Winter is solved.
Now it's summer's turn.
Summers are getting longer and hotter, yet glass is still chosen with winter in mind. It is time we started looking at the g-value.
A 10 m² west-facing window is a 4.6 kW heater.
That is how much of the sun's heat comes in through west-facing low-E double glazing in July at around 4 pm. The air conditioning has to remove it every day, all summer long. Curtains do not help: the heat is already inside.
The Ug-value measures heat loss in winter. The g-value measures how much sun gets in during summer. Two units with the same Ug can differ twofold in their g-value.
Solar data: PVGIS, European Commission, clear day.
A coating thinner than a single hair.
It stops almost two thirds of the heat.
Sometimes centimetres make the difference. Here, so do nanometres.
Solar control glass carries a coating of silver and metal oxides, around 100 nanometres thick, on the inner face of the outer pane. It lets the light through and reflects the sun's heat back out. The more layers the silver is split into, the more light gets through for the same amount of heat.
Single silver
Keeps heat in during winter. In summer, it lets through more than half of the sun's heat.
g > 0.50
Double silver
Solar control that does not look mirrored from the outside. The heat stays out, the light comes in.
0.30 < g < 0.40
Triple silver
The most light for the same heat. For office buildings and large glazed areas.
g < 0.30
- Ug 1.0, even slightly better than standard low-E (1.1)
- Same thickness, same frames, same installation
Double-glazed unit 4 + 16 + 4 mm, 90% argon.
The same reason,
a different glass.
Large glazed areas without overheating.
You design the glazing your client wants, and the g-value stays low. You receive the BoQ item description and the technical data sheet with the quote.
Knowledge base
Less heat, a smaller air-conditioning system.
Through 10 m² of west-facing glass, 2.5 kW comes in instead of 4.6 kW. The air conditioning can be smaller and runs less.
Request a consultation
A selling point for your windows.
Same profile, same installation, same thickness. You offer your customer a window that does not heat up the room in summer. We agree a price list, and we send the samples and leaflets to you.
Start working with us
A south-facing living room, without curtains.
Daylight all day, and comfortable even in August. Double glazing with solar control costs less than low-E triple glazing and deals with the summer better.
Request a quote
High Durable · HD
A hard-wearing coating that can also be glazed as single glass.
LT 9–64% · g 10–51%
HD Neutral, Diamond, Silver, Silver Grey, Light Blue, Royal Blue
Solar
Strong reflection and low light, for façades in full sun.
LT 19–21% · g 16–18%
Solar Grey, Bronze, Gold, Bright Green
High Performance · HP
Single silver and a choice of colours: neutral, silver, blue, green, bronze.
LT 35–62% · g 27–52%
HP Neutral, Silver, Light Blue, Royal Blue, Bright Green, Bronze, Amber
SuperNeutral · SN
Double silver with a very neutral look and no colour in the reflection.
LT 29–75% · g 18–40%
SN 75, SN 70S, SN 70/37, SN 70/35, SN 63, SN 51, SN 40/23, SN 29/18
eXtraSelective · SNX
Triple silver. The most light for the least heat.
LT 50–68% · g 24–32%
SNX 70, SNX 60, SNX 50
Double glazed 6 + 16 + 4 mm, 90% argon, coating on surface 2.
For the specification,
not the brochure.
The make-ups we produce most often, each followed directly by the same unit with solar control. Every row is a unit you can order.
