Windows & Doors

Windows and doors viewed from an energetic point of view – tips for planning

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Windows and doors are the eyes of a house – they give it character to the outside, let light into the interior and are themselves a style-defining element. But: Unfortunately, from an energetic point of view, they are first and foremost a large “hole in the wall” through which heat, which is expensively produced in winter, can escape to the outside, or heat can penetrate into the interior of the house in summer.

However, modern technologies also make it possible to manage the balancing act and thus produce windows and doors that on the one hand represent a real visual enrichment for the entire building and on the other hand insulate so well that they are not a gateway for a poor energy balance. And perhaps the best thing: Even beautiful old windows, perhaps with decorative bars, can be brought to an acceptable energy level by a specialist – provided the will to use the appropriate financial means.

Windows and doors – style-defining elements

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Also a style element: if the door is made of solid wood, the natural lighting of the hallway can be achieved through a skylight.

The door – calling card of the house

The first impression is crucial, this wisdom also applies to the front door. It is usually what a visitor sees first and at the same time also a safety-relevant component.

In terms of style, the door should definitely match the rest of the outer house: if you were to use an ultra-modern-looking glass and brushed steel door in a wonderfully patinated old building, you could in the worst case ruin the entire look of the house.

Sometimes essential: light

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A lot of glass means more light in the entrance area, but also easier visibility and less protection against break-ins.

Planning should focus primarily on what the hallway looks like behind the door: Does it get natural light from the windows? If he doesn’t, the door must have a glass one Passages equipped so that the lights don’t have to be on all day inside. Even the smallest windows with a side length of hardly more than ten centimeters are sufficient to let in enough light.

At the same time, such “little windows” do not compromise the burglar protection either: with ten percent of all break-ins, the front door is located in single-family houses in third place the most popular entry portals for criminals. The higher the proportion of glass in the door, the greater the likelihood that a burglar will simply break it in. Anyone who is concerned about maximum security should therefore proceed with the door glazing according to the maxim “As much as necessary, as little as possible”.

Energetically: New is better

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An old front door is a real feast for the eyes on the right house, but it presents the residents with energetic problems that are difficult to solve.

On the energetic level, new doors are usually absolutely harmless: They are in Sandwich construction manufactured so that there are many air pockets inside, through which heat and cold are very difficult to pass. Any existing windows then work on the principle of double or triple glazing and leave no room for heat loss.

However, it is important that the door is installed in such a way that it sits in the frame without distortion and there are no gaps – this video shows how to do it. With old doors, however, it is precisely the freedom from warpage that is often a problem. In addition, there is unfortunately little that can be changed in terms of the insulation itself. At most, in the case of branded products, the specialist can install improved insulation inside. If you still don’t want to do without your cherished door, you can, for example, install a second glass door directly behind it, which separates the door area from the rest of the hallway.

Windows and doors on an energetic level

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The larger the windows, the more light in the interior – but those who glaze as generously as in this picture have to dig deep into their pockets for appropriate insulating glass.

Windows as an insulating miracle

In earlier times, a phenomenon could often be observed on the windows that were simply glazed at the time in winter: Ice flowers. Because the heated room was only separated from the outside world by a millimeter-thick pane of glass, the air humidity in the room first condensed on its ice-cold surface and then closed freeze. In the case of windows in old buildings, they testify Drainage channels at the lower end of the window frame even today.

As with the doors, the same applies here: If you buy modern, you have no problem with energy. Has a contemporary triple-glazed window according to this report a heat transfer coefficient of only 0.8 W / (m² K). This means a little less cryptic: per year and square meter of window area, only as much heat escapes as can be generated with seven liters of heating oil.

When selecting the window, however, the is also important frame. And today there is absolute diversity on the market for just every conceivable design: If you are into a wood look, for example, you get plastic windows whose frames look deceptively real – but have all the advantages of modern plastic – they do not and have to warp also not be painted regularly.

From old to new

In addition, it can also be advantageous for the appearance of the house to simply modernize old windows.


If an old window has unusual formats or its appearance cannot be reproduced, a specialist has to deal with it.

It is of course ideal if the window already has double glazing. In this case, it is often even cheaper to simply have new glazing installed, possibly even triple, and thus bring the windows to contemporary energetic values, instead of replacing them completely. But it is also cheaper to do it yourself: For example, there are so-called insulating foils. These are applied inside and reflect heat back into the room – and while they do not reduce the brightness of the glass itself, they do reduce UV rays: In addition, the insulating foils, which depending on the manufacturer cost around 25 euros per square meter, prevent ultraviolet radiation gets into the interior – and protects furniture, photos and more from fading. Some products even noticeably reduce audible street noise and turn old windows into soundproof glass.


In the past, lattice windows were necessary because large glass surfaces were expensive to produce. Today they are only decorative accessories – and this look can also be achieved simply by means of strips that are mounted on the outside of the glass.

And even with very old, single-glazed windows, the specialist can often save a lot: namely, if he applies a second layer of glass, which is entirely possible depending on the construction. If the frame is then adjusted with new seals, even decades-old windows can come close to the modern in terms of their energetic values ​​- however, this approach is not cheap and should therefore only be used if there are serious reasons that do not permit replacement.

And one more tip at the end: It is important that new windows and doors do not insulate better than the walls around them. Otherwise, mold can quickly develop.

Image sources:

1) Tiberius Gracchus

2) Sam Spiro

3) Matthias Buehner

4) Buffy1982

5) Dimitry Koksharov

6) marasescumarc

7) Cara photo

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