LichtAktiv Haus, Hamburg, Germany

To demonstrate how energy-efficient architecture and high livability can be combined in the modernisation of old houses, the VELUX Group set out to turn a classic 1950s semi-detached home into a carbon-neutral building of the future with a vision of abundant natural light, fresh air, open views – and clean, renewable energy.

From classic 1950s house to a carbon-neutral home

The project transformed a so-called ‘settler house’, designed in the 1950s and situated in the Wilhelmsburg district of Hamburg, into a modern construction with a settler’s self-sufficient spirit where energy was concerned.

The home’s box-like, closed structure was reorganised into a series of open, spacious rooms flooded with natural light. A new modular extension with beautiful views of the large garden created an open kitchen, living and dining area. New openings in the roof of the extension, referred to as a ‘daylight lamp’, expanded the interior and brought in plenty of light. And a five-metre-long, garden-facing glass façade expanded the environment horizontally, with the porch becoming a link between the old and the new.

The LichtAktiv Haus also contains a master bedroom, two children’s rooms, and two bathrooms. New façade and roof windows – installed in all the rooms and positioned to ensure the best distribution of natural light and excellent natural ventilation – have dramatically increased the total window area from 18 m² to 60 m².

The energy-efficient design concept, which relies on solar energy, numerous façade and roof windows, and a natural ventilation system, turned a traditional home into a carbon-neutral one that pays tribute to the past while embracing the future.

The increase in light has been the most noticeable plus over the dark winter months. In our old flat, my first reaction was always to reach for the light switch.
In the beginning, I didn’t even know where they were in the LichtAktiv Haus – even when it’s overcast outside, it’s always bright enough inside."

Oldendorf Family, residents

Photos: Merrild Photography

Key design elements and achievements

Modular modernisation

The new LichtAktiv Haus design retained the basic structure of the existing building while adding a modular extension and applying new materials and energy-efficient technology.

Ample daylight

Daylighting design played a central role in the architectural concept of the LichtAktiv Haus, as daylight is vital to our biological rhythm and has a positive impact on our well-being and performance. Optimised, controlled daylight use also reduces the need for artificial lighting and provides useful solar gains during the winter period, significantly reducing the building’s energy consumption.

The LichtAktiv Haus project team worked with lighting designer and professor Peter Andres, using extensive daylight analyses in the early project design phase and integrating them in the dynamic process of building planning. As a result, the LichtAktiv Haus’ kitchen, dining areas and bedrooms have an excellent average daylight factor (DF) of 5% or more, while the living area has an average DF of over 10%, meaning no artificial lighting is needed during a typical day.

High amounts of daylight and generous views enable the family to fully experience the daily rhythms and seasonal changes of their surroundings. Awning blinds, on the other hand, allow them to adjust the amount of incoming daylight, prevent glare and overheating – and create a flexible, comfortable environment.

Automated, natural ventilation

Despite its lack of a heat recovery system or central air conditioning, which are often too costly to implement in older homes, the LichtAktiv Haus is able to achieve carbon-neutrality. Here, the home’s automated roof windows make a remarkable contribution by providing natural ventilation.

Together with shutters and sun screening products, the ventilation concept works as natural air conditioning. During warmer periods, the south-facing shutters remain closed at midday. On the western side, the external awnings automatically lower in the afternoon. As the day gets cooler, the shutters and awnings are raised and the windows opened to let the fresh evening air cool down the living space.

During cooler months, the shutters stay up during the day to allow passive solar heat to warm the home, closing at dusk to keep the heat inside. Automatically controlled roof windows eliminate the need for a ventilation shaft. And, depending on the home’s temperature and humidity and CO2 levels, a solar-powered control system automatically opens and closes the windows to ensure a comfortable, healthy indoor climate at all times.

Solar energy

Following a core Active House principle, the LichtAktiv Haus covers its entire energy demand, including household electricity, by using renewable energy – without losing any of its high living values such as daylight and fresh air. This is particularly challenging to achieve when renovating older homes as they often have much higher energy demands.

An air-water-heat pump and 22.5 m² of solar collectors work together to supply the home with heat and hot water. This highly efficient technology reduces greenhouse gas emissions by minimising the need for conventional energy. The home’s 75 m² of polycrystalline photovoltaic (PV) cells on the roof power the heat pump and also act as a source of environmentally friendly electricity.

Rainwater collection

Along with water-saving fixtures throughout the house, the LichtAktiv Haus is also equipped with water collectors that supply rainwater for the washing machine, toilets, and garden watering.

Daylight factor

An avarage DF below 2% generally makes a room look dull and electrical lighting is likely to be frequently used, whereas an interior will look substantially daylit when the avarage DF is above 5%

Simulations were made by the VELUX Daylight Visualizer 2, a software tool dedicated to daylighting design and analysis. For more details and download, visit

LichtAktiv Haus Daylight Visualizer


Katharina Fey (TU-Darmstadt ee) and Professor Manfred Hegger.

Work-planning architects:
Ostermann Architekten.

HL-Technik, Peter Andres Lichtplanung, TSB-Ingenieure.

Product suppliers:

Cooperation partners:
Knauf, Eternit, Grohe, Keramag, Nolte Küchen.