Window views that provide visual connections to the outdoors have been shown to have multiple positive effects on occupants (Heschong 2021). These effects include improved health, well-being (Beute and de Kort 2014), emotion (Ko et al. 2020), cognitive performance (Boubekri et al. 2020; Jamrozik et al. 2019; Ko et al. 2020), environmental satisfaction (Yildirim et al. 2007), reduced discomfort (Aries et al. 2010) and stress recovery (Ulrich 1984). A good window view may also increase the economic value of buildings (Baranzini and Schaerer 2011; Damigos and Anyfantis 2011; Turan et al. 2021). Even though many benefits from window views have been recognized, there are few design guidelines for assessing window view quality (CEN/TC 169, CEN/TC 169 2018; IWBI 2020; USGBC 2019). Moreover, the proposed approaches are not often supported by comprehensive and conclusive research findings. Although existing research has attempted to evaluate window view quality using a variety of assessment methods (Hellinga and Hordijk 2014; Li and Samuelson 2020; Mardaljevic 2019; Matusiak and Klöckner 2016; Turan et al. 2021), there is little alignment between methodologies and each of these studies only partially addresses the complex relationships between windows, outdoor and indoor conditions, and occupants (Ko et al. 2021; Waczynska et al. 2020). We lack consensus on a unified definition for window view quality that is applicable across occupancies and building types. In addition, while this is a topic of growing interest, there is limited research underway due to its complex nature, insufficient funding, and a lack of coordinated effort to move the field forward. In response to these problems, some of the authors of this editorial participated in a workshop on window view quality on October 28, 2021 at the University of California, Berkeley, which was complementary to a Virtual Symposium on Research and Design Practice Related to Window Views (“Symposium on Research and Design Practice Related to Window Views” 2021). This position statement started to take shape during this workshop. The symposium aimed to enhance interest and understanding among stakeholders regarding the benefits, complexities, and assessment methods for window views. The workshop aimed to engage the building science and design communities in this growing field, reach a consensus on the primary components of window view quality, and identify research gaps in current view assessment methods.

Daylight can reduce electric lighting in buildings. This is facilitated by sensors that relay real-time illu-minance data to a light controller. When daylight provides greater than required or desired levels of illu-minance, control actions enable electric lights to reduce their output and save energy. Occupant behaviours can block desk sensors and this reduces the amount of energy saved. However, no method exists that can be used to continuously monitor sensors to ensure they operate as intended (e.g. remain unblocked). We carried out a study in an open-plan office building in Singapore, consisting of 39 work-stations each fitted with desk illuminance sensors independently controlling a dedicated ceiling light. Power over Ethernet was used to collect individual data signals for both illuminance and power from each workstation. Data were collected across a one month period, sampling signals at every 2-minute interval. A linear support vector machine model accurately classified 99% of the data points using our sensor blocking algorithm. From 447,455 data points analysed, 12% of dataset showed that sensors were blocked and this had an estimated energy penalty of 24%. We do not recommend installing illuminance sensors at the desk. Our study highlights the usefulness of Power over Ethernet for closed-loop daylight harvesting. The data collected can be used to monitor the health of the sensors' performance to help minimise energy use. (c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

With the exponential growth in population and commensurate increased density in urban cities, access to daylight and views to nature is being severely curtailed in buildings. In parallel, increasingly urgent demands to sharply reduce building energy use and associated greenhouse gas emissions are being made to mitigate climate change. There are many challenges and performance tradeoffs associated with the building facade (i.e., daylight and view versus solar and glare control); increased prioritization of health and well-being as a fundamental human requirement could adversely affect building energy-efficiency. Given the current state of knowledge on the effects of daylight and view on health and well-being in buildings, we identify critical needs in research, tools and technologies that if satisfied may enable more effective use of daylight and view in buildings within the constraints of climate change. Lack of knowledge regarding the complex causal mechanisms of window views on human factors is a severely limiting factor in forward progress. Current models and methods to derive bidirectional scattering distribution functions (BSDFs) will need to be modified. Developers of energy-efficient window technologies will need more guidance to shape product development. Advanced window technologies and integrated design can enable attainment of both health and well-being and net zero energy goals, but considerable work will be needed to make such options turnkey and broadly available.

