, New Construction (years): 10.7   What's this?
Simple Payback, Retrofit (years): 35.1   What's this?

Simple Payback is one tool used to estimate the cost-effectiveness of a proposed investment, such as the investment in an energy efficient technology. Simple payback indicates how many years it will take for the initial investment to "pay itself back." The basic formula for calculating a simple payback is:

Simple Payback = Incremental First Cost / Annual Savings

The Incremental Cost is determined by subtracting the Baseline First Cost from the Measure First Cost.

For New Construction, the Baseline First Cost is the cost to purchase the standard practice technology. The Measure First Cost is the cost of the alternative, more energy efficienct technology. Installation costs are not included, as it is assumed that installation costs are approximately the same for the Baseline and the Emerging Technology.

For Retrofit scenarios, the Baseline First Cost is $0, since the baseline scenario is to leave the existing equipment in place. The Emerging Technology First Cost is the Measure First Cost plus Installation Cost (the cost of the replacement technology, plus the labor cost to install it). Retrofit scenarios generally have a higher First Cost and longer Simple Paybacks than New Construction scenarios.

Simple Paybacks are called "simple" because they do not include details such as the time value of money or inflation, and often do not include operations and maintenance (O&M) costs or end-of-life disposal costs. However, they can still provide a powerful tool for a quick assessment of a proposed measure. These paybacks are rough estimates based upon best available data, and should be treated with caution. For major financial decisions, it is suggested that a full Lifecycle Cost Analysis be performed which includes the unique details of your situation.

The energy savings estimates are based upon an electric rate of $.09/kWh, and are calculated by comparing the range of estimated energy savings to the baseline energy use. For most technologies, this results in "Typical," "Fast" and "Slow" payback estimates, corresponding with the "Typical," "High" and "Low" estimates of energy savings, respectively.

TAG Technical Score:  2.9

Status:

Details

Daylight Redirecting Window Film

Window Glazing: Daylight Redirecting Film vs. No film

Window film on exterior windowpanes that redirects daylight upward towards the ceiling with minimal glare to occupants, using a diffusing film on the interior pane as needed (3M).
Item ID: 513
Sector: Commercial
Energy System: Building Envelope--Windows & Skylights
Technical Advisory Group: 2014 Commercial Building TAG (#9)
Average TAG Rating: 3.21 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:
  1. This technology can potentially reduce glare and improve daylight utilization in conventional perimeter spaces as well as expanding the daylight zone to 20-30 feet - thus dramatically increasing savings. Works best on southerly orientations and in sunnier climates but has a role elsewhere.  We have developed new tools to predict performance and tested several versions.
  2. I am not familiar with the 3M technology.  From past studies on light redirecting technologies, it seems that they working well when then sun is at the right place, but not as well when it is not.

Synopsis:

3M offers a daylight redirecting film and SerraLux offers their SerraGlaze redirecting film. Both involve a thin passive acrylic film that contains micro-structured louvres to re-direct incident daylight arriving on the upper portion of the window toward the ceiling of a room. Daylight is then reflected down to light the room.  The redirecting films can be incorporated into windows for new construction or installed as retrofits.  Electricity savings occur as lighting can be turned off or dimmed.  This technology provides little savings during cloudy, overcast days. 

Daylight redirecting films (DRF) can be installed on south, east, and west facing building windows. Generally, the film is installed above a sill height of 6 feet to keep redirected sunlight out of the eyes of occupants. Performance is a function of angle of incidence of sunlight (depends on latitude, orientation of the building façade, season, time of day) and sky conditions. Outdoor views are not possible through the DRF--the appearance is similar to frosted glass. The building façade must not have deep recessed windows, trees, and nearby buildings that block the sunlight. Windows should not have tinted glass or sun control window films.

The films will work as intended but several modifications must be made can reduce cost-effectiveness and/or technical potential. First, the indoor space must have minimal vertical obstructions (for 20 feet to 25 feet). Windows area must be available above six feet from the floor. Ceilings and walls must be light colored to promote reflectance and a dimmable lighting control system is required for affected lights. Sites with vertical shades may have to install horizontal shades just below the DRF level. HVAC cooling and heating loads may increase or decrease based upon the magnitude of the solar gain versus the reduction in heat rejection from lighting sources. Users have found that a diffusing film must also be used to eliminate introduction of glare problems.

The Department of Defense ESTCP program conducted a cost and performance study for DRFs at six sites nationwide including the Bremerton Naval Hospital.  The simple payback for the northwest application (windows for examining rooms) ranged from 11 to 35 years for south, east, and west-facing windows assuming an electrical energy rate of $0.086/kWh.  Savings were found to be heavily dependent upon successful use of lighting controls, plus building location and orientation.  Savings are also dependent upon the light type (32 W fluorescent versus LED) and the existing light level that is maintained in the affected space.   

