The Design of Ecological Buildings – Lighting and Shading International Seminar on Green Housing, Guangzhou, China, June 2002 1 The Design of Ecological

The Design of Ecological Buildings – Lighting and ShadingInternational Seminar on Green Housing, Guangzhou, China, June

20021

The Design of Ecological Buildings: Shading and Lighting

Professor Yan ChenProfessor Les Norford

Department of ArchitectureMIT

Traditional shading technology New shading technology


20022

What not to do - Beijing housing: vegetation but not much shading


20023

What not to do - Balconies are enclosed and no longer provide shading


20024

What not to do – worst case

Which way is south? Where is the window shading?

Can occupants possibly be comfortable without air conditioning?


20025

The Earth’s Comfort Zones Around the world people have developed energy-efficient building forms that are suited to the climate conditions of their particular location – a form of ‘solar vernacular’.

They have developed simple solutions to the environmental challenges set before them: heat, cold , rain and wind. These solutions have been developed using a limited range of indigenous building materials, all of them renewable


20026

Climate Zones: Architecture

Boston Beijing

Ice Caps

Tundra

Mountain

Continental

Marine-West coastal

Mediterranean

Subtropical

Rain Forest

Savannas

Steppes

Deserts

40-42 N


20027

Mediterranean Climate

•Closest to the ideal climate - warm but dry with mild winters. People must protect themselves from the intense heat of summer and extreme light by shading and thermal mass.

•Life slows down in summer, as cooling is not always affordable.

•Arcades and verandahs create microclimates merging the bright outside with the cold dark indoors


20028

Shading by Buildings - Italy


20029

Marine West-coastal climate

•Not too hot, not too cold – the oceans have a calming influence on the temperature on land. The strong winds and rain that come with the cold winter make this a good environment for people to work in, as long as they have warmth and protection

•A balance is required between daylight and insulation – large windows allow natural lighting and ventilation.

•The low embodied energy of Georgian houses, using brick, wood and glass, has proved very sustainable for over 200 years


200210

Subtropical Climate

•A pleasant climate for most of the year, but summers are humid so ventilation is a necessity.

•The Japanese and Chinese developed systems of dynamic walls to create buffer zones between inside and outside, providing more comfortable summer spaces.

•Houses in the southern US use the porch as a buffer zone. In Japan the sliding screens allow maximum cross ventilation. Chinese roundhouses contain a protected fully sustainable community


200211

Solar Shading

Villa Shodhan, Ahmadabad Unite Building, Marsailles, France

•Shading devices and roof gardens provide excellent shade and comfort for south facing walls


200212

Window shading inMumbai, India


200213


200214

Even newer buildings have at least some window shading


200215

A school in Gujarat, India – note the depth of the facade


200216

Solar Shading

•Protective shading in Brazil. Adjustable louvers between fixed vertical concrete fins


200217

Housing in Zimbabwe – another deep façade and a good use of pre-

cast concrete


200218

New facade technologies

• many new high rise buildings in Europe are experimenting using double skin wall technology- allowing natural ventilation and adjusting to summer and winter climate conditions


200219

How about a very different type of high-rise building for a hot and humid tropical climate?


200220

Back to Beijing - vegetation helps reduce indoor temperatures


200221

Vegetation and shading from overhanging surfaces – looks cool and comfortable


200222

Awnings and plants


200223

Detailed View of Shading # 1:Osuna Housing, Seville, Spain

Notice strong solar orientation of the buildings on the site.


200224

Shading – relatively few windows on the west facade


200225

Winter sun for daylighting and solar heat


200226

Summer sun is blocked


200227

Detailed Look at Shading #2: Solar Village 3 Athens, Greece


200228

Align most buildings to face North-South


200229

Site orientation


200230

Shading system


200231


200232

Note depth of south facing façade


200233

Shading Design

1. Determine when shading is needed


200234

2. Determine elevation and azimuth of sun when shading is needed


200235

3. Choose a shading device – fixed ….


200236

… or movable


200237

In hot climates, south-facing windows are best because they bring in the least heat


200238

4. Determine size of shading device

Example: movable south-facing shading


200239

A word about lighting

• Relatively easy to do with houses because room sizes are small

• Still important– Reduces energy for lighting– May reduce energy for cooling– Meets human needs for sunlight and contact

with nature


200240

Assessing lighting inside a Shanghai apartment


200241

Use simulation to estimate indoor illuminance


200242

Developers and designers can get help from the research community

• Encourage and support research to find new ways of determining energy-efficient designs

• Conduct design competitions in which carefully documented estimates of energy use are a key part of submittals


200243

A new technology: automatically trading off cost of windows and insulation

against energy use

• Consider a Beijing apartment, with north and south exposures

• Vary window size, glazing type, and wall construction in each of the two walls

• Compute construction cost and operating energy

• Search for lowest operating energy for a given construction cost


200244

Search procedure

• Use the DOE-2 energy calculation program to estimate yearly energy use for heating, cooling and lighting

• Use a genetic algorithm to automatically search for the best trade-offs between operating energy and construction cost


200245

Trading off cost of windows and insulation against energy use – results of an automated search

Beijing - Pareto front [First and last generations]

0

1000

2000

3000

4000

5000

6000

2 3 4 5 6 7 8 9 10 11 12

MWh

Co

st

($)

Gen 1

Gen 100


200246

What’s best? Construction details

• The most expensive but most efficient construction uses:– Large south-facing and small north-facing

windows– Lots of insulation in both walls, but more in the

north-facing wall

• All of the optimal trade-offs use double-glazed windows


200247

Repeat for east-west apartment

Beijing East/West case- Pareto front [1st and last generations]

0

1000

2000

3000

4000

5000

6000

7000

2 3 4 5 6 7 8 9 10 11

MWh

Co

st

($)

Gen 100

Gen 1


200248

East-west apartment

• Higher energy use than an apartment facing north-south, as expected

• The most energy-efficient solution has windows of about 2 m2 in the east and west walls, compared to about 8 m2 in the south wall and 0.8 m2 in the north wall


200249

Conclusion• Developers and designers can make buildings

more comfortable and efficient, by setting high goals and working with government organizations and building scientists.

• Better control of sun and light need not be costly and can provide a distinctive and pleasing form to buildings as well as save energy for lighting and cooling.

• Researchers should be encouraged to generate new designs and to pin point trade-offs between energy use and cost.

Documents

The Design of Ecological Buildings – Lighting and Shading International Seminar on Green Housing, Guangzhou, China, June 2002 1 The Design of Ecological