Glossary of terms

Domestic and General offer a wide range of energy efficient products and are able to access funding from a wide variety of sources. While this is excellent news for our customers, we also realise that there are many terms and acronyms that are used by the company which customers may want a little extra information on.

This glossary aims to provide definitions of a wide range of terms used in this website, in our literature, by our surveyors and installers or in general terms when speaking about energy efficiency. If you come across a term that isn’t in this list and would like to know its meaning, please contact us and we will be happy to provide a definition for listing on this page. Simply click on the letter that corresponds to the first letter of the term you are interested in to head straight to that section.
































Able to Pay – This is a term that is sometimes used to refer to a customer who is willing to pay for their installation themselves, rather than utilising funding provided via the Green Deal or ECO.

Access Issues – A property is deemed to have access issues if there are obstructions, such as conservatories, garages and porches, that cause 50% or more of the property to be difficult to access. In these cases specialised equipment, such as the Thermascopic bead lance, will need to be used and the property will be deemed hard to treat.

Achilles Utilities Vendor Database – Achilles is a group that strives to promote best practice in the utilities industry, which spans across a wide variety of different sectors. Their database is considered a community for many in the industry and provides access to Achilles-approved suppliers and vendors. 

Affordable Warmth – See Home Heating Cost Reduction Obligation

Air Source Heat Pumps – One of the two types of heat pumps. Air source heat pumps utilise energy gained from the air to heat a home, either by heating the home’s water supply or by heating the air of the property. They work by absorbing energy from the air into a fluid, which is then gradually heated as it passes through the mechanism before the energy is passed into the property. They are considered a geothermal technology.

Atmosphere – A layer of gases that surround the Earth. It protects life on the planet by absorbing solar radiation, heating the planet’s surface and effecting temperature differences between day and night. The gases contained in the atmosphere included oxygen and carbon dioxide.

ATP – See Able to Pay 


BBA – See British Board of Agrément

Big Six – A term that is often used to refer to the six main energy companies operating in the UK. These companies are British Gas, E.ON, EDF, NPower, SSE and Scottish Power. ECO is placed primarily on these six companies, who are responsible for supplying energy to more than 50 million homes in the UK.

Black Mould – This is the black staining that often develops around windows as a result of damp caused by condensation. If left unchecked black mould can give rise to fungus or bacteria growth in the home, which can pollute the air and cause potential respiratory issues.

Blanket Insulation – See Rolled Fibre Insulation

Blown Bead Insulation – This is a form of cavity wall insulation that is blown into the cavity using specialist equipment. The beads are usually carbon coated and bonded together using an adhesive at point of installation. Blown beads have become the standard cavity wall insulation material for many installers as it has superior thermal efficiency to other materials, such as wool, mineral fibre and foam.

Blown Fibre Insulation – A form of loft insulation that is blown into the loft using specialised material. Because of the flexible nature of the fibre, it is easier to fit it into hard to reach spaces in the loft. This means that the fibre can provide a more complete coverage for the loft space and it is often used in cases where the loft space is obstructed by joists or the loft is not suitable for rolled fibre insulation.

Boiler Replacement – An important distinction to make from a standard boiler installation in regards to HHCRO qualification. To qualify for a free boiler under the HHCRO grant scheme you will need a pre-existing boiler of a certain rating. Straight boiler installations will not be carried out under HHCRO, however Domestic and General are able to carry out installations for ATP customers who don’t have a pre-existing boiler.

BPF – See British Plastics Federation

British Board of Agrément – This is the major authority for manufacturers and installers supplying the construction industry in the UK. The organisation offers independent approval and inspection services and their certifications are recognised by local authorities, insurers and trade associations as a key quality mark for suppliers to the industry.

British Plastics Federation – A trade association for the UK’s plastic industry. It aims to encompass the entire plastic industry supply chain, from raw material suppliers through to plastic recyclers. The association has about 450 members and a large amount of affiliates. 


Carbon – This is the element that forms the basis of many fossil fuels, in addition to being one of the most abundant substances on the planet. When mixed with oxygen it becomes carbon dioxide, which is one of the greenhouse gases that experts believe are one of the causes of global warming.

