On a daily basis, we here at Trade Access Panels, have calls from numerous customers who find U-Values very confusing, especially when it comes to understanding precisely what a U-Value is and how it affects and/or benefits their property or project.

In simple terms, U-Values measure how effective or none-effective a particular material is as an insulator. Briefly, the lower the U-Value, the better the material is as a heat insulator.

U-Values are usually used to define the thermal performance (heat loss) for a section of construction that involves more than one material. For example, a wall which may be made up of timber batons, insulation materials and plasterboard or, more specifically to Trade Access Panels, a glass or polycarbonate rooflight which may be made up of glass or polycarbonate, the PVC or aluminium frame and gas between the layers.

U-Value in Rooflights and Roof Lanterns

When we talk about the U-Value of a component such as a Rooflight or a Roof Lantern, we are describing how well or badly that component transmits heat from the inside to the outside of the building. Here in the UK, we often experience very cold winters, and we would want to be warm inside of our property, so we are much happier the lower the U-Value is. This will also help to reduce your energy bills from wasted heat transmitting from the property into the atmosphere, which is also better for the environment.


Basically, the better (or lower) the U-Value of a building is, the less energy is required to maintain a continuous comfortable environment inside the property.

How to calculate U-values?

The following equation is often used to work out the exact U-Value of a component:

U-Value (w/m²K) = the measure of structural heat loss per unit of surface area

As the calculation of U-values can be both time-consuming and very complex, there are some online U-Value calculators which we at Trade Access Panels Ltd have tried. However, many of these calculators are only available via a monthly subscription, and those which are free tend to be too unsophisticated for more complicated projects.

Briefly, the U-Value of a building component measures the amount of energy (heat) lost through a square metre (m2) of that material for every degree (K) difference in temperature between the inside and the outside.

We strive to offer the best possible U-Values wherever possible for the products from within our range. If you should require any further assistance or information then please do not hesitate to get in touch with us at 01922 500145 – sales@tradeaccesspanels.co.uk – www.tradeaccesspanels.co.uk.