Sun protection (architecture)

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The simplest form of external sun protection in buildings: a shutter.

The aim of sun protection in architecture is to protect buildings and their users from the unwanted effects of strong solar radiation . These unwanted side effects consist of glare and reflections as well as overheating of the building. Another important function is protection against UV radiation , for example to prevent furniture from fading. It is achieved through shading . Despite the sun protection, a high degree of transparency should often be maintained. Due to the large-scale use of glass in modern architecture , sun protection now plays an important role in facade design .

Depending on the position and functionality, a distinction is made between different sun protection systems that have different advantages and disadvantages. External sun protection works primarily via reflection , internal sun protection mainly via absorption .

As in the living area, the room temperatures must not exceed a certain limit value (depending on the type of activity) at workplaces, so the first measure they need is effective sun protection. In addition, in order to protect the eyes from glare from the sun or from excessive contrasts or luminance levels, a functional, variable glare protection is required, especially for computer workstations (EU Directive (EU 90/270)).


Glare protection

External sun protection: a roller shutter

In order to prevent direct glare and unwanted reflections as far as possible, the visible radiation falling into the room should be as diffuse as possible. External sun protection devices reliably protect the rooms behind them from direct radiation - albeit often at the expense of transparency.

Internal sun protection can only meet this requirement if the visible radiation changes its character and becomes diffuse when passing through the sun protection material. This is possible when using woven or perforated materials because the physical phenomenon of light diffraction occurs at the weaving or perforation holes, i.e. the transmitted radiation becomes more or less diffuse depending on the size of the hole. However, as the diffusivity of the radiation falling into the room increases, the transparency deteriorates. As a rule, foils do not have this property, which means that you can look into the "fireball" when the sun is deep; to prevent this, the light transmission would have to go almost to zero.

Protection against overheating

With regard to long-wave heat radiation, glass has a relatively high inhibiting effect. However, short-wave radiation can pass through the glass. The heat inside a building is only created through an absorption process on the surfaces exposed to solar radiation. Here, the plays Wien's displacement law of wavelengths an important role. This effect is used in the operation of greenhouses, but it is undesirable in most other buildings. The sun protection represents a measure of summer heat protection .


Sun protection should not obstruct the line of sight to the outside if possible. This demand (e.g. from occupational doctors) and the desire for effective sun protection seem to be mutually exclusive. In order to protect yourself from direct irradiation when the sun is low - this applies to east and west facades in summer and to south facades in winter - the slats of blinds and external venetian blinds must be set to approx. 30 ° (i.e. relatively steep), the view Outside in direct tanning is limited in this time window, but protects the eye from looking into the sun. From the point of view of occupational medicine, protection of the eye always has priority over an unobstructed view of the outdoors. The sun protection and the lighting of the room must therefore be carefully considered and planned; the good news - in direct sunlight there is 5–10 times more light available than in a clear or overcast sky, which means that the rooms behind can be supplied with daylight despite the shading of transparent surfaces and careful planning.

Types of sun protection

Structural sun protection

  • Building orientation,
  • Facade structure
  • Window design
  • Roof overhang

Sun protection in the area of ​​the windows

The technology is fully developed in most areas of sun protection. You can now get indoor and outdoor sun protection for almost every shape of window and conservatory . Almost all shapes can be operated manually and electrically.


External sun protection shades the object to be protected from the outside; This means that the heat conversion process described above is shifted to the outside of the building, where it can generally be controlled without any problems. The external sun protection is the most effective way of sun protection if the heat transfer by convection largely - z. B. through ventilation  - can be avoided. However, the problem of pollution and higher investment and operating costs (possibly necessary electrical operation, wind and rain monitors) cannot be neglected.

