Civil Engineering Reference
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which radon levels cannot be reduced by sub-slab depressurization; for the area
analyzed, this threshold falls in the range 50-70 Bq/m
3
.
Jiranek and Rovenska (
2010
) analyzed the cost-effectiveness of 32 houses and
found no significant difference between the types of soil depressurization systems
studied and the remaining dose level. These authors mention that ''in comparison
with enhanced natural ventilation of houses, the cost of additional heating to
eliminate the heat losses would exceed the total costs of remediation by soil
ventilation eightfold,'' thus concluding that the application of any type of sub-slab
depressurization system is a cost-effective solution.
5 Radon from Building Materials
5.1 Masonry and Decorative Materials
Until very recently, it was generally accepted that only 5 % of the indoor radon
concentration was due to building materials (Lao
1990
). This is why, for a long
time, the scientific community has not dedicated a lot of research efforts on this
issue. Radioactivity in building materials has been included in the Construction
Products Directive (Pacheco Torgal and Jalali
2011
; Pacheco Torgal et al.
2012
),
but this has still not led to any corresponding standards being adopted by the
European Committee for Standardisation.
Recently, a final proposal Directive COM 593 (
2011
) that lays down basic
safety standards for protection against the dangers arising from exposure to ion-
izing radiation has been disclosed. This proposal mentions a 2-year deadline in
order for the member states to make the transposition of the new directive into
national law.
Pavlidou et al. (
2006
) state that the majority of granitic rocks have low radon
exhalation rates.
Fokianos et al. (
2007
) mention that houses with granitic floor tiles have a higher
indoor radon concentration when compared to houses without this kind of floor;
however, they also mention that the radon concentration is not much higher than
anthropogenic radon emissions.
Chen et al. (
2010
) analyzed 33 different types of granites and mentioned that
only two of them had exhalation rates above 200 (Bq/m
2
d). These findings were
confirmed by others (Pavlidou et al.
2006
). These authors studied the combined
influence of indoor air ventilation rate and granite exhalation rates serving as floor
materials, concluding that the highest granite exhalation rate serving as floor
material in a place with a low ventilation rate (ACH = 0.3) contributes only with
18 (Bq/m
3
) to the total concentration (Table
5
).
However, to ACH levels near-zero, high exhalation rate granite can effectively
be responsible for toxic radioactive concentrations. According to these authors, the
radon concentration due to radon exhalation rate is given by
