A Quick Guide to U Values

What’s a U-Value?

A U-Value is the unit of measurement used to measure the transference of heat through a structure. In short, it’s used to determine how quickly heat can escape through a material. 

In terms of construction, the U-value is used to measure the effectiveness of insulation materials that are used in commercial, industrial and domestic buildings. The lower the U-value of a material, the slower the heat will transmit through the material, meaning the material has high thermal insulation properties.

Why is the U-value important?

Legal requirements

Introduced in legislation in 1965, u-values were brought in as a way to help make UK homes more energy efficient, but it wasn’t until 2002 that requirements became more stringent. New statutory guidelines introduced by the UK government in 2013 outlined new U-value requirements that all properties must adhere to in order to be compliant, and they’re still the values in use in construction today. This includes newly built properties and renovated properties.  

The required U-value for a property is influenced by a number of factors, including the location of the building, whether it’s a residential or commercial premises and where it’s insulation is primarily placed such as walls, floors and roofs, and finally if the building is residential or commercial.

Personal benefits 

While they might be a legal requirement, there are benefits to managing the u-values when it comes to your home. 

To start, current legislation only provides the minimum requirement needed to insulate a property, but there’s nothing stopping you from going a little bit further. By investing in high-quality insulation with high u-values, your home will be even more energy efficient, which can help you save on bills and improve your quality of life. 

Homes with insulation that have high u-values and recently installed insulation can also add some significant value to a home, which makes it a great investment for anyone looking to sell their home in the future. 


U-Value for England


U-Value for Wales


U-value for Scotland

What does W/m2K mean?

W/m2K is the unit in which the U-Value is measured. W/m2K stands for Watts-per- meter-square-kelvin. The lower this value, the better a product is at insulating a building.

You might be comfortable undertaking U-value calculations yourself, but if not there are a lot of U-Value Calculators available online to help get the best material according to the requirements of the project.

How to Calculate the U-Value?

The U-Value of an insulation product can be calculated by first obtaining its R-value. R-values are a unit of measurement which indicate how good a material is at resisting the flow of heat, and they can always be found in the product specifications. 

Here’s what the R-value calculation looks like: 

R-Value = I (Thickness of material)/ λ (Thermal conductivity of material)

U-Value = 1/ (Sum of all R-Values) 

The higher the R-value, the lower the U-value of the material

How to calculate the heat loss once you have the U-value?

Once you have the overall U-value of the materia, you’ll be able to calculate an approximate heat loss at a given temperature (outside and inside) which will help you to decide the size of the material you need for your insulation. 

Approximate Heat loss = U-value (W/m2K) x Temperature difference (inside and outside) x Surface area (m2)

For example, let’s say:

  • The U-value of the product is 0.25 W/m2K
  • Temperature inside is 22 degrees and outside is -3 degrees so the temperature difference will be (22-(-3) = 25)
  • The surface area is 100m2

So, the approximate heat loss = 0.25 x 25 x 100 = 625 W to keep the temperature inside at 22 degrees.

You will need to calculate the approximate heat loss for roof, walls, floors, doors, and windows to find the total heat loss of the building. 

We have a great range of insulation products available for every project and every pocket. Why not head over and browse the full range. If you need any help, then why not have a chat with our team? They’re always on hand through live chat, or give us a call on 020 3481 1978.

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