What is?:


Absorb: the ability to soak up by chemical or physical action - usually slowly.

ACH: air changes per hour, stated as the volume of air changed per hour / volume of room.

Airtightness: of increasing importance within the building regulations, energy efficient building design should ensure that ventilation only occurs as desired by the occupants, and not through unwanted draughts and air leakage through or around the building elements.

Alternative energy: the use of energy produced using non-carbon resources, e.g solar, wind, water, thermal etc.

Biomass: biomass is the organic materials produced by plants and trees. The term “biomass” is intended to refer to materials that do not go directly into foods or consumer products but may have alternative industrial uses. Common sources of biomass are; 
(1)agricultural wastes, e.g straw and manure from cattle, poultry, etc, (2) wood materials, e.g wood or bark, sawdust, mill scrap; (3) municipal waste, such as waste paper and (4) energy crops, such as poplar and willow. In some cases, microbial and animal metabolic wastes are also considered biomass.

Biofuel: biofuel is any fuel that is derived from biomass. It is a renewable energy source, unlike petroleum, coal and nuclear fuels.
Like coal and petroleum, biomass is a form of stored solar energy. The energy of the sun, during the growth of the plants, is ‘captured’ through the process of photosynthesis. Biofuel is commonly known as biodiesel when used in vehicles.

Biofuels can be made from oil rich crops such as rapeseed, linseed etc. Some companies also make biodiesel from waste vegetable oil from restaurants and chip shops. In South America biofuel has been made for many years from the distilation of sugar cane.

Biological oxygen demand (BOD): the amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water and used as a measure of the degree of water pollution. (Also called biochemical oxygen demand).

Borax/boron/borates: a family of natural mineral based products which have the ability to protect timber from rot, insect attack and fire (spread of flame) if applied and used correctly. Harmless to humans at normal concentrations.

Breathable sheathing: many boards are now available which are sufficiently vapour permeable to allow them to be used externally on a timber frame and allow vapour generated within the building to pass through to the outside without risk of condensation within the fabric.

Breather membrane: usually paper or a woven membrane which is used to prevent water entry to the construction, whilst allowing vapour to escape.
Breathing construction: a term used to describe vapour resistant layers within a wall or roof construction to ensure that moisture is allowed to pass safely (e.g without condensing) from the interior to the exterior of a building.

Brown roof: a roof covering comprising rubble and earth which is designed to be wildlife friendly in urban environments where certain species have adapted to inner city living.

Capilliary action/attraction: the tendancy of liquid to rise as a result of surface forces.

Carbon/Carbon dioxide C02 : CO2 is a colourless, odorless, tasteless gas, about 1.5 times as heavy as air. Under normal conditions it is stable, inert, and nontoxic. The decay (slow oxidation) of all organic materials produces CO2. Fresh air contains approximately 0.033% CO2 by volume. In the respiratory action (breathing) of all animals and humans, CO2 is exhaled.

Carbon index: an addendum to the SAP rating (see later in glossary) which measures the CO2 ‘created’ in use, expressed as a measure of the CO2 / m2 of floor area. One method of satisfying the building regulations re thermal properties.

Carbon neutral: a term used to describe a building design that consumes no fuels that will releasecarbon dioxide or uses renewable fuels as energy sources to ensure that the total production of CO2 related to a building or project is zero.

Cellulose insulation: can be manufactured from recycled newspapers (pre or post consumer waste), cellulose is shredded and treated with borax against insect and rot attack. Can be installed as loose fill, damp spray, or dry-blown to a specified density.

Closed panel construction: panels built on site with sheathing to both sides (internal and exernal) usually with insulated cavity - often using breathing wall technology and materials. Differs from panels used in typical timber frame construction which are sheathed to one side only.

Coefficient of performance (COP): an example of COP; a geothermal heat pump, operating at COP 3.5 is able to move 3.5kWh (11,946BTUh) of heat for every 1kWh it consumes. This can also be viewed as an efficiency of 350%, which compares very favourably to high efficiency (condensing) gas burning furnaces (90-99% efficient), and electric heating (100%). The COP of an air source heat pump may be 2.0 (200% efficiency) at low outdoor air temperatures before its backup electric resistance heating coils are turned on.

Cold bridge: a building term used to describe a heat loss path through a material which has a much lower thermal resistance than the surrrounding material and is placed so as to create a ‘bridge’ from the inner (warm space) to the outer (cold space) of a structure.

Desorb: to cause the relase of an absorbed substance.

District heating: heat which is generated at a central source and stored either as steam or hot water. then delivered on demand to a group of buildings. Most district heating systems in Europe distribute hot water from ‘energy centres’, where combined heat and power generation (CHP) equipment make heat and electricity at the same time.

Embodied energy: the energy required to produce a material, through extraction, manufacture, transport or installation.

Facade: the face of a building, especially the principal face.

Facultative: capable of functioning under varying environmental conditions. Used by certain organisms, such as bacteria that can live with or without oxygen.
Future proofing: to design-in an ability to adapt to future trends. this may be in the form of lifestyle trends or the availablility of resources such as fuel.

Geenhouse effect: a term used to describe the heating up of the earth by radiation from the sun being trapped with the atmosphere by atmospheric gases. These gases act as insulators preventing radiated heat from the warming of the earth from escaping to space. The gases are found naturally in the atmosphere but in recent decades, levels of some (carbon dioxide and methene in particular)have been bolstered by human activity.

Green roof: a description of a ‘living’ roof finish of some kind, usually grasses or sedum.

Heat recovery: the use of heat exchangers to extract heat from waste air or water, and transfer it into an incoming air supply.

Humidity: see Relative humidity

Hygroscopic: a feature of natural insulants such as wool or cellulose, it allows vapour to be ‘held’ within the material without condensing, and later to release it into the atmosphere. A key principle of a breathing wall specification.

