MNelson Research II: Building Envelopes + Cladding Systems

8/8/2019 MNelson Research II: Building Envelopes + Cladding Systems

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Building Envelopes + Cladding Systems

in Homes

CH.09 CH.08 CH.07 CH.06 CH.05 CH.04 CH.03 CH.02 CH.01

Maggie Nelson

Sentient Architectures: at Home

Rodolphe el-Khoury with Nashid Nabian

Research Assignment II




The Building Envelope

As Linda Brock states in her book, Designing the Exterior

Wall , the building envelope—the skin supported by the

skeleton of the structure, or the monolithic load-bearing

wall—mediates the environment and provides security.

The structure determines form while the envelope

protects, keeping rain and snow out while controlling the

relative humidity and temperature of the interior. When

designing the building envelope and choosing an exterior

wall system, keeping in mind the zone in which the

building will be constructed (see below right), the focus

should be on the following:

Stopping:

Water ingress from rain and melted snow/ice to minimizedegradation of wall components

Air ow, to minimize water entry, passage of conditioned

air, and migration of water vapor

Controlling:

Heat transfer by radiation and conduction

Water vapor diffusionto avoid condensation

Transferring Structural Loads:

Lateral loads from wind and seismis events

Gravity loads

Accommodating Differential Movement:

Between the different components within an assembly

Between the assemblies of the exterior wall

Providing the Aesthetic Face of the Building

Elements of the Building Enclosure

North American Exposure Zones h t t p : / / w w w . b e

n j a m i n o b d y k e . c

o m

h t t p : / / w w w . b

u i l d i n g s c i e n c e .

c o m

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CH.09 CH.08 CH.07 CH.06 CH.04 CH.03 CH.02CH.05 CH.01

In concept, the perfect wall has an agile handle on all

control layers of the building by the rainwater control

layer, the air control layer, the vapor control layer and the

thermal control layer on the exterior of the structure.

This layering of elements is relatively simple to justify;

for example, the placement of insulation should be on

the exterior, under the cladding. If insulation is placed

on the inside of the structure, it does not protect the

structure from heat and cold. Expansion, contraction,

corrosion, decay, and almost all other environmental

conditions should be controlled for the benet of the

structure. Interior air quality is especially important to

maintaining a safe environment, so creating an airtight

enclosure is essential to conditioning ltration, air change,

temperature, and humidity. So, with the air control layer

under the insulation layer in order that the air does not

change temperature, we have the perfect wall.

This above point outlines the perfect wall in current

practice, although certain variations exist. The gures

below show two examples. The rst is known as the

Institutional Wall, said to be the best wall that we know

how to construct; it works everywhere, in all climate

zones. The second is the best Residential wall, which

works in all but the harshest of climates.

The Building Envelope:

The Perfect Wall

The Residential Wall B o t h i m a g e s

f r o m : h t t p : / / w w w . b

u i l d i n g s c i e n

c e . c

o m

The Institutional Wall

CH 01 CH 02 CH 03 CH 04 CH 05 CH 06 CH 07 CH 08 CH 09





Water Management

One of the fundamental purposes of the building envelope

is the control of rain and other precipitation from entering

the building. Four basic wall systems to manage water

are presented below:

1. Face-sealed barrier walls

Products for an Exterior Insulation and Finish System

(EIFS) rely on complete seal at the exterior face, including

joints. Examples include face-sealed concrete block,

concrete, or stucco. Curtain walls and claddings that

rely on a single sealant bead to stop water from entering

the wall between units/panels are also examples of face-

sealed barrier walls.

2. Internal drainage plane walls

An internal drainage plane is common with stucco

applications. Using building paper or non-perforated

building wraps as the water barrier with a drainage screed

at the base increases the possibility for water drainage.

An internal drainage plane also describes walls with a

drainage plane and a water barrier under wood, ber-

cement, metal, or vinyl sidings and proprietary, drained

EIFS systems.

1. Face-Sealed Barrier Wall

2. Internal Drainage Plane Wall f r o m : L i n d a B

r o c k ,

D e s i g n i n g t h e E x t e r i o r W

a l l

f r o m : L i n d a B r o c k ,

D e s i g n i n g t h e E x t e r i o r W a l l

CH 09 CH 08 CH 07 CH 06 CH 04 CH 03 CH 02CH 05 CH 01




3. Drainage cavity walls

Although brick veneer in the past was part of a composite

masonry wall, today the backup wall is as likely to be

made of steel studs. Brick veneer requires a minimum

cavity depth of 2 inches to ensure the cavity is kept free

of mortar droppings during construction. A drainage

cavity wall is standard with many cladding systems such

as stone veneer and panel systems of metal. It is also

commonly used for wood cladding.