Baseline Example:

Baseline Description: Typical flourescent office lighting in newer office building.
Baseline Energy Use: 3.7 kWh per year per square foot

Comments:

The SMUD study determined baseline energy use to be 1.2 Watts per square foot of floor area. (Perry, 2012)  This translates to 3.7 kWh per square foot per year with typical office hours.

Manufacturer's Energy Savings Claims:

Comments:

So many variables exist that can impact performance that manufacturer's do not suggest a "typical savings" or even an "up to" savings value.

Best Estimate of Energy Savings:

"Typical" Savings: 16%
Low and High Energy Savings: 6% to 19%
Energy Savings Reliability: 3 - Limited Assessment

Comments:

In a modeling study by Sacramento Municipal Utility District, the energy savings attributable to adding the DRF to windows adjacent to an area 24 feet deep with daylight harvesting controls on the lighting system already installed, tinted windows, and vertical blinds automatically controlled was approximately 16%.  The lower range reflects an deeper study area and the upper range reflects a taller window with film on it. (Perry, 2012).

A Department of Defense study found the savings attributable to adding the DRF was 12-39 kWh per square foot of film area (Note: this is window film area, not square footage of building space).  (DOD ESTCP, 2013)

Energy Use of Emerging Technology:
3.1 kWh per square foot per year What's this?

Energy Use of an Emerging Technology is based upon the following algorithm.

Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))

Technical Potential:
Units: square foot
Potential number of units replaced by this technology: 14,412,093
Comments:

This technology is most appropriate for new construction or retrofits in the commercial sector with unobstructed solar exposure for perimeter areas near south-, east-, and west-facing windows over six feet in height above the floor.  A rough guess is that 10% to 20% of buildings might be suitable for use of the DRF technology with only 10% to 20% of this population having glazing area at heights that are suitable for DRF application.  Of the remaining building stock only those with relatively unobstructed floor plans within 24 feet of the windows and existing daylighting harvesting lighting controls should be considered.  And for these buildings, only the 24-foot perimeter of those building areas can be included as building area that is affected by this technology (assume this represents 25% of the building stock). 

This technology is appropriate for virtually all commercial building except for warehouses and unconditioned spaces. However, this will be most appropriate, typically for just the perimeter areas near south-, east-, and west-facing windows in the Northwest. The numbers for total commercial building space are taken from preliminary updated numbers from the 2013 update to the Commercial Building Stock Assessment (CBSA) using the estimates for 2014 (before the update was completed -- from early January, 2014), minus warehouse space, multiplied times the percentage of commercial space that is conditioned based on the 2009 CBSA, times our rough estimate of 25% of applicable space, which would count south-, east-, and west-facing perimeter zones.  This result is then multiplied by 15% x 15% or 0.0225 to account for solar exposure and window height yielding a total of 14,412,093 sf.

 Total Floor space   -s.f. Warehouse   non-Warehouse   % Conditioned   % Applicable   Applicable Space 
 Source   (NEEA, 2014)  (NEEA, 2009 App C)   (NEEA, 2009 App C)   (NEEA, 2009 App D, Table D-EA1)  WSU EP
 Values:           3,118,000,000      173,000,000       2,945,000,000 87.0% 25% 640,537,500
Regional Technical Potential:
0.01 TWh per year
1 aMW
What's this?

Regional Technical Potential of an Emerging Technology is calculated as follows:

Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)

First Cost:

Installed first cost per: square foot
Emerging Technology Unit Cost (Equipment Only): $0.57
Emerging Technology Installation Cost (Labor, Disposal, Etc.): $1.30
Baseline Technology Unit Cost (Equipment Only): $0.00

Comments:

The Department of Defense ESTCP Cost and Performance Report indicates a DRF cost of $11 per square foot of window film.  Installation costs for the labor and material required to install the DRF film is $25/sf.  These costs include applying the film to the inside of existing windows and then adding a third pane of glass with diffusion film applied to it, as well as installing horizontal shades to the windows below the DRF window level.  The windows are 25 square feet and the floor area is 480 square feet.  The costs per square foot of floor area are then $.57 for equipment and $1.30 for labor. 

Cost Effectiveness:

Simple payback, new construction (years): 10.7

Simple payback, retrofit (years): 35.1

What's this?

Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.

