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4/16/4
Low-E on face 3 · Argon
The simplest double unit: a 4 mm pane, a 16 mm cavity, a 4 mm pane.
Glazing solutions
The frame is what you see. The glass does the work.
In an ordinary window the glass takes up most of the area. Everything you feel beside a window — how warm it is, how loudly the street comes through, how quickly the room heats up in summer — comes first of all from the glazing, not from the frame.
This page is written so that you can choose. First from your problem, then through the parameters that appear in a quotation, then through the specifications we use routinely. If by the end you know which unit you need and why, it has done its job.
The choice
Which problem are we starting from?
Choose the situation that best describes yours. Each one leads straight to the specification that solves it.
I lose heat in winterThe glass is the coldest surface of the wall. The answer is the low-E coating and the cavity, not thicker glass.I can hear the street indoorsNoise comes in through the glass, not the frame. It calls for panes of different thickness and an acoustic interlayer.The room overheats in summerSouth and west take direct sun. Here it is the solar factor g that matters, not Ug.I am worried about broken glassWhen ordinary glass breaks, it breaks into sharp pieces. Toughening and lamination solve different problems.I want it to resist forced entryThe glass is the weak point of any window. Resistance is declared in EN 356 classes, not by impression.I have large glazed areasBeyond certain sizes the choice stops being aesthetic: weight, stiffness and the risk of falling all come into it.
The notation
How to read a specification
In a quotation the glazing appears as a string of figures. It is read from outside in: pane, cavity, pane.
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44.2/16/4
Low-E on face 3 · Argon
The outer pane is laminated: two 4 mm panes bonded with two PVB interlayers. The “44” is the panes, the “.2” the interlayers.
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44.2 Silence/16/4
Low-E on face 3 · Argon
The same laminated pane, but with an acoustic interlayer. “Silence” is the only difference — and you hear it rather than see it.
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44.6/16/33.2
Low-E on face 3 · Argon
Six PVB interlayers in the outer pane, two in the inner one. The figure after the decimal point is the only thing that changes — and it is what decides the resistance class.
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4/20/4/20/4
Low-E on faces 2 and 5 · Argon
Triple unit: three panes and two 20 mm cavities. The overall thickness reaches 52 mm and needs a profile to match.
pane of glass
laminated pane, with a PVB interlayer
gas-filled cavity
Faces are numbered from outside: in a double unit, face 1 is the outer surface of the outer pane and face 4 the one facing the room. The low-E coating normally sits on face 3 and the solar control coating on face 2. Their position is not a manufacturing detail: moved to another face, the behaviour of the unit changes.
Parameters
The figures in a quotation, briefly
Six quantities cover almost everything you will see on a glazing data sheet.
UgW/m²K
Heat transfer through the glazing
How much heat passes through the glass. Lower is better. It is calculated to EN 673 and describes the glass alone, measured at the centre of the unit — not the installed window, which also has a frame.
g%
Solar factor
How much of the sun’s energy reaches the room. A g of 58% means that almost six tenths of the energy falling on the glass gets inside. High is good in winter on a south elevation and unpleasant in summer. Determined to EN 410.
TL%
Light transmission
How much visible light passes through. Also written LT. A triple unit inevitably has a lower TL than a double: there are three panes to cross, not two.
RwdB
Sound insulation
The weighted index, to EN ISO 717-1. It is written with two adaptation terms: Rw (C; Ctr). C is used for ordinary noise, Ctr for traffic — on a busy street, Rw + Ctr is the figure that counts.
S—
Selectivity
The ratio between light and solar heat, TL divided by g. The higher it is, the more light the glass admits for the same amount of heat. It is the real criterion in solar control.
mm
The thickness of the unit
The sum of the panes and the cavities. It has to fit the glazing rebate: a 44 mm unit will not go into a 68 mm profile. Which is why the glazing is chosen together with the system, not afterwards.