4. Pressure-equalized rain-screen walls

Often referred to simply as PER walls, these are drainage

cavity walls with a vented, compartmentalized cavity to

limit air ow from one area to another, and a continuous,

structurally supported air barrier system. Pressure-

equalized joints between face-sealed cladding units are

another method of water management; these are called

pressure-equalized or PE joints.


Water Management

4. Pressure-Equalized Rain-Screen Wall f r o m : L i n d a B

r o c k ,

D e s i g n i n g t h e E x t e r i o r W

a l l

3. Drainage Cavity Wall

f r o m : L i n d a B r o c k ,

D e s i g n i n g t h e E x t e r i o r W a l l

CH 01 CH 02 CH 03 CH 04 CH 05 CH 06 CH 07 CH 08 CH 09




Cladding Systems

The term cladding denotes the visible materials on the

exterior of the wall. Cladding acts as the primary weather

barrier; it is a protective layer of materials that separates

a building’s structure and interior from exterior elements,

such as weather and sound. The cladding is often not one

material but an assembly of materials, and each material

has its own importance in blocking exterior conditions.

For example, a contemporary house will have an exterior

veneer of siding or brick, a moisture resistant plastic

wrap, insulation and a vapor barrier to protect the interior.

Many contemporary cladding systems are novel

and provide protection from the exterior with a thin

skin. Modern systems such as aluminum and glass

architectural glazing can insulate and shade a building

as well as traditional masonry and wood systems. Other

cladding systems are similar to screens, able to lter

out the wind and sun, but allowing air to ow through

the structure’s skin. Some claddings—such as insulated

glass units—perform all of the wall’s functions.

When desiging for cladding, keep in mind:

- All claddings leak, some just more than others

- Claddings need a secondary drainage plane

- Periodic cleaning is essential to maintain performance,

as is replacing sealant joints

Advanced Metallic Cladding System

Traditional Wooden Siding

h t t p : / / w w w . e

s p l a n a d e . c

o m / a b o u t_ t h e_

c e n t r e / i m a g e_

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l / C l a d d i n g / c l a d d i n g 0 1 . j p

g

h t t p : / / w w w . d

u r r e t t i n t e r e s t s . c o m / w o r d p r e s s /




Architectural Precast Concrete cladding

Composite Precast Cladding Panel

h t t p : / / w w w . c

l a r k p a c i f c . c

o m / p r o d u c t s / a r c h i t e c t u r a l / i n d e x . h

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l a r k p a c i f c . c

o m

/ p r o d u c t s / a r c h i t e c t u r a l / i n d e x . h t m l


Cladding systems can be constructed of a wider variety of

different materials. Below are several examples, although

this is not an exhaustive list. The images at right show

examples of precast concrete and composite cladding

panel systems, which hang on a steel structure.

- Masonry

- Precast Concrete

- Glass Fiber reinforced concrete (GFRC)

- Natural Stone (on concrete or CMU wall; as veneer on

aluminum honeycomb panel)

- Stucco (on wood or steel stud walls, or on concrete or

CMU walls)

- Exterior Insulation and Finish System (EIFS) (on wood

or steel stud walls, concrete or CMU walls)

- Metal sheeting or insulated metal panels

- Wood

- Glass (this can be stick built or unitized w/ aluminum

frame on steel structure)

- Composite materials

Cladding Systems




Cladding Systems:

Post-and-Beam Facades

In the 20th century, the further resolution and division of

the wall into a separate façade and loadbearing structure

is based on theoretical ideas that were developed at the

time. This led to the glass boxes that are such a common

feature of present-day cityscapes.

The next evolutionary stage was the development of the

post-and-beam façade as the logical next step in the

dissolution of the solid outer wall. Not limited to the glass

boxes in modern cityscapes, this sytem can be used for

residential construction. This system consists of storey-

high posts linked by horizontal beams. The gaps between

successive posts and beams can be made to perform

various functions, such as for cladding, lighting and

ventilation. In these standing post-and-beam façades, the

posts serve not only to transfer the wind forces and self-

weight of the structure to the ground but also to provide

support for the cladding and other functions.

