INTRODUCTION

Building envelope design is one of the most important steps in creating energy-efficient buildings that follow sustainability principles. The building envelope enables the interaction between interior and exterior, between building and the climate. Envelope design impacts in active building systems, such as artificial conditioning and lighting. Moreover, It can collaborate with the creation of more pleasant spaces. Therefore, its development should be based on principles that contribute to reduce the consumption and use of natural resources, while preserving spatial quality.

There are currently a variety of tools that contribute to building envelope design and the understanding of the climate where the building is inserted. However, the integration of these tools during the design process is often poor, especially during the early design stages. Architectural design tends to integrate quantitative performance criteria only in the advanced stages of the design process (Turrin et al, 2011;. Lima, 2012).

Parametric and algorithm processes can contribute to this integration, because they enable the automation of part of design process, and association of different disciplines in a single model. The designer can also be responsible for defining the automation process. According to Motta (1999), the entire design process, once identified, can be subject to parameterization. His work is one of the pioneers in identifying generic parameterization processes of the design process.

This article aims to present a case study that uses parametric and algorithmic tools in building envelope design on Recife/Brazil. Recife is a costal city with a tropical warm and humid climate. One of the principal strategies to bioclimatic design in Recife is shading. Thus, the solution was generated based on incident radiation computer simulations. The model was built to automate the simulation integrated with 3D modeling software, and associate the distribution of shading elements to the simulation data. The article is contextualized by the author's masters research, which approaches parameterization aspects for creating climatically optimized forms.

METHODOLOGICAL PROCEDURES

The methodological procedures used are a case study and simulation analysis. Procedures are divided into three main stages:

• Definition of shading elements by understanding the solar geometry of Recife-PE and climate. This step uses psychometric charts, solar charts and weather data from the city’s reference year.
• Definition of a parametric model in Grasshopper including incident radiation simulation in Recife as a distribution parameter of shading elements. The simulation of the incident radiation was developed in DIVA, a Grasshopper plugin that uses Energy plus and the Daysim as its calculation engine. The model uses as input: shading elements models, building envelope model, and an urban space model.
• Analysis and evaluation of results.

RESULTS

The algorithm in Grasshopper was built to use three inputs: first, a simplified modeling of the immediate surroundings; second, the architectural parti model; and third, the models of shading elements. Both are editable in the 3D software. The weather data file, the incident radiation simulation and the distribution of shading elements are parts integrated to the model. It is possible to modify parameters and easily evaluate dimensional changes. These dimensional parameters concern the distribution of shading elements, number of elements, simulation gradient scales, etc. Once established new parameters, the model automatically updates showing a new scenario. The model allows work with a variety of scenarios. In this paper is being applied to a specific case, but can be used in a future project. It is also possible the application to non-orthogonal and to organic architectural parti.

The mesh established in the model is used for simulation and distribution of shading elements. The data generated from the simulation is used to distribute the shading elements according to the modeler’s design intentions and parameter definition. The model makes it possible to carry out variations of the shading elements density based on manipulation of mesh node quantity. The model also produces data that facilitates the designer’s work, for example: the distribution of shading elements is accompanied by their quantity take off.

The results demonstrate that incident radiation in the building envelope prior to parameterization occurred in varying degrees, and incident radiation levels after optimized distribution of shading elements became almost uniform. This is due to the fact that the need for shading in an envelope is variable, as such, requires a solution that responds to this variation. The design of responses sensible to such differences is not limited to "four" building orientations and also does not have a linear characterization. The Parametric and Algorithmic approach with Grasshopper collaborates with the creation of responsive models through the use of a mesh data.

DISCUSSION

The described application explores through a parametric and algorithmic approach, responsive building design in response to energy efficiency and sustainability issues. The study characterizes an accessible process, and presents a relevant solution to the Brazilian AEC industry and climate. The application uses interoperable tools such as, Rhinoceros for geometric modeling, Diva for simulation, integrated by Grasshopper as a “graphic scripting“ tool. This combination with a “graphic scripting“ tool eventually expands the user control over the limits imposed by traditional modeling and simulation tools. In this scenario, the designer defines the algorithmic process, parameters, performance criteria, and workflow necessary to create the design solution as demanded by the architectural program and its creativity.

The study characterizes the facility to extract model information in short time intervals, and the immediate effect on the design process. The incorporation of evaluation cycles to the design process, combined with the responsive design allows greater freedom for adjustments and preparation of various combinations in response to the same design problem.

It is emphasized that this application requires professionals with "programming" abilities. However, the use of graphical scripting interfaces, such as Grasshopper, makes this approach more accessible to architects. In addition to the above, it is necessary to be familiar with mathematical thought, as well as the have the ability to organize and characterize processes.

It is understood that the technologies available for the development of architectural solutions are constantly evolving. The use of these technologies aiming to advance architectural practice is critical to improving the performance of buildings. Note that, integrated approaches are essential to design and modeling, as is the incorporation of evaluation cycles to these processes.

Future work may address the development of academic exercises that incorporate applications such as presented in design studios. The need to transform architectural practice, in response to the current scenario of the Brazilian architectural production, necessarily involves the review of architectural education and demands on its practice. Thus, this is an unparalleled moment to discuss how these issues will be part of contemporary education of architects and urban planners.