Carbon Calculations – During the course of a Green Deal Assessment, a calculation of the amount of carbon your property releases due to the energy efficiency of both the property and the homeowner will be created. This calculation is then used to inform the recommendations made as part of the Green Deal Advice Report.

Carbon Calcs – See Carbon Calculations

Carbon Dioxide – See CO2

Carbon Emission Reduction Obligation – This is an obligation that has been placed on energy companies to ensure that properties with solid walls and properties with HTT cavities receive energy efficient installations. Funding is provided to homeowners through the obligation as part of the ECO funding scheme and in many cases it is possible to receive 100% of the funding required to have a measure installed, assuming you meet the required qualifying criteria.

Carbon Footprint – This is an approximate measure of the amount of greenhouse gas emissions caused by an entity, such as a person, home or business, during the course of their day-to-day activities. It is difficult to calculate an exact carbon footprint, with the figures being more accurate when more data about fuel usage by the entity is provided. A higher carbon footprint means the entity in question is not energy efficient and thus emits high amounts of CO2 and other greenhouse gases into the atmosphere.

Carbon Saving Community Obligation – This is a funding scheme that is part of ECO and is intended to deliver insulation and a range of other measures to homes in the most fuel poor areas of the country. The scheme aims to remove as many people as possible from fuel poverty, thus improving the overall energy efficiency standards in the UK. Access to the funding is determined by postcode area.

Cavity – This is the gap, or airspace, that is between the two walls that make up a cavity wall construction. 

Cavity Clearance – The process of removing rubble, debris or old insulation from a cavity. This is often done to facilitate the installation of cavity wall insulation and, in some cases, properties that require extensive cavity clearance will qualify for grant funding due to the property being considered HTT. Domestic and General utilises the Thermextract system to clear cavities.

Cavity Extraction – See Cavity Clearance

Cavity Insulation Guarantee Agency – An independent agency that provides guarantees for cavity wall insulation installations. Installers must register with CIGA to ensure their work can receive the guarantee, which assures the customer that their installation meets pre-set requirements. CIGA was formed during consultation with the government’s Energy, Environment and Waste Directorate and the guarantees they issue cover any and all defects in workmanship or materials for cavity wall insulation measures.

Cavity Wall InsulationThis is a system of injecting insulation material into the gap between a cavity wall in an effort to reduce the amount of heat that escape a property through the walls. There are a variety of different materials that can be used in cavity wall insulation, with Domestic and General preferring the use of ThermaBead due to it’s high levels of thermal efficiency.

Cavity Wall Insulation Self Certification Scheme – A scheme that is operated by CIGA in association with the BBA. It’s main aim is to ensure that work carried out by installers registered with them complies with the requirements of the Building regulations. As such, cavity wall insulation installations carried out by registered installers are subject to independent inspections and audits to ensure they meet the quality and technical standards set out by the organisation.

Cavity Walls – These consist of two walls, or layers, of brickwork with a cavity, or airspace, between them. The construction type was popularised in the UK in the 1930s as homes with a cavity wall build suffered fewer damp problems and were better at keeping the heat in when compared to homes with a solid wall build. However they are not perfect and the cavity can be filled with insulation to ensure better heat retention in the property.

CERO – See Carbon Emission Reduction Obligation

CHAS See Constructors Health and Safety Assessment Scheme

Chartered Surveyor – A member of the Royal Institution of Chartered Surveyors, who is qualified to inspect a property and determine its suitability for a range of different measures. You will receive a visit from a chartered surveyor at the beginning of your journey with Domestic and General and their findings will be used in the subsequent stages of your customer journey.

CIGA – See Cavity Insulation Guarantee Agency

Climate Change – See Global Warming

CO2 – This is the chemical symbol for carbon dioxide, which is a gas released by many fossil fuel sources. It is considered one of the most important greenhouse gases and the majority of experts consider it to be one of the primary factors causing climate change. One of the aims of the energy efficient products installed by Domestic and General is to reduce your CO2 emissions by reducing the amount of fossil fuels you consume, in an effort to help the environment.

