advanced building skins 14 | 15 June 2012 - lamp.tugraz.at - Graz ...

Prof. Dr.nat.techn. Oliver Englhardt
Institute of Building Construction
Graz University of Technology
Copyright © with the authors. All rights reserved.
Novel Protection Against Radon
Torben Valdbjørn Rasmussen, MSc, PhD, Senior Researcher
Danish Building Research Institute, Department of Construction and Health at Aalborg
University, Dr. Neergaards Vej 15, 2970 Hørsholm, Denmark, email: tvr@sbi.aau.dk,
http://www.sbi.dk
Summary
A new principle for pressure reduction of the zone underneath the ground floor construction of
prefabricated lightweight elements were introduced and demonstrated. The principle was
demonstrated on a ground slab floor, constructed of a concrete slab on top of a thermal insulation
layer above a capillary-breaking layer mounted on stable ground. The thermal insulation and the
capillary-breaking layer consisted of a rigid insulation material. The novel solution introduced
integrates the capillary-breaking layer and a radon–suctioning layer in one element. The novel
solution introduces the radon-suction layer as a horizontal grid of air ducts with low pressure to
catch air and radon from the ground. The new principle was shown to be effective in preventing
radon from polluting the indoor air by introducing low pressure in the horizontal grid of air ducts.
A pressure lower than the pressure inside the building must be introduced. The element was
integrated into the insulation material of the ground slab floor. The element and the insulation
material were made of expanded polystyrene.
Keywords: Element, EPS, Radon, Protection
1 Introduction
Radon is a radioactive noble gas that develops as a result of the decay chains of uranium and thorium
(Clavensjö 2004). When radon decays into different radon daughters, it generates alpha, beta and
gamma radiation. Radiation is harmful to human beings. Radon originates in the ground and is the
primary source of natural radiation in most countries [1]. Therefore the geological character of the
ground, on which a building is situated, sets the level for how high the radon concentration of the
indoor air can become. Radon mainly penetrates into a building by air infiltration from the ground
through cracks or other unintended openings in the ground construction [2].
In 2009, the World Health Organization, WHO, recommended that requirements to the accepted
maximum radon concentration in the indoor air should be tightened from 200 Bq/m 3 to 100 Bq/m 3 .
The new recommendations are a result of WHOs evaluation that radon is responsible for 3-14% of
lung cancer incidents, depending on the average radon exposure in different countries [3]. These
results show radon as the second-largest cause of lung cancer; smoking is still the principal cause.
Radon exposure must be taken seriously in the fight against radon-induced lung cancer due to the large
number of people that are exposed daily in buildings and especially in residential buildings [3], as a
large number of residential buildings are built with a slab on ground. An investigation shows that if
people spend their whole life in a building with an average radon concentration in the indoor air
exceeding 200 Bq/m 3 , their risk of getting lung cancer is higher than 1%. This is far too high and
higher than what in other contexts is an acceptable single-factor risk [4]. Ensuring a good quality of
the indoor air includes a focus on radon and methods to control the radon concentration in the indoor
air.
In 2010, the requirements recommended by WHO were implemented in the Danish Building
Regulations. The Danish Building Regulations now stipulate a maximum radon concentration of 100
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