Zdravotní ústav upozorňuje na zdraví nebezpečné domy typu OKAL The Health Institute warns about health hazards of OKAL-type houses

Prague – Almost all prefabricated wooden houses of the OKAL type from the 1970s contain carcinogenic formaldehyde and asbestos fibers. They also often have issues with mold. This was stated today in a press release by the State Health Institute (SZÚ). It appeals to potential buyers to have the house inspected by an expert.

SZÚ recommends measuring formaldehyde concentrations in at least two rooms – on the ground floor and in the attic – before purchasing an older OKAL family house. The rooms must not have been ventilated beforehand, and the indoor temperature should be at least 20 degrees Celsius. Disposable indicator devices, which detect elevated formaldehyde concentrations, can also be used as a rough estimate. Formaldehyde was used as a binding agent in chipboard, and it is released as a gas.

Karel Vrbík, head of the National Reference Center for Emissions from Construction Products, warned about the naivety of potential buyers who do not find it suspicious that properties of this type are being offered for a fraction of the usual housing price. According to his information, some OKAL family houses 5+1 are being offered for one koruna. However, on the sreality.cz website, it is also possible to find an offer for a similarly sized OKAL house in original condition for 15 million korunas. Prices therefore vary.

"The construction of the house consists of a wooden post system clad with chipboard on the inside and asbestos-cement boards on the outside. The space between the inner and outer boards is filled with thermal insulation. The inner glued chipboards from the early 1970s are almost without exception a source of formaldehyde, while asbestos fibers can be released from the outer cladding," Vrbík stated.

According to him, another problem is the fill located between the cladding. "In areas with insufficient insulation, thermal bridges are created, where moisture condenses, leading to mold formation, and thus begins an endless battle with it," he added. The problem with the house is often exacerbated by the installation of new windows, which increases the concentration of carcinogenic formaldehyde due to reduced natural air exchange. Symptoms may include irritation to cough, burning eyes, and tearing.

SZÚ pointed out that before intervening in the outer cladding of the house, it is necessary to remember the asbestos-cement boards it is usually made of. These are considered hazardous construction waste and can only be handled by trained workers from specialized companies. Therefore, it is necessary to check before reconstruction whether the outer cladding contains asbestos, and to have it removed by a professional company.

When replacing thermal insulation materials, it is also important to replace the original internal cladding with new one that has guaranteed zero-emission parameters. The original boards, which still emit formaldehyde, can also be covered with special drywall boards that can actively absorb formaldehyde.

The first OKAL was built in the early 1970s, when the then national enterprise Rudné doly Jeseník purchased production and assembly licenses from the German company OKAL – Otto Kreinbaum.