Coal – One of the most prominent fossil fuels, its use has declined in homes over recent years as gas and oil are more energy efficient fuels for boilers. However it is still used in a number of UK power plants and plays a part in fuelling millions of homes in the UK. Additionally, homeowners who have a solid wall property that uses coal as its main fuel source may be entitled to a full grant for external wall insulation under the CERO scheme.

Condensation – This is water that collects as small droplets when moist or humid air makes contact with a cold surface. If left unchecked it can lead to a number of issues, such as damp patches, peeling wallpaper and possible black mould growth. The installation of insulation in a property can help minimise condensation problems as surfaces will generally be warmer due to increased retention of heat.

Condensing Boiler – A boiler type that takes advantage of a system whereby it converts water vapour that would traditionally have been expelled through the flue into usable heat. This makes them more energy efficient than older boilers and they have become the standard boiler type used in all installations bar those where special circumstances must be taken into account. 

Constructionline – An organisation that offers services to both suppliers and customers of the construction industry. For customers, the organisation provides a register of suppliers for the market. All suppliers are pre-qualified and must meet certain standards to be a part of the register.

Constructors Health and Safety Assessment Scheme – This is a non-commercial scheme that aims to provide health and safety pre-qualification for companies in the UK. The group also offers services to both suppliers and organisations looking for competent suppliers.

Cosytherm – A form of cavity wall insulation that is used in instances where blown bead insulation is deemed unsuitable for the property.

CSCO – See Carbon Saving Community Obligation

Customer Journey – This is the phrase used to describe the process the customer and DGI undertake when installing a measure at a property. It encompasses everything from the initial enquiry, through to the installation and any relevant aftercare. The length of the customer journey will differ depending on the installation. For example, a solid wall insulation measure will generally take a little longer to process and install than a loft insulation measure.

CWI – See Cavity Wall Insulation

CWISCS – See Cavity Wall Insulation Self Certification Scheme 


DEA – See Domestic Energy Advisor

DECC – See Department of Energy and Climate Change

Department of Energy and Climate Change – An organisation that aims to ensure that the UK has access to secure, clean and affordable energy suppliers. They are a ministerial department, who serve an additional aim of promoting international action on the issues presented by climate change.

Domestic Energy Advisor – A qualified advisor who is able to generate an EPC for a property and provide advise on suitable measures. They are not qualified to provide advice as part of the Green Deal, so homeowners who wish to access Green Deal finance will require a visit from a Green Deal Assessor, who is able to carry out an occupancy assessment in addition to an EPC. Customers who are able to pay for their installation themselves will often be visited by a DEA. 


ECO – See Energy Companies Obligation

EcoBatt – An insulation material that was created by Knauf Insulation and is installed as part of the Thermoshell package. It is a densely packed mineral wool slab that offers very efficient insulation without consuming large portions of room space. It is also water-repellent and non-combustible.

EcoStud – These are the studs that are used as part of the Thermoshell internal wall insulation package. They are used to affix the EcoBatt material to the walls and are considered environmentally friendly.

Energy Companies Obligation – This is a legal obligation placed on the ‘big six’ energy companies to improve the energy efficiency of homes in an effort to help people reduce their carbon footprint. The energy companies in question have to hit government-set targets as part of ECO. The obligation covers three funding streams – HHCROCERO and CSCO.

Energy Efficiency – In the context of your home this is the measure of how much energy or fuel your property uses. A less energy efficient home will generally use much more energy than a home that is considered to be efficient. There are a range of measures that can be undertaken to improve the energy efficiency of a property, such as the installation of insulation, a more efficient boiler or solar powered technology. Energy efficient properties also have lower CO2 emissions, meaning they are better for the environment as well as your fuel bill.

Energy Performance Certificate – These were introduced in 2007 and are essentially an assessment of how energy efficient a property is. The assessment takes into account the measures a property has installed to create a grade for the home. Properties that achieve a grade A are extremely efficient, with a G being the lowest grade possible. An EPC will be carried out, alongside an occupancy assessment, as part of a Green Deal Assessment.

Energy Saving Recommended Label – A label of recognition awarded by the Energy Saving Trust for products that are deemed to be extremely energy efficient. It is intended to make it easier for people to recognise which products will help them save the most energy.

