United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S8-89/001 Dec. 1989
AEPA Project Summary
Radon Reduction and Radon
Resistant Construction
Demonstrations in New York
Ian Nitschke
This report covers three tasks re-
lated to indoor radon: the demonstra-
tion of radon reduction techniques in
8 houses in each of 2 uniquely dif-
ferent radon prone areas of the State
of New York; the evaluation and re-
pair of 14 radon mitigation systems in
houses mitigated 4 years earlier, and
the development and application of
radon resistant new construction de-
signs in 15 different houses. In the
application of radon reduction tech-
niques in existing houses, tech-
niques which were applicable in ex-
tremely porous soil were not as
easily applied to houses built on a
granite ledge; combinations of tech-
niques may be required in many dif-
ficult houses before an acceptable
radon level can be achieved. During
this study basement pressurization
was applied as a radon reduction
technique for the first time. In eval-
uating previous radon mitigation in-
stallations, polyurethane sealants
which were still effective after 4 years
and butyl rubber sealants which had
failed during the first 4 years were
identified. Also, small fans commonly
used in computer applications were
shown to fail and larger in-line
centrifugal duct fans were still in
service after 4 years. The radon
resistant new construction designs
should demonstrate effective meth-
ods of sealing out radon during con-
struction; however, quality control
problems prevalent in the construc-
tion industry may make additional
laboratory tests necessary to verify
the effectiveness of some sealing
techniques.
This Project Summary was devel-
oped by EPA's Air and Energy En-
gineering Research Laboratory, Re-
search Triangle Park, NC, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Introduction
The current New York State radon-
mitigation project has three broad task
areas:
• Demonstrate Cost-Effective Tech-
niques in Existing Houses,
• Assess Previously-Installed Tech-
niques in Existing Houses, and
• Demonstrate Radon Resistant Con-
struction Techniques in New Houses.
Initial results from each of these task
areas are summarized below.
Demonstrate Cost-Effective
Techniques in Existing Houses
Sixteen single-family detached houses
were studied, eight in Albany and
Rensselaer Counties (coded with the
prefix AR), and eight along the lower
Hudson River valley in Orange and
Putnam Counties (coded with the prefix
OP). The houses represented an assort-
ment of construction styles. Most were of
wood frame construction above grade, al-
though one had full-height (two stories
plus basement) masonry walls. Substruc-
ture types included finished and un-
finished basements, crawlspaces, com-
binations of basements and crawlspaces,
and combinations of basements and slab-
on-grade houses. Both hollow concrete
block and poured foundation walls were
found, as well as a variety of heating
-------
systems and foundation openings. Initial
screening measurements of the houses
ranged from 20 to 180 pCi/l. These
screening measurements were taken
during August, September, and October
1986 for the Orange and Putnam County
houses and during October and
November 1986 for the Albany and
Rensselaer County houses.
Field teams visiting each house during
November 1986 and February 1987 per-
formed a series of diagnostic procedures
including radon grab sampling, vacuum
tests of air communication, and blower-
door tests. Connectivity beneath slabs,
within concrete block walls, and between
slabs and concrete block walls was char-
acterized using chemical smoke and
tracer gases. Health department meas-
urements of radon concentrations in the
water were also noted. The results of
these diagnostic tests were then used to
select appropriate mitigation measures.
Mitigation measures used in this task
included sealing soil gas entry routes by
caulking or parging; sub-slab depres-
surization with and without interior footing
drains; sub-film depressurization (i.e., de-
pressurization under an installed plastic
film barrier); exterior footing drain de-
pressurization; block wall depressuriza-
tion; basement pressurization; and water
treatment using granular activated
carbon, diffused bubble aeration, and
packed tower aeration. Multiple mitigation
phases were planned where possible, so
as to develop comparative data on the
effectiveness of alternative approaches.
Table 1 summarizes the mitigation
techniques installed in these houses, and
provides an estimate of the effectiveness
of each technique, based primarily on
continuous radon monitoring results in
the screening measurement location
(basement).
The performance of the various mitiga-
tion techniques installed in this task may
be summarized as follows (refer also to
Table 1).
Sealing
Caulking cracks and openings as a
stand-alone mitigation technique was
tested in six houses (AR-01, AR-09, AR-
16, AR-17, AR-20, OP-09). It produced
reductions ranging from 2% (AR-01) to
74% (AR-20), with the bulk of the
reductions above 50%. This is a sur-
prisingly strong showing for caulking
alone and may indicate the potential for
further reductions if more careful caulking
is performed.
