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Measuring solar reflectance Part II: Review of practical methods

Description: A companion article explored how solar reflectance varies with surface orientation and solar position, and found that clear sky air mass 1 global horizontal (AM1GH) solar reflectance is a preferred quantity for estimating solar heat gain. In this study we show that AM1GH solar reflectance R{sub g,0} can be accurately measured with a pyranometer, a solar spectrophotometer, or an updated edition of the Solar Spectrum Reflectometer (version 6). Of primary concern are errors that result from variations in the spectral and angular distributions of incident sunlight. Neglecting shadow, background and instrument errors, the conventional pyranometer technique can measure R{sub g,0} to within 0.01 for surface slopes up to 5:12 [23{sup o}], and to within 0.02 for surface slopes up to 12:12 [45{sup o}]. An alternative pyranometer method minimizes shadow errors and can be used to measure R{sub g,0} of a surface as small as 1 m in diameter. The accuracy with which it can measure R{sub g,0} is otherwise comparable to that of the conventional pyranometer technique. A solar spectrophotometer can be used to determine R*{sub g,0}, a solar reflectance computed by averaging solar spectral reflectance weighted with AM1GH solar spectral irradiance. Neglecting instrument errors, R*{sub g,0} matches R{sub g,0} to within 0.006. The air mass 1.5 solar reflectance measured with version 5 of the Solar Spectrum Reflectometer can differ from R*{sub g,0} by as much as 0.08, but the AM1GH output of version 6 of this instrument matches R*{sub g,0} to within about 0.01.
Date: May 14, 2010
Creator: Levinson, Ronnen; Akbari, Hashem & Berdahl, Paul
Partner: UNT Libraries Government Documents Department

Solar heat gain coefficient of complex fenestrations with a venetian blind for differing slat tilt angles

Description: Measured bidirectional transmittances and reflectances of a buff-colored venetian blind together with a layer calculation scheme developed in previous publications are utilized to produce directional-hemispherical properties for the venetian blind layer and solar heat gain coefficients for the blind in combination with clear double glazing. Results are presented for three blind slat tilt angles and for the blind mounted either interior to the double glazing or between the glass panes. Implications of the results for solar heat gain calculations are discussed in the context of sun positions for St. Louis, MO.
Date: August 1996
Creator: Klems, J. H. & Warner, J. L.
Partner: UNT Libraries Government Documents Department

Measurement of bidirectional optical properties of complex shading devices

Description: A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient. This paper describes the method of measuring the spatially averaged bidirectional optical properties using an automated, large-sample gonioradiometer/photometer, termed a ``Scanning Radiometer.`` Property measurements are presented for one of the most optically complex systems in common use, a venetian blind. These measurements will form the basis for optical system calculations used to test the method of determining performance.
Date: January 1995
Creator: Klems, J. H. & Warner, J. L.
Partner: UNT Libraries Government Documents Department

Temperature calculations of heat loads in rotating target wheels exposed to high beam currents.

Description: In heavy-ion physics, high beam currents can eventually melt or destroy the target. Tightly focused beams on stationary targets of modest melting point will exhibit short lifetimes. Defocused or wobbled beams are employed to enhance target survival. Rotating targets using large diameter wheels can help overcome target melting and allow for higher beam currents to be used in experiments. The purpose of the calculations in this work is to try and predict the safe maximum beam currents which produce heat loads below the melting point of the target material.
Date: November 29, 2000
Creator: Greene, J. P.; Gabor, R. & Neubauer, J.
Partner: UNT Libraries Government Documents Department

Measured performance of selective glazings

Description: Measurements of the net heat flow through four selective glazings in comparison with clear double glazing under late summer outdoor conditions are presented. The SHGC for each glazing is extracted from the data and shown to be angle-dependent. The method of extracting the angle-dependent SHGC from the data is checked by comparing the measured SHGC for the clear double glazing to the calculation of OW 4. 1, which is assumed to be correct. Good agreement between the two is found. The measured angle-dependent SHGC`s of the selective glazings are then used to test the OW 4.1 selective glazing calculation and good agreement is again found.
Date: July 1, 1995
Creator: Klems, J.H.; Yazdanian, M. & Kelley, G.O.
Partner: UNT Libraries Government Documents Department

