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Open Access Publications from the University of California
Cover page of A simulation-based design analysis for the assessment of indoor comfort under the effect of solar radiation

A simulation-based design analysis for the assessment of indoor comfort under the effect of solar radiation

(2019)

One of the drivers of sustainable design is to maximize daylight across the floor plan in order to decrease electric energy consumption and create more productive and healthy working spaces. However, uncontrolled incoming solar radiation can lead to significant visual and thermal comfort issues. In particular, solar radiation landing on occupants can create thermal discomfort that the HVAC system cannot compensate for, thereby causing intolerable conditions for users close to the façade. We aim to present a new climate-based annual framework, based on ASHRAE 55 appendix C (2017), to assess radiant discomfort across a space due to direct solar radiation. The framework is calculated using the hourly effective radiant field (ERF) and delta Mean Radiant Temperature (ΔMRT) across the indoor space. The Radiance-based framework coupled with the proposed Annual Radiation Discomfort metric (ARD) provides designers a robust method to assess the performance of complex fenestration systems (CFS) at reducing potential thermal discomfort caused by incoming shortwave radiation.

Cover page of Ventilation, thermal and luminous autonomy metrics for an integrated design process

Ventilation, thermal and luminous autonomy metrics for an integrated design process

(2018)

This paper proposes and evaluates an integrated workflow that simultaneously uses ventilation, thermal, and luminous autonomy for the assessment of passive design strategies, introducing a potential way to integrate these three metrics in the design process. We developed a new metric, ventilation autonomy, and assessed the advantages and limitations of applying the three autonomy metrics with building performance simulations in two climates. We developed a novel visualization to display the hourly and yearly environmental autonomy values. The results show that when we consider the three metrics together, designers may have contradicting design directions if trying to both mitigate the solar radiation and to utilize natural ventilation. The visualizations that categorize nine combinations of thermal and visual comfort along with ventilation autonomy are effective in showing the trade-offs among ventilation, thermal, and visual performance.

Cover page of Performance, prediction, optimization, and user behavior of night ventilation

Performance, prediction, optimization, and user behavior of night ventilation

(2018)

Previous studies have demonstrated a potential reduction in cooling load and improvement in comfort from the implementation of night ventilation. This paper describes the performance, in terms of indoor environmental conditions, of three buildings from both the U.S. and India that use night ventilation as their primary cooling method. The research methods used the following approach: (1) Assess the cooling strategy in relation to the adaptive comfort model; (2) Develop a hybrid model, using both first principle equations and the collected data, to predict the instantaneous air and mass temperatures within each building and use the model to assess performance of the cooling strategy; (3) Determine an optimized ventilation control strategy for each building to minimize energy and maintain comfortable temperatures. (4) Develop a statistical model using collected data to predict the window opening pattern for occupants of a building using natural night ventilation. The study yielded the following results: (1) The buildings in the mild climate are successfully keeping the indoor temperature low, but also tend to be overcooling; (2) The night ventilation strategy has very little impact on indoor conditions of the buildings in the mild climate; (3) The impact of night ventilation is less significant when there is low internal loads and heavy mass; (4) The building in the hot and humid climate is keeping the indoor temperature within the comfort bounds for 88% of the year; (5) The night ventilation strategy has advantageous impact on indoor conditons of the building in the hot and humid climate, but not enough to cool the space on its own; (6) Model predictive control has the potential to further improve the performance of night ventilation. (7) Window opening behavior for the building using natural night ventilation is most heavily dependent on indoor air temperature and mass temperature.

Cover page of Building envelope impact on human performance and well-being: experimental study on view clarity

Building envelope impact on human performance and well-being: experimental study on view clarity

(2017)

The goal of this project was to assess the visual effect of selected aspects of the building envelope on human performance and perception, first broadly, and then focused on view clarity. The initial literature review examined human factors that could be explicitly considered in building envelope design, operation and current daylight metrics. We found that debate remains on the practical applicability of these metrics, and gaps exist between daylight and other building envelope-related aspects such as view. Following the literature review, we narrowed down our research question to experimentally investigate the visual performance of fabric shading systems and electrochromic windows under both diffuse and direct sunlight conditions, and develop a view clarity rating method. We introduce and show results from an experimental study done at Lawrence Berkeley National Laboratory’s Windows Testbeds. We tested High Dynamic Range (HDR) photography techniques to capture the different view clarity through the selected building envelope layers (shades and electrochromic glass) under various sky conditions. The experimental study reveals that light fabric shades restrict the view compared to dark fabric shades, and that view clarity through a blind can be significantly reduced when there is direct sun in the field of view (at certain sun angles). The direct sun caused white-spotted visual noise at the partial area of the fabric shade. Hence, the view was more obscured by the effect of the direct sun even though in this case there was a greater vertical illuminance than the others. The study also shows the potential of HDR photography techniques to be used for a standard view clarity rating method, while noting that further support is needed from human subject testing and advanced computational image analysis algorithms.