Parging a porous poured concrete
foundation wall surface was attempted in
only one house (OP-09), and produced a
37% reduction in radon levels.
Sub-Slab Depressurization
Sub-slab depressurization without seal-
ing was used in eight houses (AR-04, AR-
05, AR-09, AR-16, AR-17, AR-19, AR-20,
OP-01), and produced reductions ranging
from 4 to 95%. Half of the reductions
were in the 90-95% range.
Depressurization in houses AR-16 and
AR-20 was applied to a sump connected
to a complete loop of interior footing
drains and resulted in the greatest
reductions of the sub-slab depressuriza-
tion systems (95 and 94%, respectively).
Active sub-slab depressurization with
sealing was used in six houses (AR-16,
AR-17, AR-20, OP-09, OP-13, OP-17),
and produced reductions ranging from 35
to 93%, with all but one house in the 82-
93% range. The 35% reduction with this
approach was seen in house OP-13, in
which exterior footing drain de-
pressurization worked dramatically better
than sub-slab depressurization.
Sub-slab depressurization at four
perimeter suction points was compared
to depressurization at a single central
suction point in house OP-01. The de-
sign, which used four perimeter suction
points and a regenerative fan, produced a
47% reduction in radon concentration,
while the design which used a centrifugal
fan and a single, central suction point
produced a 31% reduction. The most
effective radon mitigation technique for
this house was apparently outside block
wall depressurization, which resulted in
an 86% reduction, relative to pre-mitiga-
tion levels.
Sub-Film Depressurization
Depressurization beneath an installed
barrier was used in one house (OP-05) to
treat a rock outcrop which was an iden-
tified source of radon. This technique
produced an 81 % reduction in radon con-
centrations compared to pre-mitigation
levels.
Exterior Footing-Drain
Depressurization
Only one house was treated with ex-
terior footing-drain depressurization
(using an existing footing drain around
the exterior of the house). This house,
OP-13, showed a 35% radon reduction
with sealing plus sub-slab depressuriza-
tion, while sealing and exterior footing
drain depressurization showed a 79%
reduction.
Block Wall Depressurization
Outside wall depressurization (indepen-
dent of other active depressurization sys
tems) was used in three houses. Re
ductions of 98% (AR-01, with sealing
and 86% (OP-01, no sealing) were pro
duced in two houses with relative);
straightforward installations. House OP-1J
was treated with passive wall venting am
active wall depressurization. Passive ven
tilation combined with sealing produce'
reductions of only 28%; active de
pressurization improved the reductions t
59% (relative to pre-mitigation levels
The critical action for this house appear
to have been foaming the block core
above grade. This step, combined wit
active wall depressurization, resulted i
radon reductions of 96% compared I
premitigation levels.
Inside wall depressurization was als
tested in three split-level houses (on tt
inside block wall common to the basi
ment and the slab-on-grade). However,
each case, wall depressurization w<
combined with sub-slab depressurizatk
and so there are no data for inside w.
depressurization alone.
Basement Pressurization
Basement pressurization was used
only two houses, AR-09 and AR-17. F
house AR-17, pressurization reduc
initial radon concentrations by 98
Although sealing alone had produced
61% reduction in this house, the alrea
high performance of the pressurizati
system was not measurably improved
sealing. So far there are no baserm
pressurization results for house AR-09.
Water Treatment
Water .treatment was applied in 1
houses with high radon levels in
water (house OP-03 with approximat
400,000 pCi/l and house OP-05 with
proximately 200,000 pCi/l). It was
successful enough to be a stand-all
mitigation technique in either installat
nor was it expected to be since the
mary sources of radon were the ro
and soil under the foundation.
Use of a granular activated charcoa
ter reduced initial radon concentrati
by 34% in the bathroom of house OP
Adding sub-slab depressurization
sealing reduced radon levels by f
(from 21.9 to 8.8 pCi/l) in the lower I
family room. However, the radon d(
products captured in the charcoal filte
troduced serious gamma radiation p
lems near the filter which was locate
a small utility room next to the often i
laundry room and bathroom. The
-------
Table 1.
House
No.
