ADVANCED SOLAR ENVELOPE
DIGITAL TOOLS
Digital tools - such as Ladybug Tools and DIVA for the parametric design software Grasshopper - can be used to generate solar envelopes. The main settings required are location latitude, plot outline, the location of shadow lines, analysis period and daily start-end hours during which direct solar access needs to be guaranteed on surrounding facades. While the mentioned tools are the most advanced at present, they have limitations.
For example, they do not take the surrounding environment into account, making them inefficient when used in urban environments, and the start-end hour input makes them unusable for standards that require quantity of hours, such as required by the mentioned German Regulation DIN 5034-1, or percentages of hours of insolation, required by the Estonian daylight standard presented in the next section [4].
height(m) 27.00 24.00 21.60 18.90 16.20 13.50 10.80 8.10 5.40 2.70 0.00 height(m)
27.00 24.00 21.60 18.90 16.20 13.50 10.80 8.10 5.40 2.70 0.00
Figure 32
Solar envelopes generated with existing digital tools (top) and with the proposed computational workflow (bottom).
Figure 33
Sunlight hours analysis on building clusters located in urban areas in Tallinn and shaped by a solar envelope.
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Min sun light hours 11
10 9 8 7 6 5 4 3 2 1 0
Min sun light hours
ADVANCED COMPUTATIONAL WORKFLOW FOR SOLAR ENVELOPE GENERATION
A computational workflow and a novel method were developed to overcome the mentioned limitations and efficiently generate solar envelopes for urban environments, and for the time input of different standards. The current digital tools used to create solar envelopes are not effective when applied to the ‘right to light’
requirement established by the Estonian daylight standard [4].
This standard requires that existing facades are not deprived of more than 50% of their windows’ actual direct sunlight hours. This applies to each of the days included in the period ranging from the 22nd of April to the 22nd of August.
To improve the capabilities of the existing tools, a workflow was developed based on the design of an algorithm using Grasshopper and the environmental design plugin Ladybug Tools [5]. The algorithm is composed of two main sections. The first section divides the facades surrounding the plot by using sampling and computes if each sample receives direct sunlight, and during which hours of every day of the required period. Sun vectors define the hours. The second section of the algorithm calculates the required 50% of sunlight hours. The designer can thus select the sun vectors with the most significant solar altitude, which provide primary solar radiation.
The selected sun vectors are used to generate one solar envelope for each sample. The workflow guarantees that the windows of the façades receive the required solar access, thereby creating larger solar envelopes in urban environments (Figure 32). The workflow can be customised to different time ranges and various national standards. The workflow was used to generate building cluster forms that optimise direct solar access and ponder the buildable floor that is allowed in Tallinn [6] (Figure 33).
EFFECTIVE SOLAR ENVELOPES IN DENSE URBAN AREAS Building on the advanced workflow presented, a novel method was developed to generate particularly useful solar envelopes in dense urban environments such as city centres [7]. It is a subtractive method based on the culling of three-dimensional cells obtained by subdividing a built volume by extruding the plot outline (see Figure 34 and 35). After having selected the required quantity of sun vectors (sunlight hours), the algorithm tests for intersections between all the three-dimensional cells and the sun vectors raytraced backwards from each window of the facades surrounding the plot.
Figure 34
Voxels are indicating the quantity of direct solar access hours blocked on the surrounding windows.
Figure 35
Solar envelope generated with the new subtracting method.
Figure 36
Experiment directly translating the mass of a solar envelope generated with the novel method into a building form.
Each cell is thus transformed into a colour coded voxel. This colour gradient reflects the quantity of direct solar access hours that it blocks (Figure 34). This method enables the option to eliminate all the blocking cells and to keep only those that allow the required 50% on all the surrounding windows (Figure 35), or a larger quantity of cells (allowing for increased solar access of surrounding dwellings and related occupant well-being), or a portion of them, keeping those with minimal impact (i.e., those that block only a few hours of direct solar access for the total number of surrounding windows during the entire period of 123 days). In this way, the designer can evaluate the size and shape of the solar envelope in the process of negotiation between form and solar access requirements.
The subtracting method allows designers to perform direct solar access analysis on the vertical faces of the solar envelope to provide information useful for the floor plan layout of new buildings. The method allows determining the maximum size of high-rise buildings in dense urban environments through the addition of buildable mass in the upper part of the solar envelope (Figure 36). Giving architects and planners the possibility to design more efficient buildings and comfortable urban environments, the proposed methods contribute to the regenerative goals of a healthy city with maximum solar access for dwellers and support social and physiological well-being. Furthermore, the methods can be used for urban brownfield areas, highlighting the possibility for preserving pristine land and the biodiversity that populates peri-urban areas. Altogether, the tools could be used to promote citizen health and local biodiversity, thereby increasing the healthy state and the quality of life in contemporary cities.
REFERENCES
[1] C. Reinhart, Daylighting Handbook I. Fundamentals. Designing with the Sun, Cambridge, MA:
Building Technology Press, 2014.
[2] S.W. Lockley, ‘Circadian Rhythms: Influence of Light in Humans’, in Encyclopedia of Neuroscience, L.R. Squire, Ed. Cambridge, MA: Academic Press, 1994, pp. 971-988.
[3] R.L. Knowles, Sun Rhythm Form, Cambridge, MA: MIT Press, 1981.
[4] EVS 894:2008/A2:2015 Daylight in Dwellings and Offices, Estonian Centre for Standardization, 2015.
[5] F. De Luca and H. Voll, ‘Computational method for variable objectives and context aware solar envelopes generation’, in Proceedings of SimAUD, Toronto, Canada, 22-24 May 2017, M. Turrin et al., Eds. San Diego, CA: SCS, 2017, pp. 335-342.
[6] F. De Luca, ‘From envelope to Layout. Buildings Massing and Layout Generation for Solar Access in Urban Environments’, in Proceedings of the 35th eCAADe, Rome, Italy, 20-22 September 2017, A. Fioravanti et al., Eds. Brussels, Belgium: eCAADe, 2017, pp. 431-440 [7] F. De Luca, ‘Solar Form-finding. Subtractive Solar Envelope and Integrated Solar Collection
Computational Method for High-rise Buildings in Urban Environments’, In Proceedings of the 37th ACADIA, Cambridge, MA, 2-4 November 2017, T. Nagakura et al., Eds. ACADIA, 2017, pp. 212-221.