Solar heat gain through fenestration systems containing shading: Summary of procedures for estimating performance from minimal data

Description: The computational methods for calculating the properties of glazing systems containing shading from the properties of their components have been developed, but the measurement standards and property data bases necessary to apply them have not. It is shown that with a drastic simplifying assumption these methods can be used to calculate system solar-optical properties and solar heat gain coefficients for arbitrary glazing systems, while requiring limited data about the shading. Detailed formulas are presented, and performance multipliers are defined for the approximate treatment of simple glazings with shading. As higher accuracy is demanded, the formulas become very complicated.
Date: March 1, 2001
Creator: Klems, Joseph H.
Partner: UNT Libraries Government Documents Department

Solar Heat Gain Through Fenestration Systems Containing Shading: Procedures for Estimating Performance from Minimal Data

Description: The computational methods for calculating the properties of glazing systems containing shading from the properties of their components have been developed, but the measurement standards and property data bases necessary to apply them have not. It is shown that with a drastic simplifying assumption these methods can be used to calculate system solar-optical properties and solar heat gain coefficients for arbitrary glazing systems, while requiring limited data about the shading. Detailed formulas are presented, and performance multipliers are defined for the approximate treatment of simple glazings with shading. As higher accuracy is demanded, the formulas become very complicated.
Date: August 1, 2000
Creator: Klems, J.H.
Partner: UNT Libraries Government Documents Department

The New York Times headquarters daylighting mockup: Monitoredperformance of the daylighting control system

Description: A nine-month monitored field study of the performance of automated roller shades and daylighting controls was conducted in a 401 m{sup 2} unoccupied, furnished daylighting mockup. The mockup mimicked the southwest corner of a new 110 km{sub 2} commercial building in New York, New York, where The New York Times will be the major tenant. This paper focuses on evaluating the performance of two daylighting control systems installed in separate areas of an open plan office with 1.2-m high workstation partitions: (1) Area A had 0-10 V dimmable ballasts with an open-loop proportional control system and an automated shade controlled to reduce window glare and increase daylight, and (2) Area B had digital addressable lighting interface (DALI) ballasts with a closed-loop integral reset control system and an automated shade controlled to block direct sun. Daylighting control system performance and lighting energy use were monitored. The daylighting control systems demonstrated very reliable performance after they were commissioned properly. Work plane illuminance levels were maintained above 90% of the maximum fluorescent illuminance level for 99.9{+-}0.5% and 97.9{+-}6.1% of the day on average over the monitored period, respectively, in Areas A and B. Daily lighting energy use savings were significant in both Areas over the equinox-to-equinox period compared to a non-daylit reference case. At 3.35 m from the window, 30% average savings were achieved with a sidelit west-facing condition in Area A while 50-60% were achieved with a bilateral daylit south-facing condition in Area B. At 4.57-9.14 m from the window, 5-10% and 25-40% savings were achieved in Areas A and B, respectively. Average savings for the 7-m deep dimming zone were 20-23% and 52-59% for Areas A and B, respectively, depending on the lighting schedule. The large savings and good reliability can be attributed to the automatic management of the interior shades. ...
Date: February 24, 2006
Creator: Lee, Eleanor S. & Selkowitz, Stephen E.
Partner: UNT Libraries Government Documents Department

