Thermalite® blocks have a micro-crystalline cellular structure that is highly resistant to the passage of air. The fact that air permeability contributes to both the thermal and sound insulation performance of a building is recognised in the Building Regulations.
In addition to the increase of the required U-Values, Part L of the Building Regulations recommends that the air permeability limits be set at 10m³/hr/m² (at 50 pascals pressure). Thermalite's® impressive performance levels are confirmed by independent tests undertaken by BSRIA, detailed below:
Report 15055A/1
100mm Thermalite® Shield blocks 0.1m³. hr-1. m-² with acrylic sealed joints
100mm Thermalite® Shield blocks 0.1m³. hr-1. m-² Thin Layer Mortar joints
Report 15919A 100mm Thermalite® Turbo blocks 0.18m³. hr-1. m-² with acrylic sealed mortar joints
Report 16918A 100mm Thermalite® Turbo blocks 0.22m³. hr-1. m-² with acrylic sealed mortar joints
100mm Thermalite® Turbo blocks 1.04m³. hr-1. m-² with standard mortar joints
The conclusion can be drawn, that when used as recommended, Thin Layer Mortar joints offer a higher level of sealing performance than standard mortar joints.