Hemspan Ltd

Description of The Hemspan Ltd BIOHAUS® Building System

The BIOHAUS® timber frame system is a MMC Category 2 primary structural building system, manufactured offsite, and which develops Passivhaus standards of thermal performance using natural fibre insulation derived from industrial hemp.The system has been developed around two reference buildings to demonstrate its potential to deliver high performing, net zero buildings.

The structural frame comprises a conventional timber framed twin wall system that utilises materials with known performance to develop load bearing, racking and stability capacity for buildings up to 3 storeys in height – e.g. structural timber C16/C24 members, glulam beams, engineered floor & roof joists and OSB3 board. The twin wall configuration allows full-fill hemp fibre Bio Wall insulation, supplemented with layers of Bio Board on the interior to provide thermal mass, and conventional plasterboard or non-hydraulic lime plaster internal finishes, to provide fire performance.

The panels are designed to be compatible with a range of typical cladding materials supported by the system, including:

• Masonry brick or stone.
• Brick tiles.
• Rain screen cladding.
• Timber cladding.
• Render systems.

Limits on scope

• Maximum 3 storeys for residential and public use;
• Bottom members minimum 150mm above external ground level;
• Minimum 25mm drained and ventilated cavity behind external wall claddings;
• Sheathing board used in the construction must be third party approved for the proposed use (e.g., BBA, KIWA, ETA). All fixings to the supporting structure must be stainless or hardened steel. Relative Humidity in the cavity behind the wall cladding must not exceed 85% for extended periods.
• Hemspan Ltd must be contracted for the design, manufacture, supply and erection.
• A chartered structural engineer suitably experienced in the design of this type of structure must be sub- contracted for the structural analysis and design.
• Masonry wall cladding cavities should be minimum 50mm and ventilated.
• Conventional cladding, such as timber cladding, should have a minimum 25mm drained back-cavity, or as recommended by the manufacturer.
• Rendered external thermal insulation systems and/or insulated brick slip cladding systems applied to timber framed structures must have a minimum 25mm drained back-cavity.
• The structural analysis and design for the structure is undertaken by approved Structural Engineers.