We hope to be able to have technical tips here soon.  In the meantime, if you are lost in the ‘green’ terminology jungle, we have provided a short glossary of terms which are commonly bandied around and, just as commonly, misunderstood. Some of these technologies have simply been ignored in conventional (or even 'faux green') buildings. If you have any other terms that you feel could be usefully explained here, send them to This e-mail address is being protected from spambots. You need JavaScript enabled to view it

 

Air-tightness. The air tightness of a building can be ascertained during an air tightness test – sometimes known as a Blower Door-Test. The building is pressurized and areas of air leakage are identified using smoke guns or other means. This gives a measurement of air changes per hour within the building. Identifying and controlling air leakage is key to preventing energy losses through convection of warm air.

Biomass heat comes from the burning of any organic materials that can be burned and used as a source of renewable fuel. Wood, and wood waste, is commonly the material used in biomass fuel and is usually processed to make wood-pellets or wood chips. Other sources of biomass fuel produced sustainably in the UK include Miscanthus and Willow. The CO2 released when energy is generated from combustion of the biomass is balanced by the CO2 absorbed during the fuel’s production.

Carbon neutral/zero refers to zero total carbon release, brought  about by balancing the amount of carbon released with the amount sequestered or offset. Carbon zero homes use no fossil fuels to provide heating and rely on renewable energy to generate power eg: photovoltaic cells, wind turbines or biomass sources. This energy may be either generated on-site or a combination of on-site and off-site. The design, fittings, appliances and insulation properties of the building play a huge part in achieving a zero carbon building.

Carbon offsetting is the term given to the process of buying into  projects that either absorb CO2 or prevent emissions of CO2 to counteract activities that produce CO2. Examples include investing in tree planting, buying ‘green’ electricity tariffs, and contributing to energy efficiency measures in developing countries. However, whilst many of these actions may have long-term benefits for the  environment, offsetting should not be used as an excuse to relax efforts to reduce our current carbon emissions as it is current CO2 levels and emissions that need reducing.

Code for Sustainable Homes. The Code is an environmental assessment method for new homes. It aims to protect the environment by providing guidance on the construction of high performance homes built with sustainability in mind. All new homes built in the UK are now required to either be assessed under the Code for Sustainable Homes or be given a nil-rating which has to be disclosed to the home buyer. There are 6 levels of the code with Code 6 being the most sustainable and Code 1 meaning the developer really only has to perform minimal improvements on building regulations. New Government targets are for all new buildings to be zero carbon within the next decade, starting with a 25% reduction in CO2 emissions by October 2010 while CO2 emissions from existing buildings need to be approaching zero by 2050.

Embodied Energy. The embodied energy of a particular product or building material is all the energy required to grow, harvest, extract, manufacture, refine, process, package, transport, install and dispose of it. The use of materials that are in their most natural state and obtained as locally as possible ensures the embodied energy is kept to a minimum. 

Energy/heat recovery ventilation is a system that allows air-to-air heat exchange capturing the cooling or heating energy from the exhaust air before it leaves the building. The system is designed to reduce the energy required to heat or cool a building by reducing the temperature changes that often occur through ventilation systems.

Passive solar design is the use of various design techniques in a building to maximise the amount of the sun’s heat and light entering a building and therefore reducing the need for mechanical forms of heating. These techniques include effective orientation of the building, careful consideration of the location and use of rooms within the building, large south-facing windows, natural solar shading and  ventilation, and the use of thermal mass within the building. Proper consideration to passive solar design can significantly reduce heating bills. 

Photovoltaics (PVs). Solar photovoltaics (often referred to as solar panels but not to be confused with solar water heaters) are solid state cells, typically made from silicon, that convert sunlight directly into electricity. Homes and businesses may incorporate solar panels and arrays as a source of clean, renewable energy.

Rainwater harvesting system. Quite simply, this collects the rain which falls onto roofs, and stores it in a tank until it is needed. When required, the water is pumped to the point of use – eg toilets and washing machines, thus displacing what would otherwise be a demand for mains-water. 

SAP assessment (Standard Assessment Procedure). A SAP Assessment is the UK national methodology for the calculation of the energy performance of buildings. It is used to demonstrate compliance with building regulations for dwellings – Part L.

Solar panels/solar water heaters/solar thermals. The sun’s power can be used to heat or pre-heat water for use in homes and commercial buildings through the use of solar panels. The panels are often mounted on roofs or frames and orientated to maximise exposure to the sun. The water is then stored in the hot-water tank which will have back up heating to bring the water up to the required temperature if necessary. Solar water heaters are one of the most cost effective forms of renewable energy. 

Sustainably sourced timber. Statements such as ‘sustainable timber’, ‘sustainable forests’, ‘well managed forests’ and even ‘from forests where more trees are planted than are felled’ are seen on many types of timber products. However, this can often be misleading to a potential buyer and does not provide any assurance that important habitats were not destroyed during the harvesting of the timber. True sustainable timbers come from managed forests that have passed rigorous guidelines for responsible harvesting, ecosystem management and conservation, and long-term sustainable resource management. It therefore ensures that the forest will continue to flourish. The Scientific Certification Systems’ Forest Conservation Program employs the principles of the Forest Stewardship Council (FSC ) to ensure that certified forests meet standards for sound forest management. Very few, if any other certification process is as vigorous and reliable as FSC which employs a chain of custody certificate on all timber from its source to its end use.

Thermal bridge. This is the term used when unwanted heat loss or gain occurs due to conduction through a material. This can lead to significant energy losses and may also result in the build up of condensation. An example of thermal bridging is heat loss that occurs due to metal wall ties or steel framing that is insufficiently insulated between areas of temperature differences eg the internal and external environment.

Thermal store and thermal mass. A thermal store is a structure typically made from a material with high thermal mass. These materials are capable of absorbing and retaining heat (eg from the sun) and slowly releasing the heat back into the building when space temperature falls. In sustainable building, thermal stores are used as a passive means of maintaining a constant internal space temperature, therefore reducing the need for mechanical heating and cooling. These stores are often designed to be part of the internal fabric of the building, usually in the form of a high density wall situated near a heat source. Materials with high thermal mass include masonry, rock and water.

U-value. U-values apply to any material where thermal performance is important. U-values give a measure of air-to-heat transmission (loss or gain) due to the thermal conductance of the material – eg from inside to outside a building. The lower the U-value the lower the material’s thermal conductance and the better the material performs thermally.