What an insulating unit is made of
The low-E coating
A metallic film a few nanometres thick, applied to one of the cavity faces. It lets light in and reflects the room’s thermal radiation back. It is the component that lowers Ug, not the thickness of the glass.
The solar control coating
Also an applied film, but tuned to stop part of the solar energy before it gets in. It sits on face 2, the cavity side of the outer pane, so that it works before the energy reaches the unit.
The cavity and the gas
It is the space between the panes that insulates, not the glass. It is filled with argon, which conducts heat less readily than air. Krypton is better, but only in narrow cavities, below about 10 mm, and it costs considerably more.
The spacer bar
It holds the panes apart and contains the desiccant that dries the air in the cavity. The classic version is aluminium. The warm-edge is made of a composite material and reduces the thermal bridge around the edge of the unit, which is precisely where condensation appears first.
The PVB interlayer
The polyvinyl butyral film that bonds two panes into a laminated one. On breakage it holds the fragments in place. It is measured in multiples of 0.38 mm: “.1” means one interlayer, “.2” two, “.6” six.
Acoustic PVB
The same interlayer, with a soft core that damps the vibration and removes the noise peak at the critical frequency of the pane. It appears in the notation as “Silence”. It changes neither Ug nor the breakage behaviour; it changes only the acoustics.
Types
The families of glass and what each one solves
These are not alternatives from which you pick one. A single unit usually combines three or four of them.
Base
Clear and extra-clear float
Ordinary float glass has a greenish cast, visible at the edge and in thick sections. The extra-clear version, with a reduced iron content, admits more light and renders colours more faithfully. It is used where transparency genuinely matters: railings, shopfronts, thick units.
Choose it when When the edge is visible or the glass is thick.
Thermal
Low-E glass
The low-E coated pane is the basis of any modern insulating unit. The coating has an emissivity of a few per cent and sits on the cavity face of the inner pane in a double unit; in a triple, on two faces. Its position is not optional: move it and the effect is lost.
Choose it when In any unit intended for an occupied building.
Solar
Solar control glass
A more selective coating, which stops part of the solar energy while keeping the light. It is chosen on selectivity, not on how dark it looks. On large façades and on a south-west orientation it is the difference between a usable room and one that overheats.
Choose it when Large areas, south or west orientation, glazed façades.
Safety
Toughened glass (ESG)
Thermally toughened glass, to EN 12150. It withstands impact and temperature differences several times better than ordinary glass, and on breakage it crumbles into granules with no sharp edges. It cannot be cut or drilled after toughening: all processing is done beforehand.
Choose it when Doors, low panes, surfaces exposed to thermal shock.
Safety
Heat-soaked toughened glass
The same toughened glass, put through an additional thermal cycle to EN 14179, which makes panes containing nickel sulphide inclusions break in the factory. It reduces the risk of spontaneous breakage after installation — which is why it is required on façades and on overhead glazing.
Choose it when Façades, rooflights, any pane that is hard to replace.
Safety
Laminated glass (VSG)
Two or more panes bonded with a PVB interlayer, to EN ISO 12543 and EN 14449. On breakage the fragments stay bonded to the interlayer and the opening is not left empty. It is the only solution where falling through is a risk — and the only one accepted for railings and overhead glazing.
Choose it when Railings, canopies, rooflights, balustrades, upper floors.
Acoustic
Acoustic laminated
Laminated glass with an acoustic interlayer. Combined with panes of different thickness and a suitable cavity, it is the answer for a busy street or a traffic area. The manufacturer states that a solar control coating, or toughening, does not change the acoustic performance of the unit.
Choose it when Boulevards, traffic arteries, areas near stations or airports.
Burglar resistance
Security laminated
Laminated glass with several interlayers, tested to EN 356 and declared to a class. The class belongs to the tested, CE-marked product, not to the number of interlayers written in the notation. The details and the classes are in the table below.
Choose it when Ground floors, shopfronts, detached houses, spaces holding valuables.
