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A to E

Absorption coefficient (αw)

The acoustic capability of a material is quantified by its (αw) coefficient. This absorption coefficient for a material is the ratio between the acoustic power absorbed by one of this material's surfaces and the incident power. The closer it tends to be to 1, the more the material is absorbent, and therefore efficient.


Acoustics relates to the emission, propagation and reception of sounds and noises inside the same room or between different rooms.

Acoustic absorption

The incident sound energy on the walls is split into transmitted energy, reflected energy and absorbed energy. Depending on the nature and the distance of the material installed in front of the walls, it is possible to influence the quantity of energy absorbed and therefore reflected and thus improve the listening qualities in a room and lower the sound level when it is noisy.

Acoustic correction

Decreasing the impact of sound in a room by modifying the acoustic energy reflected by the walls (this is different from acoustic isolation in which case, in order to isolate one room from another, you modify the acoustic energy transmitted by the walls).

Air porosity

When fitted to external blinds, Sunscreen® fabrics from Mermet®'s collection offer efficient ventilation qualities for eliminating heat build-up between the blind and the glazing: 2,220 l/m2/s for Satiné 5500 fabric, with this value being tested using a porosimeter subject to a negative pressure of 196 Pa.

Alpha sabine (αw)

The acoustic capability of a material is quantified by its (αw) coefficient. This absorption coefficient for a material is the ratio between the acoustic power absorbed by one of this material's surfaces and the incident power. The closer it tends to be to 1, the more the material is absorbent, and therefore efficient.

Anti-bacterial (treatment)

A surface treatment applied to the fabric with the objective of protecting the fibres from being attacked by micro-organisms. Disinfectants are also called anti-bacterial or biocidal, and in this case the word “bacteria” is misused and does in fact refer to all micro-organisms (bacteria, viruses, protozoans).
Be careful not to get it confused with a bactericide: this product is a substance which kills bacteria and, preferably, nothing else. Bactericides are disinfectant, antiseptic or antibiotic.

BBC (Low Consumption Buildings)

Designates buildings whose energy consumption required for heating and air conditioning is appreciably reduced vis-à-vis standard buildings.

Breaking strength

This is the amount of force required before the fabric splits. The test is carried out on a sample 5 cm wide and is measured in decaNewtons (daN, 1 daN = ± 1 kg). 


Candela / m²

A unit for measuring luminance. The density of the light flow emitted in a given direction.


An industrial process enabling certain properties to be given to a yarn individually or to a fabric by applying a formulation onto them.

Cocktail effect

In public places where discussions by people create a high level of sound and ambient noise perceived as a hubbub. When this reaches a certain value, the people present have to raise their voices or even shout in order to continue to communicate. This escalation of the sound is called “the cocktail effect" and can be avoided by preventing the threshold at which it occurs from being reached.

Controlling background noise

Acoustic energy is broken down into transmitted energy and reflected energy. The quantity of energy reflected, and therefore the background noise, depends on the material, shape and state of the walls' surfaces. Treatment of these walls using acoustic absorption enables background noise to be controlled (incident sound energy).

Décibel (Db)

Unit for measuring the sound level. Audible levels for humans: 0 dB = hearing threshold; 120 dB = pain threshold.

Diffuse transmission factor (Tdif)

Correlation of the two factors above: Tdif = Tv – OF.It is indicated as Tvndif for the aspects of glare and shape recognition (outward visibility / night privacy). A low figure shows a better visual comfort.
However, for natural light control, it is indicated as Tvdifh . It is used to ascertain a fabric’s light diffusion capacity. A high figure means more natural light.
Tv = Tvnh = Tvnn + Tvndif

Dimensional stability of the fabric

A measurement of the deformation (dimensional variation) of the fabric after tension loading.


A façade consisting of glazed walls (single or double-glazing) separated by a ventilated air space which improves the thermal insulation and acoustic isolation. Forced circulation of the air avoids a build-up of heat in-between the two glazed walls. The incoming air can even be cooled in summer or preheated in winter.
The building's frame, which consists solely of columns, beams and slabs, offers great flexibility in terms of the interior layout, free from the constraints of windows or load-bearing walls.
The double-skin façade thus allows the volumes to be opened up to daylight whilst at the same time retaining very good heat insulation and control over incoming summer sunlight. Inside, the ambient air is renewed by a mechanical system. Adding internal solar protection from Mermet®'s collection enables the natural light to be modulated and glare to be controlled whilst at the same time still making it possible to look out, or to completely black it out.

Elongation to break point (stretching)

This is the elongation measured under a load before breaking, expressed as a percentage (ISO 1421 standard). For fabrics in Mermet® collection, it is lower than 5%, which indicates excellent stability, enabling large blinds to be made. Moreover, when not subjected to stresses, the fabrics in the Mermet® collection provide very good dimensional stability (no-load elongation ≤ 0.2 %). Refer to breaking strength.