The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilience-absorptive capacity, adaptive capacity, restorative capacity, and recovery speed -and used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out. (c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Abstract A novel semi-transparent building integrated photovoltaic (BIPV) laminate was developed and introduced in this paper. It was produced by cutting standard mono-crystalline silicon solar cells into small strips and then making electrical connections between each strip before laminating the cells between two layers of glass. The overall energy performance and energy saving potential of the BIPV insulated glass unit (IGU) under real world conditions were identified through a side by side comparative study. Compared to the reference IGU, the BIPV IGU had lower solar heat gain coefficient (SHGC) but much higher U-factor. The average HVAC electricity saving of the BIPV IGU was about 10% relative to the reference IGU. Daylighting measurement and analysis were carried out to evaluate the trade-offs associated with the BIPV IGU between daylight, glare, and lighting energy use. The results indicated that the BIPV IGU is better than the reference IGU in reducing discomfort glare. However, if the most conservative viewpoint near the window is used for the assessment, a lower transmittance BIPV IGU is required to bring the overall discomfort levels below the perceptible level. Lastly, the net energy saving potential associated with the novel BIPV IGU was identified based on the power, thermal and daylighting performance. On average, the BIPV IGU saved 16.8% of the total electricity use of the room. Further studies and improvement on the energy conversion efficiency of solar cells, the optimal transmittance as well as the thermal properties would make this technology more energy-efficient and affordable.

Building facades are key to the building systems integration necessary to realise critical health, carbon,resilience, and sustainability goals in buildings and urban habitats. In addition, facade system designand delivery may be the most rapidly developing building technology, with novel materials, assembliesand techniques introduced in the marketplace frequently. However, these developments are occurringin the long-running absence of an appropriate framework for facade system performance evaluation.There has been no general convergence on the assessment criteria nor, for the most part, on the metricsto accompany those criteria. The convergence of myriad and often competing variables that characterisethe building facade mark the development of a comprehensive integrative assessment framework asa wicked problem, The lack of such a framework inhibits meaningful development and adoption ofinnovative facade technology, leaving aesthetic considerations to drive application and compromisingthe evolution of performative system behaviour. It prohibits a meaningful comparison between facadesystems, or of new techniques with prior applications. Adoption of new facade technology is constrainedas designers, building owners, and, most importantly, authorities with jurisdiction at the level of citygovernment are unable to accurately value its performative contribution to occupants, to a buildingproject, or to the urban environment.Very early efforts and thinking in the development of a comprehensive Integrative Facade AssessmentFramework by the Facade Metrics Working Group of the Facade Tectonics Institute are documentedhere. A preliminary review of existing facade system metrics and assessment strategies reveals theyare fragmented, too narrowly focused, and lack the comprehensive integration to provide an accurateevaluation. With a strong focus on energy performance in new buildings, deep and vital considerationslike retrofit and renovation strategies, passive survivability, durability and service life, and resilience areoften neglected entirely. We outline some new directions that begin to address these gaps and suggesta data-rich, visual framework and knowledge-sharing platform to advance progress with enhancedmetrics and facade systems evaluation and comparison.

Building façades are key to the building systems integration necessary to realise critical health, carbon, resilience, and sustainability goals in buildings and urban habitats. In addition, façade system design and delivery may be the most rapidly developing building technology, with novel materials, assemblies and techniques introduced in the marketplace frequently. However, these developments are occurring in the long-running absence of an appropriate framework for façade system performance evaluation. There has been no general convergence on the assessment criteria nor, for the most part, on the metrics to accompany those criteria. The convergence of myriad and often competing variables that characterise the building façade mark the development of a comprehensive integrative assessment framework as a wicked problem, The lack of such a framework inhibits meaningful development and adoption of innovative façade technology, leaving aesthetic considerations to drive application and compromising the evolution of performative system behaviour. It prohibits a meaningful comparison between façade systems, or of new techniques with prior applications. Adoption of new façade technology is constrained as designers, building owners, and, most importantly, authorities with jurisdiction at the level of city government are unable to accurately value its performative contribution to occupants, to a building project, or to the urban environment. Very early efforts and thinking in the development of a comprehensive Integrative Façade Assessment Framework by the Façade Metrics Working Group of the Façade Tectonics Institute are documented here. A preliminary review of existing façade system metrics and assessment strategies reveals they are fragmented, too narrowly focused, and lack the comprehensive integration to provide an accurate evaluation. With a strong focus on energy performance in new buildings, deep and vital considerations like retrofit and renovation strategies, passive survivability, durability and service life, and resilience are often neglected entirely. We outline some new directions that begin to address these gaps and suggest a data-rich, visual framework and knowledge-sharing platform to advance progress with enhanced metrics and façade systems evaluation and comparison.

