Installation with Blaugelb Triotherm+ Precasings — Why It's Mandatory for nZEB Certification

The Problem Nobody Mentions at the Point of Sale

You can buy the highest-performing Salamander BluEvolution 92 PVC profile, with a Uw of 0.70 W/m²K and triple glazing with argon. If installation is incorrect, the window retains less than 60% of the thermal performance you paid for.

Why? Because of perimeter thermal bridges — the areas around the window where heat from inside escapes directly to the outside through the building material.

Blaugelb Triotherm+ precasings exist specifically to solve this problem. And for buildings that need to achieve the nZEB standard, their use is technically mandatory.

What Are Blaugelb Triotherm+ Precasings?

Blaugelb is a German manufacturer specialising exclusively in window installation systems. Triotherm+ is the top-of-the-range system for complete perimeter insulation.

A Blaugelb Triotherm+ precasing is a thermal insulating profile (λ = 0.035 W/mK) installed in the masonry opening before the window. Its role:

• Eliminates the thermal bridge between the frame and the masonry
• Creates a perfectly flat and level installation plane
• Thermally separates the interior from the exterior zone
• Allows integration of sealing tapes

Components of the Complete System

• Triotherm+ precasing — the main thermal insulating profile
• Pre-compressed butyl tape — exterior sealing (rain, wind)
• Vapour sealing tape — interior barrier (condensation)
• Controlled density polyurethane foam — cavity filling
• Special anchors and screws for fixing

How It Works Thermally

Without a precasing, the PVC frame directly contacts the masonry. Masonry conducts heat. Between interior (20°C) and exterior (−10°C), the 30°C difference creates a direct thermal flow through the masonry.

Result: condensation on the interior perimeter of the window, cold zones at the sill, additional energy costs.

With a Blaugelb Triotherm+ precasing, a material with extremely low conductivity physically interrupts the thermal bridge. The interior surface temperature stays close to room temperature. No more perimeter condensation.

Why Is It Mandatory for nZEB?

The nZEB standard, mandated by European Directive 2010/31/EU, requires primary energy consumption below 100 kWh/m²/year for new residential buildings.

The energy calculation includes all thermal transmission factors, including linear thermal bridges (Ψ — psi) around windows. Without eliminating them, nZEB certification cannot be obtained even if walls, roof and floor are perfectly insulated.

In practical terms: uninsulated thermal bridges at 10 windows can equate to 15–20 kWh/m²/year in losses — enough to miss the nZEB threshold.

Correct Installation — Step by Step

1. Preparing the Opening

The masonry opening must be 6–8 cm larger than the window on each side. Surfaces clean, dry, dust-free.

2. Installing the Precasing

Fixed with chemical or mechanical anchors. Levelling is critical — maximum deviation 2 mm per linear metre.

3. Exterior Butyl Tape

Applied to the exterior face of the precasing, before fitting the window. Continuous sealing against water and wind.

4. Fitting the Window

The window is inserted into the precasing and secured. The gap between frame and precasing (8–12 mm) is filled with medium-density PU foam — not cheap expanding foam.

5. Interior Vapour Tape

Continuous tape on the interior — prevents vapour diffusion from the room into the installation cavity, avoiding condensation buildup.

6. Finishing

Interior window sills are fixed to the precasing, not the masonry — eliminates the final thermal bridge.

Additional Cost and Return on Investment

A complete installation with Blaugelb Triotherm+ costs 15–25% more than standard installation. For a house with 12 windows, the difference: 1,500–3,000 EUR.

Return: through heating savings of 20–35%, the investment is recovered in 3–6 years. Over 30 years of window life, net savings exceed the additional cost of precasings by 5–8 times.

Conclusion

At Neofort BIZ, all our installations include the complete Blaugelb perimeter insulation system. We do not supply windows without also guaranteeing correct installation. Contact us for assessment and quote.