By 2050, we will use more energy for cooling buildings in summer than for heating them in winter. That’s what Swiss experts expect as a consequence of climate change. Choosing the right building material will therefore become increasingly important.

The months of July and August are traditionally the hottest in Europe, and climate researchers predict that heatwaves will become longer in the future. Not only the Mediterranean region is suffering from record-breaking temperatures. Even in Central Europe, residential and workspaces are increasingly turning into heat traps. According to the 2024 Climate Report by the European Commission, last year was the warmest year since records began. Based on scientific data and analysis, the report confirms the ongoing trend of rising temperatures across the continent.

Roof and façade: key entry points for heat

Around 80 percent of summer heat enters buildings through the roof. External walls are also exposed to extreme temperature fluctuations, with surface temperatures of up to 70 °C on façades and even 80 °C on rooftops.
This makes one thing clear: the choice of building material doesn’t determine whether cooling is needed, but how long cooling systems have to run and how much energy they consume. This is a decisive factor for thermal comfort and climate protection.

Massive construction buffers heat and ensures comfort

Autoclaved aerated concrete (AAC) exterior walls, such as those from Ytong or Hebel, buffer temperature peaks effectively due to their combination of bulk density and low thermal conductivity. This is known as thermal amplitude damping: heat enters the interior only slowly, and ideally not in a way that is even perceived as uncomfortable.

Combined with a massive interior wall, for example, made of Silka calcium silicate blocks, excess heat can also be absorbed and released overnight, particularly when night ventilation is used smartly. The result: a consistently comfortable indoor climate, even during prolonged periods of extreme heat.
“It’s not the absolute temperature that matters, but how long a heatwave lasts, and how it’s perceived by the people inside. Massive building elements can’t prevent heat entirely, but they make it occur less frequently and with a delay,” says Torsten Schoch, Managing Director of Xella Technologie- und Forschungsgesellschaft mbH.

Real-world measurements confirm the effect

Researches using real building data showed: in lightweight constructions (such as timber frames), critical indoor temperatures (e.g. above 27 °C) are exceeded up to eight times more often than in buildings with solid walls. When the interior walls are optimized as well – for example with calcium silicate blocks, the effect becomes even more pronounced.

Future-proof building with a view to 2045

Current climate models do not necessarily predict higher peak temperatures for Europe, but they do forecast more frequent and longer heatwaves. This means that the duration of heat in a building becomes more critical than the maximum temperature. Massive walls significantly delay indoor heat buildup, and thus help prevent overheating. Although they take longer to cool down, this thermal inertia creates a more stable and comfortable indoor climate, especially during extended hot spells.

Efficient, sustainable, and comfortable – all year round
Ytong and Hebel AAC products not only offer summer advantages. Their low thermal conductivity also helps retain warmth during the winter, without the need for additional external insulation. This allows for a monolithic, sustainable construction method that reduces both heating and cooling costs. Added benefits include sound insulation, fire protection, and fast, efficient installation.
Those who build today must plan for tomorrow’s climate, and choose building materials that ensure comfort in every season.