Electrochromic windows can reduce buildings’ energy demand and improve occupants’ comfort, yet they struggle to fully meet market needs. Now, researchers demonstrate that polymer additives improve light and solar heat modulation of reflective electrochromic windows, with potential for durable, large-scale and low-cost manufacturing.

The aim of the Windows and Daylighting Group of Lawrence Berkeley Laboratory (LBL) is to develop a sound technical base for predicting the net thermal and daylighting performance of windows and skylights. One of LBL program strengths is its breadth and depth: at one extreme, LBL can examine energy-related aspects of windows at the atomic and molecular level in its materials science studies, and at the other extreme, LBL can perform field tests and in-situ experiments in large buildings. Visible transmittance properties, improved shading design, and window management will thus assume increasing importance for maximizing energy benefits from daylight. The critical tradeoffs-between electric lighting reductions from day-lighting and cooling load increases from solar gain-help determine the combination of window properties that minimize building peak loads. LBL's studies have focused on techniques to simplify accurately the very complicated heat transfer processes that occur between the components of a building.

While the primary role of window attachments is often to moderate glare and solar heat gains, they are also able to provide additional daylight to interior spaces. For this purpose, a variety of daylight-redirecting window systems have been developed over the past 150 years. Fixed reflective systems (slats/light shelves) or prismatic systems that rely on total internal reflection work well under specific solar conditions, but generally sacrifice performance over a much wider range of incident solar angles and sky conditions. Dynamic systems - typically reflective slats - are more responsive to sun angles but have not been able to achieve optimal performance for glare and daylight redirection efficiency. A previous investigation into an adjustable, reflective blind concept first conceived of in the late 1970s showed promise but was not reduced to practice due to lack of adequate simulation and analysis tools. In this paper, this concept is further developed and its energy and visual comfort performance evaluated for four mid-latitude, temperate climates using ray-tracing simulation techniques. Results indicate significant potential lighting energy savings when compared with conventional automated reflective blinds (2.1–4.9 kWh/(m2·a), or 14%–42%, depending on climate and orientation) or, especially, manually-operated matte white venetian blinds (1.4–7.9 kWh/(m2·a), or 9%–54%, depending on climate and orientation), while maintaining acceptable or better visual comfort conditions throughout the interior space.

This paper investigated the energy performance of window attachments and analyzed the impact of window attachments' parameters on air conditioning energy consumption of residential buildings in a cooling-dominated city (Houston) and a heating-dominated city (Minneapolis). Roller and cellular shades were selected as research objects in this study. Nine parameters related to window attachment energy performance were chosen as the probable important influence factors for the parametric study. Three values, high, medium and low levels, were set for each parameter, resulting in a total of 9520 (roller) and 9072 (cellular) combinations respectively. The optical and thermal properties of each combination were calculated with Berkeley Lab WINDOW program before coupling with an EnergyPlus typical residential building model. Based on simulation results, an annual energy performance (AEP) index was proposed to rate the energy saving potential of window attachments. Key parameters which have significant impacts on air conditioning energy consumption were determined through the parameter sensitivity analysis. The research results indicated that solar transmittance and solar reflectance are the most influential factors to the energy performance of window attachments among the nine selected parameters. The current cellular shade could achieve the AEP(h) and AEP(c) of 0.19 and 0.12. Among all combinations, the best AEP(h) and AEP(c) of cellular shades are 0.68 and 0.89, respectively. Besides, as for roller shades, the current level of AEP(h) and AEP(c) are 0.14 and 0.09, and the optimal AEP(h) and AEP(c) are 0.43 and 0.79.

