Reference
Glossary
More than 100 technical terms on hemp building materials, natural insulation, thermal, moisture, acoustic and fire protection and ecological building — explained in plain language.
These definitions are for orientation only. Product values, approvals and installation rules must be checked against the current original documents before planning and installation; statements on fire, acoustic, moisture or thermal protection apply only to the respective verified assembly.
No term found.
A
A1 to A3
In an Environmental Product Declaration, A1 to A3 denote the life cycle modules raw material supply, transport to the manufacturer and manufacturing. They are often summarised as the “product stage”. A favourable A1–A3 result is not yet a full assessment of the entire life cycle.
aBG – general type approval (Germany)
The allgemeine Bauartgenehmigung (aBG) assesses a construction type, i.e. the assembly of construction products into a structure. It must be distinguished from the product-related abZ. For wall, floor or fire protection systems both types of document may be relevant together.
AbZ – national technical approval (Germany)
An allgemeine bauaufsichtliche Zulassung (abZ) is a German national proof of usability for construction products for which no harmonised technical rule exists, or only an incomplete one. The exact subject of approval, the product identity and the scope are decisive. An abZ must not be transferred to similar products without verification.
Acoustic panel
An acoustic panel is a sound-absorbing element used to reduce reflections and reverberation. Hemp acoustic panels combine an open-pored surface with renewable raw materials. Their effect depends on area, thickness, frequency, mounting depth and backing.
AgBB scheme
The AgBB scheme is a German evaluation scheme for emissions of volatile organic compounds from construction products into indoor air. It covers VOCs and SVOCs among others. Passing an emissions test says nothing about structural, moisture or fire performance.
Airborne sound
Airborne sound arises and initially propagates in air, for example speech or music. Building elements are excited and transmit the sound into adjoining rooms. Multi-layer constructions benefit from mass, decoupling and absorbent cavity insulation.
Airtightness
Airtightness prevents uncontrolled air flow through the building envelope. It reduces energy losses and protects building elements from convectively transported moisture. Junctions and penetrations are usually more critical than the surface itself.
Alkalinity
Alkalinity describes a high pH value. Lime-bound building materials are usually alkaline and can therefore inhibit the growth of certain micro-organisms. However, this property replaces neither moisture protection nor proper mould remediation.
B
Binder
A binder bonds loose plant particles into a solid building material. Depending on the application, hemp products use lime, clay, other mineral binders or polymer support and bonding fibres. The binder influences strength, moisture behaviour, fire class and recycling route.
Bio-based construction product
A bio-based construction product contains raw materials from biomass, such as hemp, wood, straw or flax. “Bio-based” does not automatically mean fully natural, free of pollutants, climate-neutral or compostable. Any assessment must consider share, origin, additives and life cycle.
Biogenic carbon
Biogenic carbon originates from biological material. Plants absorb carbon dioxide as they grow and temporarily store the carbon in their biomass. How this storage is credited in a life cycle assessment depends on accounting rules, service life and the end-of-life scenario.
Blown-in insulation
Blown-in insulation is installed mechanically into closed or open cavities. Installed density, maximum cavity height, settlement behaviour and processing approval are product-specific. A loose hemp fill is not automatically approved as a blow-in insulation material.
Bonded waterproofing
A bonded waterproofing membrane sits directly beneath tiles or other coverings and protects the substrate from water. It consists of a coordinated membrane, sealing tapes, collars and junctions. Wet-room boards do not replace it in water-exposed areas.
Building physics
Building physics examines heat, moisture, sound, light and fire behaviour in buildings. With hemp building materials the interaction of all layers matters most. A vapour-open insulation material does not automatically make an unsuitable overall assembly safe.
Bulk density
Bulk density is the mass of a building material relative to its volume, usually in kg/m³. It affects weight, heat storage, acoustics and in part strength. Hemp products range from light fibre batts to considerably denser building boards.
C
Capillary-active
Capillary-active building materials can transport and distribute liquid moisture within their pores. In internal insulation systems this can support drying back. Capillary activity does not replace waterproofing against pressing or permanently acting water.
