There are many spectacular buildings in Beijing, China. CCTV Tower and Grand Millenium Hotel is one of these and also the common denominator that the Swedish company AB C.A. Östberg has provided technology that provides energy-efficient ventilation and a good indoor climate. Östberg’s headquarters is also in the Avesta and the road to Beijing might seem long.

The CCTV building in Beijing is one of the most sensational buildings that C.A. Östberg has contributed technology to.

“Since the 1980’s we have been developing various types of fans and energy recovery units and our products are available worldwide. We are among the leading manufacturers of fans and 85 percent of our products are exported. We sell to approximately 70 countries and Asia is of course an important market for us,” says Stefan Viberg, Quality Manager at C.A. Östberg.

A good indoor climate is not so obvious

The company’s history began more than 30 years ago when founder Hans Östberg worked to construct new types of duct fans. In 1981, he started a company to manufacture and sell the fans and in 1986 the company moved from Stockholm to Avesta.

“Since the beginning, we have focused on duct fans and the ever increasing demands from politicians and markets drives us to develop the technology further. Right now, the engine operation in the fans is under the microscope and we are working to improve the steering of the engines, which reduces energy consumption,” says Stefan Viberg.

What then is a good indoor climate?

The indoor climate affects our health and athletic performance and impacts on the property owner’s and employer’s costs.

A good indoor climate is not noticeable but the opposite we notice quickly – for example, by poor air or that it is too hot or draughty. What characterizes a good ventilation system is that you do not really notice that air is constantly changed, the temperature is just right or it does not drag and is not too noisy. To design a good indoor climate is not easy when there are many factors that must work together. For example:

  • The climate outside the building and outdoor air quality.
  • What is happening in the building, such as the activities and processes at work and the number of people there.
  • The building’s design, materials and furnishings.

“A good indoor climate is not obvious and duct fans are more important in this context than what you might think,” saysViberg. “Different types of fans have different uses, but what is common to them is that they should manage the inward transport of fresh air and to ensure that the used air leaves the building. The challenge is to get the fan to work with as low noise as possible in an energy efficient manner. We were first in Europe to develop small energy recovery units with rotary heat exchangers for villas and apartments at competitive prices,” says Viberg.

A winning concept

To recover energy from the air ventilation that is pulled out of a house is not news, but to develop a better and more efficient system, the Energy Agency in Sweden held a contest. C.A. Östberg had a tie for first place for an FTX unit (exhaust – supply – heat exchange), which best met the requirements of the energy and construction industry.

The hot air heats up a wheel of corrugated aluminium sheets during the hot season that then rotates over to the “cold” side to heat the outside air before it is blown into the building.

The company’s energy recovery technologies are applied in a product called Heru ®. The system is based on the hot air heating up a corrugated aluminium sheet – a so-called rotary heat exchanger. The heated portion is then rotated over to the “cold” side to heat the outside air before it is blown into the building (see photo). Thermal efficiency is 86 percent.

The system is equipped with a particle filter that prevents dust, pollen and other particles to enter. In practice, this means that the ventilation system pumps fresh tempered and filtered outside air at several places in the house, without being mixed with the outgoing air. Heru ® consists of a metal cabinet and is similar to a refrigerator or freezer and is just as silent.

Actions against radon

C.A. Östberg fans can also be placed in a “radon well” beneath the ground next to a building to prevent radon gas being sucked into the property.

Radon gas can occur in the soil under a building and in certain building materials. People exposed to high levels of radon can develop cancer. Increasing ventilation in the building through improved ventilation reduces the dangerous radon concentration. In some cases this is not enough, and the solution is to prevent the radon from being sucked into the property. This is another use for C.A. Östberg fans.



The fan is placed in a “radon well” beneath the ground next to the property. The fan sucks the air out of the soil under the building and the result is that the air pressure in the soil is reduced. Radon gas is thereby prevented from penetrating into the building. A prerequisite for a radon well is of course that the land can breath, such as on a ridge, and that the radon gas is pumped away from the property.

The article was published in December 2013