The researchers developed a new generation of high-performance façade systems and supporting design and management tools to support industry in meeting California’s greenhouse gas reduction targets, reduce energy consumption, and enable an adaptable response to minimize real-time demands on the electricity grid. The project resulted in five outcomes: (1) The research team developed an R-5, 1-inch thick, triplepane, insulating glass unit with a novel low-conductance aluminum frame. This technology can help significantly reduce residential cooling and heating loads, particularly during the evening. (2) The team developed a prototype of a windowintegrated local ventilation and energy recovery device that provides clean, dry fresh air through the façade with minimal energy requirements. (3) A daylight-redirecting louver system was prototyped to redirect sunlight 15–40 feet from the window. Simulations estimated that lighting energy use could be reduced by 35–54 percent without glare. (4) A control system incorporating physics-based equations and a mathematical solver was prototyped and field tested to demonstrate feasibility. Simulations estimated that total electricity costs could be reduced by 9-28 percent on sunny summer days through adaptive control of operable shading and daylighting components and the thermostat compared to state-of-the-art automatic façade controls in commercial building perimeter zones. (5) Supporting models and tools needed by industry for technology R&D and market transformation activities were validated. Attaining California’s clean energy goals require making a fundamental shift from today’s ad-hoc assemblages of static components to turnkey, intelligent, responsive, integrated building façade systems. These systems offered significant reductions in energy use, peak demand, and operating cost in California.

Heat transfer through the building envelope and associated air leakage comprise the largest HVAC loads in most climates, and windows, which are known as the weakest link in the thermal envelope, are responsible for about 5 Quads, or approximately 10%, of building energy use. Therefore, windows offer a significant opportunity for building energy savings. High performance windows, such as triple glazing, though comprised of less than 2% of all US window sales in 2016 and has remained stagnant because they typically require a full and expensive redesign of the typical window sash and frame. One potential low incremental cost solution to kick start the market is upgrading the glazing with a thin-glass triple-pane design that does not require modifications to existing frame and sash. In this work, we first define the characteristics and performance of current typical residential windows through an examination of the National Fenestration Rating Council (NFRC) Certified Products Directory (CPD). With knowledge of the typical window, we determine the potential thermal performance impact of replacing typical glazing with thin-glass triple-pane glazing. Finally, with an understanding of the potential improvements to traditional performance metrics, such as U-factor, we show the energy savings potential of the thin-triple glazing in place of typical low-e windows in residential buildings is 16% in heating dominated climates such as Minneapolis, MN, 12% in mixed climates such as Washington DC, and 7% in cooling dominated climates such as Houston, TX.

To better understand why triple-pane windows are so slow to catch on and to inform the development and adoption of a new approach to insulated windows, thin triple-pane windows (or thin triples), Pacific Northwest National Laboratory (PNNL) conducted a market assessment of the window purchasing practices of new home builders in 2018-19. While there are several players who can impact the adoption of new residential window technologies, this report focuses strictly on home builders and the key part they play in new window technology adoption. A better understanding of the motivations, experiences, and concerns expressed by new home builders regarding window purchases could inform efforts to develop and deliver thin triple-pane windows and lead to their widespread acceptance in the marketplace. For the past several years, the DOE has supported the development of a thin triple-pane window that uses a center pane of thin glass and krypton gas fill to produce an insulated glass unit (IGU) with nearly the same weight and the same thickness as a double-pane IGU but with the performance of the heavier, thicker, standard triple-pane windows available today. To conduct this study, PNNL interviewed 29 home builders who have participated in the DOE Zero Energy Ready Home (ZERH) program. These builders include many of the most active builders in the DOE ZERH program. Together, they have constructed 2,534 of the 3,417 homes certified through the DOE program as of April 1, 2019. In 2018, they constructed an estimated 1,040 homes and purchased an estimated 17,800 windows. This report summarizes the key findings from these interviews.

