02440nas a2200157 4500008003900000245011900039210006900158520181800227653005202045653003202097653001602129653002502145100001902170700002102189856007202210 2013 d00aAnnual daylighting performance of a passive optical light shelf in sidelit perimeter zones of commercial buildings0 aAnnual daylighting performance of a passive optical light shelf 3 a

Sunlight redirecting systems have the potential to significantly offset electric lighting energy use in deep perimeter zones of buildings where the windows are subject to high daylight availability. New Radiance modeling tools have recently been developed and validated, enabling accurate and timely simulation analysis of the annual energy and comfort performance of these optically-complex, anisotropic systems. A parametric study was conducted using these tools to evaluate the performance of a commercially-available passive optical light shelf (OLS) in a 17.4 m deep (57 ft), south-facing open plan office zone in three climates. Daylighting efficiency, discomfort glare, and lighting energy savings with continuous dimming and bi-level switching controls were determined at varying depths within the zone. The OLS decreased lighting energy use significantly throughout the depth of the space and achieved these savings with minimal discomfort glare in the area near the window. Annual lighting energy use intensity was reduced to 1.71-1.82 kWh/ft2-yr (22-27%) over the full depth of the perimeter zone across the three climates modeled (Phoenix, Washington DC, and Minneapolis) compared to a non-daylit zone at 2.34 kWh/ft2-yr. There was a greater occurrence of discomfort glare (3-7% during daytime work hours) if the occupant was in a seated view position looking at the window from the back of the room. The system is passive, needing no adjustment during the day and over the seasons and can be used as a retrofit measure in existing buildings. These results are encouraging and demonstrate how the primary daylit sidelit area can be extended well beyond the defined limits provided by the newly adopted ASHRAE 90.1-2010 code (i.e., 1.0 times the head height of the window).

10abidirectional scattering distribution functions10abuildings energy efficiency10adaylighting10aRadiance simulations1 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/annual-daylighting-performance02991nas a2200217 4500008003900000245010400039210006900143260004200212300001000254490000700264520225800271653003202529653001602561653002402577653001902601653001202620100002902632700002102661700001902682856007202701 2013 d00aEmpirical Assessment of a Prismatic Daylight-Redirecting Window Film in a Full-Scale Office Testbed0 aEmpirical Assessment of a Prismatic DaylightRedirecting Window F aHuntington Beach, Californiac10/2013 a19-450 v103 a

Daylight redirecting systems with vertical windows have the potential to offset lighting energy use in deep perimeter zones. Microstructured prismatic window films can be manufactured using low-cost, roll-to-roll fabrication methods and adhered to the inside surface of existing windows as a retrofit measure or installed as a replacement insulating glass unit in the clerestory portion of the window wall. A clear film patterned with linear, 50-250 micrometer high, four-sided asymmetrical prisms was fabricated and installed in the south-facing, clerestory low-e, clear glazed windows of a full-scale testbed facility. Views through the film were distorted. The film was evaluated in a sunny climate over a two-year period to gauge daylighting and visual comfort performance. The daylighting aperture was small (window-to-wall ratio of 0.18) and the lower windows were blocked off to isolate the evaluation to the window film. Workplane illuminance measurements were made in the 4.6 m (15 ft) deep room furnished as a private office. Analysis of discomfort glare was conducted using high dynamic range imaging coupled with the evalglare software tool, which computes the daylight glare= probability and other metrics used to evaluate visual discomfort.

The window film was found to result in perceptible levels of discomfort glare on clear sunny days from the most conservative view point in the rear of the room looking toward the window. Daylight illuminance levels at the rear of the room were significantly increased above the reference window condition, which was defined as the same glazed clerestory window but with an interior Venetian blind (slat angle set to the cut-off angle), for the equinox to winter solstice period on clear sunny days. For partly cloudy and overcast sky conditions, daylight levels were improved slightly. To reduce glare, the daylighting film was coupled with a diffusing film in an insulating glazing unit. The diffusing film retained the directionality of the redirected light= spreading it within a small range of outgoing angles. This solution was found to reduce glare to imperceptible levels while retaining for the most part the illuminance levels achieved solely by the daylighting film.

