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Radon Programme and Czech Legislation 
Protection of New Buildings
Remedial Measures in Existing Buildings - Technical Solutions, Experiences
Human Perception of Radon Risk and Radon Mitigation
Remedial measures in existing buildings - technical solutions, experiences

Different methods were tested in the past: ventilation of indoor air with heat recovery, radon-proof membranes, protective coating of the floors, etc.

Nowadays, the sub-slab ventilation is considered the most effective system.

Principles of designing and application of various ventilation systems are published in CSN 730601 Protection of houses against radon from the soil.

Different systems:

  • one, or several perforated tubes drilled beneath existing floors (from the cellar, from an external chase, or from an internal chase);
  • one, or several radon sumps installed into the sub-floor region of the building;
  • a network of flexible perforated pipes inserted into the drainage layer of coarse gravel placed beneath the floors (reconstruction of floors necessary);
  • a combination of the above stated measures.

Example: old house with extremely high indoor radon concentrations

parameters of the ground             
cA75  = 71 kBq.m-3                             
k75  = 1.6 10-11 m2                              
RP (radon potential) = 88                                              
high radon index

average indoor radon values: about 35000 Bq.m-3 in habitable rooms; 77000 Bq.m-3 in the cellar   indoor radon concentration in the cellar was the same as the soil-gas radon concentration in the surroundings of the building
 very fast changes of indoor radon concentration were observed


Remedial measures were realized in 2005:
sub-slab ventilation and reconstruction of floors in almost all rooms;
sub-slab ventilation system consists of two independent sections
ventilation experiment:
4.8. 8.45 - 11.8. 9.30
  gradual start of the 1st section
11.8. 9.30 - 18.8. 10.15
  both sections in operation (maximum power)
  18.8. 10.15 - 22.8. 12.00
ventilation switch-off

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