A Design Guide for Early-Market Electrochromic Windows

Description: Switchable variable-tint electrochromic (EC) windows preserve view out while modulating transmitted light, glare, and solar heat gains. Consumers will require objective information on the risks and benefits of this emerging technology as it enters the market in 2006. This guide provides such information and data derived from a wide variety of simulations, laboratory tests, and a 2.5-year field test of prototype large-area EC windows evaluated under outdoor sun and sky conditions. This design guide is provided to architects, engineers, building owners, and others interested in electrochromic windows. The design guide provides basic information about what is an electrochromic window, what it looks like, how fast does it switch, and what current product offerings are. The guide also provides information on performance benefits if more mature product offerings were available.
Date: May 1, 2006
Creator: Lee, Eleanor S.; Selkowitz, Stephen E.; Clear, Robert D.; DiBartolomeo, Dennis L.; Klems, Joseph H.; Fernandes, Luis L. et al.
Partner: UNT Libraries Government Documents Department

Light-scattering properties of a woven shade-screen material used for daylighting and solar heat-gain control

Description: Shade-screens are widely used in commercial buildings as a way to limit the amount of direct sunlight that can disturb people in the building. The shade screens also reduce the solar heat-gain through glazing the system. Modern energy and daylighting analysis software such as EnergyPlus and Radiance require complete scattering properties of the scattering materials in the system. In this paper a shade screen used in the LBNL daylighting testbed is characterized using a photogoniometer and a normal angle of incidence integrating sphere. The data is used to create a complete bi-directional scattering distribution function (BSDF) that can be used in simulation programs. The resulting BSDF is compared to a model BADFs, both directly and by calculating the solar heat-gain coefficient for a dual pane system using Window 6.
Date: August 1, 2008
Creator: Jonsson, Jacob; Jonsson, Jacob C.; Lee, Eleanor S. & Rubin, Mike
Partner: UNT Libraries Government Documents Department

Global Cooling: Policies to Cool the World and Offset Global Warming from CO2 Using Reflective Roofs and Pavements

Description: Increasing the solar reflectance of the urban surface reduce its solar heat gain, lowers its temperatures, and decreases its outflow of thermal infrared radiation into the atmosphere. This process of 'negative radiative forcing' can help counter the effects of global warming. In addition, cool roofs reduce cooling-energy use in air conditioned buildings and increase comfort in unconditioned buildings; and cool roofs and cool pavements mitigate summer urban heat islands, improving outdoor air quality and comfort. Installing cool roofs and cool pavements in cities worldwide is a compelling win-win-win activity that can be undertaken immediately, outside of international negotiations to cap CO{sub 2} emissions. We propose an international campaign to use solar reflective materials when roofs and pavements are built or resurfaced in temperate and tropical regions.
Date: August 28, 2009
Creator: Akbari, Hashem; Levinson, Ronnen; Rosenfeld, Arthur & Elliot, Matthew
Partner: UNT Libraries Government Documents Department

Measuring solar reflectance Part I: Defining a metric that accurately predicts solar heat gain

Description: Solar reflectance can vary with the spectral and angular distributions of incident sunlight, which in turn depend on surface orientation, solar position and atmospheric conditions. A widely used solar reflectance metric based on the ASTM Standard E891 beam-normal solar spectral irradiance underestimates the solar heat gain of a spectrally selective 'cool colored' surface because this irradiance contains a greater fraction of near-infrared light than typically found in ordinary (unconcentrated) global sunlight. At mainland U.S. latitudes, this metric RE891BN can underestimate the annual peak solar heat gain of a typical roof or pavement (slope {le} 5:12 [23{sup o}]) by as much as 89 W m{sup -2}, and underestimate its peak surface temperature by up to 5 K. Using R{sub E891BN} to characterize roofs in a building energy simulation can exaggerate the economic value N of annual cool-roof net energy savings by as much as 23%. We define clear-sky air mass one global horizontal ('AM1GH') solar reflectance R{sub g,0}, a simple and easily measured property that more accurately predicts solar heat gain. R{sub g,0} predicts the annual peak solar heat gain of a roof or pavement to within 2 W m{sup -2}, and overestimates N by no more than 3%. R{sub g,0} is well suited to rating the solar reflectances of roofs, pavements and walls. We show in Part II that R{sub g,0} can be easily and accurately measured with a pyranometer, a solar spectrophotometer or version 6 of the Solar Spectrum Reflectometer.
Date: May 14, 2010
Creator: Levinson, Ronnen; Akbari, Hashem & Berdahl, Paul
Partner: UNT Libraries Government Documents Department

