Yeang K., Woo L. Dictionary of Ecodesign: An Illustrated Reference

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highly industrialized, densely populated areas

of North America, Europe, and Japan, but even

relatively small amounts of light can be noticed

and create problems. See also:

Sky glow

Light quality In an architectural context, a

description of how well people in a lighted

space can see to do visual tasks and how

visually comfortable they feel in that space.

Light shelf A passive mode daylight system, a

light shelf is a horizontal light-reﬂecting overhang

placed above eye level with a transom window

placed above it. This design, which is most effec-

tive in southern orientations, improves daylight

penetration, creates shading near the window,

and helps reduce window glare. Exterior light

shelves are more effective shading devices than

interior shelves. A combination of exterior and

interior will work best in providing an even

illumination gradient. See also:

Light pipe

Linear low-density polyethylene (LLPE)

Nonbiodegradable plastic used for packaging

and trash bags.

Liqueﬁed natural gas (LNG) Natural gas that

has been converted to liquid form so that it can

be stored on board a vehicle in a smaller

volume. To produce LNG, natural gas is pur-

iﬁed and condensed into liquid by cooling to –

260 °F (–162 °C). At atmospheric pressure, LNG

occupies only 1/600 the volume of natural gas

in vapor form. A gasoline gallon equivalent

(GGE) equals about 1.5 gallons of LNG.

Because it must be kept at such cold tempera-

tures, LNG is stored in double-wall, vacuum-

insulated pressure vessels. LNG fuel systems

typically are only used with heavy-duty vehi-

cles. The cooling process and cryogenic tanks

make LNG expensive. Use of LPN in place of

petroleum fuel produces fewer polluting emis-

sions. According to research by the US Depart-

ment of Energy, vehicles that use LNG (like its

counterpart compressed natural gas, CNG) emit

50–75% less nonmethane hydrocarbons, 25%

less carbon dioxide, 90–97% less carbon mon-

oxide, and 35–60% less nitrogen oxide. CNG

has a lower cost of production and storage

compared with LNG, but CNG requires a much

larger volume to store the same mass of natural

gas, and the use of very high pressures. See

also:

Compressed natural gas; Gasoline gallon

equivalent

Liqueﬁed petroleum gas See: Propane

Lithic Associated with stones and rock.

Lithosphere The solid, outermost part of the

Earth, including the crust and uppermost mantle.

The lithosphere is about 100 km (62 miles)

thick, although its thickness is age-dependent

(older lithosphere is thicker). The lithosphere

below the crust is brittle enough at some loca-

tions to produce earthquakes by faulting, such

as within a subducted oceanic plate. There are

two types of lithosphere: oceanic lithosphere,

associated with oceanic crust; and continental

lithosphere, associated with continental crust.

Lithotroph Type of bacteria that can obtain

metabolically useful energy from the oxidation

Figure 43 A light shelf preventing glare close to the

window and reﬂecting light deep into

the room

148 Light quality

of inorganic chemicals, including ammonium,

nitrite, iron, and sulfur. See also:

Autotroph;

Heterotroph

Living machine Refers to natural biological

sewage treatment plants that mimic the processes

found in wetland environments. Botanic purifying

systems that use plants, ﬁsh, bacteria and snails

to purify water on site to potable standards.

These systems can be integrated into water-reuse

systems that minimize energy, provide nitriﬁca-

tion and good nitrogen removal, eliminate most

of the residual biosolids, eliminate clariﬁers, and

allow tertiary treatment for water reuse. They

can be used in industrial facilities, resorts, and

communities, and for agricultural operations.

LLPE See:

Linear low-density polyethylene

LNAPL See: Light nonaqueous-phase liquid

LNG See: Liqueﬁed natural gas

Load The power required to run a deﬁned cir-

cuit or system, such as a refrigerator, a building,

or an entire electricity distribution system.

Load shedding Turning off or disconnecting

loads to limit peak demand.

Locally unwanted land uses (LULU) Position

of residents who oppose land uses such as toxic

waste dumps, landﬁlls, incinerators, airports, or

freeways close to their homes. Also known as

“not in my back yard” (NIMBY).