The TU Delft Library, a Post-and-beam system

Post-and-Beam Facade Diagram

f r o m : F a c a d e

s : P r i n c i p l e s o f C o n s t r u c t i o n ,

K n a a c k e t a l

f r o m : F a c a d e s : P r i n c i p l e s o

f C o n s t r u c t i o n ,

K n a a c k e t a l




Brick Rain-screen Cladding System

Wood Siding being installed as a Rain-screen

h t t p : / / w w w . m

i d w e s t c y p r e s s . c

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o m / w h y_

i n v e l o p e / i n d e x . p h p

These are common facade systems that encompass a

wide number of applications and materials, and are a

proven method for deterring rainwater intrusion into walls.

Rain screens shed most of the rain and manage the rest,

preventing moisture intrusion and the resulting premature

decay in homes. By neutralizing the forces that drive

water into the wall, rain screens can withstand extreme

environments.

All rain screens include the following elements:

- Vented or porous exterior cladding

- Air cavity (a few inches of depth is sufcient)

- Drainage layer on support wall

- Rigid, water-resistant, airtight, support wall

Simple rain screen walls are built daily from readily avail-

able materials. Walls constructed with brick veneer and

furred-out wooden clapboard are two classic simple rain

screen assemblies. Simple rain screen walls should

always have a continuous, 3/8-inch minimum clear air-

space, and should include a drainage plane at the backof the rain screen cavity.

Pressure-Equalized Rain-screens (PERs) are not com-

mon in residential construction, though commercial PER

systems are becoming more popular, which may lead to

faster, more cost-efcient, residential integration.

Cladding Systems:

Rain-Screen Facades




Cladding Systems:

Curtain Walls

Any building wall, of any material, that carries no

superimposed vertical loads. This divides walls into

bearing and nonbearing. Some common curtain wall

materials include the following, with their backup wall

usually of steel studs: aluminum and glass, prefabricated

EIFS panels, terra cotta, marble, and brick veneer. A metal

curtain wall consists of a metal frame that supports glass,

metal, stone or other cladding panels; anchored brick

veneer and precast concrete panels are also commonly

used as panelling on a metal frame. This can be installed

onsite in individual pieces (stick system) or units can be

prefabricated in a factory (unitized system).

Since the construction is practically independent of the

building’s main loadbearing structure, the curtain-wall

façade can be partitioned almost at will and cladding or

glazing used to meet the various aesthetic or functional

requirements. The vertical and lateral loads are generally

led to ground oor by oor, but special loadbearing

elements may be added to bridge longer spans.

Unlike pure post-and-beam systems, curtain walls are

suspended from above with the aid of tie rods, which has

the advantage of avoiding buckling in the posts and of

a large degree of independence from the main building

structure. Mies van der Rohe’s Federal Center in Chicago

is an example of a curtain wall, reecting the demand for

industrially produced façades that satisfy architecturalpreferences: the façade is made up of prefabricated

elements, assembled by craftsmen on site.

The Federal Center, Chicago

Curtain Wall Facade Diagram

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i m o a . e

u / i m a g e s / 1 3 3 0 8

_ l . j p g

f r o m : F a c a d e s : P r i n c i p l e s o f C o n s t r u c t i o n ,

K n a a c k e t a l




The New York Times Headquarters

A Sound-reducing Curtainwall Facade

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r i g h t s t y l e . c

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a r t s / g a l l e r y / 2 0 0 7 / n o v / 2 6 / a r c h i t e c t u r e .

p h o t o g r a p h y

Visual Aspects: Daylighting, Aesthetics

Key visual features of curtain walls are glazing appearance

and sightlines. Sightlines are dened as the visual prole

of the vertical and horizontal mullions. The sightlines are

a function of both the width and depth of the curtain wall

frame. Lateral load resistance requirements (wind loads,

spans) generally dictate frame depth. Where narrow

sightlines are desired, steel stiffeners inserted into the

hollow frame of aluminum extrusions can help reduce

frame depth. The New York Times building is a good

example of a curtain wall system that maintains sightlines

while mediating daylight.