Energy performance analysis of prototype electrochromic windows

Description: This paper presents the results of a study investigating the energy performance of three newly developed prototype electrochromic devices. The DOE-2.1 E energy simulation program was used to analyze the annual cooling, lighting, and total electric energy use and peak demand as a function of window type and size. The authors simulated a prototypical commercial office building module located in the cooling-dominated locations of Phoenix, AZ and Miami, FL. Heating energy use was also studied in the heating-dominated location of Madison, WI. Daylight illuminance was used to control electrochromic state-switching. Two types of window systems were analyzed; i.e., the outer pane electrochromic glazing was combined with either a conventional low-E or a spectrally selective inner pane. The properties of the electrochromic glazings are based on measured data of new prototypes developed as part of a cooperative DOE-industry program. The results show the largest difference in annual electric energy performance between the different window types occurs in Phoenix and is about 6.5 kWh/m{sup 2} floor area (0.60 kWh/ft{sup 2}) which can represent a cost of about $.52/m{sup 2} ($.05/ft{sup 2}) using electricity costing $.08/kWh. In heating-dominated locations, the electrochromic should be maintained in its bleached state during the heating season to take advantage of beneficial solar heat gain which would reduce the amount of required heating. This also means that the electrochromic window with the largest solar heat gain coefficient is best.
Date: December 1, 1996
Creator: Sullivan, R.; Rubin, M. & Selkowitz, S.
Partner: UNT Libraries Government Documents Department

Measured winter performance of storm windows

Description: Direct comparison measurements were made between various prime/storm window combinations and a well-weatherstripped, single-hung replacement window with a low-E selective glazing. Measurements were made using an accurate outdoor calorimetric facility with the windows facing north. The doublehung prime window was made intentionally leaky. Nevertheless, heat flows due to air infiltration were found to be small, and performance of the prime/storm combinations was approximately what would be expected from calculations that neglect air infiltration. Prime/low-E storm window combinations performed very similarly to the replacement window. Interestingly, solar heat gain was not negligible, even in north-facing orientation.
Date: August 23, 2002
Creator: Klems, Joseph H.
Partner: UNT Libraries Government Documents Department

A new method for predicting the solar heat gain of complex fenestration systems

Description: A new method of predicting the solar heat gain through complex fenestration systems involving nonspecular layers such as shades or blinds has been examined in a project jointly sponsored by ASHRAE and DOE. In this method, a scanning radiometer is used to measure the bidirectional radiative transmittance and reflectance of each layer of a fenestration system. The properties of systems containing these layers are then built up computationally from the measured layer properties using a transmission/multiple-reflection calculation. The calculation produces the total directional-hemispherical transmittance of the fenestration system and the layer-by-layer absorptances. These properties are in turn combined with layer-specific measurements of the inward-flowing fractions of absorbed solar energy to produce the overall solar heat gain coefficient. This method has been used to determine the solar heat gain coefficient of a double-glazed window with an interior white shade. The resulting solar heat gain coefficient was compared to a direct measurement of the same system using the Mobile Window Thermal Test (MoWiTT) Facility for measuring window energy performance, and the two results agreed. This represents the first in a series of planned validations and applications of the new method.
Date: October 1, 1992
Creator: Klems, J. H. & Warner, J. L.
Partner: UNT Libraries Government Documents Department

Field Evaluation of Highly Insulating Windows in the Lab Homes: Winter Experiment