Designing a zero emission neighborhood (ZEN) from an energy point of view, has the benefit of distributing loads over time by creating a mosaic of buildings which individually may not have a zero emission balance, but reach it as an ensemble. Responsive building envelopes (RBEs) are expected to play an important role in the design of ZENs and future smart sustainable cities. RBEs are useful to optimize the balance between several energy flows at single- and multi building scale, as well as to actively manage both on-site renewable- and purchased energy in addition to improving user experience and indoor comfort by providing an interactive interface with the outdoors. This article provides a review of the potential and the requirements associated with using RBEs to manage complex interactions between buildings, clusters of buildings and utility grids. A six-step pathway for the implementation of RBEs in ZEN-like projects are proposed. The six steps are related to identifying; purpose of response, scale and interdependency, functionality, trigger and control, interactions and finally to identifying technical solutions. The proposed process emphasizes the importance of defining specific information such as the responsive goal hierarchies, the scale of the responses in relation to their purpose, and the importance of the aesthetic expression to foster positive user experience.

This paper introduces a novel c-Si based building integrated photovoltaic (BIPV) laminate. It was produced by cutting standard crystalline silicon solar cells into narrow strips and then automatically welding and connecting the strips into continuous strings for laminating between two layers of glass. The overall energy performance of the BIPV insulated glass unit (IGU) including power, thermal and daylighting performance was investigated experimentally. The daily energy conversion efficiency of the active solar cell area was about 15% on sunny days, but it was less than 12% on cloudy days and overcast days. Due to the combined effect of both the semi-transparent PV laminate and the insulated glass unit, the solar heat gain coefficient (SHGC) of the BIPV IGU was as low as 0.25, which was much lower than commonly used glazing windows. Daylight analysis by means of high dynamic range (HDR) cameras and daylight glare probability (DGP) indicated that the BIPV IGU could reduce discomfort glare to some extent compared to clear glass windows. The net energy production of the BIPV IGU was estimated without considering the differences in HVAC energy use in this study. The artificial lighting energy consumption was about 431 W h/day while the average BIPV electricity production for the same period was 1940 W h/day. The net power generation was therefore 1509 W h/day for this BIPV IGU in Berkeley, California. Shading tests for the BIPV IGU were also conducted and the results revealed that the vertical configuration of solar cell wiring in the BIPV laminates was much more sensitive to horizontal shading patterns than vertical shading models. Thus, if shading was unavoidable in some cases, a reasonable arrangement of PV strings should be considered to bring down the energy loss as much as possible. Also, the impacts of environmental factors on the energy conversion efficiency of BIPV IGU were analyzed. Specifically, the power output declined by 0.42% of the peak power for each Celsius degree temperature rise. Thus, if more attention was paid to the heat dissipation issue of BIPV IGU, the overall energy conversion efficiency would be improved.

Simulation tools that enable annual energy performance analysis of optically-complex fenestration systems have been widely adopted by the building industry for use in building design, code development, and the development of rating and certification programs for commercially-available shading and daylighting products. The tools rely on a three-phase matrix operation to compute solar heat gains, using as input lowresolution bidirectional scattering distribution function (BSDF) data (10-15° angular resolution; BSDF data define the angle-dependent behavior of light-scattering materials and systems). Measurement standards and product libraries for BSDF data are undergoing development to support solar heat gain calculations. Simulation of other metrics such as discomfort glare, annual solar exposure, and potentially thermal discomfort, however, require algorithms and BSDF input data that more accurately model the spatial distribution of transmitted and reflected irradiance or illuminance from the sun (0.5° resolution). This study describes such algorithms and input data, then validates the tools (i.e., an interpolation tool for measured BSDF data and the five-phase method) through comparisons with ray-tracing simulations and field monitored data from a full-scale testbed. Simulations of daylight-redirecting films, a micro-louvered screen, and venetian blinds using variable resolution, tensor tree BSDF input data derived from interpolated scanning goniophotometer measurements were shown to agree with field monitored data to within 20% for greater than 75% of the measurement period for illuminance-based performance parameters. The threephase method delivered significantly less accurate results. We discuss the ramifications of these findings on industry and provide recommendations to increase end user awareness of the current limitations of existing software tools and BSDF product libraries.

Genentech has ambitious energy and indoor environmental quality performance goals for Building 35 (B35) being constructed by Webcor at the South San Francisco campus. Genentech and Webcor contracted with the Lawrence Berkeley National Laboratory (LBNL) to test building systems including lighting, lighting controls, shade fabric, and automated shading controls in LBNL’s new FLEXLAB facility. The goal of the testing is to ensure that the systems installed in the new office building will function in a way that reduces energy consumption and provides a comfortable work environment for employees.