prototyping smartwrap a mass customizable building … · prototyping smartwrap tm: a mass...

Paredes divisórias: Passado, presente e futuro, P.B. Lourenço et al. (eds.) 141

PROTOTYPING SMARTWRAPTM

:

A MASS CUSTOMIZABLE BUILDING ENVELOPE

KieranTimberlake

Architects

Philadelphia, PA

Prototyping SmartWrap

TM: A Mass Customizable Building Envelope 142

1.1. SmartWrapTM

, a Multifunctional Building Material

Smartwrap™ is a lightweight building envelope system developed by KieranTimberlake that

speculates on the integration of climate control, power, lighting, and information display on a

polyethylene terephthalate (PET) substrate. Conceived and developed since 2000, deep

research and development began in 2002, involving collaboration with various industry

partners to engineer and fabricate a prototype. A pavilion was created to demonstrate the

prototype at the Cooper-Hewitt, National Design Museum SOLOS exhibition in 2003, and it

later traveled to the Institute for Contemporary Art in Philadelphia, the NextFest in San

Francisco and the Zeche Zollverein in Essen, Germany.

(a) (b)

Figure 1 : (a) SmartWrapTM

Pavilion, Cooper-Hewitt National Design Museum, 2003

(b) Cellophane HouseTM

, The Museum of Modern Art, 2008

SmartWrap™ represents a new way of thinking about a building envelope. It is a dramatic

alternative to how a conventional facade is manufactured, functions and appears. SmartWrap™

replaces the conventional “bulky” wall with a lightweight composite of millimeter scale that

integrates climate control, power, lighting, and information display on a single substrate.

Through the deployment of deposition printed organic photovoltaics (OPV) and organic light

emitting diodes (OLED) onto thin polyethylene terephthalate (PET) layers, SmartWrap™ is

lightweight, energy gathering, mass customizable and sustainable. It is applicable to

commercial and residential buildings on both large and small scales. It can be mass customized

for a range of conditions and desired aesthetic programs, the printed pattern dictated by the

needs of the particular project.

Figure 2 : SmartWrap’s thickness, just 3mm, results in large surface area coverage with a

minimal volume of material relative to typical curtain wall assemblies

Kieran Timberlake 143

SmartWrap™ is designed to realize significant environmental benefits relative to current

transparent envelope systems. OPVs inexpensively harvest solar energy and off-set the total

amount of energy used by the building it encloses. OLEDs increase its multi-functionality by

generating light with the energy it harvests from the sun. SmartWrap™ is lightweight resulting

in a lower total embodied energy when compared to glass; and its thickness, just 3mm, results

in large surface area coverage with a minimal volume of material relative to glass curtain-wall

assemblies. Due to its lightness it can be erected in a fraction of conventional building time,

with greater efficiency. At the end of its useful life, SmartWrap™ can be easily disassembled

and fed into a recycling stream.

(a) (b) (c) (d)

Figure 3 : Prototype fabrication sequence, left to right (a) Screen printing circuitry (b, c)

Adhering OLED, PV and thin-film batteries (d) Testing the system

1.2. SmartWrapTM

Prototype I

During the development of the first prototype, we pursued emerging systems including phase

change materials (PCM) for temperature control; organic light-emitting diodes (OLED) for

lighting and data display, performing in conjunction with organic thin-film transistors; and

organic photovoltaic cells to power the OLED system. At the time, some components such as

OLED and PCM technologies were only emerging, and there was no developed system for

organic printing onto a substrate. For the purposes of the exhibition in 2003, it was necessary

for the systems to be adhered to the PET.

Figure 4 : The first prototype included one layer of PET with thin-film batteries, thin-film PVs

and OLEDs adhered and a second layer of PET with PCMs and aerogel insulation



(a) (b)

Figure 4 : (a) Elevation (b) Section

1.3. SmartWrapTM

Prototype II

In 2008, the second SmartWrap™ prototype was deployed at Cellophane House, an 1800 SF

dwelling commissioned by The Museum of Modern Art for the exhibition Home Delivery:

Fabricating the Modern Dwelling. To experiment with active and passive thermal strategies,

the SmartWrap™ wall assembly consisted of four functioning layers stretched on an extruded

aluminum frame, each wall panel consisting of an outer transparent PET weather barrier, an

inner PET layer with thin-film photovoltaic cells, an inner layer of solar heat and UV blocking

film and an interior layer of PET. A vented cavity between the PET layers is designed to trap

heat in the winter and vent it in the summer, reducing the amount of energy required to heat

and cool the house.

