Compare / Float glass (annealed) vs Heat-strengthened glass
Float glass (annealed) vs Heat-strengthened glass
EN 572-1/-2 · Glass
Ordinary annealed soda-lime float glass: fg,k 45 MPa, E 70 GPa, 2 500 kg/m³.
EN 1863-1 · Glass
Float glass with moderate surface prestress: fb,k 70 MPa; breaks into large pieces that stay in the frame.
Mechanical
| Property | Condition | Float glass (annealed) | Heat-strengthened glass | Difference |
|---|---|---|---|---|
| Modulus of elasticity E | — | 70 000MPa2 | 70 000MPa2 | same |
| Shear modulus G | — | 29 166MPa2 | 29 166MPa2 | same |
| Poisson's ratio ν | — | 0.22 | 0.22 | same |
| Characteristic bending strength fg,k / fb,k | — | 45MPa4 | 70MPa3 | +56 % |
| Knoop hardness HK | — | 6GPa2 | 6GPa2 | same |
Design values
| Property | Condition | Float glass (annealed) | Heat-strengthened glass | Difference |
|---|---|---|---|---|
| Modification factor for load duration kmod | instantaneous load · wind gust, 3 s | 11 | 11 | same |
| medium-term load · snow on heated buildings, 5 days | 0.491 | 0.491 | same | |
| permanent load · 15 years | 0.321 | 0.321 | same | |
| Partial factor for the material γM | annealed glass part, γM;A | 1.81 | 1.81 | same |
| surface prestress part, γM;v | — | 1.21 |
Physical
| Property | Condition | Float glass (annealed) | Heat-strengthened glass | Difference |
|---|---|---|---|---|
| Density ρ | at +18 °C | 2 500kg/m³3 | 2 500kg/m³3 | same |
Thermal
| Property | Condition | Float glass (annealed) | Heat-strengthened glass | Difference |
|---|---|---|---|---|
| Coefficient of thermal expansion α | 20–300 °C | 9×10⁻⁶ /K2 | 9×10⁻⁶ /K2 | same |
| Specific heat capacity cp | — | 720J/(kg·K)2 | 720J/(kg·K)2 | same |
| Softening temperature Tso | — | 725°C1 | 725°C1 | same |
| Resistance to temperature difference ΔT | — | 40K1 | 40K1 | same |
| Thermal conductivity λ | — | 1W/(m·K)1 | 1W/(m·K)1 | same |
Optical
| Property | Condition | Float glass (annealed) | Heat-strengthened glass | Difference |
|---|---|---|---|---|
| Refractive index n | visible light, 589.3 nm | 1.51 | 1.51 | same |
| Emissivity ε | corrected (for U-value calculation), uncoated | 0.8371 | 0.8371 | same |
Electrical and magnetic
| Property | Condition | Float glass (annealed) | Heat-strengthened glass | Difference |
|---|---|---|---|---|
| Electrical resistivity ρe | at +25 °C · 1 000 Hz | 5 × 10⁷Ω·m1 | 5 × 10⁷Ω·m1 | same |
Rows are matched by condition (thickness band, temperature, product form). A dash means the grade has no sourced value for that condition. Differences are Heat-strengthened glass relative to Float glass (annealed); for ranges the lower bound is compared.