Glossary

The property of a building or structural element that minimises uncontrolled air exchange in order to reduce heat loss. The skin of a balloon is airtight. A sieve is not.

"Aluminium-laminated" refers to the coating of an insulating material with a thin layer of aluminium foil or an aluminium coating. Polyurethane panels are available with or without aluminium lamination on both sides.

BAFA stands for “Federal Office for Economic Affairs and Export Control” and is a German federal authority. The BAFA is responsible for implementing various economic and foreign trade policy measures on behalf of the Federal Government. ( https://www.bafa.de/DE/Home/home_node.html ) Applications for funding for energy-efficiency refurbishments are submitted to the BAFA by energy advisers.

The Federal Energy Act (BEG) is a German law that sets out the legal framework for energy supply and the expansion of renewable energy in Germany. The BEG came into force on 1 July 2021, replacing the previous Renewable Energy Sources Act (EEG), the Combined Heat and Power Act (KWKG) and the Act on the Priority of Renewable Energies (EEV).

Bituminous membranes are flat, flexible building materials used to waterproof buildings and other structures. In the construction sector, they are used on flat roofs or gently sloping roofs.

In architecture and construction, concealed rafters are a special type of rafter or structural beam. Unlike conventional rafters, which are visible and support the roof covering, concealed rafters are not visible as they are hidden beneath the roof covering or ceiling cladding.

Insulation materials are classified into building material classes A and B. Insulation materials in categories ‘A1’ and ‘A2’ are non-combustible (usually mineral-based), whilst those in building material classes ‘B1’ and ‘B2’ are organic and combustible. Insulation materials in building material class B3 must not be used.

Apparent density, also known as density or mass density, is a physical quantity that describes the ratio of a substance’s mass to its volume. It is often measured in kilograms per cubic metre (kg/m³) or grams per cubic centimetre (g/cm³).

The term ‘capillary-active’ refers to the ability of a material or building material to transport and distribute liquids, such as water, through its capillaries or pores. Capillary-active materials have the property of absorbing, storing and, where necessary, releasing liquids due to capillary forces. Blotting paper is ‘capillary-active’.

Water exists in three states of matter: as water vapour – which is dry and invisible; as liquid water – including in the form of water droplets; and as ice – a solid state. Condensation refers to water’s ability to change from the ‘vapour’ state to the ‘liquid’ state. This can be seen on misted-up window panes or as condensation on a cold bottle of water taken out of the fridge.

Cosiness refers to the pleasant, comfortable and soothing feeling experienced in a room or setting.

A building’s ability to minimise energy loss and optimise energy consumption for heating, cooling and lighting.

The amount of energy saved through effective thermal insulation and other energy-efficient measures.

A method in which insulation materials are applied to the external walls of a building in order to reduce energy consumption and improve thermal comfort. (External thermal insulation composite system). In this process, insulation materials are bonded to the external wall, secured with dowels where necessary, and then rendered (= ‘composite system’). The insulation materials form a bond with the adhesive and the render that is usually inseparable.

A classification of building materials based on their fire resistance and their ability to prevent the spread of fire. See ‘Building material class’

"Building Energy Act". It is a German law that sets out the requirements for the energy efficiency of buildings.

Planting vegetation on a roof, which not only improves thermal insulation but also helps to purify the air and enhances the aesthetics. Due to evaporative cooling (‘evaporation enthalpy’), green roofs lower the air temperature in summer and create a pleasant microclimate. See also ‘climate change adaptation’

The ability of a material to absorb heat and store it over a prolonged period. See also ‘heat storage capacity’

Heat storage capacity, also known as heat capacity or thermal capacity, is a physical property of a material or a system that indicates how much heat energy, measured in joules, it can absorb when the temperature rises by 1°K per kg.     

The process by which heat flows from an area of higher temperature to an area of lower temperature.

Heating energy is the energy required to heat a building or a room to a pleasant and comfortable temperature. It is usually measured in units such as kilowatt-hours (kWh) and serves to maintain the room temperature at a desired level, particularly during the colder months. . Buildings are mostly heated using heating oil, natural gas, pellets or electricity. As a general rule, the calorific value of 1 m³ of natural gas is roughly equivalent to that of 1 litre of heating oil or 10 kWh of electricity (rounded up or down).

The term ‘hydrophilic’ describes a substance or surface that has a strong affinity for water and interacts well with water molecules. Blotting paper is ‘hydrophilic’.

