"Look deep into nature, and then you will understand everything better. "

A. Einstein



The passive solar home "CRO HAUS" in its concept uses natural materials that have low CO2 emissions in its production, and the latest technology in energy and installations. By its thermal characteristics it is categorised as passive solar house and its final version has a tendency to become completely energy- independent of public infrastructure (EEB- "energy- efficient buildings").

Basic building materials are wood as construction, straw bales as a thermal insulation, and lime mortar, gypsum board, stone, wood cladding and others.



The house is built from parts- modules that are produced in the factory. This way all the work on a construction site that depends on the weather can be avoided. Building foundation is made as a combination of strap beams and column footings.

Wall modules are made of laminated beams filled with straw bales 40 cm thick and covered with lime mortar in a metal grid on both sides. Floor is made of the same parts and ceiling construction 50 mm thick is coated with OSB panels.

All the necessary lighting, heating, water supply and drainage installations are installed inside the walls.

All the exterior doors and windows are installed in the factory.


After assembling the outer walls, the ceilings are being mounted. They don't depend on outside walls and can be installed on various hights- mezzanine. In the middle of the house there is a triple chimney with ventilation and staircase that connects the mezzanines.

On the ceiling there is an exit on the roof with a light well that allows light to reach the central part of the house.

On the south there are larger openings required for passive solar operation and for electrosolar energy exploitation, while on the north there are smaller openings on the auxiliary spaces.




Family complex consists of a family house,a garage and an annex (maximal option).

The glazed side of the facilities is facing south and it's protected from summer overheating by high deciduous greenery.


In the ground floor of the residential building there is a living room, a kitchen and a dining room, service areas and a master bedroom with a bathroom.

Living room is directly connected with a terrace and an annex. An annex can be used as an indoor swimming pool, winter garden or a hobby room with a storage.

Garage for two cars is connected with service area of the residential building.


On the first mezzanine there is a working lounge that serves all the members of the household.

On the middle mezzanine there are two children bedrooms, a bathroom and a recreation area with a whirlpool bath.

On the last mezzanine there is a work room for the maintenance of the household. The stairs are taking you onto a green roof where you can find a space to relax and enjoy the peaceful activities.

The content of the mezzanines can be organized in different way, depending on the needs of the family.


Exterior walls are made as a ventilated facade with a natural stone cladding.

It can be made as a facade with a silicone plaster finishing.


Residential building can be organized without annex, with single or double garage.


Restidential building:

Netto areas:


Ground floor: 94 m2

Mezzanines: 94 m2


Total: 188 m2

Garden: 94 m2


Total: 282 m2

Garage: 58 m2

Annex: 43 m2

Terrace: 15 m2


Total: 398 m2






Primary mean of heating is hot water which is heated by an inverter heat pump that takes geothermal energy over the ground exchanger.


All the floors and external walls are heated, no matter of the position of the mezzanine floors. This makes a unique microclimate that can be regulated by using partial heating of individual wall panels.


The space can be ventilated naturally, but ventilation through ventilation ducts is recommended, especially during the winter period. Ventilation ducts are located in the chimney by the flue pipe where through metal walls internal heated air and smoke from the fireplace exchange with cold outside air (Effect of recuperation).


Wood fireplace is designed for heating during the transitional preiod and as serves a generator of positive microclimate using its infrared radiation. Natural fire with its light and smell has a very positive effect on people's mood.



As an additional possibility, it is suggested to build a green roof, especially in urban areas where the construction sites are smaller field of construction. Roof garden is a space ideal for leisure and growing plants, but also serves as a rainwater filter. It is especially used to prevent overheating of the attic spaces during the summer. Through the light well on the roof, the whole building can be naturally ventilated very effectively, but it's also important as a zenithal lighting of the central dark

spaces in the volume.


The building has a system for collecting and a use of rainwater. A rainwater reservoir can also be used as a heat treatment needed for the heat pump.


Openings are closed with timber windows of high quality with triple glazing.

All external glazings (window holes, fences, roof glazing) are made of Photovoltaic glass, which serves as an electrosolar collector with a capture of 50- 100 W/ m2. "Smart Glass" darken during the strong insolation and produce more electricity, but also prevent overheating of the space. Special regulation allow glass surfaces to be dimmed individually. Openings can be fully closed with thermal shutters.


Lightening system uses LED lights and, together with other devices (class AAA+), it consumes very little electricity, which makes its own production of the collectors on an average sunny day enough for their own needs.


If the building can't be connected to the public sewerage system, its own pit with biological treatment is being placed. Purified water is used for watering their own green areas.





The passive solar house "CRO HAUS" uses past experiences and knowledge in the construction of passive houses and represents a small step forward with its innovative solutions in space and energy. The main desire is to factory produce a high quality building that can compete with the price of a classical building, and offers all the qualities of passive solar construction housing. Preserving the environment is achieved by using natural materials with low CO2 emissions that can be recycled.


The concept combines classic natural materials and modern high technology, which represents in term of energy and other facilities completely independent building (EEB) suitable also for living in uninhabited areas.





Dubravko Ratkajec successfully passed the course Passivehouse Designer and Consultant by the Passivhaus Institut, Darmstadt, Germany.

The concept and design copyright of the Passive Solar House using Straw is registered by Hrvatska Autorska Agencija.

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