Glass that keeps heat in during winter
and out in summer.
Where we install it
- Windows and balcony doors in aluminium, PVC or timber
- Structural and semi-structural glazed façades
- Conservatories, glasshouses and roof glazing
- Replacing old glass in existing frames
Step by step.
Every insulating unit starts from a basic make-up. Whatever the house needs is then added to it.
| Double glazed | Triple glazed | |
| Make-up | 4 + 16 + 4 Low-E, 24 mm | Low-E 4 + 16 + 4 + 16 + 4 Low-E, 44 mm |
| Light transmittance (Lt) | 81.9% | 74.1% |
| Solar energy transmittance (g) | 63.9% | 52.7% |
| Ug | 1.1 W/m²K | 0.6 W/m²K |
Triple glazing with a narrow spacer is no better than double glazing. With a narrow spacer, heat passes more quickly through the thin layer of gas. With one that is too wide, the gas starts to circulate and carries heat with it. Around 16 mm is best. Calculated to EN 673: 4 mm glass, 90% argon. Double glazed with a Sun coating, triple glazed with two low-E coatings.
Comfort all year round
A solar control coating is added to the basic make-up. It keeps the heat in during winter, keeps the sun's heat out in summer, and lets the light through.
Solar control glass| Double glazed | Triple glazed | |
| Make-up | 4 Sun + 16 + 4, 24 mm | 4 Sun + 16 + 4 + 16 + 4 Low-E, 44 mm |
| Light transmittance (Lt) | 70.5% | 63.9% |
| Solar energy transmittance (g) | 34.9% | 32.4% |
| Ug | 1.0 W/m²K | 0.5 W/m²K |
Safety, quiet, protection
One or more, depending on what the house needs.
Extras
For special requirements.
For those who
do the sums.
We make our insulating glass units on an automatic line built by Forel. Every pane is checked by a camera before assembly, and every unit is given a serial number showing the date, the make-up and the material batches. The figures in the table come from the Guardian performance calculator, for make-ups we produce every week. For your make-up, we send a technical data sheet with the quote.
Typical make-ups
| Make-up, outside to inside | mm | Ug | g | Lt | Rv | Rw | kg/m² |
|---|---|---|---|---|---|---|---|
| 4 / 16 Ar / 4 Low-E | 24 | 1.1 | 0.64 | 82% | 12% | 30 dB | 20.0 |
| 4 Low-E / 16 Ar / 4 / 16 Ar / 4 Low-E | 44 | 0.6 | 0.53 | 74% | 16% | 32 dB | 30.0 |
| 4.4.2 Low-E / 16 Ar / 4 / 16 Ar / 4.4.2 Low-E | 53.52 | 0.6 | 0.49 | 72% | 16% | 41 dB | 51.6 |
| 4 Sun / 16 Ar / 4 | 24 | 1.0 | 0.35 | 71% | 14% | 30 dB | 20.0 |
| 4 Sun / 16 Ar / 4 / 16 Ar / 4 Low-E | 44 | 0.5 | 0.32 | 64% | 16% | 32 dB | 30.0 |
| 4.4.2 Sun / 16 Ar / 4 / 16 Ar / 4.4.2 Low-E | 53.52 | 0.5 | 0.31 | 63% | 16% | 41 dB | 51.6 |
Source: Guardian performance calculator, August and October 2026. Ug to EN 673, g and Lt to EN 410. Rw is calculated by the calculator, not measured. Values are rounded. The exact figures for your make-up are given in the technical data sheet with the quote.
Ug: how much heat passes through the glass, in W/m²K; lower is better. g: the share of the sun's heat that comes in. Lt: how much daylight comes in. Rv: how much the glass reflects from the outside. Rw: how much it reduces noise. kg/m²: nominal weight of the glass, for choosing fittings. Ar is the argon fill.
Figures by make-up for solar control glassLine and sizes
| Line | Forel, fully automatic: edge grinder, washing machine, inspection camera, inspection station, gas-filling press, sealing machine |
| Maximum size | 4000 × 2500 mm; with toughened glass 2100 × 3600 mm, larger to order |
| Minimum size | Without edge grinding 320 × 180 mm · with arrised edges 320 × 260 mm · with polished edges 670 × 260 mm. Smaller pieces are made by hand. |
| Unit thickness | 12–80 mm |
| Thickness of individual panes | 3–25 mm |
| Layers | Double and triple glazed |
| Spacer | Aluminium or TGI warm edge, 6–32 mm wide |
| Spacer colour | Natural aluminium, black, grey, white |
| Gas fill | Argon |
| Sealing | Primary seal butyl Kömmerling GD 115; secondary seal Kömmerling GD 677 NA Plus (polyurethane) or structural silicone |
| Stepped edge | Up to 100 mm, on three sides |
| Shapes | Rectangular and non-rectangular shapes |
| Delivery | To the customer's address or to the building site |
Warm edge, Ψ values
| Spacer TGI-Spacer M, 6.85 mm | Double glazed | Triple glazed |
|---|---|---|
| PVC window | 0.040 | 0.038 |
| Timber window | 0.040 | 0.039 |
| Timber-aluminium | 0.044 | 0.042 |
| Thermally broken aluminium | 0.049 | 0.044 |
Ψ in W/mK, representative values for calculating the window Uw (4 + 16 + 4, Ug 1.1 and 4 + 12 + 4 + 12 + 4, Ug 0.7). Source: Bundesverband Flachglas, ‘Warm Edge’ data sheet no. 20, Technoform TGI-Spacer M, measured by ift Rosenheim.
Options
| Inner pane | Float, laminated, toughened, satin, patterned |
| Coatings | Low-E coating, solar control coating for homes, SunGuard™ HD, HP, SN, SNX for commercial façades |
Tolerances
Insulating glass units: ± 2 mm. This applies to standard sizes and thicknesses. For large formats, thicker glass and shapes, the tolerances in our Factory Standard apply.
| Unit thickness, double glazed | Deviation |
|---|---|
| Float / float | ± 1.0 mm |
| Float / toughened or patterned | ± 1.5 mm |
| Toughened / toughened | ± 1.5 mm |
| Float or toughened up to 6 mm / laminated up to 12 mm | ± 1.5 mm |
| Other make-ups with laminated glass | ± 2.0 mm |
Triple glazed: the square root of the sum of the squares of the deviations of both cavities, e.g. all panes float ± 1.4 mm.
| Maximum pane displacement | Rectangle | Shape |
|---|---|---|
| Edge length up to 2000 mm | 2.0 mm | 2.0 mm |
| 2000–3500 mm | 2.5 mm | 3.0 mm |
| Over 3500 mm | 3.0 mm | 4.0 mm |
Tolerances to EN 1279-1. The unit size tolerance is the sum of the glass cutting tolerance and the displacement. We will send the full Eurostaklo Factory Standard on request.
Standard and marking
EN 1279. We issue a Declaration of Performance and CE marking for our insulating glass units.
From the factory floor
Where it is installed
On a great many private, commercial and public buildings.
Send us the sizes.
We will send you a quote and a data sheet.
The lead time is stated with the quote. Send the sizes in whatever form suits you: PDF, CSV, Excel, or scanned handwritten sizes.
Or order a sample with coatings and compare them on your own window.