Appearance
Patterned, satin, screen-printed
Patterned, acid-etched or screen-printed enamelled glass. It adjusts privacy without cutting out the light, and it solves the opaque zones of a glazed façade, where the glass has to cover the floor slab or the insulation.
Choose it when Bathrooms, stairwells, internal partitions, façade spandrels.
Laminated
What the figure after the decimal point means
On a laminated pane, the figure before the decimal point gives the pane thicknesses and the one after it the number of 0.38 mm PVB interlayers. The latter is what decides how hard the glass is to get through.
The security laminated range and its classes
| The composition | The product | EN 356 class | Thickness | Weight | Make-up |
|---|---|---|---|---|---|
| 33.2 | STADIP PROTECT 33.2 | P1A | 7 mm | 16 kg/m² | 2 panes of 3 mm, 2 PVB interlayers |
| 44.2 | STADIP PROTECT 44.2 | P2A | 9 mm | 21 kg/m² | 2 panes of 4 mm, 2 PVB interlayers |
| 44.3 | STADIP PROTECT 44.3 | P3A | 9 mm | 21 kg/m² | 2 panes of 4 mm, 3 PVB interlayers |
| 44.4 | STADIP PROTECT 44.4 | P4A | 10 mm | 22 kg/m² | 2 panes of 4 mm, 4 PVB interlayers |
| 44.6 | STADIP PROTECT SP 510 | P5A | 11 mm | 22 kg/m² | 2 panes of 4 mm, 6 PVB interlayers |
Saint-Gobain Glass, the SGG STADIP PROTECT range. Classes are assigned to the tested product, CE marked to EN 14449.
“44.6” and “SP 510” are not the same thing
44.6 is a make-up notation. It describes two 4 mm panes bonded with six 0.38 mm PVB interlayers, that is a 2.28 mm interlayer and a nominal thickness of 11 mm. That is all. It can be produced by anyone with a lamination line.
SP 510 is the trade name of a Saint-Gobain product in the STADIP PROTECT range, declared in class P5A to EN 356. Its data sheet gives the 44.6 make-up — so the product does have that composition, but the composition alone does not confer the class.
The difference matters in two ways. First, the same P5A class also includes the variants SP 512, SP 514 and SP 518, with thicker make-ups intended for large panes — so “P5A” does not automatically mean “44.6”. And a 44.6 glass without testing and without a declaration of performance cannot be presented as P5A, however many interlayers it has.
The practical conclusion: the quotation states the make-up, and the project documentation carries the declared class of the product actually supplied. If you need a particular class, it has to be asked for explicitly from the outset.
What is tested at each EN 356 class
| Class | The test | Impact energy |
|---|---|---|
| P1A | 3 ball impacts, from 1.5 m | 161 J |
| P2A | 3 ball impacts, from 3 m | 362 J |
| P3A | 3 ball impacts, from 6 m | 724 J |
| P4A | 3 ball impacts, from 9 m | 1086 J |
| P5A | 3 × 3 ball impacts, from 9 m | 3258 J |
| P6B | 30 – 50 blows with hammer and axe | — |
| P7B | 51 – 70 blows with hammer and axe | — |
| P8B | over 70 blows with hammer and axe | — |
EN 356, the test steps as described in the Saint-Gobain Glass documentation. The steel ball weighs 4.1 kg; at the final drop it must not pass through the glazing.
Classes P1A – P5A are tested by ball drop and describe resistance to vandalism and to a quick attempt. Classes P6B – P8B are tested with hammer and axe blows, the aim of the test being to create a 40 × 40 cm opening — here what is measured is how many blows are needed, which is to say the time gained.
Solar control
Thermal insulation and solar control are two different things
Both are made with a coating applied to the glass, both appear on the same data sheet, but they solve opposite problems. Confusing them is the most common mistake in choosing glazing.
Ug
Thermal insulation deals with winter
The low-E coating reflects the thermal radiation of radiators and of objects in the room back into it. Its effect shows in Ug. A good low-E coating deliberately lets the sun in: in winter, the solar energy entering through a south-facing window is free heat.