Sound (Acoustics)

The acoustic performance of curtain walls is primarily

a function of the glazing and internal seals to stop air

leakage. The sound attenuation capability of curtain

walls can be improved by installing sound attenuatinginll and by making construction as airtight as possible.

Incorporating different thicknesses of glass in an insulated

glass unit will also help to mitigate exterior noise. This can

be accomplished by increasing the thickness of one of

the lites of glass or by incorporating a laminated layer of

glass with a noise-reducing interlayer, typically a polyvinyl

butyral or PVB. The image at right is an example of asound-reducing facade with three layers of glazing and

special sealants for acoustic control.

Cladding Systems:

Curtain Walls




Cladding Systems:

double-skin facades

One of the interesting developments that may be observed

at this time is the rise of the double façade, resulting

from the shift of various functions related to the interior

functions of the building immediately behind the façade.

For example, instead of installing ventilation systems in

the building, the ventilation can be provided by thermal

insulation between the two layers of the façade. On the

basis of experience, the initial variants of this concept

have developed into ventilation systems encompassing

one or several stories.

There are several variations on the double-skin facade,

which allow for more possibilities in creating double-skins

in retrotting situations as well as in new construction.

These are know as (1) the second-skin façade,

obtained by adding a second layer of glass over the

entire outer surface of the building; (2) the box window

facade, which includes story-high façade elements in the

system, which individual users can open at the top and

the bottom; (3) the corridor façade, with staggered air

inlets and outlets to deal with the problem of interferencebetween the ventilation systems at different levels; and

(4), the shaft-box facade, box windows or other façade

elements release their exhaust air into a shaft mounted

on the façade and extending over several oors for

greater thermal efciency. Diagrams of each of these

systems are shown on the next page.

Double-Skin Facade Diagram

Triangle Building, Cologne, Germany


K n a a c k e t a l


K n a a c k e t a l




The Box-Window Facade

The Shaft-Box Facade

A l l f r o m : F a c

a d e s : P r i n c i p l e s o f C o n s t r u c t i o n ,

K n a a c k e t a l

The Corridor Facade

The Second-skin Facade




The Interactive Envelope

The following are excerpts from the article “Robo

Buildings: Pursuing the Interactive Envelope,” which

recently appeared inArchitectural Record.

In an article published in the cyber journal Technoetic Arts

last year, British architect-academics Stephen A. Gage

and Will Thorne describe a hypothetical eet of small

robots they call “edge monkeys.” Their function would be

to patrol building facades, regulating energy usage and

indoor conditions. Basic duties include closing unattended

windows, checking thermostats, and adjusting blinds.

Increasingly, architects would like to automate their

building envelopes rather than leave energy-efcient

operation to chance (or harried maintenance engineers).As a result, the critical interface between the interior

and the elements is getting more attention—and more

animated.

One example is the Biodesign Institute, Arizona State

University, Tempe, AZ. In this project, a large, easterly

expanse of windows uses aluminum louvers that arecontrolled continuously by photocells and sun-tracking

software. The design allows occupants to control most

of the louvers in their ofces using their PCs, although

at above 8 feet from oor level the louvers are controlled

automatically.

(all images on this and following page are from:

http://archrecord.construction.com/resources/conteduc/

archives/0604edit-1.asp)

“Edge monkeys” are robots that would close win-

dows, check thermostats, adjust blinds, etc.

The Biodesign Institute, Tempe, Arizona





captioncaption

Harder to predict are the benets of hybrid envelope

systems, in which two or more interactive strategies are

combined. Many European architects have integrated

ventilation, shading, and other active technologies

into double-wall facades that serve as primary space

conditioners. Unlike Cannon’s Occidental Chemical

building, early double envelopes had few moving parts.

(Some Europeans use the term “active facade” to describe

any ventilated double wall, regardless of operability.) More

recent projects feature more “edge monkeys”: automated

hoppers, vents, and shades.

An extreme example is the philology library by Foster and

Partners at Berlin’s Free University, completed last year.

The four-story, orblike enclosure—with an underoor

air plenum—is engineered for free cooling for about

seven months of the year using natural ventilation. A

checkerboard cladding of aluminum and glazed panels

protects an inner glass-ber membrane. Operable panels

close during cold weather, and fresh air is drawn from

outside through the oor cavity and into the envelope

void. A concrete internal structure provides thermal mass

and radiant cooling and heating of recirculated air. The

client expects about 35 percent energy savings over a

comparable facility.