The emissivity of a material is its ability to re-emit the energy received through conduction (heat/cold). A fabric with a low level of emissivity will limit the effect of inward radiation by limiting how cold it feels in winter and how hot it feels in summer. The energy emitted through this reflection
is kept inside so reducing air conditioning and heating consumption which in turn helps reduce energy consumption.

EN 13363-1 Standard - The simplified method

Calculates approximate values for the total solar energy transmittance (gtot) of glazing and shading combined. Inputs for this calculation are solar integrated optical and thermal parameters of glazing and shading. The calculation procedure is straightforward and can easily be performed in a spreadsheet.

EN 13363-2 Standard - The detailed calculation method

Calculates more precise values for the total solar energy transmittance (gtot) of glazing and shading combined. This calculation is based on the spectral transmission and reflection data of the solar protection device and the glazing. The calculation requires specialized software to solve the non-linear system of equations. The outcomes of calculations according to EN 13363-2 are suited as input for cooling load calculations.

EN 14501 Standard

Published in 2006, the European standard EN 14501 - "Blinds and shutters. Thermal and visual comfort. Performance characteristics and classification" states the properties that must be taken into consideration to measure the solar protection performance of fabrics. The standard is based on a number of criteria and establishes various comfort classifications:

  • for thermal comfort: the solar factor
  • for visual comfort: control of opacity, privacy at night, vision to the exterior, glare control, use of natural light, colour rendering.

There are 5 levels of performance classification:

  • 0 - very little effect
  • 1 - little effect
  • 2 - moderate effect
  • 3 - good effect
  • 4 - very good effect

The EN 14501 standard defines the total solar factor gtot (fabric + glass) as the most important property for thermal comfort and the Tv value for visual comfort.

EN 14716 Standard - Stretched ceilings

This European standard specifies the characteristics, specifications and test methods for stretched ceilings consisting of sheets or fabrics held by a fastening system. It also sets the compliance assessment method for them.

Enduris™ Glass Core

This label guarantees the technical characteristics of Sunscreen® fabrics: mechanical resistance, dimensional stability and high-level durability. At the origin of this technology: glass.

  • Lightweight but extremely strong : very good stability, very little elongation,
  • High resistance to heat and is totally non-flammable,
  • Chemically inert, pure mineral.

Enduris™ Glass Core expertise lies in an entire production process including:

  • High quality glass fibre
  • Specific formulation
  • Expertise in yarn coating
  • Superior weaving technique
  • ISO certified production and quality management systems
  • Commitment to customer satisfaction
  • Research and development at the cutting edge of technology

A new standardized European classification system for the reaction of products to fire which will gradually replace the former French system (M0, M1...). It consists of 7 levels of thermal performances :

  • A1 and A2: non combustible products
  • B: hardly combustible products
  • C: combustible products
  • D: highly combustible products
  • E: highly flammable products making a major contribution to the spread of the fire
  • F: no performance determined


Another classification is added regarding the smoke production "smoke opacity" rated "class s" and the burning droplets production "burning droplets" rated "d".


Words from F to J

F to J

Fire classification

Products for construction, decoration, etc. are classified in accordance with their performance in the event of fire. This is determined by tests which involve subjecting the products to thermal stress. Their behaviour in the presence of fire is therefore assessed against inflammability performance criteria.

- In France the M classification, consisting of 6 categories: M0 - Incombustible / M1 - Non-inflammable / M2 - Not readily flammable / M3 - Medium inflammability...

- There is also the European EUROCLASSES classification which takes into account the smoke released and any droplets dispersed. The classification system has 5 categories: A1, A2, B, C, D, E, F.

- There are numerous country-specific classification systems: FR (Flame Retardant), BS (British Standard), B1 (German DIN 4102), AS (Australian Standard), C UNO (Italian)...

Fire resistance

The capability of a material to avoid spreading flame and thus to avoid fuelling a fire. The fabrics in Mermet® collection comply with the most stringent fire safety standards in the world, in particular the M1 (non flammable) fire classification in France, B1 in Germany, BS in Great Britain, Class Uno in Italy, JIS in Japan, FR in the USA, AS in Australia, etc.


The capacity of a panel of fabric to remain flat when used for its application.


GREENGUARD is the world's first voluntary certification regarding the emission of pollutants, specifically created for products for interior use. This certification states that the samples submitted to the programme must meet contaminant emission thresholds. Products with GREENGUARD certification comply with emission levels for over 360 VOCs and a limit on total combined chemical emissions (TVOC).