Description: This field evaluation of highly insulating windows was undertaken in a matched pair of 'Lab Homes' located on the Pacific Northwest National Laboratory (PNNL) campus during the 2012 winter heating season. Improving the insulation and solar heat gain characteristics of a home's windows has the potential to significantly improve the home's building envelope and overall thermal performance by reducing heat loss (in the winter), and cooling loss and solar heat gain (in the summer) through the windows. A high quality installation and/or window retrofit will also minimize or reduce air leakage through the window cavity and thus also contribute to reduced heat loss in the winter and cooling loss in the summer. These improvements all contribute to decreasing overall annual home energy use. Occupant comfort (non-quantifiable) can also be increased by minimizing or eliminating the cold 'draft' (temperature) many residents experience at or near window surfaces that are at a noticeably lower temperature than the room air temperature. Lastly, although not measured in this experiment, highly insulating windows (triple-pane in this experiment) also have the potential to significantly reduce the noise transmittance through windows compared to standard double-pane windows. The metered data taken in the Lab Homes and data analysis presented here represent 70 days of data taken during the 2012 heating season. As such, the savings from highly insulating windows in the experimental home (Lab Home B) compared to the standard double-pane clear glass windows in the baseline home (Lab Home A) are only a portion of the energy savings expected from a year-long experiment that would include a cooling season. The cooling season experiment will take place in the homes in the summer of 2012, and results of that experiment will be reported in a subsequent report available to all stakeholders.
Date: June 1, 2012
Creator: Parker, Graham B.; Widder, Sarah H. & Bauman, Nathan N.
Partner: UNT Libraries Government Documents Department

An Exploratory Energy Analysis of Electrochromic Windows in Small and Medium Office Buildings - Simulated Results Using EnergyPlus

Description: The Department of Energy’s (DOE) Building Technologies Program (BTP) has had an active research program in supporting the development of electrochromic (EC) windows. Electrochromic glazings used in these windows have the capability of varying the transmittance of light and heat in response to an applied voltage. This dynamic property allows these windows to reduce lighting, cooling, and heating energy in buildings where they are employed. The exploratory analysis described in this report examined three different variants of EC glazings, characterized by the amount of visible light and solar heat gain (as measured by the solar heat gain coefficients [SHGC] in their “clear” or transparent states). For these EC glazings, the dynamic range of the SHGC’s between their “dark” (or tinted) state and the clear state were: (0.22 - 0.70, termed “high” SHGC); (0.16 - 0.39, termed “low” SHGC); and (0.13 - 0.19; termed “very low” SHGC). These glazings are compared to conventional (static) glazing that meets the ASHRAE Standard 90.1-2004 energy standard for five different locations in the U.S. All analysis used the EnergyPlus building energy simulation program for modeling EC windows and alternative control strategies. The simulations were conducted for a small and a medium office building, where engineering specifications were taken from the set of Commercial Building Benchmark building models developed by BTP. On the basis of these simulations, total source-level savings in these buildings were estimated to range between 2 to 7%, depending on the amount of window area and building location.
Date: August 1, 2010
Creator: Belzer, David B.
Partner: UNT Libraries Government Documents Department

Total System Performance Assessment- License Application Design Selection (LADS) Phase 1 Analysis for Higher Thermal Loa (Feature 26)

Description: The objective of this report is to evaluate the effect of potential changes to the TSPA-VA base case design on long-term repository performance. The design feature that is evaluated in this report is a higher thermal load (Feature 26 or F26). The following paragraph briefly describes the motivation for evaluating higher thermal loading. Higher thermal load has been identified as a design feature that might have a beneficial effect on long-term repository performance. A higher thermal load will increase temperatures and decrease relative humidity on the waste package surface. The decrease in relative humidity may delay the onset of corrosion, thus delaying the failure of waste packages and the release of radionuclides from the engineered barrier system (EBS). For the current calculation a thermal load of 109 MTU/acre (metric tons of uranium per acre) is considered. Two cases are evaluated, one with the base case inventory and a higher thermal load and a second with an increased inventory that would cover the current repository footprint at the higher thermal load. This report documents the modeling assumptions and calculations conducted to evaluate the long-term performance of higher thermal loading. The performance measure for this evaluation is dose-rate. Results are presented that compare the dose-rate time histories with the new design feature to that for the TSPA-VA base case calculation (CRWMS M&O, 1998a).
Date: June 11, 1999
Creator: Erb, N.
Partner: UNT Libraries Government Documents Department