London Agreement 1990 amendment to the

1987 Montreal Protocol, an international agree-

ment to regulate and decrease ozone deplet-

ing sources. The London Agreement of 1990

stipulated that the production and consump-

tion of compounds that deplete ozone in the

stratosphere—chloroﬂuorocarbons (CFCs), halon

(bromoﬂuorocarbons), carbon tetrachloride, and

methyl chloroform—were to be phased out by

2000 (2005 for methyl chloroform). See also:

Montreal Protocol on Substances that Deplete the

Ozone Layer

Longitude Distance east or west on the Earth’s

surface measured as an arc of the equator in

degrees up to 180.

Loose-ﬁll insulation Insulation made from rock-

wool ﬁbers, ﬁberglass, cellulose ﬁber, vermicu-

lite or perlite minerals, and composed of loose

ﬁbers or granules; can be applied by pouring

directly from the bag or with a blower.

Lotic waters Flowing waters, as in streams

and rivers.

Low-carbon design See:

Zero-carbon design

Low-density polyethylene (LDPE)

Nonbiodegradable plastic used for bottles, bags,

ﬁlms, and plastic wrapping.

Low-emissivity windows and (window) ﬁlms

Commonly called “low-e windows”. These

energy-efﬁcient windows have a coating or ﬁlm

applied to the surface of the glass to reduce heat

transfer through the window. This ﬁlm is nor-

mally positioned on the inside surface of a

double-pane window, as the low-e surface mate-

rial can easily be scratched or degraded. The

low-e coated glass side should be placed on

the “warm” side of the window. In hot climates,

the low-e side should be oriented to the outside

of the structure; in cold climates, the low-e side

should be on the glass pane in the interior

space. Double-low-e windows have a low-e

surface coating on both panes and can be

effective in both cold and warm conditions.

Low-ﬂush toilet A toilet that uses less water

than a standard one during ﬂushing, for the

purpose of conserving water resources.

Low-ﬂush toilet 149

Low-impact development Sustainable land-

scaping that can be used to replicate or restore

natural watershed functions and/or address

targeted watershed goals.

Low-slope roof Roof surface with a maximum

slope of 2 inches rise for 12 inches (5/30.5

cm) run.

Low-throughput economy Economy based on

working with nature by recycling and reusing

materials and resources, preventing pollution,

conserving resources and matter, living within a

population’s capacity to carry itself in an envir-

onment while maintaining biodiversity. See also:

High-throughput economy

Lower atmosphere Also known as the tropo-

sphere layer, which affects most of the people

on Earth; extends roughly 5 miles (8km) above

the poles and 10 miles (16 km) above the equa-

tor, and contains about 75% of the total mass of

the atmosphere. Because of its closeness to the

Earth’s surface, nearly all water vapor and solid

particles (from forest ﬁres, volcanoes, and the

burning of fossil fuel, for example) are found in

this sphere. All of Earth’s plant and animal life

exists within the troposphere or the waters

beneath it.

LPG Liqueﬁed petroleum gas. See:

Propane

LULU See:

Locally unwanted land uses

Lumen One lumen equals one candela across

one steradian, and is a measure of luminous

ﬂux, which is adjusted to the human eye’s per-

ception of the light’s power. Lighting ef ﬁciency

or efﬁcacy is measured in lumens per watt.

Incandescents typically have an efﬁcacy in the

range 15–20 lm/watt. Ultra-high efﬁcacy lighting

can achieve over 120 lm/watt.

Lumen method Most common method of

daylighting analysis in the USA. Variables are

sky conditions, position of the Sun, room size,

glazing area, and transmission characteristics such

as overhangs, shades, and blinds. This calcula-

tion is limited to predicting the amount of illu-

mination on a centerline ﬁve feet (1.5 m) from

the window, ﬁve feet from the back wall, and at

a point midway between.

150 Low-impact development

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Maglev See: Magnetic levitation

Magnesium oxide (MgO) cement A cement-

like material that produces much lower carbon

dioxide (CO

) emissions than Portland cement.

It uses MgO rather than calcium oxide, together

with a lower-carbon method of obtaining the

MgO. As CO

is a major greenhouse gas, it is

beneﬁcial to the environment to reduce its

emission whenever possible. MgO cement is also

a good industrial binder.