Carbon footprint
A carbon footprint records greenhouse gas emissions and, where applicable, stored biogenic carbon within defined system boundaries. Claims such as “CO₂-negative building material” require a traceable, product-specific calculation. Transport, service life and disposal can change the result.
Carbon storage
Plant-based building materials store biogenic carbon for the duration of their use. The actual climate effect depends among other things on origin, production energy, service life and end-of-life. “Carbon storage” is therefore not automatically the same as “CO₂-negative”.
CE marking
CE marking shows that a construction product has been assessed under a harmonised standard or an ETA and that its performance has been declared. It is not a general quality seal and no guarantee of suitability in every project. What counts are the declared performances and the intended use.
Cellulose
Cellulose is an insulation material made from processed paper or plant fibres. It is often blown in or offered as a batt. Compared with hemp, the raw material form, installation method, additives and product documentation differ.
Centre-to-centre spacing
Centre-to-centre spacing is the distance from the middle of one stud, rafter, joist or other member to the next. For insulation batts it determines the cutting dimension; for building boards it determines the required support and fastening. The manufacturer's maximum spacing must be observed.
Circular building
Circular building designs buildings so that elements can be used for a long time, repaired, dismantled and reused. Material passports, demountable connections and single-material layers support this aim.
Circularity
Circularity describes how well a product can be reused, separated or recovered at a high level after use. Demountable fastenings and single-material layers are advantageous. Adhesive bonds and dense coatings can hinder deconstruction.
Clay paint
Clay paint is a vapour-open interior coating on a clay basis. It can pair well with clay renders and suitable natural building boards. Abrasion resistance, substrate and use should be checked beforehand.
Clay render
Clay render uses clay as a binder and can buffer moisture. It is frequently applied to hemp, clay or mineral render carrier boards. Before direct application, adhesion, reinforcement, layer thickness and drying must be clarified.
Climate-neutral
Climate-neutral means that remaining greenhouse gas emissions have been offset or avoided within a defined balance. Without a system boundary, period, calculation and a clear treatment of offsetting, the term is not meaningful. For building materials, concrete EPD data are usually more transparent.
Compressive strength
Compressive strength describes a material's resistance to compressive load. For hemp-lime blocks, insulation boards and loose fills it must be checked exactly which test method and unit were used. An insulation material is not load-bearing merely because a compressive strength is stated.
Compressive stress at 10 % deformation
This characteristic value describes the stress reached at a defined deformation of an insulation material. It is used to assess insulation under compressive load. It is not the same as the permissible permanent load of a complete floor or roof assembly.
Condensation
Condensation occurs when water vapour condenses on or within a building element. Causes can be low temperatures, high indoor humidity, air leakage or unsuitable layer sequences. Critical assemblies require moisture verification.
Construction moisture
Construction moisture enters a building through concrete, screed, mortar, render, rain or wet materials. Even vapour-open constructions can be damaged if too much moisture is trapped. Sufficient drying should be verified before closing up building elements.
Cradle to Cradle
Cradle to Cradle describes a concept of closed technical or biological cycles. The term should not be equated with simple recyclability. A corresponding certification applies only to the specifically certified product and the stated level.
D
Declaration of Performance – DoP
In the Declaration of Performance the manufacturer declares the performance of a construction product for its essential characteristics. It is closely linked to CE marking and a harmonised standard or ETA. Product code and version must match the goods delivered.
Deconstruction
Deconstruction is the dismantling of a building or element at the end of its use. Screwed constructions that can be separated by material type are usually more circular than fully bonded composites. Deconstruction planning can begin as early as the tender stage.
Design value of thermal conductivity
The design value is the thermal conductivity to be used in building physics calculations under defined conditions. It may differ from the declared value λD. Which value applies depends on the product documentation and the relevant jurisdiction.
DIBt
The Deutsches Institut für Bautechnik is a technical authority in German construction. Among other things it issues national technical approvals (abZ) and general type approvals (aBG). For any application, the current original version of the respective document is decisive.
Dry screed
Dry screed consists of factory-made board elements installed without wet screed. It can be laid on suitable levelling fills. Edge junctions, evenness, compressive load capacity and load distribution must be observed.
