What is a U-Value?

Good question! I’m Andy Parkin, Managing Director of the Multi Award Winning Speed Screed. Today I’m here to give you a little more insight into U-Values; I’ll talk about what they are, what sort of value you would like, the unit of measurement and a few other geeky bits which hopefully you’ll enjoy!

A brief description of What is a U-Value.

A few years ago I might not have even been here talking to you today about U-Values. But an understanding of U-Values and how they are measured has become more important because of the justifiable drive to make all buildings more environmentally efficient and sustainable.

What is a U-Value?

Simply put, the U-Value is the way we measure the transfer of heat through a section of a building (in standard conditions and via every type of heat transfer).

It gives you an idea of how badly or well heat transfers from the inside to the outside via a certain component. A low U-Value means that heat transfers at a slower pace, a higher rate means heat transfers at a quicker pace; you want to have as low a U-Value as possible. Always shoot for a lower U-value!

What is a component?

By component, we mean any material used to assemble a building; it could be brickwork, plaster, concrete or glass. The U-Value of a building is derived by determining how much heat travels through each component and then how much is lost per square metre of component.

What is the unit of measure?

The unit of measure for U-Values is W/m²K. This breaks down to the rate of heat flow (Watts) through a square metre of a structure where a temperature differential of 1 degree Celsius exists.

U-Values and Building Regulations Approved Document Part L

In the Building Regulations Approved Document Part L, the U-Value of a building is considered, and we will assume that a new building is always referred to. Its important to note that achieving a satisfactory U-Value is not a tick box exercise; it is taken seriously and the complete building is considered. There are two main things to consider:

The design of the building must enable you to prove that the carbon dioxide emission rate (DER – Dwelling CO2 Emission Rate) does not exceed the Target CO2 Emission Rate (TER) or the maximum emission rate.

Secondly, you will have to be able to articulate energy loss through the building fabric (the DFEE – Dwelling Fabric Energy Efficiency); this must not exceed the Dwelling Target Fabric Energy Efficiency (TFEE) or the maximum target allowance.

U-Value Calculator

There are a number of good U-Value calculators online; they are worth a look and can give you a rough idea of the type of U-Value you’ll come out with. It’s worth noting that some are designed with build-up in mind, whereas others are linked to a certain brand of insulation and have been developed by the manufacturers; so exercise caution in terms of the portability of U-Value results across different products.

I’m hoping you are now up to speed with U-Values,  and if you have any questions please contact us.