Magnetic levitation Also known as maglev or

magnetic suspension. Alternative propulsion

system for transportation, particularly trains. A

method by which an object is suspended

above another object with no support other

than magnetic ﬁelds. The electromagnetic force

is used to counteract the effects of the gravita-

tional force. Maglev suspends, guides, and pro-

pels vehicles via electromagnetic force. This

method can be faster than wheeled mass

transit systems, potentially reaching velocities

comparable with turboprop and jet aircraft (500

km/h; 310 mph). The maximum recorded speed

of a maglev train is 581km/h (360 mph),

achieved in Japan in 2003. The ﬁrst commercial

Maglev was opened in 1984 in Birmingham,

UK, covering some 600 meters (1968 feet)

between its airport and rail hub, but was closed

in 1995 because of technical problems. The

only currently operating high-speed maglev line

of note is the initial operating segment demon-

stration line of the German-built Transrapid

train in Shanghai, China, which transports

people 30 km (18.6 miles) to the airport in

just 7 minutes 20 seconds, achieving a top

velocity of 431 km/h (268 mph), averaging

250 km/h (150 mph).

There are two primary types of maglev tech-

nology: i) electromagnetic suspension (EMS),

which uses the attractive magnetic force of a

magnet beneath a rail to lift the train up; and

ii) electrodynamic suspension (EDS), which

uses a repulsive force between two magnetic

ﬁelds to push the train away from the rail. In

current EMS systems, the train levitates above

a steel rail while electromagnets, attached to

the train, are oriented toward the rail from

below. The electromagnets use feedback con-

trol to maintain a train at a constant distance

from the track, at approximately 15 mm (0.6

inches).

In EDS, both rail and train exert a magnetic

ﬁeld and the train is levitated by the repulsive

force between these magnetic ﬁelds. The mag-

netic ﬁeld in the train is produced by either

electromagnets (as in JR-Maglev) or by an array

of permanent magnets (as in Inductrack). The

repulsive force in the track is created by an

induced magnetic ﬁeld in wires or other con-

ducting strips in the track. At slow speeds, the

current induced in these coils and the resultant

magnetic ﬂux is not large enough to support the

weight of the train. For this reason, the train

must have wheels or some other form of landing

gear to support it until it reaches a speed that

can sustain levitation. Propulsion coils on the

guideway are used to exert a force on the mag-

nets in the train and make it move forward. The

propulsion coils that exert a force on the train

are effectively a linear motor: an alternating

current ﬂowing through the coils generates a

continuously varying magnetic ﬁeld that moves

forward along the track. The frequency of the

alternating current is synchronized to match the

speed of the train. The offset between the ﬁeld

exerted by magnets on the train and the applied

ﬁeld creates a force, moving the train forward.

Maize See:

Corn

Make-up air Air brought into a building from

outside to replace exhaust air.

Management of outputs Design strategies to

manage materials and energy in the built form

and its servicing systems. There are four design

strategies: one-through, open-circuit, closed-

circuit, and combined open-circuit. See also:

Closed-circuit system design strategy; Combined

open-circuit system design strategy; Once-through

system design strategy; Open-circuit system design

strategy

Manual D Manual developed by the Air Con-

ditioning Contractors of America (ACCA) which

covers designing and sizing duct systems for

residential and commercial space.

Manual J The standard method for calculating

residential cooling loads developed by the Air

Conditioning Contractors of America (ACCA).

Manual N Standard method for calculating

commercial cooling loads developed by the Air

Conditioning Contractors of America (ACCA).

Mariculture Cultivation of marine organisms

for use as a food resource.

Marsh See:

Wetlands

Masonry stove A type of heating appliance

similar to a ﬁreplace, but much more efﬁcient

and clean-burning. Made of masonry and has

long channels through which combustion gases

give up their heat to the heavy mass of the stove,

which releases the heat slowly into a room.

Often called a Russian or Finnish ﬁreplace.