Drying reserve
Drying reserve is the ability of a building element to release unforeseen moisture again. Vapour-open or humidity-variable layers can support it. A sufficient reserve must nevertheless be plausible both in calculation and in construction.
Drywall
Drywall denotes non-massive interior construction and is at the same time part of the product name Hemplith® Drywall. Drywall constructions are built without a massive, water-rich method, for example with studwork, insulation and board cladding. Hemplith® Drywall is described for internal walls and claddings, but not for wet rooms.
Drywall construction
Drywall construction creates non-load-bearing walls, ceilings and claddings predominantly from a substructure, insulation and boards. Hemp construction boards and hemp insulation batts enable vapour-open, bio-based variants. Fire, acoustic and load requirements apply to the complete assembly.
E
Ecological building
Ecological building takes energy, climate, resources, health, durability and deconstruction into account. Material choice is an important part, but floor area efficiency, construction, service life and building operation also count.
Embodied energy
Embodied energy denotes the energy required for raw material extraction, manufacture, transport, installation, maintenance and disposal of a product. Its exact extent depends on the system boundary considered.
EN 13501-1
EN 13501-1 is the European standard for classifying the reaction to fire of construction products. Classes range in principle from A1 to F and are partly supplemented by information on smoke development and flaming droplets.
End-of-life
End-of-life denotes the phase after the use of a construction product. Deconstruction, reuse, recycling, energy recovery and disposal affect the environmental balance. Coatings and composite constructions can hinder high-quality deconstruction.
Energy efficiency
Energy efficiency means achieving a desired building function with the lowest possible energy input. Insulation is an important element, but airtightness, thermal bridges, building services, windows, shading and user behaviour also play a part.
EPD – Environmental Product Declaration
An EPD provides quantified environmental information about the life cycle of a product. It is based on defined product category rules and is normally independently verified. An EPD is not a blanket statement that a product is “environmentally friendly”.
ETA – European Technical Assessment
An ETA assesses the essential characteristics of a construction product on the basis of a European Assessment Document. It can form the basis for a Declaration of Performance and CE marking. Its scope must be observed exactly.
ETICS – external thermal insulation composite system
An ETICS is a coordinated facade system of insulation, adhesive, fastening, reinforcement and finishing render. Individual components must not be combined arbitrarily. Hemp insulation boards may only be used within a system verified for that purpose.
External insulation
With external insulation the insulating layer sits outside the load-bearing wall. This often reduces thermal bridges effectively and keeps the existing wall on the warm side. Weather protection, plinth, window junctions, fastening and system approval must be planned in detail.
F
Fire protection
Fire protection covers preventive measures against fire ignition, fire spread and danger to people. Product fire class, fire resistance of the element, junctions, penetration seals and escape routes must be considered separately. Natural building materials require just as robust evidence as conventional ones.
Fire protection board
A fire protection board is intended for fire safety applications. Whether it enables a particular fire resistance follows only from the tested system assembly. The fire class of the individual board is not sufficient for this.
Fire resistance
Fire resistance describes how long a complete building element meets defined requirements in the event of fire. Examples are EI30, EI60 or REI90. The evidence applies only to the tested or classified assembly.
Flanking transmission
Flanking sound is transmitted via adjoining elements alongside the actual separating element. Good insulation values of a wall board alone therefore do not guarantee good sound insulation in the building. Junctions and secondary paths must be planned as well.
Formaldehyde
Formaldehyde is a volatile chemical compound that can be emitted from certain binders and products. For indoor products, tested emission values are more meaningful than blanket advertising claims. Several Hemplith® boards are described as formaldehyde-free or emission-tested.
Friction-fit batt
A friction-fit batt is an elastic insulation material that holds itself in place between building elements. For a gap-free installation it is cut slightly wider than the bay. Hemp insulation batts can be used as a natural friction-fit batt.
Friction-fit oversize
The friction-fit oversize is the excess width of an insulation batt relative to the clear bay dimension. According to the data sheet, Hemplith® Flex is installed with about 1 cm oversize. Too little creates gaps; too much can deform the batt.