The term ‘hydrophobic’ is used to describe a substance or surface that repels water or does not interact with water.

An insulation bag – marketed under the name ‘Thermobag’ – consists of two films: on the inside, a highly tear-resistant vapour barrier (sD value: 2 m equivalent air layer thickness) and, on the outside, a vapour-permeable, waterproof and similarly tear-resistant underlay membrane (sD value: 0.2 m equivalent air layer thickness), sealed at the bottom.

The mass of the insulation material per unit of volume (usually m³), which can affect its insulating properties. Blown-in insulation materials must be installed at a specific density to prevent them from settling over time.

An inverted roof, also known as a reverse roof or inverted roof waterproofing, is a special type of roof construction in which the usual sequence of roof layers is reversed. Unlike conventional roofs, where the waterproof layer (usually the roof membrane or roofing sheet) is installed beneath the thermal insulation, in an inverted roof the roof membrane is placed over the insulation layer. Inverted roofs are constructed using XPS boards.

The personalised renovation roadmap helps you plan the renovation of your detached house, semi-detached house or block of flats step by step. It also provides you with a long-term and detailed overview of possible renovation measures and their potential savings.

The term ‘lambda’ in the context of insulation refers to the thermal conductivity or the heat transfer coefficient (λ-value) of an insulating material. The λ-value indicates how well a material conducts heat. The lower the λ-value, the better the material’s insulating properties. The unit of measurement is ‘W/mK’.

The term ‘minimally invasive insulation’ refers to a method of thermally insulating buildings in which the external building envelope is modified with minimal intervention or alterations in order to improve thermal insulation. All blow-in insulation methods are minimally invasive.

Measures to prevent damp-related problems in insulation, which can cause damage and mould growth.

Insulation installed along the outer perimeter of a building to minimise heat loss into the ground. Perimeter insulation refers to the insulation of basement walls in contact with the ground or beneath the concrete slab on which the building rests.

Primary energy content is a metric that indicates the energy content of a raw material or energy source in its original form, before it is converted into various forms of energy or processed. This figure is important for assessing the total energy consumption and energy efficiency of various energy sources.      

Measures to prevent heat loss and keep a building warm, often through thermal insulation. Synonymous with ‘thermal protection’

A rafter spacer is a structural component used in the roof structure of buildings to stabilise the rafters and facilitate the installation of insulation between them.

The term ‘ridge purlin area’ refers to a specific area or zone within a roof truss or roof framework. This area is normally situated at the highest point of the roof, where the ridge purlin runs. The ridge purlin is a horizontal beam that runs along the ridge line of the roof and connects the upper ends of the rafters or roof trusses.

A boulder, also known as a pebble or river stone, is a fragment of rock that has been smoothed by the erosion of rocks or rock strata in rivers, streams or other bodies of water.

An area of the building envelope that has a higher heat flux than the surrounding surface, which can lead to heat loss. Synonymous with ‘thermal bridge’.

An area characterised by an increased heat flux and which contributes to heat loss, often due to poor insulation. Thermal bridges in buildings include: concrete lintels, solid walls, concrete slabs, and many others. Synonym for ‘thermal bridge’

A measure of a material’s ability to conduct heat. Lower thermal conductivity means better insulation performance. See also ‘Lambda’

Thermal insulation is the protection of a building against excessive heat loss or heat gain.

A measure of heat loss through a building component, such as walls, roofs or windows. The lower the U-value, the better the insulation performance. It is expressed in watts per square metre Kelvin (W/m²·K). The lower the U-value, the better the building component.

Vapour barriers are membranes made from various materials that are installed on the insulation layer of a building. They prevent moisture from penetrating insulated parts of the building and thus prevent mould from forming.

A vapour barrier is a continuous, flat layer with a defined water vapour diffusion resistance, which reduces the diffusion of water vapour from the air into a building component.

The term ‘breathable’ refers to a material’s ability to allow water vapour to pass through whilst remaining impermeable to liquid water. This property is also well known in the context of ‘functional clothing’.

The wall coping is the upper edge of a wall or masonry structure. It forms the top of the wall.

Water vapour diffusion resistance, often referred to as the ‘μ-value’ or ‘diffusion equivalent resistance’, is a parameter used in building physics and building materials engineering. It describes the ability of a building material or component to impede the passage of water vapour through its surface. The water vapour diffusion resistance indicates how effectively a material can limit the diffusion of water vapour.

Insulation materials that are water-repellent and prevent damp problems in the insulation.