For many architects, the European tradition of

customizing an off-the-shelf, unitized, double-wall

product presents a safe and effective entrée into the

world of interactive facades. Less prevalent is the craft-

based approach used by Thom Mayne for Caltrans

District 7 Headquarters in Los Angeles, which opened

in late 2004. There, Morphosis Architects pulled apart

the envelope’s functional elements, “redelegated” them,

and coordinated their job-site “reassembly” among seven

exterior subcontractors, says project leader Pavel Getov.

The result combines a large photovoltaic array and

independently controlled, automated elements within a

multiple-layer facade. The prominent shading layer of perforated metallic panels on east and west facades cuts

initial solar heat gain by about 15 percent. The screen

hangs about 1 foot from the slab edges of a weather-wall

of metal framing, gypsum sheathing, and PVC membrane.

In this way, the intervening space functions partly as

convective cavity. One thousand or so of the scrim

panels, corresponding to ribbon windows behind, openor close daily. Those on the east close in the morning,

those on the west in the afternoon. For longevity, the

architects specied stainless-steel hardware and a single

pneumatic lift per panel, rather than the pair of electrical

actuators originally considered. A rooftop sensor signals

the panels to close during high winds.

Caltrans District 7 Headquarters, Los Angeles

On the building’s South side, large photovoltaic

panels form a brise-soleil.




Frameless glass panels at Aurora Place, London

Diagram of the Double-skin Cladding on the upper

levels of Aurora Place

Recent thinking on active envelopes mirrors that for

m/e/p design generally: avoid complexity and, therefore,

very integrated schemes. Some projects, such as

Arup’s Plantation Place , have explored highly localized

automation. There, sensors mounted on the inner facade

detect solar conditions for each tenant zone. Solar blinds

in specied areas raise or lower autonomously, depending

on the local temperature, sun strike, and occupant

preferences. Natural ventilation rates are determined

locally as well. Like the robotic edge monkeys, however,

such islands of control need occasional global guidance—

and the will to ignore the people they serve. “You can’t

rely on human input,” says Arfon Davies, an associate

with Arup Lighting in London. “And if automatic shadingcontrols are independent from the BAS, they should still

be able to send a signal to the BAS to indicate a fault.”

Another reference is the Arup Associates-designed

Aurora Place in London. At the upper levels of the

building, the outer layer of double-skinned facade is

made up of frameless glass panels, angled at 3 degrees,with open joints. Behind the screen is a walkway used for

maintenance. Tenants can open the windows to provide

natural cooling. The window blinds are automatically

raised or lowered based on current conditions in each

tenant zone. The blinds are accessible from the outside

for cleaning and maintenance.

For the complete Robo-buildings article, refer to:

http://archrecord.construction.com/resources/conteduc/

archives/0604edit-1.asp





Smart Materials + New Technologies

The eld of smart materials and the development of

new material technologies for architectural applications

is rapidly changing. This section is only a sampling of

emergent materials for building facades that are currently

in use.

Smart Paints and Coatings

Painting and coatings are ancient techniques for changing

or improving the characteristics or performance of a

material. The development of smart paints and coatings

gives these old approaches new capabilities. Smart

paints and coatings can generally be classied into:

- High performance materials- Property-changing materials

- Energy-exchanging materials

For example, thermochromic paints are widely used

to provide a color-change indicator of the temperature

level of a product; this is an example of a property-

changing material. Similarly, electrochromic windowscan darken automatically when the sunlight is more

intense, regulating light and room temperature. Energy-

exchanging materials used in paints or coatings also have

many direct applications, such as the use of natural and

synthetic luminescent materials. These coatings absorb

energy from light, chemical, or thermal sources and re-

emit photons to cause uorescence, phosphorescence,or photoluminescence.

Thermochromic Glass Tile

Electrochromic windows for climate control.

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o m / u n c a t e g o r i z e d / n o r t h e r n

- l i g h t s -

h e a t - r e s p o n s i v e - t i l e




Electro-optical glass in its two states

Dichroic glass fns support a curtain wall

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h t t p : / / w w w . a

l e x s t a c h e l e k . c

o m / b l o g / ? p = 2 8

Electro-optical glass is another property-changing

material. Essentially, while the electro-chromatic effect is

the change in color, the electro-optic effect is a change in

optical properties of something in response to an electric

eld, which has implications for user interaction. Smart

Glass is probably the most common practical use of this

effect. Using a switch the user can toggle the voltage, this

change in electrical current affects the particle directoin

and thus the visual transparency in a sheet of glass.