H
Half-timbered wall insulation
When insulating a half-timbered wall, the historic fabric, driving rain, timber moisture, clay or lime infill panels and junction details must be considered together. Hemp batts, hemp fills or hemp-lime can be suitable components. Internal insulation should be planned using building physics.
Healthy building
Healthy building aims at low-pollutant, comfortable and hygienic interiors. This includes low-emission products, moisture protection, ventilation, thermal comfort and good acoustics. Without defined criteria the term is not a technical proof.
Heat capacity
Specific heat capacity describes how much heat one kilogram of material can absorb per kelvin of temperature change. Together with bulk density and thickness it influences the heat storage of a building element.
Heat storage capacity
Heat storage capacity describes how much heat a building element can absorb and release with a time delay. It depends not only on specific heat capacity but also on mass, layer thickness and heat transfer.
Hemp
Hemp is a fast-growing crop. In construction, mainly the fibres and shivs are used. The term alone does not describe a finished construction product, since processing, binder, density and additives determine the technical properties.
Hemp building board
A hemp building board usually consists of hemp shivs or hemp fibres and a binder. Depending on the formulation it can serve as a drywall board, render carrier, acoustic board, insulation board or wet-room board. Density, strength, fire class and field of application differ per product.
Hemp concrete
Hemp concrete is a common but technically misleading name for hemp-lime. The material consists of hemp shivs, a mostly lime-based binder and water. It is generally an insulating infill or envelope material and must not be treated like structural concrete.
Hemp construction board
A hemp construction board is a rigid board made of hemp fibres or hemp shivs with a binder. Depending on the version it serves as internal cladding, render carrier, insulation, wet-room or acoustic board. Application, fire class and fastening should be checked before selection.
Hemp felt
Hemp felt is a thinner, flexible fibre product. Depending on the version it is used for joints, service runs, impact sound decoupling or as a supplement in timber construction. Intended use and compressive load capacity must be checked per product.
Hemp fibre
Hemp fibres come from the bast section of the hemp stalk. They have good tensile strength and are used for insulation batts, rigid insulation boards and fibre additives. For dimensionally stable insulation products, support fibres are often added.
Hemp insulation
Hemp insulation denotes insulation materials made of hemp fibres or hemp shivs. It can be supplied as batts, boards, stuffing material or loose fill. Typical benefits include good thermal insulation, moisture buffering and sound absorption; the product-specific documentation is what is binding.
Hemp insulation batt
A hemp insulation batt is a flexible insulation material made of hemp fibres and support fibres. It is particularly suited to timber construction, roof, wall and drywall. Hemplith® Flex is a hemp fibre insulation batt with a declared thermal conductivity of 0.040 W/(m·K).
Hemp insulation board
Hemp insulation boards are more dimensionally stable and usually denser than flexible batts. Depending on the product they may be intended for facades, walls, ceilings or roofs. Hemplith® Therm is a rigid hemp fibre insulation board.
Hemp insulation material
Hemp insulation is made from the fibres or shivs of industrial hemp. It is available as flexible batts, rigid boards or loose fill. Typical applications are roof, wall, ceiling, floor and drywall construction.
Hemp shivs
Hemp shivs are the light, woody parts inside the hemp stalk. They have a porous structure and are used as aggregate for hemp-lime, loose-fill insulation, building boards and acoustic products.
Hempcrete
Hempcrete is the English term for hemp-lime. Despite the ending “concrete”, it is normally not structural concrete. Loads are usually carried by timber, steel or other structural frames.
Hemp-lime
Hemp-lime is a mixture of hemp shivs, mineral binder and water. It can be used as a block, cast in situ, sprayed or as a prefabricated element. Hemp-lime combines comparatively low bulk density with thermal insulation, heat storage and moisture buffering.
Hemp-lime block
A hemp-lime block is a factory-formed block made of hemp shivs and mineral binder. It can be used for insulating external and internal walls, infill panels or internal insulation. Hemplith® Block is an example; the load-bearing structure must be planned separately.