Energy Efficient Electrochromic Windows Incorporating Ionic Liquids

Description: One approach to increasing the energy efficiency of windows is to control the amount of solar radiation transmitted through a window by using electrochromic technology. What is unique about this project is that the electrochromic is based on the reduction/oxidation reactions of cathodic and anodic organic semi-conducting polymers using room temperature ionic liquids as ion transport electrolytes. It is believed that these types of coatings would be a lower cost alternative to traditional all inorganic thin film based electrochromic technologies. Although there are patents1 based on the proposed technology, it has never been reduced to practice and thoroughly evaluated (i.e. durability and performance) in a window application. We demonstrate that by using organic semi-conductive polymers, specific bands of the solar spectrum (specifically visible and near infrared) can be targeted for electrochemical variable transmittance responsiveness. In addition, when the technology is incorporated into an insulating glass unit, the energy parameters such as the solar heat gain coefficient and the light to solar gain ratio are improved over that of a typical insulating glass unit comprised of glass with a low emissivity coating. A minimum of {approx}0.02 quads of energy savings per year with a reduction of carbon emissions for electricity of {approx}320 MKg/yr benefit is achieved over that of a typical insulating glass unit including a double silver low-E coating. Note that these values include a penalty in the heating season. If this penalty is removed (i.e. in southern climates or commercial structures where cooling is predominate year-round) a maximum energy savings of {approx}0.05 quad per year and {approx}801 MKg/yr can be achieved over that of a typical insulating glass unit including a double silver low-E coating. In its current state, the technology is not durable enough for an exterior window application. The primary downfall is that the redox chemistry fails ...
Date: November 30, 2008
Creator: Boykin, Cheri; Finley, James; Anthony, Donald; Knowles, Julianna; Markovic, Richard; Buchanan, Michael et al.
Partner: UNT Libraries Government Documents Department

THERM 2.0: a PC Program for Analyzing Two-Dimensional HeatTransfer through Building Products

Description: THERM is a state-of-the-art, Microsoft Windows{trademark}-based computer program developed at Lawrence Berkeley National Laboratory (LBNL) for use by building component manufacturers, engineers, educators, students, architects, and others interested in heat transfer. Using THERM, you can model two-dimensional heat-transfer effects in building components such as windows, walls, foundations, roofs, and doors; appliances; and other products where thermal bridges are of concern. THERM's heat-transfer analysis allows you to evaluate a product's energy efficiency and local temperature patterns, which may relate directly to problems with condensation, moisture damage, and structural integrity. THERM's two-dimensional conduction heat-transfer analysis is based on the finite-element method, which can model the complicated geometries of building products. The program's graphic interface allows you to draw cross sections of products or components to be analyzed. To create the cross sections, you can trace imported files in DXF or bitmap format, or input the geometry from known dimensions. Each cross section is represented by a combination of polygons. You define the material properties for each polygon and introduce the environmental conditions to which the component is exposed by defining the boundary conditions surrounding the cross section. Once the model is created, the remaining analysis (mesher and heat transfer) is automatic. You can view results from THERM in several forms, including U-factors, isotherms, heat-flux vectors, and local temperatures. This version of THERM includes several new technical and user interface features; the most significant is a radiation view-factor algorithm. This feature increases the accuracy of calculations in situations where you are analyzing non-planar surfaces that have different temperatures and exchange energy through radiation heat transfer. This heat-transfer mechanism is important in greenhouse windows, hollow cavities, and some aluminum frames. THERM is a module of the WINDOW+5 program under development by LBNL. WINDOW+5 is the next generation of the WINDOW software series and is ...
Date: December 8, 1997
Creator: Windows and Daylighting Group
Partner: UNT Libraries Government Documents Department