Mass mixing ratio (Chemical engineering) Mass

of water vapor per unit mass of dry air. See also:

Absolute humidity

Figure 44 Electrodynamic suspension

Source: Wikipedia

152 Maize

Materials cycle Natural cycle in which mate-

rials are used, decomposed, and returned to the

ecosystem to be used again. In humanmade

materials cycles, materials are used, recycled,

and reused. In both systems, waste is minimized

or eliminated. See also:

Aerated static pile

Materials ﬂow analysis Calculation of the

transfer of natural and manufactured materials,

resources, and capital out of a built system

compared with those ﬂowing in. Also examines

the stocks, ﬂows, and transformation of energy

and materials within the systems. Assesses sus-

tainability, cost savings, improved regulations,

and infrastructure and economic activity.

Matter-recycling economy Economy based on

recycling as many materials and resources as

possible, to allow economic growth to continue

without depleting resources or producing excessive

pollution of the environment.

MCFC See:

Molten carbonate fuel cell

Mechanical and electrical systems See: HVAC

Heating, ventilation, and air-conditioning

Mechanical waste separator Device that

separates waste by category for recycling.

Mechanical recovery system More complex

version of the mechanical waste separator (see

Figure 46).

Mechanically stabilized earth Combination of

soil, soil reinforcement, and facing panels that

increase the strength of soil in order to support

built structures such as roadways, bridges,

retaining walls and noise barriers. The soil rein-

forcement consists of horizontal layers of metallic

or geosynthetic materials.

Mechanically ventilated crawlspace system

System designed to increase ventilation within a

crawlspace, achieve higher air pressure in the

crawlspace relative to air pressure in the soil

beneath the crawlspace, or achieve lower air pres-

sure in the crawlspace relative to air pressure in

the living spaces, by use of a fan.

Medium-temperature solar collector Functions

like an indirect solar water heating system, but

is used for heating built space. It has a larger

collector array area, larger storage units, and a

more complex control system. It can also be adap-

ted to provide solar water heating, and can supply

30–70% of residential heating requirements.

Figure 45 A mechanical waste separator

Medium-temperature solar collector 153

This type of solar collector will raise the heat

transfer ﬂuid to 20–150 °F (–6.7 to +66 °C) above

ambient. Applications can include domestic hot

water and space heating. See also:

Indirect solar

water heater

Megawatt (MW) 1000 kilowatts or 1 million

watts. Standard measure of electric power plant

power-generating capacity.

Membrane A permeable layer in a fuel cell

that acts as an electrolyte as well as a barrier

ﬁlm separating the gases in the anode and

cathode compartments of the fuel cell. See also:

Fuel cells

MEPS See:

Molded expanded polystyrene

Mercury (Hg) Air pollutant and soil con-

taminant. Heavy metal. A naturally occurring

element in the Earth’s crust. Commonly found in

air, water, and soil, and exists in several forms:

elemental or metallic mercury, inorganic mer-

cury compounds, and organic mercury com-

pounds. When coal is burned, mercury is

released into the environment. Fossil fuel power

plants, especially coal-ﬁred plants, generate the

greatest mercury emissions to the air in the

USA, accounting for over 40% of all domestic

human-caused mercury emissions. Municipal

waste incinerators are also a large source of

mercury emissions. Burning hazardous wastes,

producing chlorine, breaking mercury products,

and spilling mercury, as well as the improper

treatment and disposal of products or wastes

containing mercury, can also release it into the

environment. Mercury tends to accumulate in

the food chain. Mercury exposure at high levels

can harm the brain, heart, kidneys, lungs, and

immune system of people of all ages. See also:

Air pollution; Heavy metals; Soil contaminants

Mesophyte Plants that require only moderate

amounts of water for growth.

Mesosphere Atmospheric layer above the stra-

tosphere and below the thermosphere. It is the

middle layer and lies 31–50 miles (17–80 km)

above the Earth’s surface. Temperatures are usually

very low. See also:

Mesosphere; Stratosphere;

Troposphere

Mesotrophic Pertaining to a lake or other body

of water characterized by moderate nutrient

Figure 46 A mechanical recovery system

154 Megawatt (MW)

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concentrations and moderate productivity in

terms of aquatic animal and plant life. See also:

Eutrophic; Oligotrophic

Metabolite Compound produced from human

digestion of contaminants; serves as biomarker

of exposure.