AR-01
AR-04
AR-05
AR-09
AR-16
AR-17
AR-19
AR-20
OP-01
OP-03
OP-05
OP-06
OP-09
OP- 7 3
OP-16
OP -17
Summary of Results from Demonstration of Techniques in Existing Houses
Integrated Radon Concentration (pCi/l)
Percent
Style Phase Mitigation Technique Before After Reduction
Raised
Ranch
Split-
level
Split-
level
Split-
level
Cape
Cod
Cape
Cod
Colonial
Ranch
Colonial
Bi-level
Ranch
Ranch
Colonial
Bi-level
Raised
Ranch
Bi-level
1
2
1
2
1
2
1
2
3
4
1
2
3
1
2
3
4
5
1
1
2
3
1
2
3
1
2
3
1
2
3
0
1
2
1
2
1
2
3
1
2
Sealing
Sealing plus OWD
SSD
SSD plus IWD plus sealing
SSD
SSD plus IWD
SSD
SSD plus IWD plus sealing
Sealing only
Sealing plus BP
SSD (interior footing drain)
Sealing only
SSD plus sealing
SSD
BP
Sealing only
SSD plus sealing
BP plus sealing
SSD
SSD (interior footing drain)
Sealing only
SSD plus sealing
SSD (regenerative fan 4 suc.pts)
SSD (centrifugal fan 1 suc.pt)
OWD
Charcoal filter
Filter plus SSD plus sealing
Filter plus SSD plus sealing plus aeration
SFD
SFD plus OWD
SFD plus OWD plus aeration
(Long-term control house)
Sealing (parge walls, seal cracks)
SSD (regenerative fan 4 suc.pts)
Sealing plus EFDD
Sealing plus SSD
Sealing plus passive OWD
Sealing plus active OWD
Sealing plus active OWD plus foaming
Sealing plus passive SSD
Sealing plus active SSD
17.5
17.5
22.8
22.8
21.3
21.3
22.5
22.5
22.5
22.5
15.5
15.5
15.5
23.6
23.6
23.6
23.6
23.6
30.4
35.7
35.7
35.7
20.6
20.6
20.6
37.3
21.9
21.9
232
232
160.3
7.2
23.5
23.5
13.9
13.9
55.4
55.4
55.4
37.1
37.1
17.1
0.4
13.2
2.2
4.2
1.9
1.5
0.4
9.9
NA
0.8
5.7
1.7
2.2
0.5
9.1
1.6
0.5
29.1
2.3
9.3
6.4
11.0
14.3
2.8
24.8
8.8
3.0
44.2
8.5
1.0
--
14.7
3.4
2.9
9.1
40.1
22.7
2.3
39.3
3.1
2
98
42
90
80
91
93
98
56
NA
95
63
89
91
98
61
93
98
4
94
74
82
47
31
86
34
60
86
81
96
99
—
37
86
79
35
28
59
96
-6
92
BP = Basement pressurization
EFDD = Exterior footing-drain depressurization
IWD = Inside wall depressurization
NA = Data not yet available
OWD = Outside wall depressurization
SFD = Sub-film depressurization
SSD = Sub-slab depressurization
system combined diffused bubble
aeration with charcoal filtration (after
aeration), sealing, and sub-slab depres-
surization for a reduction in the lower
level family room of 86% compared to
pre-mitigation radon levels.
A third method of removing radon from
water was also tested temporarily in
house OP-03, in which the aeration was
provided by air blowing through a packed
tower. Two tower lengths were used.
Radon concentrations in the water were
reduced by more than 99% with the
charcoal filter, more than 99.5% with the
diffused bubble aeration system, approxi-
mately 85% with the packed short tower
aeration system, and approximately 92%
with the packed tall tower aeration sys-
tem. Since the radon stripped from the
water in aeration systems is vented to the
outdoors, gamma radiation is not a prob-
lem (unlike charcoal filter systems where
radon and progeny are trapped in the
filter medium).
In house OP-05, aeration was not
tested independent of sub-film depres-
surization and wall depressurization.
Starting at a pre-mitigation crawlspace
level of 232 pCi/l, a combined sub-film
and wall depressurization system pro-
duced a 96% reduction in radon con-
centrations to 8.5 pCi/l in the crawlspace.
Addition of a diffused bubble aeration
system brought the radon levels to 1
pCi/l on the first floor. (Average reduction
of radon in the water was over 99%.) This
-------
house had very high initial radon levels.
The aeration system produced a
significant reduction in living area radon
levels, treating a radon source from the
water which the other techniques did not
address.