Figure 5 : Wall section showing PET layers and air cavity with proposed venting strategy


(a) (b) (c) (d)

Figure 6 : (a) Custom table for stretching PET on aluminum frames (b) Application of thin-film

PVs and copper circuitry (c) SmartWrapTM panel installed in "chunk" (d) Panels stacked

The SmartWrap™ walls at Cellophane House™ are comprised of seventy-four panels, each

containing four functioning layers stretched on an aluminum frame. It was necessary to test

methods of tensioning the PET to the extruded aluminum frames and adhering the thin-film PV

cells and circuitry. The fabricator built a custom table to stretch the PET, designed to

accommodate a variety of frame sizes, to achieve the best balance of tension and stability for

the aluminum frames. The table included a template to guide the fabricators in placing the thin-

film PVs. Seventy-four panels were created and factory installed into the “chunks” that

comprised the off-site fabricated house.

Figure 7 : SmartWrapTM

enclosures on east and west facades at Cellophane HouseTM

The thermal performance of the SmartWrap™ technology was tested for three months from

July to October. Monitors on the west facade of the house collected thermal data to provide a

more complete understanding of the insulative capacities of the building envelope, the efficacy

of the thermal stack, and the dynamics between outdoor temperatures and the interior

environment of the house. Because the house was in the shadow of much taller buildings for

most of the day, sensors were placed on the west elevation, the only location with direct solar

exposure. Self-contained pendant temperature sensors were suspended inside the cavities of the

2nd, 3rd, and 4th floors, logging data every thirty minutes. This data showed how the skin

responded to large-scale patterns such as diurnal cycling and to smaller, more rapid events such

as exposure to direct solar radiation and sudden drops in temperature caused by thunderstorms.

Interior relative humidity and dry bulb temperature from the 3rd floor were monitored and

logged; and exterior solar radiation, ambient temperatures, and relative humidity were recorded

from a roof-mounted weather station. A digital anemometer was used to analyze airspeed

within the cavity of the building envelope.



Figure 7 : Sensor locations on west facade and roof

Figure 8 : Sensor types used to monitor temperatures within and around the wall assembly

Figure 9 : Composite average of interior and exterior temperatures (July-October)

compared to thermal comfort target


Rather than draw solid conclusions from the data, our monitoring exercise raised further

questions and brought certain considerations into focus for further investigation. These include

deepening our understanding of the physics of how infrared blocking film interacts with

sunlight, a study of the correlations between sun angle and the transmission of solar radiation

energy, and strategies to improve insulation in a lightweight structure with low thermal mass.

We discovered that the house kept relatively cool throughout the hot, humid summer. This was

due in part to the low thermal mass of the structure which allowed it to cool down rapidly and

fully at night. The fact that it did not overheat during periods of peak sunlight points to the

effectiveness of the thermal buffering in the double-layer SmartWrap™ wall system, and the

efficacy of infrared shielding and natural ventilation.

After the exhibition, the house was un-stacked from the top down, disassembled, and placed in

storage for redeployment at a new location, with the SmartWrap™ panels remaining intact.

1.4. Next Steps in SmartWrapTM

Development

Our current research is focused on an analysis of the components of SmartWrapTM

,

specifically, the energy gathering characteristics of organic photovoltaic (OPV) cells. We

analyzed a surface area approach to OPV technology integration proposed for SmartWrapTM

,

presenting a calculation of the required surface area of OPV module coverage to meet the

energy demands of an energy efficient residence. Accounting for climatic location, OPV

module orientation, and OPV power conversion efficiency (PCE), we determined the ability of

a building-integrated organic photovoltaic (BIOPV) system to meet the electricity demands of

buildings. Findings were presented at the ENERGY FORUM on Solar Building Skins in

Bressanone Italy in December 2010.

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