Comments:


For an application in the northwest (Bremerton Naval Hospital), it was determined that simple paybacks based upon lighting energy savings were in the range of 11 to 35 years, based upon building and window orientation, occupancy, and current lighting system operation.  This payback is based upon an electrical energy rate of $0.0836/kWh.  The DOD report didn't provide kWh savings, they instead used a unit of full-load equivalent hours (FLE) that electric lights could be turned off.  The paybacks calculated indicate savings on the order of 12 to 39 kWh per square foot of DRF window film applied.  (DOD ESTCP, 2013)  Note: Square foot in this discussion is related to the square feet of DRF window film applied (not square feet of building floor area).

Reference and Citations:

NEEA, 01/01/2014. Total Pacific Northwest Building Stock Based on Preliminary Numbers from the 2013 Update to the CBSA
Northwest Energy Efficiency Alliance

CADMUS, 12/21/2009. Northwest Commercial Building Stock Assessment (CBSA): Final Report
Prepared by the CADMUS Group for the Northwest Energy Efficiency Alliance

U.S. Department of Defense DOE ESTCP, 12/01/2013. Cost and Performance Report: Daylight Redirecting Window Film
Environmental Security Technology Certification Program

Anothai Thanachareonkit, 10/26/2013. Empirical Assessment of a Prismatic Daylight-Redirecting Window Film in a Full-Scale Office Testbed
Buildings Technologies Group, LBNL , IESNA 2013 Annual Conference

Tim Perry, 12/14/2012. Advanced Sidelighting Products
Sacramento Municipal Utility District (SMUD)

Rank & Scores

Daylight Redirecting Window Film

2014 Commercial Building TAG (#9)


Technical Advisory Group: 2014 Commercial Building TAG (#9)
TAG Ranking: 7 out of 44 Technologies (2014 Commercial TAG strategies ranked separately)
Average TAG Rating: 3.21 out of 5
TAG Ranking Date: 03/17/2014
TAG Rating Commentary:

  1. This technology can potentially reduce glare and improve daylight utilization in conventional perimeter spaces as well as expanding the daylight zone to 20-30 feet - thus dramatically increasing savings. Works best on southerly orientations and in sunnier climates but has a role elsewhere.  We have developed new tools to predict performance and tested several versions.
  2. I am not familiar with the 3M technology.  From past studies on light redirecting technologies, it seems that they working well when then sun is at the right place, but not as well when it is not.