Hemplith® Aquaboard
Hemplith® Aquaboard is a mineral-bound hemp construction board for internal walls, ceilings, roof surfaces and wet rooms. The product is described as a non-load-bearing cladding and render carrier board. In wet and splash water areas a suitable waterproofing membrane remains necessary.
Hemplith® Block
Hemplith® Block is a hemp-lime block for wall, insulation and infill applications. The product combines insulating effect and masonry function, but must not be assumed to be load-bearing masonry without structural verification.
Hemplith® Drywall
Hemplith® Drywall is a lightweight, vapour-open drywall board made of hemp shivs and a binder described as formaldehyde-free. It is intended for non-load-bearing internal walls, wall and ceiling claddings and as a carrier for lime and clay renders.
Hemplith® Fill
Hemplith® Fill is a hemp-based levelling and loose-fill insulation. It is described for floors, ceilings, joist layers and cavities among others. Installed density, settlement, load distribution and the covering layer must suit the assembly.
Hemplith® Flex
Hemplith® Flex is a flexible hemp fibre insulation batt for roof, wall, bays and drywall. It is friction-fitted with a slight oversize and almost no gaps. The current product data sheet and the associated ETA should be checked during planning and tendering.
Hemplith® Mineralboard
Hemplith® Mineralboard is a mineral-bound, vapour-open hemp board. It serves as a render carrier, internal cladding, and moisture-active internal insulation and renovation board. The data sheet specifically envisages vapour-open lime and clay surfaces.
Hemplith® Therm
Hemplith® Therm is a rigid hemp fibre insulation board for thermal and acoustic insulation. The data sheet describes applications on walls, ceilings, roofs and facades. External applications require a fully approved system.
Hygrothermal behaviour
Hygrothermics describes the coupled heat and moisture behaviour of building elements. Temperature affects moisture and vice versa. Dynamic simulations can be useful for demanding roof, facade and internal insulation assemblies.
I
Impact sound
Impact sound is generated by footsteps or other mechanical excitation of a floor. Effective protection requires elastic decoupling, suitable mass and an execution free of sound bridges. A loose fill alone guarantees no particular impact sound value.
Independent wall lining
An independent wall lining is an additional internal wall leaf in front of an existing wall. It can accommodate services, insulation or a new surface. On external walls the moisture profile behind the lining must be examined.
Indoor air
Indoor air is influenced by ventilation, humidity, use, furniture, cleaning agents and construction products. Low-emission building materials can contribute to prevention. However, a single product guarantees no particular indoor air quality.
Indoor climate
Indoor climate covers temperature, humidity, air movement, surface temperatures and air quality. Sorptive natural building materials can buffer humidity peaks but replace neither heating nor ventilation.
Industrial hemp
Industrial hemp refers to hemp varieties grown for industrial or agricultural purposes. In construction their fibres and shivs are used. The building properties only arise through defined processing and product manufacture.
Installed density
Installed density describes the mass of an installed loose insulation material per unit volume. It affects thermal conduction, settlement, sound insulation and material demand. For loose-fill and blown insulation it should be documented and checked.
Insulation between rafters
With insulation between rafters the insulation material sits between the roof rafters. Flexible hemp insulation batts are particularly suitable thanks to their friction fit. In addition, airtightness, sub-roof, moisture protection and thermal bridges at the rafters must be observed.
Insulation felt
Insulation felt is a flexible insulation material that is friction-fitted between rafters, joists or studs. Hemp felt or hemp insulation batts can be installed with a suitable oversize and almost no gaps. Too little width creates gaps; excessive compression can impair performance.
Internal insulation
With internal insulation the insulating layer is applied on the room side of an external wall. It changes the temperature and moisture profile of the existing wall. Driving rain, thermal bridges, timber beam ends, junctions and capillary moisture transport must be examined carefully.
L
Lambda value
The lambda value λ describes the thermal conductivity of a material in W/(m·K). The lower the value, the lower the heat flow at the same thickness. For a U-value, all layers and surface heat transfer resistances are additionally required.
Levelling fill
A levelling fill compensates for unevenness or differences in height in floors and ceilings. Hemplith® Fill is an example of a hemp-based levelling and loose-fill insulation. Settlement, installed density, layer thickness and a load-distributing cover are decisive for performance.
