Summer heat protection is the architectural and technical solution to rising outdoor temperatures. It determines whether your home stays pleasantly cool or becomes unbearably hot. Whether in new construction or renovation—if you install suitable sun protection early on, you won’t need energy-intensive air conditioning systems; instead, you can effectively limit heat gain through windows and the building envelope. This allows you to save energy in the long term.
In this article, you’ll learn what summer heat protection entails, which standard governs it, and how you can ensure a comfortable indoor climate in the long term with ROMA sun protection systems.
Do you need advice on summer heat protection?
Summer thermal protection prevents rooms from overheating due to solar radiation—without the need for air conditioning.
DIN 4108-2 specifies the requirements for summer heat protection and is part of the GEG certification.
External sun protection, such as Roller Shutters, External Venetian Blinds, and Textile Screens, is the most effective single measure.
The FC value measures the effectiveness of the sun protection—the lower the value, the better.
Passive cooling through sun protection and nighttime ventilation saves energy and costs in the long term.
Subsidies for summer heat protection may be available.
Summer heat protection encompasses all structural and technical measures designed to prevent interior spaces from overheating due to solar radiation. The goal is to achieve a comfortable indoor climate without the use of air conditioners and the electricity they consume.
It is important to distinguish this from winter thermal insulation: While winter thermal insulation focuses on keeping heat inside the building, summer thermal insulation aims to prevent excessive heat from entering in the first place. Therefore, external window shading —that is, sun protection on the outside of the glass—is crucial.
Legally, summer heat protection is regulated by DIN 4108-2. This standard defines the conditions under which a buildingis considered to be adequately protected against overheating in the summer. It takes into account factors such as the location, orientation, and size of window areas, the heat storage capacity of building components, and existing sun protection measures. Factors such as window area, room volume, orientation, and overhang angle also factor into the calculation.
Depending on the building type, there are two methods for verifying summer heat protection:
Simplified verification: based on parameters such as window-to-wall ratio, orientation, and shading.
Dynamic verification: using a simulation of indoor temperature throughout the day, for more complex buildings.
If summer heat protection requirements are not met, structural measures or retrofits are necessary. If in doubt, consult your architect or a qualified energy consultant. Your ROMA specialist partner will help you find the right solution for your building.
For new and renovated buildings, the following applies: Proof of summer heat protection must be provided as part of the energy certification. This requirement is a component of the Building Energy Act (GEG) and applies to all residential buildings as well as many non-residential buildings. For owner-occupied buildings without major renovations, there is no general requirement to provide proof—but even in these cases, it is worth investing in effective sun protection.
Certain performance metrics are crucial for verifying a building’s summer heat protection. They help objectively evaluate the effectiveness of glazing and shading elements and optimize them in a targeted manner.
G-value: indicates how much solar energy enters the building through the glazing. The lower the value, the better the protection.
FC value: indicates how much solar heat still enters the interior despite sun protection—on a scale from 0 (no heat) to 1 (no protection). Exterior sun protection achieves the best results here.
Overhang angle: The angle of a fixed structural element (e.g., balcony slab) that influences shading.
These values help building owners take targeted measures and implement summer heat protection in accordance with building codes.
Effective summer heat protection not only enhances living comfort—it also protects health, reduces energy costs, and makes buildings future-proof. In poorly protected rooms, the indoor temperature can quickly rise above 30 degrees. This puts a strain not only on the circulatory system but also on physical performance.
In addition, the increasing number of hot days is leading to growing demand for air conditioners—with correspondingly high electricity consumption. Those who implement structural measures early on reduce their cooling needs in the long term and save on energy costs. Summer heat protection is therefore a key component in reducing the cooling needs of buildings.
Controlling heat gain not only improves your quality of life but also saves energy in the long run—that’s real added value. That’s why we at ROMA specifically focus on exterior sun protection that blocks heat before it enters the building.