| Make-up, outside to inside | mm | Ug | g | Lt | Rv outside | Absorptance | Rw (C; Ctr) | Selectivity | |
|---|---|---|---|---|---|---|---|---|---|
| Our best sellers, each followed by the same unit with solar control | |||||||||
| Double glazed 24 mm | |||||||||
| IG 4+16+Low-E 4 [24 mm] | 24 | 1.1 | 63.9% | 81.9% | 12.4% | 14.0% | 30 (−1; −4) dB | 1.28 | |
| IG Sun4+16+4 [24 mm] | 24 | 1.0 | 34.9% | 70.5% | 13.6% | 21.4% | 30 (−1; −4) dB | 2.02 | |
| Double glazed 24 mm, satin | |||||||||
| IG Sat 4+16+Low-E 4 [24 mm] | 24 | 1.1 | 62.9% | 80.5% | 12.2% | 15.8% | 30 (−1; −4) dB | 1.28 | |
| IG Sun4+16+Sat 4 [24 mm] | 24 | 1.0 | 34.9% | 69.3% | 13.6% | 22.0% | 30 (−1; −4) dB | 1.99 | |
| Double glazed 20 mm | |||||||||
| IG 4+12+Low-E 4 [20 mm] | 20 | 1.3 | 63.9% | 81.9% | 12.4% | 14.0% | 30 (−1; −3) dB | 1.28 | |
| IG Sun4+12+4 [20 mm] | 20 | 1.2 | 35.0% | 70.5% | 13.6% | 21.4% | 30 (−1; −3) dB | 2.01 | |
| Triple glazed 44 mm | |||||||||
| IG Low-E 4+16+4+16+Low-E 4 [44 mm] | 44 | 0.6 | 52.7% | 74.1% | 15.9% | 20.6% | 32 (−1; −5) dB | 1.41 | |
| IG Sun4+16+4+16+Low-E 4 [44 mm] | 44 | 0.5 | 32.4% | 63.9% | 16.1% | 24.2% | 32 (−1; −5) dB | 1.97 | |
| Triple glazed 36 mm | |||||||||
| IG Low-E 4+12+4+12+Low-E 4 [36 mm] | 36 | 0.7 | 52.7% | 74.1% | 15.9% | 20.6% | 31 (−1; −5) dB | 1.41 | |
| IG Sun4+12+4+12+Low-E 4 [36 mm] | 36 | 0.7 | 32.5% | 63.9% | 16.1% | 24.2% | 31 (−1; −5) dB | 1.97 | |
| Triple glazed 44 mm, single coating | |||||||||
| IG 4+16+4+16+Low-E 4 [44 mm] | 44 | 0.9 | 58.6% | 75.0% | 18.7% | 19.1% | 32 (−1; −5) dB | 1.28 | |
| IG Sun4+16+4+16+4 [44 mm] | 44 | 0.8 | 32.5% | 64.7% | 17.9% | 22.6% | 32 (−1; −5) dB | 1.99 | |
| For façades | |||||||||
| IG SNX 50 8+16+Lami 4.4.2 [32.76 mm] | 32.76 | 1.0 | 24.0% | 49.4% | 10.2% | 39.9% | 38 (−2; −5) dB | 2.06 | |
| IG Lami SN70S 6.6.2+16+10 [38.76 mm] | 38.76 | 1.0 | 36.2% | 68.1% | 10.9% | 39.7% | 43 (−2; −5) dB | 1.88 | |
| IG Sunguard SG 8+16+Low-E 8 [32 mm] | 32 | 1.1 | 25.4% | 29.1% | 23.9% | 58.2% | 35 (−1; −4) dB | 1.15 | |
Source: Guardian performance calculator, October 2026. Ug to EN 673, g and Lt to EN 410. Rw is calculated by the calculator, not measured. Selectivity is Lt divided by g. 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 outside: how much the glass reflects from the outside. Absorptance: how much solar energy the glass absorbs, warming up as it does. Rw: how much it reduces noise. Selectivity: how much light you get for each unit of heat; higher is better. Sun is a double-silver solar control coating, Low-E is a heat-retaining coating, Sat is satin glass. All units with 90% argon. The glass is float.
With solar control glass
Urbarija nursery
Guardian Sun 39™
g 0.34 · Lt 63%
Selectivity 1.85
Eurostaklo office
Guardian SunGuard™ SNX 50, triple glazed
g 0.22 · Lt 43.9%
Selectivity 2.02
Send us your opening schedule.
We will send back calculations for each orientation.
A free consultation for architects and developers, with Ug/g calculations and a proposed coating for each façade.