Life cycle assessment
A life cycle assessment examines the environmental impacts of a product or system across defined life cycle stages. Typical categories are global warming potential, primary energy and resource consumption. Results are only meaningfully comparable with a comparable functional unit and system boundary.
Lime render
Lime render is a mineral render with lime as the binder. It is often vapour-open, alkaline and can be combined with hemp-lime or mineral-bound hemp boards. Substrate, render strength and layer build-up must be coordinated.
Load distribution layer
A load distribution layer spreads point and area loads over a soft or loose insulation layer. Examples are dry screed elements or suitable wood-based assemblies. Dimensioning depends on use, span and substrate.
M
Material moisture
Material moisture denotes the water present in a building material. Excessive moisture can change thermal conduction, strength, dimensional stability and microbial behaviour. Moisture should be checked before sensitive layers are installed.
Mineral binder
Mineral binders harden through chemical or physical processes. They include, for example, lime, clay in certain applications and cementitious systems. Cement-free does not automatically mean purely plant-based or compostable.
Mineralboard
In the Hemplith® range, Mineralboard is a mineral-bound hemp construction board. It is used as a render carrier, drywall, internal insulation and renovation board. The term is not a general standard designation and should be used with the full product name.
Moisture buffering
Moisture buffering is a material's ability to absorb water vapour for a short time and release it again later. It can contribute to more balanced indoor conditions. It cannot compensate for persistent moisture or water ingress.
Moisture content
Moisture content describes the amount of water contained in a material. It affects thermal conductivity, weight, dimensional stability and microbial risk. Test values under a defined climate are not automatically identical to site conditions.
Moisture protection
Moisture protection covers measures against precipitation, ground moisture, service water, condensation and harmful construction moisture. This includes waterproofing, driving rain protection, airtightness, drying reserves and suitable surfaces.
Mould
Moulds grow where there is sufficient moisture and suitable nutrients. Surface moisture, temperature, time and contamination are decisive. Mould-resistant building materials do not prevent growth if the building physics conditions remain unfavourable.
Mould remediation
Mould remediation covers identifying the cause, protective measures, proper removal and reinstatement. Moisture sources and thermal bridges must be eliminated. A renovation board alone does not solve the cause.
N
Natural building material
Natural building material is not a uniformly protected technical term. It usually refers to materials made predominantly of mineral or renewable raw materials. For selection, the exact constituents and performance evidence matter more than the label.
Natural insulation material
Natural insulation materials are based predominantly on renewable or natural raw materials, such as hemp, wood fibre, cellulose, flax, cork or sheep's wool. Thermal conductivity, fire behaviour and moisture suitability differ per product.
O
ÖKOBAUDAT
ÖKOBAUDAT is a German database of life cycle assessment data sets for construction products and buildings. It is used for building LCAs and sustainability assessments. Generic data sets are not always identical to product-specific EPD data.
P
PES bico fibre
PES bico is a bicomponent polyester fibre that stabilises natural fibres in insulation batts or boards. According to the data sheet, Hemplith® Flex and Therm contain 15 per cent of these bonding fibres. These products are therefore not entirely free of plastics.
Pest resistance
Pest resistance describes resistance to insects or rodents. Mineral treatment can make materials less attractive. It does not replace structural pest protection and should only be claimed product-specifically.
Phase shift
Phase shift describes the time delay of a temperature wave passing through a building element. It is often mentioned in connection with summer thermal protection. Without the complete assembly and boundary conditions, a single figure in hours has only limited meaning.
R
Reaction-to-fire class
The reaction-to-fire class describes the fire behaviour of a construction product. In Europe classification is normally carried out to EN 13501-1, for example B-s1,d0 or C-s2,d0. It must not be confused with the fire resistance of a complete building element.
Recyclable
Recyclable means that a product can technically be fed back into a recovery process. Whether this happens in practice depends on separability, contamination, infrastructure and economic viability. The claim should name a concrete recovery route.