Examples of external sun protection are:

  • Shutters - shutters, mostly made of wood with slats that fold in front of the window
  • Roller shutters - Horizontal slats, mostly made of plastic , which are rolled up and then slide in side guide rails in front of the window
  • Awnings , sun sails - textile shading
  • External Blinds - Horizontal slat structures that can be lowered and raised
  • Brise soleil at the Ahmedabad Textile Mill Owners' Association House by Le Corbusier
    Brise soleil - slats made of concrete, metal or wood, often rotatable (not with concrete)
  • Balconies - if dimensioned correctly, provide shade from high sun in summer, while more direct sunlight is possible in winter
  • Deciduous trees - have the advantage that the leaves fall off in the cold season and thus enable direct sunlight

In the window


Internal shading is used primarily for weather-independent glare protection. As sun protection, they are significantly less effective than external systems and only if the degree of reflection is high (> 50%), which requires either white or very light curtains or special metal coatings.

  • Internal sun protection: a blind
    Blinds - Horizontal slat structures that can be lowered and raised
  • Rollo - textile curtains and foils that are rolled up above the window
  • Pleated blinds and pleated blind or pleated blind called - textile curtains are folded above or below the window
  • Lamellar curtain
  • Foil blinds are vapor-coated with aluminum on the outward side and reflect up to 80% of the sunlight (sometimes also selectively and thus light-changing). You can see through film blinds, but it is possible that the external cover is falsified.
  • Sun protection film is usually a film made of polyethylene terephthalate (PET) that is permanently applied to the window, but otherwise corresponds to the above-mentioned film roller blind in terms of its properties.
  • Interior shading - with the exception of fixed sun protection films - corresponds in all points to the EU occupational safety directive - the most important criterion is the adjustability and the ability to drive away the systems. The occupational health and safety directive aims to protect the eyes; In direct sunlight, a glare protection with a light transmission of <3% is required; in the case of large differences in luminance, such as light clouds, the value can also be 15%.

Overview of advantages and limitations

External sun protection Internal sun protection Lamellae in the space between the panes Solar control glass
functionality +++ + ++ +
maintenance + ++ + +++
price + +++ + ++

But there are a lot more aspects to consider: Dynamic shading (inside and outside) enables optimal use of solar energy and daylight in the course of the day and year; Solar control glass, on the other hand, permanently reduces the entry of energy and often also daylight, which leads to a significant deterioration in the energy balance. Sun protection built into the glass is easy to care for, but replacing it in the event of a defect is very time-consuming and expensive. In principle, one should also ask how the sun protection effect comes about - classic shading temporarily reduces the amount of energy and light as needed; Sun protection glass and sun protection films achieve their effect by selectively capping certain spectra - they manipulate natural daylight, so to speak. This technology is so sophisticated that, in spite of the intervention in the solar spectrum, the color rendering is mostly quite good, the traditional color rendering index Ra as a quality feature has more or less had its day. Light not only makes visible (enables visual perception), it controls and other things. a. also the circadian rhythm of living things; The effects that selectively changed daylight in the interior have on people has only been partially researched.


Shading calculations can be derived from VDI guideline 2078.

The horizontoscope is a quick and easy tool that enables you to determine on site at which times of the day and seasons obstacles cast a shadow on a point.

Trades involved

The interior decorator usually supplies the internal sun protection, often also awnings and external blinds. The roller shutter and sun protection technician (roller shutter and blind builder) is responsible for external sun protection and serves the areas of summer and winter heat protection, burglary protection, wind and rain protection, sound insulation, glare and privacy protection, light control and darkening.

In some cases, window manufacturers also have some sun protection products in their range. The specialist company for building automation takes over the implementation of the automatic control of the sun protection.

The providers of cleaning services for sun protection systems are part of the Verband Deutscher Sonnenschutzreiniger e. V. (VDS) organized.


  • Wolfgang Maurer: Sun protection systems: assessment criteria for planning . In: das bauzentrum , 2/88, trade journal for architects and civil engineers, p. 70 ff.
  • Wolfgang Maurer : Assessment criteria when planning sun protection systems . In: Roller shutter + sun protection , 3/88, trade journal for the roller shutter and blind construction trade, p. 20 ff.

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