Thermal requirements

Building Regulations

Building Regulations are divided into four parts with regard to conservation of energy in buildings (Part L). L1 deals with domestic, L2 with non-domestic. L1A is new build, L1B refurbishment, and similarly L2A new build and L2B refurbishment. The requirements of L2 are that an iSBEM calculation - interface for the Simplified Building Energy Model (or equivalent approved calculation) - be carried out. This inputs every aspect of the building and its energy consumption. The U values in the main elements of the building are obviously key, however also heat loss through details, energy consumption for lighting, water heaters, even the hand driers in the toilets must be considered.

This necessary data must be input into iSBEM.This includes U values - the heat lost through a system, measured in watts per metre squared per degree Kelvin. Also, the psi value, which is heat lost through details and interfaces between systems. This would include drip flashings, jambs, cills, ridges and eaves details, but also steelwork penetrations of the building envelope. And finally the Air Tightness is input.

BS10211 parts 1 and 2

System manufacturers must provide calculation through finite element analyses in accordance with BS10211 parts 1 and 2 to demonstrate the U values of their systems. This calculation method is highly complex, and models all heat loss, cold bridges and connections.
If you look closely at the illustration you can see the slightly lighter blue patch - this represents where a small amount of heat is being lost through the bracket of the spacer bar.

Because of the complicated calculation method for establishing the U value of a given system, it is becoming more important for specifiers to rely on the expertise of the system manufacturers to achieve these figures. The specifier states the desired U value, the System Manufacturer provides the system and build up to achieve this U value, backed up by calculation in accordance with Building Regulations and British Standards.

3D Modelling

The process to comply with building regulations requires 3D Thermal modelling using a specific software system. The following slides show the modelling process of a Built up System, with the various components labelled.The whole process from start to finish takes approximately between 4 & 6 hrs depending on the complexity of the detail. All details are thermally modelled and are registered onto our database.

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