Energy Saving Trust – A non-profit organisation that is funded mostly by the British government. The Energy Saving Trust aims to promote the use or renewable energy and energy efficient technologies, with the overall objective of reducing the amount of carbon dioxide being released into the atmosphere. The group is impartial and can offer advice on a wide variety of energy issues.

EPC – See Energy Performance Certificate

EST – See Energy Saving Trust

EWI – See External Wall Insulation

EXOR -An organisation that aims to foster relationships between buyers and suppliers. Companies that are EXOR accredited are recognised by the group as being particularly reliable suppliers, who focus on compliance within their industry.

Exterior Wall Insulation – See External Wall Insulation

External Wall Insulation – This is the most effective method for insulating solid wall properties and involves the application of insulation material to the outer walls of a property. This material is then coated with a layer of render, which comes in a range of colours and can be given a decorative effect where required. The installation process is more involved and complex than with other forms of insulation, however it can have a massively positive effect on the energy efficiency of a home. 


Feed In Tariff – This is a mechanism that aims to improve the uptake of measures that use renewable energy. It is primarily used for photovoltaic solar panel installations, with homeowners receiving a contract that guarantees a certain rate of pay for any excess energy that is generated by their solar panels. The rates are reviewed on a quarterly basis and are subject to change, however a contract signed on a payment rate will be valid at that rate for the length of the contract.

Fibre Insulation – This is the insulation material that is used in the majority of loft insulation installations, either being blown into the loft or formed into rolls which are then used to blanket the loft.

FiT – See Feed In Tariff

Fossil Fuel – These are fuels that were formed via natural processes due to the decomposition of buried organisms. The fuels are formed over the course of millions of years and are the predominant fuel source used across the world. the most common fossil fuels include coal, petroleum and natural gas, all of which contain high levels of carbon. Unfortunately, this means that the consumption of fossils fuels releases CO2 into the Earth’s atmosphere, which contributes towards global warming. Additionally, fossil fuels are not renewable fuel sources and will eventually run out through continued usage.

Fuel Poor – See Fuel Poverty

Fuel Poverty – A home is in fuel poverty if the homeowners spend at least 10% of their income on the fuel bill. This generally indicates that the property is not energy efficient and could be improved with a range of different measures. Income, the amount of people living at the property and energy prices all play a part as well. 


Gas Safe Register – The official gas registration body in the UK. All gas engineers must be on the gas safe register to carry out boiler installations or any other work on properties or facilities that use gas. The organisation replaced CORGI in 2009 and carries out independent inspections on installers and installations in addition to providing education for customers regarding gas safety.

GDA – See Green Deal Assessor

Geothermal Energy – A form of thermal energy that is generated and stored in the earth. This can be utilised for a range of measures, with ground source heat pumps being a primary example. Geothermal energy is a renewable energy source and is slowly becoming more prominent.

Global Warming – This is the rise of the average temperature of the oceans and atmosphere of the planet since the late 19th century. The majority of experts believe that the phenomena is caused by an increase of greenhouse gases in the Earth’s atmosphere, particularly CO2. Domestic and General’s products are intended to combat global warming by reducing the CO2 emissions of your property.

Golden Rule – This is the fundamental principle behind the Green Deal. It states that the repayments you make on a finance package taken out as part of the Green Deal will never exceed the amount of money you save on your energy bill as a result of having the measure installed.

Grant – Funding provided to people who qualify for a free measure under a range of schemes, including HHCRO, CERO, CSCO and others. Grants can cover part or all of the cost of an installation in the cases where they are applicable.

Green Deal – The Green Deal is the government’s flagship energy efficiency scheme and aims to make advice and measures available to as wide a spectrum of people as possible. The Green Deal is based on a finance mechanism called the ‘Golden Rule‘ and is supported by ECO. At its core the Green Deal offers homeowners a range of measures based on a Green Deal Assessment, which are then paid for through the property’s energy bills.

Green Deal Advice Report – This is the report that is generated following  a Green Deal Assessment. It will detail the current energy efficiency of the property in addition to what measures can be undertaken to make the property more energy efficient. The report will combine information gained from the Occupancy Assessment and the Energy Performance Certificate for this purpose and must be lodged before any Green Deal financing can be approved.

