Case study Ludwigshafen

Over 1,800 windows, aluminum facade retrofitted without demolition

A 1970s building: precast concrete facing panels with massive aluminum elements behind them. ALU-THERMIC insulated and re-clad the exposed aluminum surfaces around the new windows – without touching the concrete panels.

Location: Ludwigshafen am Rhein, Germany
Built: 1977
Windows: over 1,800
Construction period: Q4 2025 – Q4 2026
Floors: 8
Color: RAL 7015 slate gray

Aerial view after the retrofit: high-rise and low-rise wings with light ribbed panels and slate-gray window bands — After

Aerial view of the complex before the retrofit: high-rise and low-rise wings with courtyard, a telecom tower on the left — Before

The project in figures

1,800+

windows in the concrete facing panels

7 × 4 m

aluminum elements behind each panel

30 mm

special insulation, λ 0.034 W/(m·K)

3 mm

aluminum, powder-coated

30 cm

concrete parapet

about 12

months of work

The starting point

The building dates from the 1970s and served Germany's federal postal service, the Deutsche Bundespost, for many years. After years of vacancy it was to be retrofitted for energy efficiency and given a visual upgrade – to serve as an office building.

The facade is solidly built: precast concrete facing panels, and behind each panel an aluminum facade element roughly 7 meters wide and 4 meters high. A great deal of heat escaped through these aluminum surfaces.

The concrete facing panels had to stay – that was a given. What was needed was a way to insulate and seal the old aluminum facade without demolition, adapted to the tolerances each panel has developed over some 50 years.

Aerial view of the complex in Ludwigshafen before the retrofit: high-rise, low-rise wings and courtyard — Before the retrofit, January 2025: high-rise and low-rise wings around a courtyard – more than 1,800 window openings. Photo: Weisenburger Bau GmbH

The solution, step by step

The windows were replaced; ALU-THERMIC insulated and re-clad the aluminum surfaces around them – almost entirely from the outside and without touching the concrete facing panels.

New windows

The old window sashes were removed and replaced with new PVC windows with triple glazing.
Aluminum surfaces insulated

The aluminum surfaces left exposed around the windows received 30 mm of special insulation with λ 0.034 W/(m·K). The pilaster strips between the concrete facing panels were overclad with the ALU-THERMIC profile.
Insulation profile and window sill in one

Below the windows, the insulation profile is combined with a window sill. It covers the 30 cm concrete parapet completely and sheds water cleanly.
Parapets, corners, intermediate profiles

The larger areas between the parapets were insulated with compressed stone wool; the corners and the old aluminum profile between the windows were insulated as well.

Row of windows on the roof terrace with the new window sill and insulated slate-gray aluminum cladding — Insulation profile and sill in one: the cover spans the full parapet.

Technical overview

Key data of the method – they apply to every project.

Thermal performance

Uninsulated aluminum profiles reach 5 to 7 W/(m²K), depending on when they were built. With 30 mm of special insulation, the U-value drops to 1 to 2 W/(m²K) – the exact value depends on the size of the covered profile, because edge effects count.

Fire protection

The special insulation meets building material class B2 under DIN 4102-1 (normally flammable), class B1 (flame-retardant) on request. Larger areas such as parapets are insulated with compressed stone wool.

Warranty and durability

5-year warranty. The insulation material lasts 30 years – even in sunlight and fully exposed to the weather.

Funding

Funding is possible. It is handled by the project's specialist planners.

Explained on site

How do you retrofit an aluminum facade when the concrete facing panels have to stay? The project team shows how on the roof terrace. In German, with English subtitles.

Before the retrofit

The building in 2024 and early 2025, before work on the facade began. Photos: Weisenburger Bau GmbH.

Drone shot at roof level: the high-rise before the retrofit, a telecom tower on the left, the city behind — At roof level: concrete facing panels and window bands alternate on every floor.

Aerial view of the high-rise before the retrofit: two wings with light concrete facing panels, a flat roof in front — Between the concrete panels: the window bands of the old aluminum elements.

The building's entrance before the retrofit: canopy, steps and weeds in the paving — The entrance after years of vacancy.

Close-up of the old aluminum frames: weathered bronze-colored profiles between the concrete panels — The old aluminum frames up close, marked by some 50 years of weather.

Building corner up close: two ribbed concrete facing panels with a pilaster strip between them — One of the pilaster strips between the concrete facing panels – they were later overclad with the ALU-THERMIC profile.

Project gallery

The high-rise during the works and after the retrofit.

View from the flat roof of the retrofitted high-rise with ribbed panels and slate-gray window bands — From the roof of the low-rise wing: the high-rise after the retrofit.

Close-up of the facade: light ribbed panels with slate-gray window bands in between — The concrete parapets stayed; the aluminum surfaces are insulated and re-clad.

Building corner with ribbed panels and large ground-floor windows — The corners were insulated as well.

High-rise during the retrofit: finished on the left, still scaffolded on the right — During the works: finished on the left, still in scaffolding on the right.

Oblique aerial view of the high-rise with the transmission mast on the roof — The aerial view captures the size of the building, which is to house around 580 workstations.

What this project proves

For owners of similar buildings, what counts is what has worked at scale.

Large scale

More than 1,800 windows in about a year: the method is designed for entire buildings, not just individual surfaces.

The existing structure stays

No demolition, no new facade: the concrete facing panels were kept and the existing aluminum structure was insulated.

Tailored, not standard

After some 50 years, every panel has its own tolerances. Insulation, sealing and covers were adapted to each opening.

Coordinated on site

Planned and carried out together with the general contractor on site – from the window replacement to the last cover.

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