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Fenestration and the Sun
Published in Matt Fajkus, Dason Whitsett, Architectural Science and the Sun, 2018
“Daylight factor” is the proportion of light inside a space relative to the light level outside the space or structure. It is the direct result of aperture percentages and placement, and it can be calculated as a quantitative value. This ratio provides some sense of the amount of light transmitted into a space; the desirable amount varies depending upon functional program and climate, yet it is typically between 1% and 10%. The illuminance diagrams of Figures 9.1a–o visually illustrate this principle, and are intended to provide an intuitive resource for designers as a supplement to charts and graphs. The diagrams visually depict the difference in illuminance as variables change, including latitude, solar orientation, and aperture size. Convention establishes that the effective horizontal reach of daylight into a space is 2.5 times the height of an aperture in the facade, although the illuminance diagrams show that it is largely dependent on latitude and solar orientation factors. “Daylight autonomy” is indirectly related, as it is the percentage of time that a certain level of illuminance is reached throughout the year, and therefore the amount of time that no electric light is needed in a space. Based on a desired amount of lux in a space, this may also be loosely inferred from the illuminance diagrams.
Daylight performance predictions
Published in Jan L.M. Hensen, Roberto Lamberts, Building Performance Simulation for Design and Operation, 2019
As a design metric, the daylight factor promotes several design measures that are known to enhance the daylight in a space, such as high window-head heights, high reflective ceiling and wall finishes, narrow floor plans, and large façade and skylight openings with high transmittance glazings. A weakness of the daylight factor, or any other daylight availability metric, is that it promotes one-dimensional, ‘the more the better’ approach to daylighting. Taking this to the extreme, the daylight factor optimized building has a fully glazed building envelope. Therefore, the use of other daylighting metrics is required to keep the daylight factor ‘in check.’
Luminous Environment Design Strategies
Published in Chitrarekha Kabre, Synergistic Design of Sustainable Built Environments, 2020
The daylight factor can be determined by hand calculation methods using tables of pre-calculated components for typical simple geometries, usually rectangular rooms with a wall of windows (IESNA 2013). The Building Research Establishment (BRE) has developed a set of protractors to provide percentages of direct reading of the sky component. Daylight factors from individual windows can be added to produce the daylight factor due to all the windows. In most cases, daylight factor levels in rooms are measured at work plan height (e.g. 0.85 m above the floor), leaving a 0.5 m border from the walls around the perimeter of the work plane.
External shading form-finding: simulating daylighting and dynamic view access assessment
Published in Journal of Building Performance Simulation, 2022
Mina Pouyanmehr, Peiman Pilechiha, Umberto Berardi, Phillippa Carnemolla
The performance metrics analysed in this study are Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE). sDA describes how much of a space receives sufficient daylight, and ASE describes how much of a space receives excessive direct sunlight, causing visual discomfort (glare). The daylight performance measurements for both sDA and ASE in this study align with the requirements documented in LEED v4. These include that the percentage of area meeting sDA requirements needs to be at least 75% (sDA300/50% ≥ 75%), and that 10% of a space should have direct sunlight of more than 1000lux for a maximum period of 250 h per year ASE (ASE1000,250 ≤ 10%). To meet the LEED v4 requirements (USGBC 2020), sDA is calculated with dynamic internal blinds, and follows what is known as the 2% rule. This rule states that openings in a building must be designed such that natural light, when available, provides an average daylight factor of not less than 2% (Committee 2012). This rule does not apply to ASE calculation. The concepts of sDA and ASE are explained in further detail in the following paragraphs.
Exploring blind spots in collaborative value creation in building design: a creativity perspective
Published in CoDesign, 2021
Michael Mose Biskjaer, Aliakbar Kamari, Stina Rask Jensen, Poul Henning Kirkegaard
Architects often join the early conceptual design phases where creative freedom is high while knowledge about the project in its entirety is limited (Zeiler, Savanovic, and Quanje 2007). Decisions here often have a relatively big impact on the final design (Bragança, Vieira, and Andrade 2014), underlining the importance of each architect’s ability to collaborate with experts from other disciplines. In the case of Vestmyra Skole, the client and their advisors established more ambitious goals for indoor climate than what the national building regulations prescribed. As an example, a daylight factor of five percent was set as a requirement in all primary educational spaces to secure evenly lit spaces. This prompted a higher level of early-stage interdisciplinary collaboration than in similar IDP projects. The architects realised that referring to experience from previous projects could be a blind spot when attempting to fulfil the new ambitions to literally go ‘above and beyond.’ Therefore, they tried to broaden their understanding of the quantitative aspects of daylight and used simulation tools alongside conventional tools to be able to enter into a dialogue about the quantity and quality of daylight (Jensen and Kirkegaard 2015).
Spatiotemporal expression and application of urban residential solar rights based on CityGML-LADM
Published in International Journal of Digital Earth, 2023
Chengcheng Liu, Haihong Zhu, Lin Li, Jianfang Ma, Feng Li
The daylight factor is a fundamental metric used to assess the indoor daylighting of buildings. It is defined as the ratio of the illuminance at a given position inside a building to the simultaneous illuminance on a horizontal plane outside the building, under an unobstructed hemisphere of the overcast sky (Arecchi, Messadi, and Koshel 2007; Iversen et al. 2013). Mathematically, it is expressed as. where is the illuminance due to daylight at a position on a given plane indoors, and is the outdoor illuminance at the same time and location.