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Consult, Consider, Design, Deliver

Welcome to CAINE CONSULTING, the specialist web-based service providing the latest Building Control Part L1A & L2A Compliance service for all UK Domestic & Commercial Buildings. The calculation method, known as the Combined Method, is set out in BS EN ISO 6946

What is a U-value?
A U value is a measure of heat loss in a particular building element . It is expressed in W/m2k, and details the amount of heat lost in watts (w) per square metre of material (for example wall, roof, floor etc.) when the temperature (k) outside is at least one degree lower.In a simplistic approach the lower the U- value, a low U- value usually indicates high levels of insulation. U-values are useful as it is a way of predicting the composite behavior of an entire building element rather than relying on the properties of individual materials.

Why use U-values?
U-values are important because they form the basis of any energy or carbon reduction standard. In practice, nearly every external building element has to comply with thermal standards that are expressed as a maximum
U-value. Knowledge of how to simply calculate U-values at an early stage in the design process, avoids expensive re-working later on in a project. It allows the designer to test the feasibility of their project at an early stage to ensure it is fit for purpose and will comply with regulatory frameworks.

How to understand U-values?
In order to calculate
U-values it is important to first understand, Thermal Conductivity, Thermal Resistance and Thermal Transmittance.

Lambda (Thermal Conductivity) Thermal conductivity is the rate at which heat is transmitted through a material, measured in watts per square metre of surface area for a temperature gradient of one Kelvin per metre thickness - simplified to W/mK. The Lower the value, the better the thermal efficiency of the material.

Calculating U-Values
CAINE CONSULTING, use programs to calculate U-values according to the procedures defined in:
ISO 6946:2007 (for most element types)
ISO 13370:2007 (for floors)
ISO 10077-1:2006 (for windows)
BRE Digest 465 (for steel framed elements)
BRE IP 10/02 (for Z-spacer elements)
SCI Technical Information Sheet P312 (for rail-and-bracket elements)

U-value Calculations