GREENGUARD Gold certification takes the very highest emission thresholds into account in order to guarantee that emissions from certified products are unable to affect sensitive persons (children, ill people, etc.). This certification is often demanded by purchasers for schools, hospitals and retirement homes. In addition to setting strict thresholds for pollutant emissions, products with GREENGUARD Gold certification also comply with the provisions of California Section 01350, as required under many regulations and programmes, as is LEED® certification for sustainable buildings.

Greenhouse gases (GHGs)

Heated by the sun, the earth reflects back part of the energy in the form of infrared rays, which carry heat. GHG emissions prevent some of these rays from rejoining the atmosphere. This is how the Earth retains some of its heat, remaining at an average temperature of 15°C. Examples of greenhouse gases from human activity: CO2, methane and nitrogen oxide.


Or total solar factor. Percentage of solar energy which actually penetrates into a room through the blind and glazing. A low value means good thermal performance.

High Environmental Quality - HQE®

The environmental quality of a building is "the aptitude of all inherent characteristics, equipment and the land to meet the requirements associated with controlling the impact on the exterior environment and creating a comfortable and healthy interior environment" (NF P 01.010). The HQE® (High Environmental Quality) approach is a voluntary initiative that takes environmental criteria into account defined in 14 target areas, and applies to construction and/or development projects.


Light flow from a light source, that reaches a surface. It is measured in Lux (Lx).

Words from K to P

K to P


The luminous intensity emitted by a surface. It is measured in Candela per m² (Cd/m²).

Mechanical resistance

Measures the capacity of the fabrics to resist a certain amount of force applied to them. The main measurements are breaking strength, tear resistance, and resistance to fold.

Nanometer (nm)

Unit of length equalling one billionth of a metre or 10-9 m.

NF EN 13120 Standard - Internal blinds

Internal blinds – Performance requirements standards, including safety

This applies to all interior/exterior blinds and similar products, irrespective of their design and the type of materials used (venetian blinds, roller blinds, vertical blinds, etc.).


NF EN 13561 Standard - External blinds

External blinds – Performance requirements standards, including safety

This applies to all interior/exterior blinds and similar products, irrespective of their design and the type of materials used (venetian blinds, roller blinds, vertical blinds, etc.).

Oeko-tex Standard 100 label

This quality label certifies that the fabrics from Mermet®'s collection contain no chemicals hazardous to the health and safety of users. In particular, this quality label guarantees their harmlessness with regard to risks of irritations and allergies. Furthermore, all these fabrics are guaranteed lead-free.

Openness factor (OF)

In short, this coefficient expresses the percentage of holes in a fabric. According to the European standard, it is considered to be independent of colour, but for fabrics with the same weave, it must be measured using the darkest colour in the range.

Words from Q to U

Q to U


Registration, Evaluation, Authorization and Restriction of Chemicals

European Regulation covering chemical substances on the market in order to be able to control their effects on health and the environment. In force since June 2008, it applies to all producers, importers, distributors and users of chemical substances and products.

Resistance to bad weather

In addition to exposure to bright artificial light, the test samples are also sprayed with water under set conditions. To assess their resistance, the sample's deterioration is compared to that of a referencecontrol sample protected from the water with a pane of glass (ISO 105 B04).

Resistance to fold

A sample of fabric folded in two is flattened by a cylinder weighing 5 kg. The breaking strength is then determined for this brittle zone according to ISO 1421 standard. This is a deciding factor for making pockets.


Persistence of a sound phenomenon after the emission of sounds has ceased. Acoustics experts distinguish reverberation by its tailing off, colouration, and reinforcement. The reverberation period is the time that a sound takes to decay by 60 dB after the sound source has stopped. It is measured in seconds.

RT 2005 - French thermal regulations 2005

A French decree that applies to all buildings for which planning permission is applied for after 1 September 2006 and which sets out the standards which must be complied with by new constructions and extensions. Its objective: to reduce energy consumption by 15% versus the previous regulation, RT 2000.
This covers insulation, ventilation, building design, use of renewable energy, permeability to air, thermal bridges, solar protection and lighting.

RT 2012 - French thermal regulations 2012

The purpose of the thermal regulation RT2012 is to limit the energy consumption of new buildings, whether homes, shops & offices or other uses. Compliance with these new standards requires energy consumption to be divided by three vis-à-vis RT2005. Such a reduction requires bioclimatic considerations to be taken into account and a precise definition of the scope before selecting equipment. RT2012 also covers comfort during the summer months.

Signal-to-noise ratio

This specifies the extent to which spoken words stand out from the noise. This noise may be brought about by sources inside or outside the room. The higher the signal-to-noise ratio, the greater the intelligibility of the spoken words. Determination of this ratio is directly linked to the sound's decay within the space.