What you want is a low Ug and, usually, a high g.
g
Solar control deals with summer
The selective coating stops part of the solar energy before it gets in, while trying to let the visible light through. Its effect shows in the solar factor g and in the light transmission TL. The ratio between them, the selectivity, says how well it achieves that separation.
What you want is a low g at a the highest possible TL.
A modern solar control unit also insulates — the tables below show the same Ug of 1.0 W/m²K for every version. The reverse does not hold: a purely insulating unit does no solar control. Which is why the choice is not “better or worse” but “for which orientation”.
When it is recommended
South and west, large areas
South and west façades take direct sun in the second half of the day, when the building has already warmed up. This is where solar control genuinely changes the temperature in the room.
Glazed façades and curtain walls
It is the ratio between glazed area and room volume that decides. Above a certain proportion of glazing, internal blinds can no longer cope.
Loft conversions and glazed roofs
Sloping glazing takes the radiation almost square on at midday. This is where overheating appears fastest.
Offices and spaces with internal gains
People, computers and lighting already produce heat. The solar load adds to it, and the cooling plant is sized on the sum of the two.
North — usually not
A north façade takes no direct sun. There, a solar control coating needlessly cuts both the winter gain and the daylight.
Alongside shading, not instead of it
An external louvre stops the sun before it reaches the glass and remains the most effective solution. Solar control is used where external shading is not possible or not sufficient.
Solutions
The specifications we use
Each one solves a particular problem. The exact thicknesses are confirmed against the glazing rebate of the chosen profile and the real size of the opening.
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4/16/4
Low-E on face 3 · Argon
The starting point
Thermal comfort, double glazing
The standard unit for a domestic window: two 4 mm panes, a 16 mm cavity, a low-E coating on the cavity side of the inner pane. It fits any common PVC, timber or aluminium profile.
What it solves
- Heat loss through the glass
- The cold surface beside the window
- Condensation on the glass where temperature differences are large
Worth remembering A 16 mm cavity is the optimum for argon. Wider brings nothing: the gas starts to circulate inside and carries heat with it.
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4/20/4/20/4
Low-E on faces 2 and 5 · Argon
For demanding requirements
Thermal comfort, triple glazing
Three panes and two cavities. It substantially lowers heat transfer and raises the temperature of the inner glass surface — which is why the feeling of a draught beside the window also goes away.
What it solves
- Buildings with high thermal requirements
- Large windows, where the cold surface matters
- Bedrooms on exposed façades
Worth remembering A 52 mm triple unit needs a deep profile and weighs almost twice as much. The weight is checked against the hardware before ordering, not after installation. Acoustically, a symmetrical triple is no improvement: 4/15/4/15/4 is measured at 32 dB, below an asymmetric double.
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44.2 Silence/16/4
Low-E on face 3 · Argon
For street frontages
Acoustic comfort
One acoustically laminated pane and one thin pane on the other side of the cavity. The asymmetry is deliberate: two identical panes share the same critical frequency and let noise through at the same point. The acoustic interlayer then removes what peak is left.
What it solves
- Road traffic, where Rw + Ctr is what counts
- Commercial areas and busy roads
- Bedrooms facing the street
The closest tested specification published by the manufacturer:6 / 15 argon / 44.2 SilenceRw 41 (-2; -6) dB — that is, Rw + Ctr = 35 dB
Worth remembering The interlayer manufacturer states that, acoustically, it makes no difference which side of the cavity the laminated pane sits on. The position is chosen for another reason: inward if the pane has to stop a fall, outward if it has to resist forced entry from outside.
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44.2/16/4
Low-E on face 3 · Argon
The standard where there is a risk of falling
Safety on breakage
The laminated pane is made of two 4 mm panes and two PVB interlayers. On breakage the opening is not left empty: the fragments stay bonded to the interlayer. The equivalent product in the Saint-Gobain range is classified P2A to EN 356.