Dichroic glass is glass containing multiple micro-layers of

metal oxides which give the glass specic color-changing

properties, with the color change as a function of the

angle of incident light or of the viewing angle. Dichroicglass can be made in more than 100 patterns and

different colors including gold/blue, violet/gold, and blue/

green. The material is made with the same technology

and coatings used to produce anti-reective panels: ultra-

thin, microscopic layers of metal oxides vacuum-sprayed

onto a glass surface, creating various transmitted and

reective colors.






ETFE

Ethylene tetrauoroethylene, ETFE, a kind of plastic,

was designed to have high corrosion resistance and

strength over a wide temperature range. Compared to

glass, ETFE lm is 1% the weight, transmits more light

and costs 24% to 70% less to install. It’s also resilient

(able to bear 400 times its own weight), self-cleaning

(due to its nonstick surface) and recyclable. On the other

hand it is prone to punctures by sharp edges, therefore

it is mostly used for roofs. In sheet form as commonly

employed for architecture, it is able to stretch to three

times its length without loss of elasticity. Employing heat

welding, tears can be repaired with a patch or multiple

sheets assembled into larger panels.

An example of its use is as pneumatic panels to cover the

outside of the football stadium Allianz Arena or the Beijing

National Aquatics Centre (a.k.a. the Water Cube of the

2008 Olympics) - the world’s largest structure made

of ETFE lm. The panels of the Eden Project are also

made of ETFE and the Tropical Islands have a 20,000 m²window made of this translucent material.

The ETFE facade of the Water Cube

Allianz Arena, Munich.

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3D solar cells being developed at Georgia Tech

3D solar cells will be exible and inexpensive

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a - 3

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3D Solar Cells

Unique three-dimensional solar cells that capture nearly

all of the light that strikes them could boost the efciency

of photovoltaic (PV) systems while reducing their size,

weight and mechanical complexity. The new 3D solar

cells capture photons from sunlight using an array of

miniature “tower” structures that resemble high-rise

buildings in a city street grid. The cells could nd near-

term applications in architecture, as well as for powering

spacecraft, and by enabling efciency improvements in

photovoltaic coating materials, could also change the way

solar cells are designed for a broad range of applications.

The GTRI photovoltaic cells trap light between their tower structures, which are about 100 microns tall, 40

microns by 40 microns square, 10 microns apart -- and

built from arrays containing millions of vertically-aligned

carbon nanotubes. Conventional at solar cells reect a

signicant portion of the light that strikes them, reducing

the amount of energy they absorb. Because the tower

structures can trap and absorb light received from manydifferent angles, the new cells remain efcient even when

the sun is not directly overhead.





Green Facades

A green wall is a wall, either free-standing or part of a

building, that is partially or completely covered with

vegetation and, in some cases, soil or an inorganic

growing medium. There are two main categories of green

walls:

- Green façades -- composed of climbing plants either

growing directly on a wall or, more recently, specially

designed supporting structures, where the plant shoot

system grows up the side of the building while being

rooted to the ground

- Living walls -- modular panels are often made of

stainless steel containers, geotextiles, irrigation systems,a growing medium and vegetation; plant material may be

on the interior or exterior of the building.

Green walls are often in urban environments where the

plants reduce overall temperatures of the building. Plant

surfaces do not rise more than 4–5 °C above the ambient

temperature and thus help mitigate the potential heatabsorption in the summer. Their mass also helps insulate

in the winter. These walls may also be a means for water

reuse, as plants may purify slightly polluted water (such

as greywater) by absorbing the dissolved nutrients.

Celebrated French botanist Patrick Blanc is credited as

the inventor of the Vertical Garden, le mur végétal , after

many observations in natural environments. He has

created numerous interior and exterior vertical garden

installations worldwide.

A close-up a vertical garden by Patrick Blanc.

The vertical garden at the Caixa Forum, Madrid.

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The Mur Végétal by Patrick Blanc at the Musée du Quai Branly, Paris.

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Documents

MNelson Research II: Building Envelopes + Cladding Systems