Guide to typical U values (W/m²/°C)
| External Walls | |
|---|---|
| 9″ Sold Brick | 2.2 |
| 11″ Brick-block cavity (no insulation) | 1.0 |
| 11″ Brick-block cavity (insulated)) | 0.6 |
| Internal Walls | |
| 4.5″ Brick/plaster | 2.2 |
| Plasterboard/ 4″ studding/plasterboard | 1.8 |
| Floor | |
| Solid concrete | 0.8 |
| Suspended timber | 0.7 |
| Roof | |
| Corrugated asbestos | 5.7 |
| 4″ solid concrete | 4.0 |
| Flat roof 25mm insulation | 0.9 |
| Flat roof 50mm insulation | 0.6 |
| Glazing | |
| Single glazing | 5.6 |
| Double glazing (air cavity) | 2.8 |
| Double glazing (argon gas cavity) | 2.6 |
| Double glazing low E glass (air cavity) | 1.8 |
| Double glazing low E glass (argon gas cavity) | 1.5 |
| Doors | |
| Timber | 2.4 |
| Insulated Roller Shutter | 1.4 |
| Uninsulated Roller Shutter | 4.0 |
The following figures apply to naturally ventilated buildings only. If a building has fan-forced ventilation then the number of air changes per hour will be much higher.
| Building | Typical Air Changes per Hour |
|---|---|
| Shop | 1 |
| Office | 0.9 |
| School | 0.7 |
| Warehouse | 0.5 |
| Hall | 0.8 |