Internal Insulation: Costs, Materials & Subsidies 2026

October 5, 2026

6 minutes

For older buildings or listed facades, internal insulation is often the only option for energy-efficient renovation. As of 2026, this measure noticeably reduces heating costs, but requires professional planning to prevent mould formation.

Key Facts About Internal Insulation

An overview of the most important facts and figures regarding internal wall insulation:

Heating Cost Savings: Professional internal insulation reduces annual heating costs by around 10 to 15 percent.
Costs per Square Metre: Prices for materials and tradespeople in Switzerland typically range between 70 and 200 CHF per square metre.
Cantonal Subsidies: If the insulation achieves a maximum U-value of 0.20 W/m²K, cantons often pay subsidies of 40 to 100 CHF per square metre.
Loss of Space in the Room: Classic insulation materials take up 4 to 9 centimetres of room depth, while high-performance insulation materials like aerogel only require 1 to 3 centimetres.
Risk of Mould: Without a correctly installed vapour barrier or capillary-active materials, there is a risk of severe moisture damage to the masonry.

Choosing the right material and professional execution are crucial for the success of the renovation.

Important Technical Terms Simply Explained

U-value (Thermal Transmittance)

Indicates how much heat is lost through a building component. The lower the value, the better the insulation effect. A U-value of ≤ 0.20 W/m²K is often required for subsidies.

Vapour Barrier

A foil or coating that prevents warm, moist indoor air from penetrating the insulation layer and condensing there.

Thermal Bridge

A weak point in the building envelope (e.g., at window connections) through which heat escapes more quickly to the outside. Condensation often forms here.

Capillary-active

Materials (such as calcium silicate) that can absorb, temporarily store, and release moisture from the indoor air without developing mould.

You will encounter these terms when planning internal insulation:

Insulation Materials in Comparison

Classic Insulation Boards (EPS / Mineral Wool)

Ideal for

Cost-conscious renovations where a space loss of 8 to 9 centimetres (including substructure) is not an issue.

Cost Range

Usually between 70 and 130 CHF per square metre (including installation).

Risks and Disadvantages

Strictly requires an absolutely tight vapour barrier. Flaws in the foil pose a risk of mould formation.

Who should do it?

A specialist company (drywaller or painter) to guarantee airtightness.

Ecological & Capillary-active Insulation Materials

Ideal for

A healthy indoor climate. Materials like wood fibre, cellulose, or calcium silicate naturally regulate moisture.

Cost Range

Medium price segment, often between 120 and 180 CHF per square metre.

Risks and Disadvantages

The insulation effect per centimetre is often slightly lower than with synthetic materials, which is why the layer must be thicker.

Who should do it?

Specialised tradespeople, as the walls must be precisely prepared beforehand.

High-performance Insulation (Aerogel)

Ideal for

Small rooms, expensive urban locations, or narrow window reveals where every centimetre of living space counts. Requires only 1 to 3 centimetres of thickness.

Cost Range

Very expensive, often from 150 to over 250 CHF per square metre.

Risks and Disadvantages

The material is very sensitive. If the granules are crushed during installation, they lose their insulation effect.

Who should do it?

Exclusively certified professionals.

Planning and Implementing Internal Insulation

Internal insulation significantly affects building physics. Proceed systematically to avoid structural damage.

Have the Building Condition Checked

Have an expert check the external wall for moisture and driving rain protection. Internal insulation may only be applied to dry, intact walls. **Attention:** Damp walls pose a risk of massive mould formation.

Select the Insulation System

Decide together with the specialist company whether direct bonding, a substructure (facing shell), or capillary-active insulation without a vapour barrier is the best choice for your rooms.

Apply for Subsidies

It is mandatory to submit the subsidy application to the canton **before construction begins**. Check whether the chosen material achieves the required U-value (usually ≤ 0.20 W/m²K).

Professional Installation

The tradesperson applies the insulation material and ensures a seamless vapour barrier. Connections to ceilings, floors, and windows must be sealed particularly carefully to avoid thermal bridges.

Interior Cladding and Finish

Finally, the wall is clad with gypsum fibre boards or plastered directly. The wall can then be painted or wallpapered as usual.

Document all steps and keep the invoices for the payout of the subsidies.

Frequently Asked Questions About Internal Insulation

Here you will find answers to the most important questions regarding costs, materials, and risks.

How much does internal insulation cost in Switzerland?

As of 2026, you should expect costs between 70 and 200 CHF per square metre. The price depends heavily on the chosen material (EPS is cheaper, aerogel is very expensive) and the effort required for a possible substructure.

How much heating costs can be saved through insulation?

Depending on the initial condition of the old building and the chosen insulation thickness, annual heating costs can be reduced by around 10 to 15 percent.

Are there subsidies for internal insulation?

Yes. The building programme of the federal government and cantons often supports wall insulation with 40 to 100 CHF per square metre. The prerequisite is usually that a maximum U-value of 0.20 W/m²K is achieved after the renovation and the application was submitted before construction began.

How much living space do I lose due to the insulation?

With direct bonding of classic insulation materials, you lose approx. 4 to 5 centimetres per external wall. With a substructure, it is 8 to 9 centimetres. High-performance insulation materials like aerogel, on the other hand, only require 1 to 3 centimetres.

Why is a vapour barrier so important?

The vapour barrier prevents warm, moist indoor air from penetrating the cold wall and condensing there. Without this protective layer, mould will inevitably form in the insulation, unless special capillary-active systems are used.

For a binding cost estimate, it is best to obtain quotes from local specialist companies.