What it solves
- Windows reachable from ground level
- Windows with a low sill
- Spaces used by children
Worth remembering Lamination and toughening solve different problems. Toughened glass crumbles harmlessly but leaves the opening empty; laminated glass stays in the frame. Where both are required, the glass is toughened and then laminated.
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44.6/16/33.2
Low-E on face 3 · Argon
Ground floor and shopfronts
Burglar resistance
The outer pane has six PVB interlayers — the composition Saint-Gobain sells as SP 510 and declares in class P5A. The inner pane stays laminated but thin, to keep the unit asymmetric and avoid adding weight needlessly.
What it solves
- Ground-floor windows and doors
- Shopfronts and retail spaces
- Detached houses, with no close neighbours
What is documented for the outer pane, taken on its own:44.6 (SP 510), 11 mmEN 356 class P5A · EN 12600 class 1(B)1 · Rw 35 (-1; -2) dB
Worth remembering The resistance class belongs to the tested, CE-marked product, not to the notation. A “44.6” without a declaration of performance is not P5A glass. At order stage the class is requested explicitly and goes into the project documentation.
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6/16/4
Selective low-E coating on face 2 · Argon
For sunlit façades
Solar control
The outer pane carries a selective coating that stops part of the solar energy while letting the light through. This is exactly the reference make-up on which the manufacturer declares its values, so here the figures apply to the unit, not only to the product.
What it solves
- Overheating of rooms facing south and west
- Glazed façades and curtain walls
- Reducing the cooling load
Declared values for this make-up, with COOL-LITE SKN 176 II:6 / 16 argon 90% / 4, coating on face 2TL 70% · g 37% · Ug 1.0 W/m²K · selectivity 1.9
Worth remembering A selective coating also changes the appearance from outside. The same product is kept across a façade; otherwise differences in reflectance show from one opening to the next.
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6/16/SP 510
Selective low-E coating on face 2 · Argon
Glazed ground floor, exposed to the sun
Solar control and security, together
The solar control coating sits on the outer pane, while the inner pane is P5A laminated. This is the specification for a glazed ground floor facing south or west, where both the sun and easy access from outside are a problem.
What it solves
- Sunlit shopfronts and retail spaces
- Residential ground floor with large areas
- Buildings where cooling and security are both required
Declared values for this make-up:COOL-LITE SKN 176 II / 6 – 16 argon / SP 510TL 68% · g 0.37 · Ug 1.0 W/m²K · 32.3 mm
Worth remembering The unit is 32.3 mm. It will not fit every profile, and it weighs considerably more than a 4/16/4. The system is chosen together with the glazing.
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66.2/16/6/16/44.2
Low-E on faces 2 and 5 · Argon
Sliding units and generous glazing
Large areas, a complete solution
A triple unit with laminated panes outside and inside, for large sliding or façade panes. Lamination covers safety against falling, the stiffness of the pane and its acoustic behaviour, all at once.
What it solves
- Sliding units with large leaves
- Glazed walls down to floor level
- Panes that need both safety and acoustics
Worth remembering Beyond certain sizes, the weight of the pane decides the system and the hardware. It is calculated before the specification is fixed, not after the glass has been ordered.
The specifications above describe the make-up, not a guaranteed performance. Where a figure appears, it belongs to exactly the make-up written beside it and comes from the glass manufacturer’s documentation. The values for your project are declared on the unit actually ordered and go into the project documentation: a 4/16/4 with some low-E coating and one with a new-generation coating look identical in notation and behave differently.
Performance
Figures, complete with their make-up
The values below are published by the glass manufacturer and apply to exactly the make-up given at the head of each table. They do not transfer to another unit.
