Green Buildings

Buildings as energy consumers

Historical techniques for passive ventilation: Malqafs, badgirs, and

Hassan Fathy

Temperature moderation and raiwater conservation: Green roofs

Kenneth Yeang and the green skyscraper

1950

2000

2015

Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

Brundtland Report (1987)

What is Sustainability?

• U.S. average “footprint” of 19 acres per person.

• Worldwide available “footprint” of 4.5 acres per person.

• 19 / 4.5 = 4.25

www.ecofoot.org

28%

32%

40%

Buildings

US Energy Use

Transportation

Industrial

Diagram 1. Energy Flow, 2005(Quadrillion Btu)

Energy Information Administration / Annual Energy Review 2005 3

Consumption99.89

kSupply104.54

Exports4.64

Petroleum2.46

Other2.18

gCoal23.05

Natural Gas18.76

Crude Oil10.84

a

NGPL 2.32b

Nuclear Electric Power 8.13

Renewable Energy 6.06c

Petrole

um

28.87

d

Other5.39

e

FossilFuels85.96

j

Renewable Energyc 6.06

Nuclear Electric Power 8.13

DomesticProduction

69.17

Industrial 31.98

l

Commercial 17.97

l

Transportation 28.06

l

Residential

21.87

l

Coal22.83

Natural Gas22.64

h

Petroleum40.44

i

Imports34.26

FossilFuels54.97

Adjustments1.11

f

a Includes lease condensate.b Natural gas plant liquids.C Conventional hydroelectric power, wood, waste, ethanol blended into motor gasoline,

geothermal, solar, and wind.d Crude oil and petroleum products. Includes imports into the Strategic Petroleum Reserve.e Natural gas, coal, coal coke, and electricity.f Stock changes, losses, gains, miscellaneous blending components, and unaccounted-for

supply.g Coal, natural gas, coal coke, and electricity.h Includes supplemental gaseous fuels.

i Petroleum products, including natural gas plant liquids.j Includes 0.04 quadrillion Btu of coal coke net imports.k Includes, in quadrillion Btu, 0.34 ethanol blended into motor gasoline, which is accounted for

in both fossil fuels and renewable energy but counted only once in total consumption; and 0.08electricity net imports.

l Primary consumption, electricity retail sales, and electrical system energy losses, which areallocated to the end-use sectors in proportion to each sector’s share of total electricity retailsales. See Note, “Electrical Systems Energy Losses,” at end of Section 2.

Notes: • Data are preliminary. • Values are derived from source data prior to rounding forpublication. • Totals may not equal sum of components due to independent rounding.

Sources: Tables 1.1, 1.2, 1.3, 1.4, and 2.1a. (DOE 2005)

Commercial= 18%

Residential= 22%

energy in quadrillion BTUs

U.S. Energy Use

Building Resource Use

Average

Savings of

Green

Buildings

ENERGY

SAVINGS

30%

CARBON

SAVINGS

35%

WATER

USE

SAVINGS

30-50%

WASTE

COST

SAVINGS

50-90%

Source:

Capital E

‘Green’ Buildings Save

Sustainability and Buildings

Five Areas:

Site

Water Efficiency

Energy & Atmosphere

Materials & Resources

Indoor Environmental Quality

Sustainability and Structures?

1. How does sustainability relate to the other three S’s: social, symbolic, and scientific?

2. Is sustainability the fourth ‘S’ of structural art?

3. Has sustainability been achieved by any of the works of structural art we have studied? How?

Efficiency

Technology & Cost

Low

High

Low High

Technology, Cost & Efficiency

Efficiency

Technology & Cost

Low

High

Low High

Tunneling Through

Technology, Cost & Efficiency

The Cost Barrier

Passive Heating and Cooling

Hassan Fathy (1900-1989)

Malqaf = wind catcher

Bernoulli Effect

Badgir

Traditional Construction Modern Concrete Construction

12 THE ARUP JOURNAL 1/2003

Energy grading

For BedZED, Arup developed a technique to evaluate andmatch renewable energies to energy demands.

Until all energy sources have their full environmental costfactored into their retail price, making renewable energiescost-effective is quite a challenge. The technique is ‘energy grading’: ranking the full range of possible renewablesources against end-use energy needs, to generate achecklist of building design priorities. The key issue is tomatch the lowest possible grade of source against the gradeof the end demand. This process also involves mappingdemand and availability, given that most renewable energiestend to be more finite and need coupling via energy storageto allow this demand/availability match.

Designing the building concept around these principlesallows the most cost-effective use of renewables. Covering a building in photovoltaic (PV) solar electric collectors mayshow environmental awareness and highlight new energytechnologies, but in energy grading terms, PV’s modest output and current high cost suggest there may be morepragmatic ways to provide renewable energy.

Energy grading highlights interesting issues, like the inherentinefficiency of many conventional systems that consumehigh-grade energy and deliver only low-grade energy tobuilding users. Should we be using so much high-gradeelectricity to drive pumps and fans for what is in effect low-grade energy for room comfort needs?

