Source: mejordealuminio.com /  Lab TECNALIA

Thermal insulation: let’s be clear. Falsehoods surrounding “the warmth of PVC and cold of aluminium”

Thinking that PVC is warmer to the touch and aluminium is colder and, therefore, you will be insulated better  by plastic windows, is false. Maybe it is warmer to the touch (it is plastic) but the window as a whole will have a thermal transmittance value which MUST include the glass and have the same values as an aluminium frame. It is the assembly as a whole and its values, and not only the frame and the material that we must consider for energy savings.

A window is an assembly including the frame and glass. Glassless windows are not fitted.

The consumer is often misled when talking about the thermal transmittance of the whole window, but referring actually only to the thermal transmittance of the frame profile.  It is portrayed as if it were much more decisive than it actually is, and the arguments and the influence that it has are manipulated in the following manner:

A window comprises a frame and glass. The glass is 80% of the whole window. When analysing the transmittance values, the assembly as a whole must be analysed, including the glass, since this is the true value. Analysing only the profile will bring up erroneous values. Nobody fits a glassless window.

If the frame is made from aluminium, plastic or another material, the window’s thermal transmittance value is not so important, since the material only represents 20% of the total. The type of glass used will produce windows with greater or lesser transmittance values

Such a simple fact is constantly manipulated by plastic (PVC) window manufacturers, since they only compare the transmittance of the frame and not the unit as a whole. With arguments that PVC is warmer and aluminium is colder that are merely comparisons between plastic and metal, advertisers make us believe that the window will have an alleged total saving thanks to the material with which the frame has been manufactured. This is false.

The gimmick of plastic (PVC)

So why don’t they calculate the whole assembly? Easy. Because when adding the glass, which makes up 80% of the window, the alleged saving due to transmittance only represents 20% when the frames are changed.

It is in this 20% where the materials must be compared.

Choosing aluminium is choosing a future.

When this false advantage disappears, there are other factors to discuss such as quality, durability, resistance, aesthetics, security, recycling, sustainability, etc., where plastic always comes off worse.