Reinforcing mesh
Reinforcing mesh is embedded in a render or filler layer to distribute stresses and limit cracking. Material, mesh size, overlap and position within the render system must match. With natural building materials, glass fibre, jute or other system-compatible meshes may be used.
Render carrier board
A render carrier board creates a suitable substrate for render. Hemplith® Mineralboard, Aquaboard and Drywall can perform render carrier functions depending on the application. Joints, reinforcement, fastening and render type are system-dependent.
Render substrate
A render substrate is the surface onto which render is applied. It must be sufficiently sound, clean, suitably absorbent and free of separating layers. Hemp boards can be good render carriers but require a coordinated render system.
Renewable raw materials
Renewable raw materials are biologically renewed over comparatively short periods. Hemp, wood, straw and flax are examples. Sustainability additionally depends on cultivation, processing, transport, additives and land use.
Reverberation time
Reverberation time describes how long a sound event decays in a room. Excessive reverberation times impair speech intelligibility and comfort. Acoustic panels reduce reverberation time if area and position are planned appropriately.
Room acoustics
Room acoustics describes the sound conditions within a room. Important quantities are reverberation time, speech intelligibility and sound distribution. Hemp acoustic panels can absorb sound and at the same time serve as a visible surface.
S
sd-value
The sd-value is the water vapour diffusion-equivalent air layer thickness of a building element. It is approximated as material thickness times μ-value. A small sd-value stands for low, a large one for high diffusion resistance.
Silentlith® acoustic pro
Silentlith® acoustic pro is a visible acoustic panel made of hemp shivs and a mineral binder described as cement-free. It is intended for walls and ceilings indoors. Acoustic performance and fire class are to be taken from the current product documentation.
Smouldering behaviour
Smouldering is slow combustion without a visible flame and can be relevant for fibrous or porous materials. Normal reaction-to-fire classification does not fully capture every smouldering risk. Product and system documentation should therefore be checked carefully.
Sorption
Sorption is the uptake and release of water vapour at internal and external material surfaces. Sorptive building materials can dampen fluctuations in indoor humidity. This must not be confused with arbitrary water absorption.
Sound absorption
Sound absorption describes the proportion of sound energy that is not reflected at a surface. The weighted sound absorption coefficient αw summarises frequency-dependent measured values. Mounting depth and backing influence it considerably.
Sound absorption coefficient αw
αw is a single-number value for assessing sound absorption. A higher value generally means stronger absorption, but the frequency distribution remains important for room planning. Silentlith® acoustic pro achieves different αw values depending on the test set-up.
Sound bridge
A sound bridge is a rigid connection through which structure-borne sound bypasses a planned decoupling. Typical examples are incorrectly placed screws, continuous profiles or non-decoupled junctions.
Sound insulation
Sound insulation limits the transmission of sound between rooms or from outside to inside. What is assessed is always the protection provided by the element or building, not just the absorption of a single material. Flanking paths, joints and services can considerably worsen the result.
Splash water area
The splash water area is a zone with increased water exposure, for example at the building plinth or in showers. Stricter requirements apply there to waterproofing, surfaces and junctions. Vapour openness alone offers no adequate protection.
Staggered joints
Staggered joints mean that rows of boards or blocks are not laid with continuous cross joints. The bond improves stability and reduces the risk of cracking. Minimum offsets are given in the processing guidelines.
Structure-borne sound
Structure-borne sound propagates within solid building elements. Impact sound is a particular form of it. Decoupling, elastic intermediate layers and the avoidance of rigid sound bridges are decisive for protection.
Stud/rafter bay
A bay is the space between studs, rafters or joists. Flexible hemp insulation batts can be friction-fitted there. The insulation must meet timber, services and adjoining elements without gaps.
Substructure
The substructure carries boards, claddings or facades. It can be made of timber or metal. Spacings, cross-sections, fastening and corrosion protection must suit board weight, use and loads.
Summer thermal protection
Summer thermal protection limits the overheating of interior spaces. Besides insulation and thermal mass, windows, external shading, night ventilation, internal loads and building location are decisive.
Support fibre
Support fibres give loose natural fibres dimensional stability. Thermally bonding fibres are frequently used in hemp insulation batts. Type and proportion affect processing and recycling.
