As temperatures rise during the summer months, so too do indoor temperatures. The aim of summer thermal protection is to protect buildings, rooms, and therefore users from high outdoor temperatures and the resulting heat build-up from solar radiation. The indoor environment should be perceived as pleasant and comfortable without being too damp or dry.

Summer thermal protection is not just about comfort, but also about keeping people healthy and productive, especially in hot weather. Studies show that performance decreases steadily at room temperatures above 78°F (26°C). Summers are getting hotter and hotter due to climate change, it is more important than ever to find ways to keep buildings cool while optimizing energy consumption.

An effective summer thermal protection has a positive impact on various parameters such as:

• Comfort: One of the main reasons for summer thermal protection is to improve user comfort. High temperatures can lead to discomfort and make it difficult to concentrate and complete daily tasks efficiently. Appropriate thermal protection contributes to a pleasant room temperature, promotes well-being, and increases productivity.
• Health: Excessive heat can pose significant health risks, especially to vulnerable populations such as the elderly, children, and people with certain medical conditions.
• Energy efficiency: The implementation of measures for thermal protection in summer generally also contributes to energy efficiency by reducing the need for excessive cooling. By minimizing heat gains through insulation, in addition to reflective coating layers and shading elements, buildings require less energy to maintain comfortable temperatures.
• Environmental impact: The excessive use of air conditioning and other cooling systems contributes to the emission of greenhouse gases and exacerbates climate change. By reducing cooling requirements through effective summer thermal protection, we can reduce our ecological footprint and minimize our environmental impact.

Implementing appropriate measures and strategies is crucial to creating sustainable and resilient buildings that can cope with the challenges of rising temperatures.

Cause of Overheating in Buildings

A variety of factors influence the overheating of the indoor environment in the hot summer months. The most important of these include: Outdoor temperature, solar radiation, building orientation, building envelope, air circulation, internal heat sources such as electrical appliances and lighting, thermal storage capacity of materials, and the size and number of windows. These factors are within the project team’s sphere of influence and their impact can be analyzed and optimized through variant studies.

Practical Tips and Recommendations for Optimizing Thermal Protection in Summer

To avoid costly planning changes, it is important to consider thermal comfort as early as the schematic design phase. Three main factors should be taken into account: the building envelope, the building services equipment for the room air conditioning, and possible user interventions such as natural ventilation via windows or other opening elements. Otherwise, not only in the warmer months but also the HVAC systems and their energy requirements.

By integrating energy-efficient and sustainable principles in terms of thermal protection in the summer, we can create buildings that provide optimum comfort while advancing the goals of sustainability and environmental responsibility.

Here are some practical measures and solutions for improving thermal protection in summer:

• Automated Solar Shading Systems: The integration of automated solar shading, such as motorized shutters, screen shades, or window awnings, makes it possible to regulate the amount of solar radiation in the interior area as required. Sensors enable these systems to regulate automatically to prevent overheating by closing when there is intense solar radiation and opening when the sky is overcast.
• Optimization of the Thermal Building Envelope: An optimized thermal building envelope can help reduce heat transmission and solar radiation via windows into the building and thus minimize the heat buildup in interior spaces. The heat gain in the building can be reduced, for example, by avoiding thermal bridges, improved thermal insulation, and highly efficient glazing (U-value and g-value).
• Optimization of Thermal Mass in Building: The use of building materials with high thermal storage capacity can help to absorb excess heat during the day and release it slowly later, resulting in a more even room temperature and a delay in rising temperature.

By implementing the described solutions, reducing the solar heat into indoor spaces, and optimizing the thermal performance of the building envelope, the thermal protection of buildings during summer can be significantly improved.

Calculation and Analysis Methods   

In Germany, proof of summer thermal protection for residential and non-residential buildings became mandatory for the first time with the Energy Saving Ordinance 2009 (EnEV). This is carried out in accordance with DIN 4108-2 Part 2: Minimum requirements for thermal protection. In November 2020, the EnEV was replaced by the Building Energy Act (GEG).

The following factors should be taken into account when calculating summer thermal protection  based on DIN 4108-2 Part 2:

• Climate Data: The accuracy of the climate data for the specific location of the building is crucial. This includes information on solar radiation, temperature, humidity, wind speed, and direction.

  

• Building Geometry and Orientation: The size, shape, and orientation of the building influence its exposure to solar radiation and prevailing winds. Simulations should take these factors into account in order to determine the heat gains and losses of the building.
• Building Materials and Insulation:  The thermal properties of the building and insulating materials have a significant influence on the thermal performance of the building. Simulations should consider the effect of materials used and their thermal conductivity, thermal storage capacity, and resistance to heat transfer.
• Shading and Glazing:  During simulations, it is crucial to evaluate and pay close attention to the effectiveness of shading devices such as canopies, awnings, and louvers in reducing direct solar radiation and minimizing associated heat gains. The type and properties of the glazing (e.g. U-value and g-value) should also be taken into account.
• Ventilation and Airflow:  Natural ventilation and the associated airflow (e.g. cross ventilation, position of windows, …) in the building play a decisive role in maintaining thermal comfort in the summer months. The air exchange rates and the effectiveness of ventilation strategies such as cross ventilation and shaft ventilation (e.g. atrium with opening elements in the roof) should be analyzed in simulations.
• Utilization and internal heat gains:  The number of users, appliances, lighting, and other internal heat sources contribute to the building’s internal heat gains.

Taking these factors into account, the cooling requirements and energy consumption of the building can be predicted accurately.

Predictive Calculation Method

Due to continuously rising outdoor air temperatures, we recommend that future climatic conditions be factored in for the evaluation of the thermal protection in the summer. The relationship between “Level Indicator 5-1” (technical report of the JRC of the European Commission) and summer thermal protection lies in their common goal of ensuring a comfortable and healthy indoor environment for building occupants, especially during the warm months.

It is therefore advantageous to evaluate the summer thermal protection using the “Level Indicators” (Level 5-1). To this end, a worst-case scenario (medium-to-high severity) for future climatic conditions in 2030 and 2050 will be analyzed. This more accurately maps the influence of climate change on the thermal impact of the building and ensures that the design of the building is robust enough to cope with summer climate extremes.

Case Study – Variant Analysis

At Baumann Consulting, we offer proof of compliance with summer thermal protection and analyze the building and its services equipment to identify improvement measures to optimize the indoor environment. These are developed further together with the project team.

The figure below illustrates how the g-value impacts comfort. The simulated building is a mixed-use building. The summer thermal protection simulation results show that the permitted overheating hours are significantly exceeded over the year.

 In the planning variant, this was over 500 hours for zone 1 on the ground floor. Only the reduction of the g-Value to 0.38 and the modification of the window area fulfilled the requirements.

It is therefore important to determine the optimum properties required for a comfortable indoor environment.