Interstitial condensation: created where warm moisture laden air migrates through the building fabric and condenses onto a cold surface within the fabric, potentially leading to both damage to the fabric, and to an unhealthy internal environment.

Life cycle analysis (LCA): this is a methodology that identifies the environmental impacts associated with the life cycle of a material or product in a specific application, thus identifying opportunities for improvement in environmental performance. Abbreviated LCA.

Lignin: naturally ocurring ‘adhesive’ in wood. High levels of lignin in woods used for some compressed wood fibre boards reduces the need to use synthetic adhesives.

Low-e glazing: low-e (low emittance) refers to a metallic oxide coating applied to the inner face of a double or triple glazed unit, and which reduces heat loss through the glass, thereby improving the thermal perfomance of the unit. Can also reduce solar overheating and light levels.

Microporous finishes: usually attributed to paints, stains and waxes, which may be naturally produced or petrochemical based, which allow vapour to be released from the material they cover, whilst remaining impermeable to water.

Moisture content: most natural materials will contain moisture to some extent - for example seasoned timber can still contain between 8 and 18% moisture in use, but at these levels will not rot or suffer insect or mould attack.

Natural: a very imprecise term which is used to describe a variety of products, some of which may have a petro-chemical base, but which would on the whole be manufactured from non-petrochemical ingredients.
Organic: an often misleading term which has come to be a little abused in recent years. Two descriptions follow:
1. chemical term relating to or defining material that contains carbon, chiefly of biological origin. For instance coal and oil are organic compounds as are humans. Organic compounds are often not safe or toxin free as the term has come to suggest.
2. used to describe food or farming methods where chemicals are avoided in the production of food and even non-food crops such as cotton, wood and other fibres.

Ozone: a colourless, toxic, unstable gas formed from oxygen and electrical discharge or ultraviolet light. It differs from oxygen by having three atoms rather than two. Ozone is a pollution when it occours at ground level usually as a result of high traffic concentrations. However, natural ozone at high levels in the atmosphere prevents harmful ultraviolet rays from reaching the surface of the earth. (see ODP below).

Ozone depletion potential ODP: the potential for the manufacturing process of a material (usually the ‘blowing’ of foam based insulants) to release chemicals that are known to destroy the ozone layer around the earth. CFCs and HCFCs are the most common, and have largely been replaced by air.

Passive: a building term describing a structure or component that needs no mechanical assistance to operate. For instance: passive solar design uses the structure of the building and it’s solar orientation to collect energy from the sun. A further example would be a thermostatic radiator valve where the air temperature in a room will cause a wax capsule to expand or contract, thus allowing hot water to flow or not.

Passive stack ventilation: the use of building shape and design to produce sufficient natural ventilation without the use of electrically powered fans. Stack ventilation uses vertical ducts to stimulate natural airflow due to the ‘flue’ effect.

Recycling: the reprocessing (breaking down and reforming) of an existing material to manufacture a new material for a new use.

Re-use or reclaimed: the re-use of whole and intact building materials in their originally produced form. Often refered to as architectural salvage.

Relative humidity: this is the amount of moisture within the atmosphere, or a material, expressed as a % of the total saturation moisture content that could be contained.

Renewable resources: materials or energy sources which can be replaced, hopefully within the lifetime of the product e.g timber can be re-grown.

Renewables / non-renewables: material from a source that is renewable (e.g wood) versus that which is not or which has a finite non-renewable supply (e.g fossil fuels).

Resource depletion: the specification of certain materials, products or processes can lead to habitat damage, environmental degredation, and rarity e.g fossil fuels, peat, Welsh slates.

SAP rating: an energy rating system for housing which measures the cost in £ / m2 floor area. Now a pre-requisite for calculating the Carbon Index which is one method of satisfying the building regulations re thermal performance of housing.

SIPs: structurally Insulated Panels, or prefabricated wall or roof elements produced from petro-chemical based insulation boards bonded to timber based boards.

SUDS: sustainable Urban Drainage System. Aims to reduce the water load on the man-made drainage systems, and to reduce flood risk, by designing the external environment to redistribute rainwater falling onto a site via porous surfaces, etc.

Thermal conductivity: Is a measure of the rate of energy or heat flow through a material, stated as W/mK.

Thermal properties: the characteristics of a building material which define how heat, or energy, passes through the material e.g thermal resistance and density.

Thermal resistance: this is a measure of resistance to heat flow given a specified thickness of a material and a temperature difference each side.
Urban heat island effect (UHI): an urban heat island (UHI) is an urban area which is significantly warmer than its surroundings. As population centres grow in size from village to town to city, they tend to have a corresponding increase in average air temperature, due to the mass of the buildings.

U-value: a measure of heat transmission through a building part or a given thickness of insulating material, expressed as (W/m2K) that will flow in 1 hour through 1 square metre of the structure or material from air to air with a temperature diff of 1°C.

Vapour barrier: usually in sheet or brush-on form, used in ‘non-breathing’ construction to prevent water vapour from entering the construction. Unreliable due to difficulties in effecting a seal.

Vapour permeability: vapour permeable materials allow moisture to migrate from inside to outside of building fabric in a controlled manner. BS5250 suggests that vapour should permeate through external sheathing materials at a rate 5 times that of the internal sheathing or lining material so as to reduce the risk of interstitial condensation.

Volatile organic compounds (VOCs): VOCs are organic chemical compounds that have high enough vapour pressures under normal conditions to significantly vaporize and enter the atmosphere during use, application or drying out of a paint or other coating.

Water conservation: the design of water useage and waste systems to minimise wasteage, reduce flooding and un-necessary re-processing to ensure that an essential primary resource remains readily available.