Published on January 14, 2021

Dowell ThermaLineTM

What is a U-value?

A U-value is a measure of heat transfer/loss in a building element such as a wall, floor or roof. It can also be referred to as an ‘overall heat transfer co-efficient’ and measures how well parts of a building transfer heat. This means that the higher the U-value the worse the thermal performance of the building envelope.

U-value is a measure of heat transfer/loss in a building element. Lower U-values indicate higher levels of insulation.

A low U-value usually indicates high levels of insulation. They 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.

Reference source: John Brennan [online] Available: (13 November 2014)

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