The principal requirement of a cladding system is that it keeps the weather out and provides a building envelope within which the climate can be controlled in a cost effective manner.

The ability of the external cladding system to be weather and watertight depends on the nature of the various components making up the cladding system and its design. The long term performance will depend on the durability of the system and its ability to withstand the combined effects of heat, rain, frost and other environmental effects.

The system will also have to withstand thermal and moisture movements as well as the mechanical effects of wind and impact.
 

The continual pursuit of improved thermal insulation for buildings increases the risk of condensation within the wall structure. Please consult BS 5250: 1989: “Code of Practice for control of condensation in buildings” for the method for calculating the insulation value of the external wall and the risk of condensation with the wall. Please also refer to BRE Digest 369, February 1992.

Removal of moisture from the wall structure and insulation, e.g. by the use of a ventilated rainscreen system or cladding with high vapour permeability, can significantly improve the U-value of the wall.

See here the U-value

In general, an external cladding system will need to meet requirements for thermal insulation. Exposed walls of buildings should achieve a maximum U-value of 0.45W/m²K and semi-exposed walls should achieve a maximum U-value of 0.60W / m²K.

MASTERCLAD^® calcium silicate boards by Intumex can be used for wall claddings in all categories. In areas prone to vandalism or abnormally rough use, the number and spacing of supports as well as the type of fixings used should be reviewed in order to minimise the risk of malicious or accidental damage.

This table gives the different categories from E2 to E5.

 Buildings in Singapore are sub-divided into 6 categories, A~F, according to their exposure to impact, with category A being the highest level of impact resistance.