Green Deal Assessment – The first major step in obtaining finance under the Green Deal. This will be carried out by a licensed Green Deal Assessor and will be used to inform a Green Deal Advice Report. At this point you will also be offered advice on which measures may be suitable for your property and of any grant funding you may be eligible for under ECO.

Green Deal Assessor – A qualified assessor who will visit your home to carry out a Green Deal Assessment as part of the process that needs to be followed to obtain finance via the Green Deal. The assessor will carry out an EPC and occupancy assessment, which will then be used to create a Green Deal Advice Report.

Green Deal Finance – This is provided to the homeowner as part of their Green Deal Plan and will pay for the agreed measures to be installed. This money is then paid back using savings made through the bill payer’s electricity bill. These repayments must be compliant with the Golden Rule.

Green Deal Installer – A qualified installer who is able to install any measures recommended as part of a Green Deal Advice Report. They may specialise in one or multiple measures and are the only people who are registered to carry out energy efficient installations as part of the Green Deal. They can be identified through the Green Deal Installer quality mark.

Green Deal Plan – Upon completion of a Green Deal Assessment your assessor will discuss what energy efficient options are available to you and create a Green Deal Advice Report that will be used by a Green Deal Provider to create your Green Deal Plan. This plan will detail the measures that can be undertaken at your property in addition to hashing out the conditions of your finance. This will then be used as the basis for the payments made through your energy bill, which must be compliant with the Golden Rule.

Green Deal Provider – A provider is responsible for arranging a Green Deal Plan for those who are interested in taking out Green Deal finance. They will sort out the financial details of the plan and arrange for a Green Deal Installer to install the measures agreed as part of the plan. Furthermore, they will be the first port of call for customers who have an issue with their plans and will be responsible for handling customer care issues and providing information to new bill payers when they move into a Green Deal property.

Green Room – A promotional vehicle that showcases a wide range of energy efficient technologies from the heating and home improvement sectors. The Green Room is staffed by fully trained advisors who are able to answer any questions about the measures installed by DGI, with the help of a wide range of physical exhibits.

Greenhouse Gas – The technical definition of a greenhouse gas is a gas that absorbs and emits radiation within the thermal infrared range. Whilst this definition isn’t relevant to homeowners on a general level, it is important to note that carbon dioxide (CO2) is a greenhouse gas and contains the most potential for global warming of all the greenhouse gases. It is typically emitted by fossil fuels, which are the primary energy source of most UK homes.

Ground Source Heat Pumps – One of two main types of heat pumps. A ground source heat pump will utilise geothermal energy to provide heating to the home. They work by absorbing heat from the ground into a special fluid. This fluid heats up as it passes through the mechanism and is then used to heat water for the property. 


Hard to Treat – This relates to any cavity wall property that can’t have insulation installed via traditional means. This includes properties that are three storeys or above and properties that have narrow cavities. Additionally, properties that require extensive remedial work, such as cavity clearance, may also qualify. Grants are available for HTT installations as part of CERO.

Heat Pump – A heat pump is a geothermal measure that makes use of naturally occurring energy to heat your home. They generally come in two varieties: air source pumps and ground source pumps.

HHCRO – See Home Heating Cost Reduction Obligation

Home Heating Cost Reduction Obligation – One of the grant funding schemes that has been created as part of ECO. Also known as ‘Affordable Warmth‘, the scheme is intended to provide funding for boiler replacementscavity wall insulation and loft insulationGrants are provided to those who meet the eligibility requirements that are part of the scheme.

HTT – See Hard to Treat 


Insulation – In relation to the products offered by Domestic and General, insulation is any material that can be used to insulate the walls of a home. The material used will vary depending on the type of property and type of insulation required. For example, a cavity wall property will usually require the company’s ThermaBead insulation.

Interior Wall Insulation – See Internal Wall Insulation

Internal Wall Insulation – This is a type of solid wall insulation and involves the placement of insulation material onto the inner walls of a property. It is generally a secondary choice when compared to external wall insulation, due to the loss of room space incurred and the fact that the CERO funding scheme does not currently provide funding for the work.