Technical Score Details

TAG Technical Score: 2.9 out of 5

How significant and reliable are the energy savings?
Energy Savings Score: 2.6 Comments:
  1. The savings only exist if controls for daylighting are properly installed and commissioned and electric lighting is then decreased when adequate daylight is provided.
  2. The significance, of course, depends on orientation. The presenter indicated that the savings reported were likely for south-facing glazing. So the impact is limited by orientation.
  3. "Lighting remains a large load in commercial buildings- even with the relentless improvements in LEDs- their real market penetration will be slow due to cost, complexity, etc for another decade or so. And daylight carries with it many real but somewhat unquantifiable benefits- I'm not a fan of counting ""productivity"" savings in $ although there are some real effects here- its too complex and too many variables to reliably attach $. But owners and occupants ""like"" spaces with views and daylight - we know that. Since the systems use sunlight the multiplier is very large- 1 sq ft of technology can light 50-100 sf of floor under good conditions.This technology does two things that are of value- it can improve ""real"" daylight savings in the perimeter zone- <15 ft by decoupling light and glare; and it can double the zone of savings- to about 30 ft deep ( although savings wont be as large in that zone."
  4. Savings are dependent on having a good daylighting layout, clerestory/non-view windows, and a daylighting control system that works.
  5. The issue is the extent of savings. If it is 20% of only lighting and only in south facing zones or, as Steve says, roughly half the space, then it is limited overall. And it would only apply to certain situations, not most buildings. Not most existing buildings for sure. And savings are tied to the type of basleine lighting system (must have daylight sensors and dimming controls etc.).
  6. It looks like energy savings is only on deep office spaces with south facing windows, maybe west? Not sure what order of magnitude savings is if you change to LED troffers and what is added expense for daylighting controls? 20% of lighting savings in space applied, can be a small savings.
  7. Daylighting is a significant efficiency opportunity. This technology makes daylighting more cost-effective and feasible.
  8. "My main reservation is the high payback cost on retrofit applications (> 20 years).As a new construction measure it has advantages however there are other architectural design features that can incorporates to reduce glare and improve daylight penetration."
  9. The savings are based upon the integration with lighting and building controls as well as the geometry of the building and work space. These complications make the energy savings difficult
How great are the non-energy advantages for adopting this technology?
Non-Energy Benefits Score: 2.8
Comments:
  1. Non-energy benefits of daylighting are widely accepted.
  2. Per comment above a well daylighted space will almost always be preferable and a market advantate compared to non daylight space. There is real confusion over where the value comes from - is it spectrum, directionality and "modeling" of the horizontal flow of light, variability, - and/or simply the view and connection to the outdoors- the biophilia theme. I dont think its critical at this point to understand all the details- but I think we know with some confidence that the "package"- done properly- e.g. no glare- is a market winner.
  3. Some glare control, but only top portion of window where it is applied.
  4. Seems like a great way to bring daylight into the space with very little change to the look of the space. Not sure if you can install film without installing extra glass pane for diffusion or if you could install it on top part of floor to ceiling window. We may be testing this in CA office buildings.
  5. Daylighting systems seem to make an important contribution towards helping people be more effective in their workplaces. Certainly, they're popular and contribute towards productivity. This technology makes daylighting more likely to be installed.
How ready are product and provider to scale up for widespread use in the Pacific Northwest?
Technology Readiness Score: 3.4
Comments:
  1. I have been interested in this film for some time, and have requested technical data from 3M, but haven't received very much, so I am not sure if it's really ready, and if window manufacturers are ready to incorporate into their products. I am mostly interested in opportunities for retrofits, and this application appears to be farther behind in readiness.
  2. 2nd and 3rd generation prototypes have been field tested with "good" results. There is room for improvement in efficiency, in glare reduction and in cost reduction. Market entry in the NW might help drive that. The NW is not the ideal market- given need for direct sun- but probably good enough to make it worthwhile. Some locations inland in the NW might be better starting points with more sunlight
  3. Ready to go, but limited number of manufacturers (or unknown from the presentation).
  4. Product made in a roll-to-roll process by a major manufacturer. Also, there's a smaller company that competes. As a result, it's likely manufacturers could quickly ramp up to meet any imaginable demand.
How easy is it to change to the proposed technology?
Ease of Adoption Score: 3.2
Comments:
  1. Not an easy retrofit. Also, really only applicable to clerestory windows.
  2. It should be easily adopted once available in standard window offerings.
  3. Skilled users who understand lighting and daylight and the lighting controls integration issues would not have major problems- although there will be learning curves, need for tools, demos, etc. Average users may have trouble with controls integration- getting daylight sensors to work right in the real world is still a challenge- there is lots of new activity in this area that may make easier
  4. At first glance it seems relatively easy to install where conditions are appropriate, i.e. clerestroy or some separation between lower and upper glass. Films are applied regularly in the industry but exact alignment would be the challenge.
  5. Depends on if they have daylighting controls installed already and if they have celestory windows already and if they have dimmable light fixtures already.
  6. In new construction it's extremely easy. In a retrofit situation, it could take some fiddling.
  7. The application and energy savings is complicated especially for retrofits better for new construction - yet the savings are depended upon other system integration and operation
Considering all costs and all benefits, how good a purchase is this technology for the owner?
Value Score: 2.5
Comments:
  1. I think the value could be there if the windows are in need of replacement anyway, and the redirecting film is used in conjunction with a heat mirror film or a gas fill or new frames or other technologies to increase the overall window u-value, decrease SHGC, and decrease infiltration.
  2. Consider energy and non energy its a good package.This assumes some further development of the technology is completed and there is help to launch some early demos and get the details right. An owner with the right team (and willingness to tolerate moderate paybacks) should be able to do this. Costs should come down in a few years as experrience and volume increase.
  3. Seems like a good potential measure but that the application is quite limited. Good alternative to light shelves in new construction applications. May be more difficult to identify retrofit opportunities where the building has good daylighting potential (including having the necessary lighting controls) that is being underutilized and this window film will provide the means of making use of that daylighting.
  4. "Is the question ""how good for consumer? Or ""How good for the region?""It is marginal for the consumer and probably better, in aggregate (across all appropriate applications), for the region. I just can't see a program around this."
  5. Need to verify costs for controls and film and energy saving benefits to answer this question. Depends on how deep a space is being affected.
  6. More work still needs to be done to better understand the economics of this product. Highly dependent on baseline conditions and the overall economics of daylighting in general. Range of simple payback periods calculated so far varies widely from sufficiently cost-effective to clearly non-cost-effective. Certainly, more economical than light shelves.
  7. The owner has to be motivated and have deep energy savings goals and monitoring of the operation


Completed:
5/2/2014 8:56:02 AM
Last Edited:
5/2/2014 8:56:02 AM
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