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Martin Jiránek
E-mail: jiranek@fsv.cvut.cz
CZECH TECHNICAL UNIVERSITY
Faculty of Civil Engineering, Praha
Department of Building Structures
Thákurova 7, 166 29 Praha 6, Czech Republic
RADON PREVENTIVE
AND REMEDIAL MEASURES
IN THE CZECH REPUBLIC

History of radon prevention in the Czech
Republic
• Realization of preventive measures became obligatory in
1991 by the degree of Ministry of Health
• Since 1991 each building built on a building site with
medium or high radon index must be protected against
radon from the soil
• We estimate that approx. 2/3 of new buildings require
protection, i.e. 12.000 each year
• Since 1991 the preventive measures were realized in
approx. 200.000 buildings

ČSN 73 0601
Protection of buildings against radon from
the soil, 1995, 2000, 2006
ČSN 73 0602
Protection of buildings against radon and
gamma radiation from building materials, 2000, 2006
Radon – Building Context
– detailed manual for
building professionals
Documentation supporting the design
Principles of designing and application of various types of
radon reduction techniques are presented in the following
standards:

The type and the degree of protection depends on the
“radon index”
of the building site (low, medium, high).
Radon index
Principle of protection
Low
No special protection is required.
Medium
The basic measure is a
radon-proof
insulation.
High
Radon-proof insulation is usually
combined with:
sub-slab depressurization
air gaps ventilation
mechanical ventilation of indoor air
PRINCIPLES OF PROTECTION

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Radon-proof insulation
radon diffusion coefficient
of the insulation must be
measured
durability
must correspond to the lifetime of the building
Prohibited materials
Radon-proof insulation is selected from standard
waterproofing materials.
Bitumen membranes with Al foil and plastic membranes with
dimples (Delta, Platon, Tefond, etc.)

Determination of the Rn diffusion coefficient
Systematic testing started in 1995 according to the method
developed by the Faculty of Civil Engineering in
cooperation with the National Radiation Protection Institute
The Czech test method is accredited by the Czech
Accreditation Institute
Up to now more than 400 materials obtained throughout
Europe have been tested
The tests of radon diffusion coefficient are required by the
Czech technical standard ČSN 73 0601 „Protection of
buildings against radon from the soil“

Summary of radon diffusion coefficient
measurements
1,00E-15
1,00E-14
1,00E-13
1,00E-12
1,00E-11
1,00E-10
1,00E-09
1,00E-08
1,00E-07
Epoxy paint
PU paint
Bentonite geotextile
Prehydrated bentonite
PE coated bentonite geotextile
HDPE laminated to bentonite
Cement coatings
Polymer cement coatings
Bitumen coatings
Bitumen membranes
Modified bitumen membranes
Modified bitumen and HDPE film
Bitumen membranes with Al film
PVC-P membranes
Recycled PVC-P membranes
HDPE membranes
HDPE dimpled membranes
LDPE membranes
PE vapour barriers
TPO membranes
PP membranes
EVA membranes
EPDM membranes
CPE membranes
ECB membrane
PVB membrane
Radon diffusion coefficient (m2/s)
Measured by the Faculty of Civil Engineering of CTU
and National Radiation Protection Institute

Application of the radon diffusion coefficient
for the design of radon barriers
1. Limit for the maximal value of D
Applied for example in Ireland (max D = 12.10
-12
m
2
/s )
2. Limit for the minimal thickness of the membrane
Applied for example in Germany (d 3l)
3. Calculation of the membrane thickness in
dependence on the soil and building characteristics
Applied for example in Czech Republic

Thickness of the radon-proof insulation
C nV
lC
A
A
dl
dif
S
f
w
..
....( )
.arcsinh
1
C
s
…radon concentration in the soil gas (Bq/m
3
)
…..radon decay constant (0,00756 h
-1
)
d
…..thickness of the membrane (m)
l
….. radon diffusion length in the membrane
l
= (
D
/ )
1/2
(m)
D
…. radon diffusion coefficient in the membrane (m
2
/h)
1
…safety factor
A
f
A
w
.floor and wall areas in contact with the soil (m
2
)
n
……ventilation rate (h
-1
)
C
dif
…fraction of reference level caused by diffusion (Bq/m
3
)

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Verification of the air-tightness of joints by the
radon diffusion coefficient
SBS modified bitumen
membrane
(7,1
0,2).10
-12
Overlap joint sealed by
torching
(8,6
1,0).10
-12
Self-adhesive overlap
joint
1,2.10
-8
- 1,7.10
-11
Joints of self-adhesive membranes should be sealed by torching.
HDPE dimpled membrane
(4,1
0,1).10
-12
Overlap joint sealed by self adhesive tape
(7,4
0,7).10
-10
According to CSN 73 0601 it is not permitted to apply dimpled
membranes for radon barriers.