Likewise, are the high-grade electrical energy needs of heat-pumps appropriate for delivering heating and cooling? It emphasizes the significant cost benefits of passive solarheating and passive cooling for room comfort, and the cost-effectiveness of designing buildings for reduced energydemand in the first place.

Zero-heating homes

One result of applying energy grading at BedZED was toquestion the need for conventional room space heating, in which a system is simply sized to provide comfort, with regulation minimum thermal insulation. Yet many buildingshave internal heat gains from people and their activities. So why not size the insulation, with thermal mass heat storage, so that this heat is sufficient to provide space heating through day and night, thus avoiding the need forany conventional heating? As the UK Building Regulationshave increased thermal insulation minimum standards, sothe proportion of the year when heating is needed has shortened. Yet the system cost does not reduce in proportion.So - what level of insulation will completely eliminate theheating system and hence reap a capital cost dividend?

Building physics

The design aim was to reap these cost and energy dividendsby fully exploiting the building envelope and fabric as primarymodifiers of the indoor climate, to the point where completemechanical systems could be omitted.

For UK mainstream housing this early design analysis time israre because the industry tends to work to rigid perceptionsof market expectations. At BedZED the project team wascommitted to demonstrate the viability of the principles evenbefore land purchase. As is often the case, much complexanalysis was needed to demonstrate that such a simplesolution is achievable.

In thermal analysis terms the availability of heat from occupants, appliances, cooking, washing, and solar heat ishighly variable both in timing and quantity. There are otherparameters, too, like the extent of glazing: at times it cancontribute useful solar heat, yet be the largest heat losscomponent. Also, steady-state building energy flows do notnecessarily represent reality. Low-grade heat will take time topass through a thick wall during which external influencingconditions will change, often to the extent that the heat maynot pass through at all, but instead reverse its flow. Adjustingthe thermal capacity and thermal insulation characteristics ofmaterials and energy transfer mechanisms can significantlyaffect what happens to the energy and whether it can then bereused. Many of the construction industry’s usual materials,with their significant thermal inertia, can give significantly different results from steady-state theory.

Dynamic thermal analytical and simulation tools, plus real weather data sequences, established the material performance and building massing needed for the zero-heating homes: the first time, it is believed, that suchadvanced computer tools - developed over the past 10years for analysing passive cooling techniques in officebuildings - have been used on a major housing project. For BedZED, these were the tools needed to show that normal home heating might be omitted. Super-insulatedhomes with extensive areas of exposed high thermal capacity materials could thus match heating needs againstnaturally occurring passive internal and solar heat gains.

The analyses revealed several different ‘design worst’ cases.The very coldest outdoor air temperatures usually relate toclear night skies, which in turn most often relate to daytimesolar heat gain. Extended periods of overcast skies are critical, although they normally relate to higher outdoor airtemperatures. Different occupant lifestyles are also factors;for example, how much top-up heating makes for the comfort of a new-born child? Then there is the prolongedabsence of occupants from home, with their consequentlack of contribution to heat gains.

Ensuring room temperatures do not fall when this happensis another critical design case, given the absence of a large heating system to recover temperatures when theoccupants return. Terraced blocks work well for reducedoverall heat loss, as long as large temperature differences inadjacent homes are avoided. Building envelope airtightnessis particularly critical. For the north-facing workspaces they could have lower machine heat gains than a typicaloffice, ie if used as live-work studios, and thus need somesupplementary background heating.

Computer analysis and simulation can explore solutions toall possible scenarios, allowing the design to pursue thesimplicity of passive heating in a robust solution.

• In summer - produces cooling.

• In winter - stores passive heat gains until needed.

• Highly insulated = 0.1 W/m2k.• Windows = triple glazed.• Airtightness = 2 AC/HR @ 50Pa.• Sun space = double-glazed to

room and to outside.

Minimumover-shadingby adjacentbuildings

• Extensive south-facing giving good, passive solar heat gain, glazed buffer sun space.• Minimum north glazing for daylight.

Sun spaceHomeWork Circulation

• North-facing windows.• Good daylight.• Minimum solar heat gain.

Exposed thermal mass:

Foul water treatment

Septic tank

Rainwaterstore

Electricity

Hot water

Low-energy lighting and appliances

Bio-fuelCHP

PV to charge electric cars

Wind-drivenventilation withheat recovery

Rainwater collection

IT wiredLow flush WC

5. Building physics.

6. Mechanical and electrical systems.

‘BedZED fullyexploited theenvelope andfabric of thebuilding as theprimary modifiersof the indoor climate, so thatcompletemechanical systems couldbe omitted.’

Green or Vegetated Roofs

51

Ken Yeang

(1948 - )

Population density

Sustainability and Structures?

1. How does sustainability relate to the other three S’s: social, symbolic, and scientific?

2. Is sustainability the fourth ‘S’ of structural art?

3. Has sustainability been achieved by any of the works of structural art we have studied? How?