Solar control, double glazing 6 / 16 / 4 mm — coating on face 2, 90% argon
| The glass product | TL | g | Ug | External reflection |
|---|---|---|---|---|
| COOL-LITE SKN 176 II (on PLANICLEAR or ORAÉ) | 70% | 37% | 1,0 W/m²K | 13% |
| COOL-LITE SKN 076 II (on DIAMANT) | 71% | 38% | 1,0 W/m²K | 15% |
Saint-Gobain Glass, COOL-LITE SKN 176 / 176 II data sheet. TL and g to EN 410, Ug to EN 673.
The declared selectivity for SKN 176 II is 1.9. The coating must be placed on face 2, with edge deletion before assembly, and the pane must be toughened and heat soaked.
The same unit, three different coatings — 6 / 15 argon / 44.2 Silence
| The outer pane | Coating on face | TL | g | Ug | Rw (C; Ctr) |
|---|---|---|---|---|---|
| ECLAZ ONE — thermal insulation only | 3 | 78% | 0,58 | 1,0 W/m²K | 41 (-2; -6) dB |
| PLANISTAR SUN — insulation + solar control | 2 | 70% | 0,37 | 1,0 W/m²K | 41 (-2; -6) dB |
| COOL-LITE XTREME 70/33 — solar control | 2 | 69% | 0,33 | 1,0 W/m²K | 41 (-2; -6) dB |
Saint-Gobain Glass Benelux, STADIP SILENCE brochure. Values to EN 410, EN 673, EN 1279 and EN ISO 717.
This is the table that shows the difference between thermal insulation and solar control most clearly: Ug is identical for all three at 1.0 W/m²K, and the acoustics are identical, because the make-up is the same. All that changes is how much sun gets in — from 58% to 33% — and with it how much light is left.
The same three coatings, on a laminated triple unit — 66.2 Silence / 20 argon / 44.2 Silence
| The outer pane | Coating on face | TL | g | Ug | Rw (C; Ctr) |
|---|---|---|---|---|---|
| ECLAZ ONE | 3 | 76% | 0,53 | 1,0 W/m²K | 50 (-2; -7) dB |
| PLANISTAR SUN | 2 | 68% | 0,35 | 1,0 W/m²K | 50 (-2; -7) dB |
| COOL-LITE XTREME 70/33 | 2 | 67% | 0,32 | 1,0 W/m²K | 50 (-2; -7) dB |
Saint-Gobain Glass Benelux, STADIP SILENCE brochure. Values to EN 410, EN 673, EN 1279 and EN ISO 717.
Both panes are acoustically laminated and the cavity increases to 20 mm. The acoustic result rises by 9 dB on the previous table, at the same Ug.
Solar control over burglar-resistant glass — 6 / 16 argon / SP 510
| The configuration | TL | g | Ug | Overall thickness |
|---|---|---|---|---|
| COOL-LITE SKN 176 II / 6 – 16 – SP 510 | 68% | 0,37 | 1,0 W/m²K | 32,3 mm |
Saint-Gobain Glass, product data sheet (inner pane SP 510, 10.3 mm; 90% argon fill).
Solar control and burglar resistance are not mutually exclusive: the coating sits on the outer pane and the P5A laminated pane on the inside. The overall thickness of 32.3 mm has to be checked against the glazing rebate before ordering.
Laminated glass on its own, with no cavity — the 44.6 make-up
| The composition | Thickness | TL | g | Ug | Rw (C; Ctr) |
|---|---|---|---|---|---|
| 44.6 | 11 mm | 88% | 0,76 | 5,28 W/m²K | 35 (-1; -2) dB |
| 55.6 | 13 mm | 87% | 0,75 | 5,23 W/m²K | 36 (-1; -2) dB |
| 66.6 | 15 mm | 87% | 0,74 | 5,17 W/m²K | 37 (-1; -3) dB |
| 88.6 | 19 mm | 86% | 0,72 | 5,07 W/m²K | 39 (-1; -3) dB |
Saint-Gobain Glass, STADIP PROTECT P5A data sheet (2 PLANICLEAR panes + 6 PVB interlayers of 0.38 mm). EN 12600 class: 1(B)1. EN 356 class: P5A.