Effective thermal insulation starts with the design phase—but there are also many measures that can be implemented in existing buildings:
Exterior sun protection: Roller Shutters, External Venetian Blinds, and Textile Screens block the sun’s rays before they hit the window glass.
Solar-control glazing: reduces the G-value but allows less daylight to enter.
Roof overhangs and greenery: passive shading provided by architectural elements or plants.
Ventilation and nighttime cooling: ventilate strategically in the morning and evening; keep windows closed during the day.
Interior sun protection: less effective, but can be useful as a supplement in some cases
Combining several of these measures provides long-term protection for your home against overheating in the summer.
What can you do about heat in a room? Use sun protection
To evaluate summer heat protection, the so-called solar heat gain coefficient (Svorh.) is useful; it expresses the potential heat gain through window areas relative to the room’s size. The lower the value, the better the room is protected against overheating.
The solar heat gain coefficient is calculated using the formula specified in DIN 4108-2:
Svorh. = ∑Aw,J ·gtot,j /AG
Svorh : Solar heat gain coefficient
Aw,J : Window area [m²]
gtot,j: Total energy transmittance (including solar shading)
AG : Net floor area of the room [m²]
Let’s assume a 25 m² living room with two windows facing southwest has a total glazed area of 4.5 m². The windows are equipped with exterior shading, which reduces the total solar heat gain coefficient (gtot) to approximately 0.15. The solar heat gain coefficient is calculated as follows:
Svorh. = (4.5 × 0.15) ÷ 25 = 0.027
This corresponds to a value of only 2.7% —and is thus well below the 25% limit recommended in DIN 4108-2 . The result shows that the room is well protected against overheating in the summer, particularly thanks to the exterior sunshades. Anyone planning a construction project or carrying out a renovation should consult with a distributor early on to plan thermal insulation.
“Those who consistently prioritize summer heat protection can do without active cooling —or significantly reduce its use. Passive cooling means preventing heat from entering in the first place, rather than expending significant effort to remove it later. External sunshades, nighttime ventilation, and heat-retaining building components work together to achieve this—without electricity consumption, without noise, and without ongoing costs. Air conditioning systems, on the other hand, are energy-intensive and costly, and their waste heat actually further warms the urban climate.”
A well-designed summer heat protection system not only prevents rooms from overheating but also ensures greater comfort, reduced cooling needs, and preservation of property value in the long term. Roller Shutters, External Venetian Blinds, and Textile Screens are particularly effective—ideally when automated and precisely tailored to the building.
ROMA offers high-quality ,custom-made sun protection that has proven its worth in both new construction and renovation projects. Get advice now or find a specialist partner near you.
Winter insulation keeps heat inside the house — summer insulation keeps heat out. Both aspects should be considered holistically to ensure a comfortable indoor climate and low energy costs year-round. High-quality insulation, modern windows with appropriate glazing, and exterior sun protection systems such as Roller Shutters, External Venetian Blinds, and Textile Screens allow both goals to be efficiently combined.
Summer heat protection provided by external Venetian blinds is significantly more effective than interior sun protection, since the majority of the sun’s rays are blocked outside the window. As a result, considerably less heat enters the building. While interior systems such as roller shades or curtains can reduce glare, they offer little protection against heat gain because the glass is already heated.
External Venetian blinds with adjustable slats also allow for flexible light control without having to sacrifice natural light—a clear advantage for comfort and the use of natural light while providing heat protection.
Certification is required for new construction and for renovations that involve changes to window areas. It is part of the GEG certification and must be provided by the designer. Your ROMA specialist partner can help you select a system that meets the requirements. How do summer and winter thermal insulation differ?
DIN 4108-2 establishes minimum requirements for summer thermal protection in buildings. It defines the conditions under which a building is considered to be adequately protected against overheating and serves as the basis for compliance verification under the GEG.
Summer heat protection encompasses all measures that prevent rooms from overheating due to solar radiation. These include exterior sunshades, as well as structural measures and ventilation strategies.