Surface temperature
The internal surface temperature affects comfort and mould risk. It depends on outdoor temperature, room temperature, U-value, thermal bridges and air movement. Internal insulation can raise the room surface temperature but must be carefully planned at junctions.
T
Tapered insulation
Tapered insulation creates a sloping surface so that water can drain in a controlled way. Loose fills can level out heights but require a verified assembly against settlement and moisture. Flat roofs demand particularly careful planning.
Tensile strength
Tensile strength describes a material's resistance to tensile stress. For insulation boards, tensile strength perpendicular or parallel to the board plane can denote different properties. Test method and direction must therefore always be stated.
Thermal bridge
A thermal bridge is an area of increased heat flow, for example at corners, floor edges, windows or fastenings. The internal surface temperature there is often lower. Good detail design reduces energy losses and mould risks.
Thermal bridge free construction
Fully thermal bridge free construction is practically almost impossible. The aim is an assembly with minimised thermal bridges, a continuous insulation plane and well-planned junctions. Thermal bridges can be assessed by calculation.
Thermal conductivity
Thermal conductivity λ indicates how well a material conducts heat. Lower values mean better insulation at the same thickness. Moisture, temperature and bulk density can affect thermal conduction.
Thermal envelope
The thermal envelope separates heated from unheated areas or from the outdoor climate. Insulation, airtightness and thermal bridges must be executed within it as continuously as possible. Joints and junctions are particularly prone to defects.
Thermal insulation
Thermal insulation reduces the flow of heat through building elements. Hemp fibre, hemp-lime and hemp fills achieve this with different thermal conductivities and installed densities. The required thickness follows from the complete assembly and the energy target.
Timber frame construction
Timber frame construction uses load-bearing timber studs with cladding on both sides and insulation in the bays. Hemp insulation batts fit such bays well. Air barrier, wind barrier, service routing and moisture protection remain central planning tasks.
U
U-value
The U-value describes heat transmission through a complete building element in W/(m²·K). The lower the value, the better the thermal protection. All layers, thicknesses and surface heat transfers are needed for the calculation.
V
μ-value – water vapour diffusion resistance factor
The μ-value indicates how much more strongly a building material resists water vapour diffusion than an air layer of the same thickness. From μ and material thickness the sd-value can be approximated. Small μ-values stand for a low diffusion resistance.
Vapour diffusion
Vapour diffusion is the movement of water vapour through building materials driven by a vapour pressure gradient. It must be distinguished from moisture transport by air flow. Proper airtightness is therefore indispensable even in vapour-open constructions.
Vapour retarder
A vapour retarder limits the transport of water vapour through a building element. Its sd-value must suit the complete assembly and the climatic boundary conditions. With humidity-variable vapour retarders the diffusion resistance changes with ambient humidity.
Vapour-open
Vapour-open building materials have a comparatively low resistance to water vapour diffusion. This can support drying and moisture buffering. Vapour-open means neither air-permeable nor waterproof and is no guarantee against moisture damage.
Ventilated facade
In a ventilated facade there is a ventilated cavity between the insulation or wind barrier and the external cladding. It supports the removal of any moisture that has penetrated. Fire barriers, ventilation cross-sections, fastening and driving rain protection must be planned system-specifically.
VOC
VOCs are volatile organic compounds that can pass from materials into indoor air. Product emissions are measured in test chambers under defined conditions. Low emissions from one building material do not replace an overall assessment of the interior.
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Wet-room board
A wet-room board is intended for elevated indoor humidity. Hemplith® Aquaboard is an example. In areas subject to direct water exposure, an additional standard-compliant bonded waterproofing membrane is required.
Wind barrier
The wind barrier protects the outer face of insulation from air flow through it and from weather ingress. It must be windtight, secure at junctions and sufficiently water-shedding for the assembly. It must be distinguished from the room-side air barrier.
WUFI
WUFI is a family of software for the dynamic simulation of heat and moisture transport in building elements. It is used for complex or moisture-critical constructions. Its validity and results depend substantially on material data, climate data and boundary conditions.