IWI – See Internal Wall Insulation 


Joist – A joist in regards to a loft is usually a length of timber or steel that is used to support the structure of the building. They will occasionally cause obstructions that need to be worked around during the installation of loft insulation. 



Lambda Value – This is a measure of the insulation value of a specific material. The value is not affected by the material’s thickness and can therefore be used to compare the insulation values of various materials against one another. The harder it is for heat to pass through a material, the lower the lambda value.

Loft Insulation – This involves lining the floor of a loft with an insulating material in an effort to increase the energy efficiency of a home. Typically DGI use a fibre insulation, which is either blown into the loft or rolled out in a layer. Loft insulation is the easiest of all of the insulation types to install, but it can play a large part in reducing the amount of CO2 released into the atmosphere from a property. 


MCS – See Microgeneration Certification Scheme

Measure – This is one of the technical terms used by Domestic and General for an energy efficient improvement. You may occasionally hear a surveyor or installer make mention of installing a measure, in which case they will be talking about whatever improvement you are having, or looking to have, installed.

Microgeneration Certification Scheme – A quality assurance scheme that certifies products that utilise renewable energy sources to generate heat and electricity. It is an internationally recognised brand and, in the UK, it is supported by the Department of Energy and Climate Change. Technologies and installers must be accredited by the scheme to ensure customers are eligible for a variety of financial incentives, including the Feed in Tariff and the Renewable Heat Incentive.

Mortar Joint –  These are the spaces in between bricks that are filled with mortar or grout. They can be made in a variety of different fashions, depending on the build of the property. Properties with raked or thin mortar joints may qualify for grant funding for cavity wall insulation due to them being considered hard to treat. 


Narrow Cavity – While the majority of homes with a cavity wall construction have a regular cavity, some were built with a cavity that is below 50mm. These cavities are classed as narrow and are considered hard to treat. Such properties can still have cavity wall insulation, which can often be fully funded under the CERO funding scheme.

National Blown Bead Association -An organisation that represents BBA approved system holders who supply blown bead insulation, such as ThermaBead, for cavity wall insulation. The group also works to improve accountability within the sector.

National Energy Action – A national charity with a primary aim of eradicating fuel poverty in the UK. The group also campaigns for greater investment in energy efficiency to further aid those who are vulnerable.

National Insulation Association – An organisation that represents the insulation industry as a whole throughout the UK. The group’s members include manufacturers and installers and all involved in the organisation are committed to improving standards within the industry.

Natural Gas –  This is another one of the major fossil fuels that is in common usage throughout the UK. Following processing, where impurities are removed, it is used for a variety of reasons, including electricity generation and home heating. It is the most common fuel type used by boilers in the UK.

NBBA – See National Blown Bead Association

NEA – See National Energy Action

NIA – See National Insulation Association 


Occupancy Assessment – This is an assessment of how you use energy in your home and is personalised to the homeowner, rather than being a measure of the energy efficiency of the property itself. It can be used to provide tips on how to reduce energy consumption through alteration of your daily habits and will generally be undertaken alongside an EPC as part of a Green Deal Assessment.

Office of Gas & Electricity Markets – The government regulator for the electricity and natural gas markets in the UK. The authority aims to protect consumer interests by promoting competition within the energy industry. This includes responsibilities for reduction of greenhouse gases and the security of supply of gas and electricity throughout the UK.

OFGEM – See Office of Gas & Electricity Markets

OFTEC – See Oil Firing Technical Association

Oil – Oil is a product that can be created using a range of different substances, including petroleum. It has a wide variety of uses, with many homes utilising it as a fuel source for a boiler or other heating equipment. 

Oil Firing Technical Association – An organisation that sets the standards for installations in the domestic oil heating industry. They operate in a similar manner to the Gas Safe Register and all technicians who install oil boilers for Domestic and General are required to be certified by OFTEC. 


Petroleum – Petroleum is a fossil fuel that is generally extracted through drilling. In most cases it is refined into oil or other fuels for a variety of different uses. It forms the basis of oil and some LPG fuels, which are both fairly common home fuel sources.