This table is here to show something that is often misunderstood: lamination does not insulate. A Ug of 5.28 W/m²K is the value of a laminated pane taken on its own, which is effectively the value of single glazing. The insulation comes from the cavity and the low-E coating, so the laminated pane has to be built into an insulating unit.
Ug is the centre-pane value, to EN 673, and does not describe the installed window, which also has a frame. Light transmission and solar factor are determined to EN 410. Values can differ between the toughened and the untoughened version of the same coating, even with an identical make-up.
Acoustics
How much comes through, on tested make-ups
The table below is the only honest way to discuss the acoustics of a glazing unit: each figure sits next to the make-up on which it was measured.
Tested specifications — outside / cavity / inside
| The make-up | Rw (C; Ctr) | Rw + Ctr | Overall thickness |
|---|---|---|---|
| 4 / 15 / 4 | 29 (-1; -4) dB | 25 dB | 23 mm |
| 6 / 15 / 4 | 35 (-1; -5) dB | 30 dB | 25 mm |
| 4 / 15 / 33.2 | 36 (-2; -5) dB | 31 dB | 26 mm |
| 6 / 15 / 44.2 | 39 (-2; -6) dB | 33 dB | 30 mm |
| 44.2 / 15 / 33.2 | 40 (-2; -6) dB | 34 dB | 31 mm |
| 6 / 15 / 44.2 Silence | 41 (-2; -6) dB | 35 dB | 30 mm |
| 66.2 / 15 / 44.2 | 43 (-2; -6) dB | 37 dB | 37 mm |
| 10 / 15 / 44.2 Silence | 44 (-2; -6) dB | 38 dB | 34 mm |
| 66.2 Silence / 20 / 44.2 Silence | 50 (-2; -7) dB | 43 dB | 42 mm |
| 4 / 15 / 4 / 15 / 4 | 32 (-2; -6) dB | 26 dB | 42 mm |
| 6 / 15 / 4 / 15 / 44.2 | 41 (-2; -6) dB | 35 dB | 49 mm |
| 6 / 15 / 6 / 15 / 66.2 Silence | 45 (-2; -6) dB | 39 dB | 55 mm |
Saint-Gobain Glass Benelux, SILENCE range. The indices are expressed to EN ISO 717.
How to read the table
The column Rw + Ctr is the one that matters on a street. Ctr is the adaptation term for sources with a high low-frequency content — urban traffic, slow trains, distant aircraft. On a busy artery, a unit with Rw 41 and Ctr −6 behaves like one of 35 dB.
Compare the first two rows: moving from 4/15/4 at 6/15/4 brings 6 dB simply because the panes are no longer identical. Then compare 6/15/44.2 with 6/15/44.2 Silence: the same make-up, the only difference being the acoustic interlayer, and the result rises by a further 2 dB.
A symmetrical triple, 4/15/4/15/4, stays at 32 dB — below an asymmetric double with a laminated pane. A triple unit is chosen for thermal performance, not for noise.
The manufacturer states that a solar control or thermal insulation coating, like toughening, does not change the acoustic performance of the unit. In an asymmetric double unit, neither does the side on which the laminated pane sits — its position is chosen for safety reasons.
A drop of 1 dB is imperceptible, one of 3 dB is clearly audible, and one of 10 dB is felt as halving the noise. And one more thing: the acoustic performance of a window is not given by the glazing alone. The frame, the installation, the shutters and the ventilation grilles all enter into the final result.
Applications
What each place in the building asks for
One building can carry three kinds of glazing. The requirements come from where the pane sits, not from preference.
Windows and doors
Here it is Ug and the thickness of the unit that decide. The glazing rebate sets what will fit, and the orientation of the room sets whether a solar control coating makes sense as well.
Requires Double or triple unit with low-E; laminated on windows reachable from ground level.
