If you've recently requested quotes for replacing your old windows, you've almost certainly heard (and read) the term "Energy Glass" or "Low-E Glass". Every professional promises that with this glass your home will be warmer and your electricity or heating oil bills will drop dramatically.
Yet when you look at an energy glass pane, you see no difference from the old, plain glass in your house. Both are perfectly transparent. How is it possible for a transparent piece of glass to make such a huge difference in thermal insulation? What exactly does "Low-E" mean? Let's strip away the technical jargon and reveal the impressive technology hidden on the glass - completely invisible to the naked eye.
The term Low-E comes from Low Emissivity, meaning low thermal radiation.
To understand how it works, we first need to understand how we lose heat from our home in winter. When you turn on your radiator, air conditioner or fireplace, the objects inside the room (walls, furniture, even your body) warm up. These warm bodies emit heat in the form of invisible infrared radiation.
If you have plain (old) glass, this infrared radiation passes through with remarkable ease and "escapes" into the freezing outdoor environment. Your home cools down, and you are forced to burn fuel continuously to replenish the lost heat.
This is exactly where Low-E technology intervenes. During the manufacturing of energy glass at the factory, one of its surfaces is sprayed with a microscopic, invisible coating of noble metals (mainly silver).
This coating is so thin (thousands of times thinner than a human hair) that it remains perfectly transparent to visible light (so you can see outside perfectly), but it acts as a thermal mirror against infrared radiation!
Imagine a cold January evening. You've turned on the heating in your living room.
The heat (infrared radiation) travels towards the window, trying to escape outside.
As soon as it "hits" the energy glass, the Low-E metallic coating reflects it (blocks it) and sends it back into the room.
The heat is trapped inside the home.
The room heats up much faster, the thermostat reaches the desired temperature and switches off, dramatically reducing energy consumption. At the same time, the glass itself is no longer "freezing" to the touch (like old glass), eliminating that cold feeling when sitting near the window.
The short answer is Yes.
According to the current KENAK (Building Energy Performance Regulation), you can no longer install plain (clear) double glazing in a new build or a major renovation. The legislation requires very low heat loss coefficients (U-value), which only Low-E energy glass (or the even more advanced Four-Season glass) can achieve.
Furthermore, subsidy programmes like "Exoikonomo" exclusively fund windows fitted with certified energy glass panes.
Many homeowners, trying to reduce renovation costs, consider asking for "plain double glazing instead of energy glass." This is the biggest financial mistake you can make.
The price difference (per square metre) between plain double glazing and energy glass is now very small (often less than €10-15/m²). However, the money saved on heating bills that energy glass will provide will pay back this small difference from the very first winter! From the second year on and for decades to come, energy glass simply puts money back in your pocket.
Return to category.
Go to categoryReturn to the central guide.
Go to guide