Photovoltaics – A method of generating electricity through the conversion of solar radiation into direct current electricity. Power generation using this method involves the use of photovoltaic solar panels and it is one of the most commonly used renewable energy sources on the domestic level. It is the third most important sustainable energy source in the world.

Photovoltaic Solar Panels – These are solar panels that convert sunlight into usable electricity, which can then be fed into a home’s overall electricity supply or sold on as part of the Feed in Tariff. A Solar PV system can help to reduce both your energy bills and your carbon footprint, in addition to providing additional income for any excess energy generated. These panels differ from thermal solar panels, as they are not used to provide warm water for a home heating system.

Plasterboard – This is commonly used as part of an internal wall insulation installation to provide a finish to the internal walls. It covers the insulation material used in the process and will provide a ‘new wall’ finish to all installations.

Polypearl – A form of blown bead insulation that is occasionally used in instances where ThermaBead is deemed unsuitable.

PV – See Photovoltaics 



R Value – This is the resistance of a material to heat trying to pass through it. The R value is affected by a material’s thickness and the value can be increased by increasing the thickness of the material in question. It is traditionally used to measure loft insulation in addition to being part of the calculation that creates a property’s U Value.

Raked Mortar Joints – A mortar joint is considered raked if it is recessed to a degree whereby it is impossible to install cavity wall insulation using standard practices without causing damage to the brickwork. In these cases a property will be deemed hard to treat and will usually be eligible for grant funding.

Remedial – This is the name given to any additional work that needs to be carried out following the installation of a measure, often due to unforeseen circumstances. A remedial will often be carried out free of charge as long as the issue raised was caused by an installation carried out by Domestic and General.

Render – In the context of installations carried out by Domestic and General, render is generally used as part of an external wall insulation installation. It is typically applied over the insulation material used as part of the process and is typically a premixed cement. It can be applied in different colours and with different finishes, depending on the requirements of the homeowner.

Renewable Energy – This is energy that has been generated from any fuel source that can be replenished, such as solar power, wind, rain and geothermal sources. This is contrary to fossil fuel sources and renewable energy sources are viewed by many to be the future of the energy efficiency sector. Renewable energy fuels a number of different measures installed by Domestic and General Insulation, including solar PV and heat pumps.

Renewable Heat Incentive – A payment system that is fairly similar in operation to the Feed in Tariff. It offers payments to people who generate heat using renewable energy sources and is currently only available to commercial premises. However, current plans for the scheme include an extension to domestic properties in Spring 2014. This means that homes with thermal solar panels and heat pumps will be able to claim cash as part of the scheme, once it is made available.

RHI – See Renewable Heat Incentive

RICS – See Royal Institution of Chartered Surveyors

Rolled Fibre Insulation – A form of loft insulation that is also often known as blanket insulation. This form of insulation is the most readily available for lofts and differs from blown fibre insulation as the rolls need to be cut and fitted into the loft space.

Royal Institution of Chartered Surveyors – An organisation that was founded in the UK in 1868 with the aim of regulating and raising the standards of the surveying industry. The group was granted the royal charter in 1881 and has since gone on to establish itself as a global presence. The chartered surveyors who are members of the organisation will generally be the first people to visit a homeowner who is interested in an energy efficient measure and will determine the suitability of the property for the measure in question. 


Sheep’s Wool Insulation – A form of loft insulation that, as the name suggests, is made out of sheep’s wool. This is a rarely used form of insulation and will generally only be installed on request from the customer.

Solar Photovoltaic – See Photovoltaic Solar Panels

Solar Power – This is the name for the process of converting sunlight into electricity. Photovoltaic solar panels utilise the photoelectric effect to convert the sun’s rays into electricity, meaning that a solar PV system uses solar power to provide electricity to a home.

Solar PV – See Photovoltaic Solar Panels

Solar Radiation – The technical term for sunlight. It is crucial to the correct operation of both photovoltaic solar panels and thermal solar panels. It is also be considered a renewable energy source.