10abuildings energy efficiency10adaylighting10amicrostructure film10aprismatic film10awindows1 aThanachareonkit, Anothai1 aLee, Eleanor, S.1 aMcNeil, Andrew uhttps://facades.lbl.gov/publications/empirical-assessment-prismatic02354nas a2200229 4500008003900000245013200039210006900171260001200240300001000252490000800262520159100270653003201861653001801893653001801911653001201929100002101941700001801962700002101980700001802001700002902019856007602048 2013 d00aAn empirical study of a full-scale polymer thermochromic window and its implications on material science development objectives0 aempirical study of a fullscale polymer thermochromic window and  c09/2013 a14-260 v1163 a

Large-area polymer thermochromic (TC) laminated windows were evaluated in a full-scale testbed office. The TC interlayer film exhibited thermochromism through a ligand exchange process, producing a change in solar absorption primarily in the visible range while maintaining transparent, undistorted views through the material. The film had a broad switching temperature range and when combined to make an insulating window unit had center-of-glass properties of Tsol=0.12-0.03, Tvis=0.28-0.03 for a glass temperature range of 24-75°C. Field test measurements enabled characterization of switching as a function of incident solar irradiance and outdoor air temperature, illustrating how radiation influences glass temperature and thus effectively lowers the critical switching temperature of TC devices. This was further supported by EnergyPlus building energy simulations. Both empirical and simulation data were used to illustrate how the ideal critical switching temperature or temperature range for TC devices should be based on zone heat balance, not ambient air temperature. Annual energy use data are given to illustrate the energy savings potential of this type of thermochromic. Based on observations in the field,a broad switching temperature range was found to be useful in ensuring a uniform appearance when incident irradiance is non-uniform across the facade. As indicated in prior research, a high visible transmittance in both the switched and unswitched state is also desirable to enable reduction of lighting energy use and enhance indoor environmental quality.

10abuildings energy efficiency10aSolar control10aThermochromic10awindows1 aLee, Eleanor, S.1 aPang, Xiufeng1 aHoffmann, Sabine1 aGoudey, Howdy1 aThanachareonkit, Anothai uhttps://facades.lbl.gov/publications/empirical-study-full-scale-polymer02357nas a2200229 4500008003900000245008900039210006900128260001200197300001200209490000700221520162300228653003201851653002001883653001601903653002701919653002301946653002601969100002101995700002402016700001902040856006802059 2012 d00aEnd User Impacts of Automated Electrochromic Windows in a Pilot Retrofit Application0 aEnd User Impacts of Automated Electrochromic Windows in a Pilot  c04/2012 a267-2840 v473 a

Automated electrochromic (EC) windows, advanced thermally-improved window frames, and a dimmable lighting system were installed in a single, west-facing conference room in Washington DC. The EC windows were commercially-available, tungsten-oxide switchable devices, modulated automatically between either fully clear or fully tinted transparent states to control solar gains, daylight, and discomfort glare. Occupants were permitted to manually override the automated EC controls. The system was monitored over a 15-month period under normal occupied conditions. The last six months were used in the analysis. Manual override data were analyzed to assess the EC control system design and user satisfaction with EC operations. Energy and comfort were evaluated using both monitored data and simulations.

Of the 328 meetings that occurred over the six month period, the automatic system was manually overridden on 14 or 4% of the meetings for reasons other than demonstration purposes. When overridden, occupants appeared to have switched the individual zones with deliberation, using a combination of clear and tinted zones and the interior Venetian blinds to produce the desired interior environment. Monitored weekday lighting energy savings were 91% compared to the existing lighting system, which was less efficient, had a higher illuminance setpoint, and no controls. Annual performance was estimated using EnergyPlus, where the existing condition met the ASHRAE 90.1-2007 prescriptive requirements except for a higher window U-value. Annual energy savings were 48% while peak demand savings were 35%.

10abuildings energy efficiency10acontrol systems10adaylighting10aElectrochromic windows10aIntegrated systems10aIntelligent buildings1 aLee, Eleanor, S.1 aClaybaugh, Erin, S.1 aLaFrance, Marc uhttps://facades.lbl.gov/publications/end-user-impacts-automated00704nas a2200181 4500008003900000245014600039210006900185260001200254490001500266653005200281653003200333653001600365653001300381653001500394100001900409700002100428856007300449 2012 d00aA validation of the Radiance three-phase simulation method for modeling annual daylight performance of optically-complex fenestration systems0 avalidation of the Radiance threephase simulation method for mode c05/20120 vApril 201210abidirectional scattering distribution functions10abuildings energy efficiency10adaylighting10aradiance10avalidation1 aMcNeil, Andrew1 aLee, Eleanor, S. uhttps://facades.lbl.gov/publications/validation-radiance-three-phase