June 16, 2025, 10:00 am | Read time: 4 minutes
A good insulation is more important than ever in times of an energy crisis. The less heat is lost, the more heating costs can be saved. However, there are several misconceptions about this topic. A consumer advocate provides clarification.
Building insulation allows for reduced energy costs while protecting the climate. Additionally, insulation often forms the basis for using modern heating systems, frequently in conjunction with self-generated photovoltaic energy. “It’s important to know that insulating the roof or walls almost always pays off, is generally cheaper than a new heating system, and saves a lot of CO2,” says Christian Handwerk, energy expert from the Consumer Center NRW. “We advise consumers to check the order of energy efficiency measures before making energy investments in their homes. Building insulation usually comes first.” However, there is a lot of misinformation and persistent prejudices about building insulation. What are the most common misconceptions about insulation?
1. Misconception: Insulation is not financially viable
This is already one of several misconceptions surrounding insulation. Insulating exterior walls is often more cost-effective than installing a new heating system, even considering typical subsidy grants. Moreover, building insulation leads to significant energy savings.
An insulated exterior wall, for example, allows only 10 to 15 percent of the original energy amount to escape. In most cases, the investment in building insulation pays off within less than 15 years. Additionally, renovated walls have a lifespan of more than 40 years, enabling long-term cost savings. The same applies to roof insulation.
Although the payback period for roof insulation is somewhat longer than for facade insulation, it is also worthwhile in the long run. Another advantage is that the value of the property increases through the energy upgrade of the roof or facade. The extent of this increase varies depending on the location but contributes to the overall positive balance of exterior insulation.
More on this: How worthwhile is insulation really for the climate and your wallet?
2. Misconception: Insulation material is hazardous waste
This statement about insulation is also among the common misconceptions. The common insulation materials used today are expanded polystyrene (EPS) and extruded polystyrene foam (XPS). Previously, these insulation boards contained a flame retardant classified as hazardous. Therefore, insulation materials installed before 2016 must now be disposed of separately. Since 2016, such insulation materials can neither be sold nor used in Germany. Other insulation materials like mineral wool or natural insulation materials are not affected by this hazardous waste discussion.
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3. Misconception: Glass wool is harmful to health
Similar to the topic of “hazardous waste,” this has not been true for many years, as the composition of the insulation material has changed. Since 2005, no glass or rock wool has been sold in Germany that would be classified as carcinogenic. The fibers of the material have been further developed, so this type of insulation wool can be considered harmless. However, it can be irritating upon direct skin contact, so it is advisable to wear gloves when handling it. There is no health risk.
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4. Misconception: Insulation increases fire risk
This misconception mainly refers to EPS foam boards, which are considered the most commonly used insulation material in the building sector. Studies and statistics from experts show that facade insulation with EPS rarely influences the course of a fire.
In the rare cases where fire incidents occur, it is often due to an improper condition of the entire external thermal insulation composite system (ETICS). The ETICS includes the insulation material, fastening methods (gluing/doweling or rail system), and plaster layers. Statistically, the highest fire risk in residential buildings is in the kitchen area.
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5. Misconception: Insulation can cause mold
A widespread misconception is that components like walls or ceilings become too impermeable after insulation, thereby impairing moisture regulation. Most insulation materials, such as the commonly used EPS foam boards, are not dense enough to cause this problem.
An installation error could be sealing the insulation from the outside, i.e., from the cold side, too tightly, for example, by using unsuitable exterior plaster. Properly executed building insulation by a qualified professional always reduces the risk of mold formation.