Reducing residential cooling requirements through the use of electrochromic windows

Description: This paper presents the results of a study investigating the energy performance of electrochromic windows in a prototypical residential building under a variety of state switching control strategies. We used the DOE-2.1E energy simulation program to analyze the annual cooling energy and peak demand as a function of glazing type, size, and electrochromic control strategy. A single-story ranch-style home located in the cooling-dominated locations of Miami, FL and Phoenix, AZ was simulated. Electrochromic control strategies analyzed were based on incident total solar radiation, space cooling load, and outside air temperature. Our results show that an electrochromic material with a high reflectance in the colored state provides the best performance for all control strategies. On the other hand, electrochromic switching using space cooling load provides the best performance for all the electrochromic materials. The performance of the incident total solar radiation control strategy varies as a function of the values of solar radiation which trigger the bleached and colored states of the electrochromic (setpoint range); i.e., required cooling decreases as the setpoint range decreases; also, performance differences among electrochromics increases. The setpoint range of outside air temperature control of electrochromics must relate to the ambient weather conditions prevalent in a particular location. If the setpoint range is too large, electrochromic cooling performance is very poor. Electrochromics compare favorably to conventional low-E clear glazings that have high solar heat gain coefficients that are used with overhangs. However, low-E tinted glazings with low solar heat gain coefficients can outperform certain electrochromics. Overhangs should be considered as a design option for electrochromics whose state properties do not change significantly between bleached and colored states.
Date: May 1, 1995
Creator: Sullivan, R.; Rubin, M. & Selkowitz, S.
Partner: UNT Libraries Government Documents Department

Visual quality assessment of electrochromic and conventional glazings

Description: Variable transmission, ``switchable`` electrochromic glazings are compared to conventional static glazings using computer simulations to assess the daylighting quality of a commercial office environment where paper and computer tasks are performed. RADIANCE simulations were made for a west-facing commercial office space under clear and overcast sky conditions. This visualization tool was used to model different glazing types, to compute luminance and illuminance levels, and to generate a parametric set of photorealistic images of typical interior views at various times of the day and year. Privacy and visual display terminal (VDT) visibility is explored. Electrochromic glazings result in a more consistent glare-free daylit environment compared to their static counterparts. However, if the glazing is controlled to minimize glare or to maintain low interior daylight levels for critical visual tasks (e.g, VDT), occupants may object to the diminished quality of the outdoor view due to its low transmission (Tv = 0.08) during those hours. RADIANCE proved to be a very powerful tool to better understand some of the design tradeoffs of this emerging glazing technology. The ability to draw specific conclusions about the relative value of different technologies or control strategies is limited by the lack of agreed upon criteria or standards for lighting quality and visibility.
Date: September 1, 1996
Creator: Moeck, M.; Lee, E.S.; Rubin, M.D.; Sullivan, R. & Selkowitz, S.E.
Partner: UNT Libraries Government Documents Department

Energy efficient louver and blind. Final technical progress report, third quarter 1996

Description: In the month of July, we completed the energy testing at Lawrence Berkeley Labs. The final testing was done with blinds in 15 degree position. This is a comfortable blind angle that allows for view of the outside while allowing for natural light to enter the room. It was found that the energy savings are much higher at this angle. At zero degree blind angle the savings were 150W/sq. meter, in the 15 degree the heat gain is cut by 225W/sq. meter. During the same period the heat gain in control chamber was 500W. (See graph plotting {open_quotes}Sample Heat Flows{close_quotes} From July 21 to 29 on next 3 pages). The heat gain reduction achieved in tests if used in commercial blinds, would result in an energy pay back period or one year and nine months.
Date: October 14, 1996
Creator: Khajavi, S.
Partner: UNT Libraries Government Documents Department