How Ytong Performs in Both Heat and Cold

As summers grow hotter and winters remain demanding, buildings must perform under increasingly extreme conditions. The choice of building material plays a key role in comfort and energy efficiency. Ytong autoclaved aerated concrete demonstrates how one solution can deliver reliable thermal performance in both hot and cold climates.

27 January, 2026

Building for a Changing Climate: The Growing Role of the Building Envelope

Europe’s climate is changing rapidly. According to EU climate data, 2024 was the warmest year on record, and climate models predict that heatwaves will become longer and more frequent. At the same time, cold regions continue to require highly effective thermal protection to minimize heat loss during long winters. As a result, buildings today must balance two opposing requirements: protection from overheating in summer and heat retention in winter.
The building envelope plays a decisive role in meeting both challenges. Roofs and external walls account for the majority of heat exchange with the environment. Up to 80 percent of summer heat enters a building through the roof, while façades can reach surface temperatures of 70 °C or more. The choice of construction material does not determine whether cooling or heating is required — but it strongly influences how long systems must operate and how much energy they consume.

Performance in Hot Climates: Thermal Mass as a Shield Against Heat

In warm and Mediterranean climates, summer thermal protection is critical. Lightweight constructions heat up quickly and transfer external temperatures almost directly to the interior. Massive wall systems behave very differently. Thanks to the combination of low thermal conductivity and suitable density, Ytong AAC significantly dampens temperature peaks.
This effect — known as temperature amplitude damping — delays heat transfer into the building. In practice, this means that external heat reaches interior spaces later in the day or not at all, especially when combined with intelligent night-time ventilation. When paired with massive internal walls, such as Silka calcium silicate units, excess heat can be stored temporarily and released during cooler night hours.
Measured building data confirms the effect: indoor temperatures above critical thresholds (for example 27 °C) occur up to eight times more frequently in lightweight constructions than in massive wall systems. Optimized internal walls further enhance this performance.
Spain offers several compelling examples. Passivhaus and low-energy buildings such as the Ca la Siesta and Peñoncillo single-family homes in Jávea and Malaga demonstrate how Ytong helps maintain stable indoor temperatures even during prolonged summer heat. By reducing the need for active cooling, these buildings lower electricity consumption and improve comfort in a region where cooling demand is rising rapidly.

Performance in Cold Climates: Efficient Insulation Without Additional Layers

The same properties that protect against heat in summer provide clear advantages in cold climates. In regions such as Iceland, buildings must minimize heat loss, withstand extreme weather, and remain durable over decades. Autoclaved aerated concrete meets these requirements through its intrinsic insulation: millions of evenly distributed air pores act as an integrated thermal barrier.
With very low lambda values — as low as 0.07 W/(mK) for Ytong blocks — high energy standards can be achieved using monolithic wall constructions, often without additional external insulation. This homogeneous structure also reduces the risk of thermal bridges, contributing to consistent energy performance and long-term reliability.
A pioneering semi-detached house in Garðabær, near Reykjavik, illustrates this clearly. Built almost entirely from Ytong, the project faced exceptional conditions during construction: snowstorms, extreme cold and, even frequent earthquakes linked to nearby volcanic activity. Despite these challenges, the building met all requirements for structural stability, thermal efficiency and sustainability. For the homeowners, Ytong proved to be not only an energy-efficient solution but also a forward-looking alternative to conventional Icelandic construction methods.

Two Climate Zones, One Principle: Comfort and Efficiency All Year Round

Comparing projects in Spain and Iceland reveals a common principle: effective thermal performance depends less on climate zone and more on building physics. Massive, well-insulating materials slow down heat transfer — whether heat is trying to enter the building in summer or escape it in winter.
This thermal inertia will become increasingly important as climate patterns evolve. Forecasts suggest that future challenges will not necessarily be higher peak temperatures, but longer periods of sustained heat. Buildings that heat up slowly offer a clear advantage in terms of comfort, health and energy consumption. Although massive structures also cool down more slowly, this stability becomes an asset during extended heatwaves.
From an economic perspective, the benefits are equally compelling. Reduced heating and cooling costs, durable construction, high fire and sound protection, and efficient installation make AAC a robust, future-ready choice. Ytong shows that sustainable construction is not a compromise — but a reliable solution for year-round comfort, regardless of geography.

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