This design/research endeavour undertaken at the Institute for Advanced Architecture of Catalonia for the Academic year 2013/1, presents an exploration of potential Architectural applications of colour changing materials, namely Photochromic Powders. The project speculates optimal design solutions for building skins, along with an efficient use of smart materials while incorporating high-end fabrication techniques and digital tools necessary for the simulation of the anticipated material behaviour under changing environmental conditions.

This project understands material intelligence as a cooperative agent in the architectural design, making possible the spontaneous response of a built construction to a spectrum of stimuli while contributing to a dynamic, visually engaging and communicative quality of building skins.

CHROMATIC SKINS:

Terms like “interactive” and “transformative” are already well established within the architectural jargon. nonetheless, this design proposal suggests dynamism through the use of an inherent material property to shift state in response to changing energy fields. This main property of smart materials opens doors to the design of passive systems, the ultimate ambition in mainstream practice, which we, in turn, attempt to achieve in this research.

Through material testing, we deduce that the application of Photochromics in architecture is best suited passive shading! Light and heat regulating glazing. We propose a versatile system that derives its intelligence from:

1. Photochromics – As an intelligent material

2. A parametric design tool – Adaping building skins to better-optimised forms and material allocation, in response to local environmental conditions at every point along the surface.

…………………………………………………………………………………………………………..PARTI | Suggested Workflow

Photochromic systems allow for shading whenever needed, thanks to the inherent chemical properties that turn them proportionally dark to the intensity of UV light. However, this technology remains subject to great challenges, one of which is the economic factor that renders these systems impractically expensive. Tinting our high-rise glazed buildings all in the photochromics simply sounds unreasonable. On the other hand, environmental analysis and simulation tools today are quite advanced and allow for accurate calculations of solar radiation and lighting received by any surface of almost any material in a particular location in the world. The dynamic behaviour of colour change materials can even be simulated, given the right algorithm that can feed the looping system with updated real-time data. We decided that the material must be efficiently distributed, allocated where needed. Hence, a visualisation of the year-round solar path must be available, and a corresponding mapping of solar rays of any physical body becomes necessary to determine an optimised allocation of Photochromic pigments.

A digital tool based on Parametric logic is developed. The project becomes twofold: a digital part proceeded by physical realisation. The tool makes possible the formal optimisation of any surface or geometry. The resultant skin pattern can later be verified using environmental analysis tools such as Ecotect, Radiance and Daysim for quantitative data. After checking performance, the skin is tessellated and further detailed for construction. Our design concept features curved glazing, integrating photochromic pigments within the protective films. Hence, thermoforming is suggested and vacuum forming has been employed as the main technique for fabricating our prototypes. For the latter, photochromics are mixed with an epoxy resin that is later applied to the surface following the digital pattern.

A digital tool based on a Parametric logic is developed. The project becomes twofold: a digital part proceeded by physical realisation. The tool makes possible the formal optimisation of any surface or geometry. The resultant skin pattern can later be verified using environmental analysis tools such as Ecotect, Radiance and Daysim for quantitative data. After checking performance, the skin is tessellated and further detailed for construction. Our design concept features curved glazing, integrating photochromic pigments within the protective films. Hence, thermoforming is suggested and vacuum forming has been employed as the main technique for fabricating our prototypes. For the latter, photochromics are mixed with an epoxy resin that is later applied to the surface following the digital pattern.

………………………………………………………………………………….PARAMETRIC DESIGN TOOL | Double-fold

The solar path is tracked and projected on the surface. “Louvre” like elements are developed suggesting the perpendicular angle to solar rays. The dot pattern developed against the material distribution, in the case, that of photochromic pigments. These are located in areas most exposed to the sun and are therefore activated accordingly.

……………………………………………………………………………………………………………SAMPLE SKIN | Steps

This project presents not typical construction detail but rather a typical process where the given surface is subject to refinement using the parametric tool that will project solar rays and allocate the Photochromic panels. The resultant surface will then be panelised and corresponding structural concept will be developed.

……………………………………………………………………………………………………………FABRICATION | Vacuum Forming 

The “machine” consists of the suction box having a grid of tiny holes and a bigger one where the vacuum pipe goes; the frame that holds the plastic throughout from heating to meeting the mould surface. Air tightness is a crucial parameter for ensuring good results. Handles were added to keep our hands from burning in the oven.

The fire is started and the acrylic sheet is firmly fixed to the upper part of the box. Using long handles, the sheet is inserted into the fireplace, slightly moved around the uniform heating of the surface, the acrylic starts to melt slowly developing a “belly”. It is at this point that the sheet is taken out to be immediately applied to the mould, fixed in place, and closing off completely with the base box ensuring airtightness. This is crucial for the suction to be effective enough in forming the surface. This process is aided by a manual heat gun, used to melt the surface further to perfection. The process is far from being error-free. The “belly” creates wrinkles as it meets the wavy surface of the mould; hence a reduced mould size and reduction of time of keeping the sheet in the fireplace.

Considerations| Margins of Error

1. Degree of Heating
2. Sizes (Machine, mould, sheet)
3. Sufficient air suction (holes)
4. Geometry (depth, spacing)
5. Air tightness
6. Speed of application
7. Complimentary use of the heat gun