Metal Natural mineral resource with the

characteristic of good conductivity of electricity

and heat.

Metal-insulator-semiconductor (MIS) New

generation of solar cell in which the inner elec-

trical ﬁeld is produced by the junction of a thin

oxide layer to a semiconductor.

Methane (CH

) Air pollutant and toxic che-

mical. A hydrocarbon that is a greenhouse gas

with global warming impact estimated to be

20 times greater than that of carbon dioxide

(CO

). It reacts with the Sun’s radiation and

other chemical compounds to form ozone

). Methane is produced through anaerobic

decomposition of waste in landﬁll, animal diges-

tion, decomposition of animal wastes, production

and distribution of natural gas and petroleum,

coal production, and incomplete fossil fuel

combustion.

Methane and CO

are the main constituents

of landﬁll gas, which is the greatest contributor

of atmospheric methane. Consequently, it has a

signiﬁcant impact on global warming and climate

change.

Methane is also a primary constituent of

natural gas and an important energy source.

As a result, efforts to utilize methane emis-

sions can provide signiﬁcant energy, economic,

and environmental beneﬁts. See also:

Air pol-

lutants; Landﬁll gas; Ozone precursors; Toxic

chemicals

Methane hydrates A natural gas located

below marine hydrate deposits. It is being

researched to allow commercial production of

methane from hydrate deposits. As it is believed

to have the potential to provide clean energy,

new technology is being developed to ensure

safe drilling and to minimize the impact on

seaﬂoor stability and deep-sea life. More

research is needed to understand the role

hydrate plays in climate change and the carbon

cycle.

A methane hydrate is a cage-like lattice of

ice, inside which are trapped molecules of

methane (the chief constituent of natural gas).

(The name for its parent class of compounds,

“clathrates”, comes from the Latin word meaning

“to enclose with bars”.)

Methane hydrates generally form in two types

of geological setting: i) on land in permafrost

regions where cold temperatures persist in shal-

low sediments; ii) beneath the ocean ﬂoor at

water depths greater than about 500 m (about

1640 feet), where high pressures dominate. The

hydrate deposits themselves may be several

hundred meters thick.

Today, methane hydrate has been detected

around most continental margins. Around the

USA, large deposits have been identiﬁed and

studied in Alaska, the west coast of California

to Washington, the east coast offshore of the

Carolinas and in the Gulf of Mexico. World-

wide estimates of the natural gas potential of

methane hydrate approach 400 million trillion

cubic feet. If just 1% of the methane hydrate

could be recoverable, the USA could more

than double its domestic natural gas resource

base. It is a viewed as a feasible alternative to

fossil fuels. Natural gas requires relatively low

capital costs to build new natural gas-ﬁred

equipment.

Methanol (CH

OH) Also known as methyl

alcohol or wood alcohol. Liquid fuel formed by

catalytically combining carbon monoxide (CO)

with hydrogen in a 1:2 ratio under high tem-

perature and pressure. Methanol is an alternative

Methanol (CH

OH) 155

fuel. Commercially, it is usually manufactured

by steam reforming natural gas. It is also formed

in the distillation of wood. It is usually com-

bined with gasoline to form M85 (85% metha-

nol and 15% gasoline), and is used in dual-fuel

vehicles. Methanol can also be used to make

methyl tertiary butyl ether (MTBE), an oxygenate

that is blended with gasoline to enhance octane

and create cleaner-burning fuel.

Methanotrophs Bacteria that use methane as

food and oxidize it into carbon dioxide.

Methyl alcohol See:

Methanol

Methyl bromide (MeBr) Toxic chemical. A

class I ozone-depleting substance. It is an odor-

less, colorless gas used as an agricultural soil

and structural fumigant to control a wide variety

of pests. See also:

Toxic chemicals

Methyl chloride (CH

Cl) Toxic chemical. Com-

bining methanol and hydrochloric acid gives

methyl chloride and water: CH

OH + HCl !

Cl + H

O. USEPA has classiﬁed methyl

chloride as a group D carcinogen. Low levels of

methyl chloride occur naturally in the environ-

ment. Higher levels may occur at chemical

plants where it is made or used. It has been

found to have adverse health affects in humans.