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Thermal protection X radon protection
Thermal insulation XPS 80 mm
Perimeter air gap
Head joint – free of
mortar
Hollow clay blocks
Internal plaster
Perimeter air gap
Hollow clay
blocks
Damp-proof
membrane
(DPM)
Thermal
insulation
Section A - A
Thermal insulation XPS 80 mm
Perimeter air gap
Head joint – free of
mortar
Hollow clay blocks
Internal plaster
Perimeter air gap
Hollow clay
blocks
Damp-proof
membrane
(DPM)
Thermal
insulation
Radon-proof insulation must prevent radon from penetrating through
an air gap between perimeter thermal insulation and foundations
Elimination
of thermal
bridges
should not
result in
radon
bridges

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Eliminating radon bridges
Interrupting an air gap between perimeter thermal insulation and
foundations
Hollow clay blocks
Radonproof
membrane
Continuous HDPE
membrane with airtight
joints
HDPE corner strip
Bitumen radonproof
membrane
Bit. bonding primer
Protective fabric

Combined systems
Combined systems are applied in
houses with habitable rooms on the
floors in direct contact with the soil,
when:
Highly permeable gravel layer is placed under the house
Floors resting on the soil are equipped with under-floor
heating
Radon index of foundation soils is high

Vertical exhaust PVC pipe
Roof fan or rotating cowl
to improve the draught
Drainage layer of
coarse gravel
Interconnecting
PVC pipe
Perforated flexible
pipes
Radon-proof
insulation
Vertical exhaust PVC pipe
Roof fan or rotating cowl
to improve the draught
Plastic foil with
dimples forming
an air gap
Vented air gap between
concrete slab and radon-
proof insulation at a
height from 10 to 20 mm
Radon-proof insulation
+ sub-slab ventilation
Radon-proof insulation
+ air gaps ventilation
Combined systems

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Sub-slab ventilation systems

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Geometry of sub-slab ventilation systems

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Floor air gaps ventilation
An air gap below the radon-proof membrane
Air gap
Radonproof
membrane
Concrete base
Exhaust pipe
Airtight pipe
penetration
Vent holes

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Floor air gaps ventilation
An air gap above the radon-proof membrane
Radonproof
membrane
Air gap
Airtight joint to the the wall
Exhaust pipe
Airtight socket
joint
Collar
Self-adhesive
tape

REMEDIATION OF EXISTING BUILDINGS
The type and the degree of remedial works depend on the
level of indoor radon concentration
and results of
diagnostic measurements
performed in the building.
Indoor radon concentration < 600 Bq/m
3
Simple methods
(sealing of entry routes, improving ventilation, etc.)
Indoor radon concentration > 600 Bq/m
3
More effective methods
(sub-slab depressurization, replacement of
existing floors, mechanical supply and exhaust air ventilation)

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Natural ventilation supported by outdoor air inlets
Mechanical exhaust air ventilation with outdoor air inlets
Types of outdoor air inlets
Outdoor
air inlet
Exhaust fan
Window registers
Wall registers
Improving ventilation

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Improving ventilation
Mechanical supply and exhaust air ventilation - local
ventilation units with heat recovery
Intended for application in particular rooms with the floor area < 45 m
2
.
Typical characteristics:
Power: 4 – 25 W
Air flow: 15 – 60 m
3
/h
Noise level: 17 – 49 dB(A)
Efficiency of heat
recovery:
<
75 %

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Network of flexible perforated pipes
inserted into the drainage layer

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Perforated tubes drilled from the external trench

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Example of application
Indoor radon
concentration before
mitigation:
1 145 Bq/m
3
Fan NPV 190/125 above the
terrain
Drilled pipes
60
mm, D = 5,0 m
PVC
110 mm
PVC
110 mm
PVC
80 mm
PVC
125 mm
WC
LIVING
ROOM
BEDROOM
KITCHEN
HALL
BATHROOM
STOREROOM
Single family house

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Details of remedial measures
Existing floor
Drilled pipe
60 mm
PU foam
Borehole Ø
80 mm
PVC pipe
Ø 60 mm
PVC pipe Ø
80 – 125 mm
Backfill
Backfill
PVC pipe Ø
80 – 125 mm
PVC pipe Ø
125 mm
Wall
Fan at the
height min.
600 mm
above the
terrain

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Details of remedial measures

Indoor radon concentration after remediation
During active ventilation indoor radon concentration
decreased to the mean value 152 Bq/m
3
.
0
200
400
600
800
1000
1200
1400
6.11.10
8.11.10
10.11.10
12.11.10
14.11.10
16.11.10
18.11.10
20.11.10
Radon concentration (Bq/m3)
kuchyň
obývací pokoj
ložnice
Kitchen
Living room
Bedroom
Fan in operation
Fan in operation

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Perforated tubes drilled from the cellar

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Example of application
Indoor radon
concentration before
mitigation:
3 240 Bq/m
3
LIVING ROOM
+
KITCHEN
WC
BATHROOM
HALL
RESTROOM
Single family house

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Details of remedial measures
PVC
80 mm
Exhaust PVC
pipe
125
mm inserted
in a free flue.
Fan installed
above the
roof.
PVC
100 mm
PVC
125 mm
Drilled pipes
60
mm, D = 5,0 m
CELLAR
Drilled pipe
60 mm,
D = 2,5 m
Drilled pipe
60 mm,
D = 3,0 m

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Details of remedial measures
Drilled pipe
60 mm
PU foam
Borehole
Ø 80 mm
PVC pipe
Ø 60 mm
PVC pipe Ø
80 – 125 mm
Existing floor
Brick vault

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Details of remedial measures
Fan NPV
190/125 at
the top of
the
chimney
Exhaust
PVC pipe
125 mm
inserted in
a free flue.

Indoor radon concentration after remediation
During active ventilation indoor radon concentration
decreased to the mean value 223 Bq/m
3
.
0
1500
3000
4500
6000
16.12.10
18.12.10
20.12.10
22.12.10
24.12.10
26.12.10
28.12.10
30.12.10
Radon concentration (Bq/m3)
př. - pokoj s krbem
př. - obýv. pokoj + kuchyň
patro - obývací pokoj
patro - ložnice sever
Fan in operation
Fan in
operation
Living room
Bedroom, 2
nd
floor
Restroom
Liv. room, 2
nd
floor

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Perforated tubes drilled from the internal pit

THANK YOU FOR YOUR ATTENTION