World’s first Passive House in Kranichstein, Germany

On my last trip I visited Darmstadt, a German city located in the southern part of the Frankfurt Metropolitan Region. So, as an architect specializing in ecofriendly building design, I could not miss the opportunity to visit the world’s first Passive House in Kranichstein.

It is a row of four houses with a floor area of 156m² each, designed by the architects Prof. Dr. Bott / Ridder / Westermeyer and were built by Dr. Wolfgang Feist in 1991.

The three-storey terraced housing complex is divided into four equal homes and are sheltered beneath a large sloping planted roof. The house’s geometry, the orientation, the size and layout of the openings and the use of building materials with high thermal conductivity properties achieve thermal comfort and the healthy indoor air quality. 


A sunroom, placed on the north side of the complex, created an additional insulating layer, while offering a delightful entrance space.

The aim of this first prototype Passive House was to reduce the unnecessary heat losses through walls, roofs and windows so that a heating system would became completely irrelevant. In order to realize this promising concept they used existing components, such as lime-sandstone masonry walls, a rafter roof and wooden windows. However, a series of building components were developed such as the triple-glazed windows which were manufactured by the glass company Vegla (Saint Gobain today). Also, some components had to be manufactured separately in the workshop and therefore were more expensive in comparison with conventional construction components. This was also the case of the four central ventilation units which they equipped with specially developed direct current fans and a control unit for air quality. This balanced supply air and exhaust air ventilation system with a highly efficient counterflow air-to-air heat exchanger is continuously operating. Fresh air is supplied to the living and sleeping areas in each house and the stale air (extract air) is drawn away from the humid rooms, e.g. kitchen and bathrooms, in equal quantities. 

Cross-section of the Passive House in Darmstadt-Kranichstein.

The houses are equipped with solar collectors for the provision of domestic hot water and a subsoil heat exchanger for preheating the fresh air.

At the beginning of 2016, the western house of the complex was equipped with a brand new photovoltaic array with a surface of 26 m², reducing its primary energy balance further to meet the new Passive House Certification, Passive House Plus. The Photovoltaic system and solar collectors combined with the use of a subsoil heat exchanger, for preheating the fresh air, cover the energy needs for heating, hot water and electricity of the home with a sufficient surplus.

During construction in 1991, hundreds of sensors where placed in the individual building components in order to check the achievement of objectives. For the past 27 years, this air-tight, highly insulated and well-built terraced housing complex has been continuously put to the test. The results show that the house still offers high energy efficiency, comfort and savings, while at the same time having a very low ecological footprint.

Selected project details of the World’s first Passive House:

Architect: Prof. Dr. Bott / Ridder / Westermeyer
Building services: Ingenieurburo InPlan, Dipl.-Ing. Norbert Starz
Building physics: Dr. Wolfgang Feist

Construction type: masonry construction
Annual heating demand (PHPP): 14 kWh /(m2a )
Heating load (PHPP): 10 W/m2
Primary energy requirement (PHPP):  61 kWh /(m2a ) on heating installation, domestic hot water, household electricity and auxiliary electricity
Air tightness (PHPP):  n50 = 0.22/h
Basement ceiling: Surface finish on fibreglass fabric, 250 mm polystyrene insulation boards, 160 mm concrete, 40 mm polystyrene acoustic insulation,
50 mm cement floor finish, 8-15 mm of parquet, adhesive, sealing solvent-free. U-value: 0.13 W/(m2K)
Walls: Fabric reinforced mineral render, 275 mm of expanded polystyrene insulation (EPS) (installed in two layers at that time, 150+125 mm), 175 mm sand-lime brick masonry, 15 mm continuous interior gypsum plastering; wood-chip wallpaper, emulsion paint coating. U-value: 0.14 W/(m2K)
Grass roof: Humus, non-woven filter, root protective membrane, 50 mm formaldehyde-free chip board. Wooden light-weight beam construction (I-beam of wood, stud link of hardboard), counter lathing, sealing with polyethylene sheeting bonded without jointing, gypsum plasterboard 12.5 mm, wood-chip wallpaper, emulsion paint coating and an entire cavity 44.5 cm filled with blown-in mineral wool insulation. U value (hall roof): 0.10 W / m²K
Windows frames: Wooden window with polyurethane foam insulated framework (CO2-foamed, HCFC free, handcrafted) U-value: 0.79 W/2K
Glazing: Triple-pane low-e glazing with Krypton filling: Ug-value 0.7 W/(m²K). g -value = 50%
Entrance door: French window door with additional, handcrafted insulation the frame. U-value: 0.78 W/2K
Ventilation: controlled ventilation system with heat recovery (TemoVex, DK, measured heat recovery 80%. Counterflow air-to-air heat exchanger; Located in the cellar (approx. 9°C in the winter), carefully sealed and thermally insulated, the first one to use electronically commutated DC fans.
Heating installation: a wall-mounted condensing boiler (12 kW) for all four houses, very small radiators on the inner walls
Domestic hot water: Solar system with vacuum flat panels supported by the gas condensing boiler