Technical talk


The word ‘value’ is one used a great deal in the industry. It is often paired up with a specific letter, which can lead to much confusion or misunderstanding. Read below for how we can help simplify the jargon.

What is a Lamda-value?

The lambda value, also known as ‘K-value’ or ‘λ-value’, measures a product’s thermal conductivity in units of W/m·K.

Good insulation will have a low lambda value as possible to reduce heat loss. So, the lower the value of lambda a product has, the better it is at keeping the heat in.

What is an R-value?

The R-value of a product measures its thermal resistance in units of m²·K/W.

By dividing the thickness of a material in metres by its lambda value, you can find how well it resists heat transfer at a specific thickness.

So, products with a high R-value at a low thickness indicate the best insulation. This means it is as good at reducing heat loss as its thicker counterparts.

What is a U-value?

U-value is a sum of the thermal resistances of layers that make up an entire building element, for example, a roof, wall or floor. It also includes adjustments for any fixings or air gaps.

A U-value value shows the ability of an element to transmit heat from a warm space to a cold space in a building, and vice versa. This is measured in units of W/m²·K. So, the lower the U-value, the better the building element is for insulation.

It’s worth noting that the building element’s U-value is incredibly important as there are certain criteria that should be met, according to building regulations and standards in the United Kingdom.


We are PAS2030-19 and TrustMark licenced/certified and specialise in the installation of Spray Foam, EWI and IWI in domestic and commercial properties.

We operate across London and the South-East of England.

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