Solar absorption (As)

This factor measures the proportion of the solar radiation absorbed by the fabric alone. A low percentage indicates low absorption of solar energy by the fabric.

Solar energy

Any solar radiation is partly transmitted (Ts) through the fabric, absorbed (As), or reflected (Rs) by the fabric. The sum of the 3 equals 100.  Ts + Rs + As =100 % of the solar energy

Solar factor of standard glazing - g

Solar factor of the glazing. This is an indication given by manufacturers of glazing. The standard EN 14501 defines 4 reference glazing: :

  • A : single clear glazing (solar factor of standard glazing gv = 0.85 / U value thermal transmittance = 5.8 W/m²K)
  • B : double clear glazing (solar factor of standard glazing gv = 0.76 / U value thermal transmittance = 2.9 W/m²K)
  • C : low emission double glazing (solar factor of standard glazing gv = 0.59 / U value thermal transmittance = 1.2 W/m²K)
  • D : reflective double glazing with a low emission layer (solar factor of standard glazing gv = 0.32 / U value thermal transmittance U = 1.1 W/m²K)
Solar radiation

Any solar radiation is partly transmitted (Ts) through the fabric, absorbed (As), or reflected (Rs) by the fabric. The sum of the 3 equals 100.  Ts + Rs + As =100 % of the solar energy

Solar reflectance

Proportion of solar radiation reflected by the fabric. A high percentage means the fabric performs well at reflecting solar energy.

Solar transmittance

Proportion of solar energy transmitted through the fabric. A low percentage means the fabric performs well at reducing solar energy.

Sound (bass, mid-range, treble)

An auditory sensation produced by a rapid variation in air pressure. An acoustic vibration which is propagated in the form of a mechanical wave. It is characterised by the frequency (Hz) and the sound level (dB).

Sound level

Difference of sound intensity (Refer to the definition for Decibel.)



Active protection against fire by spraying water.

Stability of colours

(ISO 105 B02). Whatever the colour (except for white which is not rated), after being exposed for 300 hours to bright light (samples subjected to heat of 45°C, exposure to artificial or natural light), the fabrics in Mermet® collection attain an index of 7 out of 8 according to the reference scale (the blue range). This means discolouring by light remains very low. This test corresponds to natural ageing over 4 to 5 years (study conducted at the CNEP).


A technical specification approved by a recognised standardisation body for repeated or continuous application, with which compliance is not compulsory… (Directive 98/34/EC)
There are different status types for standards:
- National standards: in France they are designated by the letters NF
- European standards: these are developed by CEN, the European Committee for Standardisation, and are designated by the letters EN. They must be transposed into national standards and, in the case of France, become NF EN.
- International standards: these are developed by ISO, the International Standardisation Organisation.
Standards specify how performance levels are established (testing or calculation method), or the performance levels themselves and their classification.

Standard ISO 9001

Certification in accordance with the ISO 9001 standard recognises the efficiency of a company's organisation and makes it possible to guarantee customer satisfaction and trust. But it does require a precise definition of the processes and instructions, as well as ongoing monitoring.


A family of products from Mermet® collection that brings together transparent fabrics which always enable image definition through the fabric.


Tear resistance

This is the force required to tear a pre-cut sample of fabric. This test is vital for external blinds exposed to bad weather that is sometimes extreme, or which may come into contact with a piece of framework likely to tear the edges of the fabric.

Thermal breakage

A major temperature difference between two zones near glazing can give rise to breakages commonly referred to as breakages due to thermal shock. The presence of blinds can have a double effect on the temperature of the glazing. On the one hand, these devices' reflections of solar radiation (light objects) and radiant energy (dark objects) contribute to increasing the temperature. On the other hand, the lack of air circulation in the space between the glazing and the shading device minimises the glazing's heat loss. It is recommended that you link the space between the glazing and the shading device using air from the room, and increase the distance between the glazing and the shading device as best you can (40 to 50 mm).

Total solar factor

Or gtot factor. Percentage of solar energy which actually penetrates into a room through the blind and glazing. A low value means good thermal performance.


Ultra violet radiation transmittance (Tuv)

Blockage of UV rays

Indicates the percentage of ultra-violet radiation with wavelengths of 280 to 380 nm (nanometres) passing through the fabric. UV radiation accelerates natural ageing. All forms of solar protection provide protection in relation to UV rays.

Words from V to Z

V to Z

Visible light reflectance (Rvnh)

Proportion of light reflected by the fabric.

Visible light transmittance (Tvnh or Tv or TL)

Total percentage of light radiated through the fabric over a wavelength of 380 to 780 nm (nanometers), called the visible spectrum (total illumination).


The interweaving of warp yarns (vertical) and weft yarns (horizontal), creating the motif.


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