Top 5 Eco-Friendly Insulation Materials for Walls in Germany

After World War II, Germany focused on rebuilding fast, which meant thin, non-insulated walls were the norm for decades. Along with cheap heating costs at the time, sustainability also wasn’t a major concern.

However, with rising heating expenses and growing environmental awareness, energy-efficient technologies, like building insulation, have become popular for reducing long-term costs and minimizing environmental impact.

Is Insulation Necessary for My Building?

While insulation isn't strictly mandatory under the Gebäudeenergiegesetz (GEG), there are thermal performance requirements you need to meet. You can still opt for thick walls instead of external insulation if they achieve the required U-values. Some do choose this route, but if you prefer thinner walls and better thermal efficiency, insulation is a practical choice. Not only does it reduce heating costs, but it also minimizes energy consumption, helping you save on long-term expenses. Moreover, insulating your building in an appropriate manner is an eco-friendly solution that contributes to a more sustainable future by reducing your carbon footprint and supporting environmental preservation.

The Drawbacks of Conventional Insulation Methods

For decades, External Thermal Insulation Composite Systems (WDVS) have been the go-to for insulating building exteriors in Germany. Conventional insulation materials like polystyrene (EPS) and mineral wool dominate the market because they are affordable and widely available.

While EPS is technically recyclable, large-scale recycling systems are still years away from being widely implemented. Until then, most discarded insulation is incinerated or sent to landfills, contributing to resource loss and environmental harm. Until a truly eco-friendly solution is in place, this issue will persist—making it crucial to seek a sustainable alternative today rather than relying on an uncertain future recycling system.

We here at Archiformus have prepared a list of our top 5 ecofriendly insulation materials for your old and new construction:

1. Hemp

Hemp insulation is a sustainable material derived from rapidly grown hemp plants, requiring minimal pesticides. It offers excellent thermal performance, breathability, and moisture regulation, making it ideal for timber-framed structures and interior walls. While hemp insulation manages moisture well in areas with moderate humidity, it may degrade over time with prolonged exposure to high moisture levels. Therefore, it's best suited for environments where humidity levels are controlled and not consistently high.

2. Wood Fiber

Wood fiber insulation is produced from sustainably sourced softwood chips and shavings, making it a renewable and recyclable option. It offers strong thermal and acoustic insulation properties while also being biodegradable. However, its lower resistance to moisture means it performs best in external thermal insulation composite systems (WDVS) conditions where the outside air is dry.

3. Cellulose

Cellulose insulation is made from recycled newspaper and treated for fire and pest resistance, making it one of the most eco-friendly insulation options available. It has excellent thermal performance and the ability to adapt to irregular spaces, effectively reducing air leakage. Due to its moderate moisture absorption, it is best suited for dry wall cavities and timber-framed buildings, where it can provide effective insulation without the risk of excessive moisture retention.

4. Cork

Cork is a natural, renewable material harvested from the bark of cork oak trees without harming the trees. It is resistant to moisture, mold, and pests, offering great thermal and acoustic insulation. Cork’s impermeability to gases and liquids makes it ideal for facades and areas with controlled moisture exposure, though prolonged moisture could affect its performance over time.

5. Mineral Foam Boards

Mineral foam boards, like calcium silicate boards, are made from inorganic materials that are recyclable and non-toxic. Their superior water resistance and breathability make them ideal for damp environments like basements and historic masonry, where moisture control is crucial. These boards also offer excellent fire resistance, making them a durable, fire-safe choice for older buildings.

Comparison of Insulation Materials

When selecting an eco-friendly insulation material, it's important to consider multiple key factors including thermal performance. Following is a comparison of these key factors along with the U values for each material.

The U values are approximate range at a thickness of 10 cm, which gives a practical idea of how each material performs in terms of heat loss. Keep in mind that these values may vary based on specific products and conditions.

Insulation Material	U-Value (W/m²K) ↓	Fire Resistance	Acoustic Insulation	Compatibility with Existing Structures
Hemp	0.038 - 0.045	Medium	Medium	Good for timber frames, interior walls
Wood Fiber	0.038 - 0.050	Low	High	Best for dry conditions, WDVS
Cellulose	0.038 - 0.040	Medium	Medium	Suitable for roof and wall cavities
Cork	0.037 - 0.040	High	High	Great for facades, humid areas
Mineral Foam Boards	0.045 - 0.060	Very High	Medium	Best for damp walls, basements, old masonry

Note: For the same thickness, EPS (polystyrene) has a U-value of 0.32 W/m²K. Eco-friendly materials may require thicker walls, but the lasting sustainability benefits make it a worthwhile trade-off.

Long-Term Value with Archiformus

What you choose from the options above will naturally depend on your budget and material availability. However, at Archiformus, we always prioritize solutions that offer long-term value. While some options may be more affordable upfront, our focus is on sustainability and durability. We believe in creating homes that not only meet your comfort and maintenance needs but also contribute to a greener, more sustainable future. Together, we share the responsibility of building with eco-friendly materials that protect the environment for years to come.