It is common knowledge that a thermos bottle keeps cooled matter cold and heated things hot. Nowadays, refridgerators are extremely insulated and everyone knows that otherwise, they would be bad power guzzlers. Have you ever fancied the idea to keep your fridge door ajar? Certainly not.

An air-conditioned building is nothing else than a huge refridgerator. But what can be observed during these hot summer days? Air conditioning is set to arctic temperatures and doors/windows are left wide open. Cooling energy is wasted, and the costs for its generation often exceed the heating costs of winter times. You may wonder, what this has got to do with ‘warm edge’. Now, of course, the thermal insulation of the building envelope matters for this question.

Despite the incredible heat of the summer, it should be comfortably cool inside a building. It is necessary to prevent the heat from getting into the building. Once it is inside, it requires a lot of effort and costs to get it out again.

It is always the heat that moves – provided there is a temperature gradient, no matter in which direction. For a heated building, a) transmission heat losses, i.e. direct heat transfer through the building envelope (walls, roof, windows, etc.) and b) ventilation heat losses through joints, leaky or in extreme cases open windows and doors have to be considered. As a matter of principle, the same mechanisms are working for air-conditioned buildings, only in opposite direction. On top are the effects of solar radiation through the glazing.

Meanwhile, it is well known that in winter, it is much more comfortable to live in a building with excellent thermal insulation. But not everybody realizes that the heat does not care if it moves from roomside to outdoors or from outdoors to the roomside.

Compared to a poorly insulated one, in a highly-insulated building it takes much longer for the summer heat to transfer to the inside – provided doors and windows are kept close, to prevent the hot air from getting in. (Over the long term, of course, this requires a controlled ventilation with heat recovery). The lower temperatures of the night are used for cooling the building down, and as soon as the outer temperature comes close again to the roomside temperature in the morning, all windows are closed and if possible shaded. Then, even during these days of extreme summer heat, you can stay inside a highly insulated building at comfortable 24 °C (75 °F), and this for outer temperatures of 32 °C (90 °F) and more.

What do you actually need for a highly insulated building? Highly insulated walls, highly insulated and air-tight windows with triple glazing – of course with warm edge for the glazing edge bond – plus exterior shading, to keep the unwanted solar radiation outside. (Don’t forget an energy-efficient controlled ventilation system!). Without the thermally improved spacers, i.e. with conventional aluminum spacers in the edge bond, the windows would have loopholes all around their glass edges, quickly conducting the heat to the inside.

Therefore: Investing right means making investments in saved energy, with improved thermal insulation of buildings. This is easy on your budget and protects the climate.

Heat, that is not allowed to penetrate into a building, does not require a costly air condition to transport it out again. It’s so simple.