Solar Thermal – See Thermal Solar Panels

Solid Wall – Solid wall construction was the favoured type for homes until the popularisation of cavity walls. A solid wall is exactly what it says on the tin – a single, solid wall. Unfortunately, properties built with these walls do not retain heat very well, making them prime candidates for solid wall insulation. However, due to the nature of solid walls, the installation of insulation for such properties is a more involved and time consuming process than it would be for a property with cavity walls.

Solid Wall Insulation – This is a system that allows Domestic and General to insulate solid wall properties. It generally involves the placement of insulation material on the properties home, which is then overlayed with a coat of render or plasterboard. Both external wall insulation and internal wall insulation fit into this category, and each has its own advantages and disadvantages.

Solid Wall Insulation Guarantee Agency – An organisation established with the intention of providing independent and uniform guarantees for solid wall insulation installations in the UK. The guarantee provided by the group is a requirement for any solid wall measure installed under the CERO funding scheme.

Stud Wall Insulation – This is one of the primary types of internal wall insulation and is the only one currently installed by Domestic & General. Installation involves placing slabs of insulation material onto the internal walls of a property, thus reducing the amount of space in the room slightly, and fixing them to the walls using studs.

Sustainable Energy – See Renewable Energy

SWIGA – See Solid Wall Insulation Guarantee Agency 


ThermaBead – ThermaBead is a cavity wall insulation material offered by Domestic and General and is used in the majority of our cavity wall installations. The material is a bonded polystyrene bead solution that offers increased thermal efficiency when compared to traditional fibre insulation. At its core, the material is a combination of carbon-coated beads and an adhesive that bonds them together.

Thermal Efficiency – This is a measure of how well an insulation material maintains heat. Materials with a poor thermal efficiency will not be good for insulation, whereas those with a high thermal efficiency will be utilised to make a home more energy efficient wherever possible.

Thermal Solar Panels – These panels differ from photovoltaic solar panels because they convert the sunlight they absorb into heat energy, which is then used to provide hot water for the home rather than electricity. These panels need to be carefully situated to ensure they absorb the optimal amount of light, however they are generally able to account for 50-70% of a home’s heating requirements and can reduce energy bills and your carbon footprint.

Thermascopic Bead Lance – This is a device developed by Domestic and General for use on cavity wall properties that cannot be insulated via traditional means due to some form of obstruction. Typically this includes conservatories, garages or porches. Many of these properties would have been considered hard to treat in the past, however the lance allows installers to overcome many access issues to install insulation.

Thermoshell – A form of internal wall insulation that was developed by Knauf Insulation. The material comprises of EcoStud and EcoBatt.

Thermextract – A solution developed by Domestic and General that is used to extract debris and old insulation from cavity walls, often in preparation for cavity wall insulation to be installed. It will often be utilised as part of remedial work required for a hard to treat installation.

Thin Cavity – See Narrow Cavity

Thin Mortar Joints – When a property’s mortar joints are so thin that installing cavity wall insulation using standard techniques would cause damage to the walls it is considered to have thin mortar joints. Usually the joint will be between 5-10mm and will lead to the property being classed as hard to treat. 


U ValueThis is a measure of a construction type’s rate of heat loss. They are not related to any type of material, but rather the construction type as a whole. This is calculated using the property’s various lambda and R values.

UF Foam – A form of cavity wall insulation that is used in instances where blown bead insulation is deemed unsuitable for the property.

UVDB – See Achilles Utilities Vendor Database 


Vent Wedge – A solution to the potential problem of condensation that can be caused by installing loft insulation into a property. Upon installation of loft insulation, a loft will become significantly cooler than it was before. This creates the risk of condensation, with the wedges ensuring moist air can escape the loft.

Voltage Optimisation – The control of voltage supplied to appliances in your home, ensuring that they use the smallest amount of electricity required to run correctly. This ensures that, on a whole, your household appliances use less electricity, thus reducing energy bills. 


Walltherm – A form of cavity wall insulation that is used in instances where blown bead insulation is deemed unsuitable for the property.

Warm and Well – An initiative run by local government in Gloucestershire with the aim of raising the public’s awareness about the benefits of insulation by providing advice and referring people towards grant and funding schemes. Domestic and General Insulation is the accredited installer for the scheme, which has seen thousands of lofts and cavities insulated since October 2001.