Hot summers: facade insulation also protects from overheating

Junge Frau sitzt auf einem Sofa vor einem Ventilator und lässt sich den Wind ins Gesicht pusten

Buildings can often heat up more quickly than the residents care for. What many people do not know: an appropriate thermal insulation protects from summer heat. In the meantime, the so-called summer heat protection is prescribed by law. Here we explain what’s it all about and what protects buildings from heat.

How is summer heat protection regulated?

The climatic change brings us hotter and hotter temperatures; that is why summer heat protection of buildings becomes more and more important. Large window surfaces with sun protection have an overheating as a result. Overheated rooms constraint the indoor climate and are detrimental to our health. The Building Energy Law (German abbreviation: GEG) regulates the heat protection of buildings and requires quite a bit from building owners in this respect already during the planning stage.

The basic idea: buildings should reach an energy efficiency. Neither they should not cool down, nor heat up. Rooms should reach a pleasant temperature level without energy-intensive heating or air climate installations.

Heat protection in new buildings

For new buildings the pre-said GEG law (formerly Energy Saving Directive EnEv) prescribes a summer heat protection in accordance with the standard DIN 4108-2. A corresponding evidence must be provided. The advantage in case of a new building: already in the planning stage all measures which play a role on the cooling of living rooms, can be integrated. By incorporating sun protection elements, such as external venetian blinds into the building envelope at an early stage, no costly conversions are required later on. Thus, a strong heating up of the building is specifically reduced from the beginning.

Heat protection in existing buildings

As a rule, there is no retrofitting obligation for existing buildings. When one however renovates at a large extent or extends its building, one has to demonstrate an efficient summer heat protection. In this case - like for new buildings - § 14 of the GEG law (DIN 4108-2) is valid, too.

How can summer heat protection be measured?

The heat protection must be calculated for each house and evidence must be provided. Here there are two methods:

The simplified evidence method with so-called values of the solar energy input:

The building rooms which are subject to an increased sun exposition are assessed according to a specific system defined in the GEG law (in accordance with DIN 4108-2). For this purpose, the existing value of the solar energy input through the transparent parts of the building for each room is assessed and compared with the allowed value. The common technical language uses the word "allowed value of solar energy input". Factors like location, ratio between window and floor surface, slope of windows and orientation of windows must be considered.

The thermic building simulation:

For each room the temperature run over one year is simulated per computer and measured. Here, there is a limit for a certain number of so-called "overtemperature degree hours". An overtemperature degree hour occurs when the operative room temperature during one hour is exactly 1°K above the maximum permissible room temperature. The evidence is given for each critical rooms; the results are then transferred to other rooms.

As a rule, the following point is valid for both calculation methods: the "allowed number of sun hours" (German abbreviation: Szul) for the specific region must be respected - but without air conditioning. If the limit is exceeded, a compensating sun protection via awnings, blinds or Venetian blinds must be installed. The condition is that the shading system is fastened to the building. Anyone building with a forward-looking vision, already plans a sun protection today.

Which factors must be respected in case of heat protection?

The storage capacity and thermal conductivity of a building -  and as a result the room temperature – depends upon many factors. For this reason, the building should always be examined from all angles when planning the summer heat protection. Furthermore, the most important factor is the individual behaviour of the residents besides the architectonic circumstances.

Blocking out of summer heat through the construction method

The type of construction and the building material have a significant effect on the indoor climate. For example, massive walls dampen the rise temperature because they take longer to heat up themselves. In addition, they store heat during the day and release it again in the cool evening hours. Solid masonry in combination with exterior thermal insulation has proven to be particularly effective. This is because the thicker and above all denser, i.e "heavier" a wall is, the better it shields against heat. Generally speaking, houses insulated from the outside do not heat up as quickly and let less heat in from the outside. Overhanging roofs, wide balconies and green facades also contribute to thermal insulation, as they protect rooms behind them from direct solar heat and keep them cool.

Take the window factor into consideration

The proportion of glass in architecture has been increasing continuously for years. Windows play a central role in thermal insulation. Their size, number and orientation as well as the type of glazing have a significant influence on the interior temperature.

Integration of shading in the thermal insulation system

Sun protection in the form of awnings, roller shutters, internal or external venetian blinds can be specifically used to block out heat from interior rooms through glass surfaces. In principle, exterior sun protection is more efficient than interior sun protection because it intercepts heat before it can enter the rooms. Many residents prefer external venetian blinds to classic roller shutters because their slats allow more daylight into the rooms, depending on their position.

No matter which system is chosen, it is crucial for reliable thermal protection that the insulation level remains intact during installation. The building attachments must be professionally fastened to the insulation system in order to avoid thermal bridges. A secure solution is offered by integrated system solutions, such as the prefabricated external venetian blind boxes of Saint-Gobain Weber. They are individually configurable and can be perfectly integrated into the building insulation.

Ensuring a good indoor climate with one’s own behavior

The best shading is useless if it is not used correctly. On hot days, residents should therefore shade rooms and keep windows and doors closed. At night, on the other hand, systematic ventilation is necessary so that a constant exchange of air can take place. In this way, a pleasant temperature and healthy indoor air are achieved in the building.

How does thermal insulation cool the house?

It is well known that a well-insulated house helps to reduce heating costs in winter. But many people are not aware that insulation also protects against summer heat. In principle, the insulation layer of the exterior walls works like a thermos flask. Hot things keep it warm, cool things keep it cold. It is therefore important to prevent the house from heating up in the first place by taking appropriate shading measures. Then the thermal insulation can keep the cool temperature inside. Consequently, exterior insulation with additional shading makes air conditioners and fans, with their high energy consumption, superfluous. The less energy spent on heating or cooling, the better it is for your wallet and the environmental balance of the building. Thermal insulation is therefore a sensitive and sustainable solution.

Whether new or existing buildings, external thermal insulation composite systems (ETICS) are used particularly often. Here, for example, fully mineral insulating boards, such as those used for weber.therm A 100, A 200 with an insulating layer thickness of 14 to 16 centimeters are bonded to the facade. An ETICS usually has a slimmer overall structure, fewer thermal bridges and is more cost-effective than a ventilated curtain facade. Last but not least: the be-all and end-all of thermal insulation is always its professional application. Thermal insulation therefore belongs in professional hands.

An optimal system build-up

The concept of walls with separate functions is well suited in terms of summer heat protection - as well as for winter cold protection. Such walls are defined as follows: they consist of a mean solid masonry (for example with lime sandstones) in combination with an external thick-layer thermal insulation. Thanks to its high density, this construction method works as a natural heat accumulator. It extracts excess heat from the room air, stores it and releases it back into the room air when temperatures drop. The thickness of the insulation layer will help to decide individually how strongly the exterior wall should be insulated. Sun protection in the form of awnings, roller shutters, internal or external venetian blinds can be used to block out heat from interior rooms through glass surfaces.



The construction of such a valuable wall is rounded off by an algicide-free exterior render based on natural materials and a lime-based interior plaster. All these factors contribute to a pleasant indoor climate.