Sliding units and large glazed areas
The pane becomes heavy and long. Pane thickness, stiffness and breakage behaviour all matter equally, because a large leaf is not easily replaced.
Requires Laminated panes, often on both sides; weight check for the hardware.
Façades and curtain walls
The work involves large areas and opaque zones at floor level. The glass has to look identical across the whole façade, so it is ordered from the same product and, ideally, from the same batch.
Requires Solar control, opaque zones by applied enamel, toughening with Heat Soak Test.
Railings and Juliet balconies
The pane takes horizontal loading and is, by definition, where someone could fall. There is no version in which laminated glass is optional.
Requires Laminated, usually toughened and laminated; all processing completed before toughening.
Canopies, verandas, rooflights
The glazing is overhead. If it breaks, what falls must not injure anyone, and the pane has to stay in the structure until it is replaced.
Requires Laminated is mandatory for the lower pane; Heat Soak Test toughening for the exposed pane.
Interiors: doors, partitions, furniture
Here the glass no longer insulates, it divides. It is used monolithic and toughened, with worked edges and any hardware cut-outs made before toughening.
Requires Toughened, ground and polished edges, CNC cut-outs.
References
The standards that appear in the documentation
EN 1279
Insulating glass units: make-up, sealing, durability and test methods.
EN 673
The calculation method for Ug, the heat transfer through the glazing.
EN 410
The method for determining light and solar characteristics: TL, g and the reflectances.
EN 12150
Thermally toughened glass: properties, testing and breakage pattern.
EN 14179
Heat Soak Test: the thermal cycle that makes toughened panes containing nickel sulphide inclusions break in the factory, so that they do not break spontaneously after installation.
EN ISO 12543
Laminated glass and laminated safety glass: definitions, make-up and appearance of the product.
EN 14449
Laminated glass and laminated safety glass: conformity assessment and CE marking.
EN 12600
The soft-body impact test. The classification takes the form 1(B)1, where the first figure is the drop height and the last describes the mode of breakage. Ordinary laminated glass is usually classified 2B2, security laminated 1B1.
EN 356
Resistance to manual attack. Classes P1A – P5A are tested by dropping a 4.1 kg steel ball from increasing heights; classes P6B – P8B by blows with a hammer and axe.
EN 12758
Glass in building and airborne sound insulation: how the acoustic performance of a glazing unit is declared.
EN ISO 717-1
Expressing sound insulation as a single number, Rw, with the adaptation terms C and Ctr.
EN 1096
Coated glass: the durability classes of the applied coating.
Before ordering
What we decide together
Façade orientation
South and west take direct sun; north almost none. The same house can have solar control on one elevation and ordinary glazing on another.
Real-world noise
A quiet street, a boulevard or a traffic artery. The difference shows in Rw + Ctr, not in Rw.
The position of the pane
At ground level, on an upper floor, where someone could fall, or overhead. This is what decides whether lamination is mandatory and on which side of the cavity it sits.
The glazing rebate
The profile you choose limits the thickness of the unit. Glazing and system are chosen together.
Size and weight
Large panes change the hardware and sometimes the system. The weight is calculated, not estimated.
The appearance from outside
Selective coatings have their own reflectance. On a single façade the same product is kept throughout, for a consistent appearance.
A professional note
A figure without its specification means nothing
Ug, g, TL and Rw are properties of one precise make-up: the glass product, the pane thicknesses, the cavity width, the gas and the position of the coating. Moved to another unit, the figures no longer apply. Which is why on this page every value appears together with the specification it belongs to, and where a specification we use has no published tested equivalent, we have said so openly and shown the closest documented make-up alongside.
The same applies to resistance classes: they belong to the tested, CE-marked product, not to the notation written in the quotation. The values for your project come from the data sheet of the unit actually ordered and go into the project documentation.
Next step
Not sure which glazing you need?
Tell us which way the rooms face, how noisy it is outside and which window system you have in mind. We will propose the right unit and put it in the quotation.
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