Guide to typical U values (W/m²/°C)

External Walls
9″ Sold Brick2.2
11″ Brick-block cavity (no insulation)1.0
11″ Brick-block cavity (insulated))0.6
Internal Walls
4.5″ Brick/plaster2.2
Plasterboard/ 4″ studding/plasterboard1.8
Floor
Solid concrete0.8
Suspended timber0.7
Roof
Corrugated asbestos5.7
4″ solid concrete4.0
Flat roof 25mm insulation0.9
Flat roof 50mm insulation0.6
Glazing
Single glazing5.6
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
Timber2.4
Insulated Roller Shutter1.4
Un-insulated Roller Shutter4.0

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