Cover page of Balancing Thermal and Luminous Autonomy in the Assessment of Building Performance

Balancing Thermal and Luminous Autonomy in the Assessment of Building Performance

(2017)

This paper proposes and evaluates a novel approach that simultaneously uses thermal and luminous autonomy for the assessment of human-centered passive design strategies, introducing a potential way to integrate these two metrics in the design process. In this study, we assessed the advantages and limitations of applying the two autonomy metrics with energy and lighting simulations in two climates. We developed a novel visualization to display the hourly thermal and luminous autonomy values for an entire year. The results showed that when we consider the two metrics together, designers may have contradicting design directions to mitigate the solar radiation; for example, the space is overly cool, but it is overlit at the same time, or the space is overly warm, but the daylight metrics predicts it is underlit. The visualization categorizes thermal and visual comfort in nine combinations allowing the designers to understand the trade-off relationships between thermal and visual aspects of the space.

Cover page of Window signalling systems: control strategies and occupant behaviour

Window signalling systems: control strategies and occupant behaviour

(2013)

Signalling systems that tell building occupants when to open and close windows have become a popular strategy for balancing the comfort benefits of manual windows with the efficiency benefits of automation in mixed-mode buildings. Data from surveys, interviews and site observations in 16 US buildings reveal a diversity of design objectives, control sequences and circumstances to anticipate when designing buildings with window signalling systems. The signals had the strongest influence on occupants’ use of windows when they were visible, the logic behind the controls algorithms was clearly understood, and they were seen as an informational device linked to an explicit internal policy that has to do with efficient and comfortable building operation. Lower levels of participation occurred when occupants tend not to pay attention to their windows, or the signals, unless they are uncomfortable, at which point it matters little what the signals indicate. However, occupants who do discover value in the signals are more likely to be more satisfied with their personal control. Occupants’ reasons for opening windows may include the desire for fresh air or air movement, which is as important to them as temperature adjustment, but admittedly difficult to program into the controls’ algorithms. 

Cover page of Window signalling systems: control strategies and occupant behaviour

Window signalling systems: control strategies and occupant behaviour

(2013)

Signalling systems that tell building occupants when to open and close windows have become a popular strategy for balancing the comfort benefits of manual windows with the efficiency benefits of automation in mixed-mode buildings. Data from surveys, interviews and site observations in 16 US buildings reveal a diversity of design objectives, control sequences and circumstances to anticipate when designing buildings with window signalling systems. The signals had the strongest influence on occupants’ use of windows when they were visible, the logic behind the controls algorithms was clearly understood, and they were seen as an informational device linked to an explicit internal policy that has to do with efficient and comfortable building operation. Lower levels of participation occurred when occupants tend not to pay attention to their windows, or the signals, unless they are uncomfortable, at which point it matters little what the signals indicate. However, occupants who do discover value in the signals are more likely to be more satisfied with their personal control. Occupants’ reasons for opening windows may include the desire for fresh air or air movement, which is as important to them as temperature adjustment, but admittedly difficult to program into the controls’ algorithms. 

Cover page of Adaptive Comfort in Mixed-Mode Buildings: Research Support Facility, National Renewable Energy Lab

Adaptive Comfort in Mixed-Mode Buildings: Research Support Facility, National Renewable Energy Lab

(2013)

The RSF is performing well for the occupants in terms of indoor environmental quality (IEQ), particularly with respect to air quality. The building scores in the 90th percentile of the buildings in the CBE database for thermal comfort and air quality satisfaction. Nevertheless, less than 80% of the building’s occupants are satisfied with temperature, air movement, and air quality, so there is room for improvement to meet the code standard.

The new survey methods allowed us to explore how occupants use and view their windows. The windows were rated extremely highly in terms of accessibility, usability, and responsiveness; however, they are not used as often as expected. Only 6% of window users adjust their windows on a daily basis, compared to 38% weekly and 41% monthly. The most frequently cited reason for opening windows is fresh air, followed by wanting to feel cooler, and then the desire to increase air movement.  Other reasons for opening and closing windows include the desire to save energy or increase the connection with the outdoors.  From this it is clear that people operate windows for more than just thermal comfort.

Cover page of Human Behavior Meets Building Intelligence: How Occupants Respond to “Open Window” Signals

Human Behavior Meets Building Intelligence: How Occupants Respond to “Open Window” Signals

(2012)

Designs for low-energy buildings increasingly incorporate operable windows for the benefits of personal control, environmental quality, and architectural value. In practice, however,there are unresolved debates about whether operable windows can be integrated with mechanical systems to optimize both comfort and energy efficiency. Signals that inform occupants about when to open and close their windows (usually red/green lights) have become a popular solution. These systems essentially propose a compromise between manual and automatic control philosophies, asserting that information from the building can influence behavior while retaining the fundamental benefit of personal control. Results from interviews, site visits and surveys of 16 U.S. case studiesshow mixed results. Signals play a role in window use behavior for only a minority of occupants under normative management/education practices. However, greater participation is possible given efforts to communicate the tangible benefits of the devices. Office type (shared or private), visibility of the signals from workstations, reliability of the signal modes, and a range of personal circumstances (noise, wind, window hardware) also influence participation.If conceived as reinforcement to an internal policy rather than as an element of the building controls, this technology holds promise for a wide range of building and user types, and the programming can be flexible and adaptable as circumstances change in our rapidly changing built environment.