Assess Previously Installed
Techniques in Existing Houses
A pioneering infiltration, ventilation, and
indoor air quality survey of 60 New York
State houses in the Niagara Mohawk
Power Corporation service territory was
conducted in 1982-83. Fourteen of these
houses were discovered with moderately
high radon levels (from 1.9 to 49.8 pCi/l
in the lowest level). Early in 1984, low-
cost radon mitigation techniques were
installed, including sealing, sealing and
sub-slab depressurization, crawlspace
isolation/ventilation, and heat-recovery
ventilation. These mitigation systems
represent some of the earliest systems
installed in the U.S. (not associated with
the mining industry) using low-cost
common residential construction
materials and methods. It was thought
useful to return to these installations,
inspect the longevity of the various
components of the systems, and assess
their long-term effectiveness.
Each of the 14 houses was visited in
late 1986 and 1987, during which a
thorough inspection was made to assess
the wear and tear of system components,
observe any settling of the house struc-
ture that produced new cracks in the
foundation walls and floor, and determine
if any deliberate or inadvertent changes
may have been made by the home-
owners that could have contributed to a
change in system performance. During
conversations with the homeowners, an
assessment was also made of their satis-
faction with the mitigation system. Among
the factors discussed were noise, comfort
level, and usability of the space. In most
houses more detailed diagnostic tests
were also performed to assess the ef-
fectiveness of the existing radon mitiga-
tion system. Among the diagnostic tests
were smoke stick tests to determine
leaks, air-flow measurements, sub-slab
communication tests, and pressure
measurements in the suction pipe of sub-
slab depressurization systems relative to
the indoor air. In some cases a tracer gas
test was used to check for leaks and/or
sub-slab communication. Short-term
radon concentrations were measured
using grab samples and charcoal
canisters. If parts of the system did not
appear to be working satisfactorily, these
components were replaced, updated, or
redesigned and re-installed. Short-term
radon measurements were then repeated
using charcoal canisters, followed by
long-term radon measurements using
alpha-track detectors.
The mitigation techniques employed in
this task include:
• Sealing (houses NM-26 and NM-41,
see Table 2),
• Heat-Recovery Ventilation (houses
NM-16, NM-19, NM-28, NM-29,
NM-51, and NM-56, see Table 3),
• Sub-Slab Depressurization (houses
NM-02, NM-05, NM-12, NM-21,
NM-31, and NM-37, see Table 4).
Each of these groups is summarized
below.
Sealing
The sealing that was performed in
houses NM-26 and NM-41 was the
simplest and least expensive (above
$300 and $400 for materials and labor in
1984) radon mitigation technique with the
least effect on the lifestyle of the home-
owners. Unfortunately, it probably also
had the least effect on radon levels. The
decrease in long-term average radon
concentrations, that may have occurred
after sealing in 1984, was overwhelmed
by larger radon reductions in the summer
of 1987, when windows were left open,
and by an increase in radon concen-
trations in the fall of 1987 when windows
were closed again (see Table 2 houst
NM-26). For house NM-41, long-term ra
don reductions in the basement (co
incidentally) did not change from 1984 t<
1986. Although the polyurethane caull
used to seal cracks and small opening;
appeared to be in good condition, there
was some shrinkage of the concrete use(
to cover an unpaved basement floor are;
and a sump. It appears that the greates
practical problem with this technique i;
the difficulty in finding all the openings ii
the foundation so that the radon does no
find another (slightly more difficult) patl
to enter the house once other opening:
are closed.
Since year-long average radon levels ii
the living areas of both houses wen
moderate, further mitigation is probabl
not required, except to provide for mor
natural ventilation during the non-heatini
season. However, if permanent, dramati
reductions of radon were required, sub
slab depressurization systems in thes
houses would have a high likelihood c
success, based on experience wit
similar houses.
Heat-Recovery Ventilation
Six houses used heat-recovery ver
tilators (HRVs) as a method of reducin
radon (houses NM-16, NM-19, NM-2J
NM-29, NM-51, and NM-56, see Table 3
The HRVs were easy to install b
experienced HVAC contractors, wil
moderate initial costs (approximate)
$1,000 for equipment and labor in 1984
economical to operate (usually less the
70W, operating part-time), provided tr
expected ventilation rate, required essei
tially no maintenance, and performe
very quietly. Besides reducing rado
other benefits of operating a HRV mei
tioned by homeowners include the redu
tion of odors, and the control of humidi
levels. However, the reduction of rad<
was less than expected from calculatir
the increase in air exchange rate due
the HRV. As for the houses that we
Table 2. Assess Previously Installed Techniques
Summary of Sealing Results
Integrated Radon Concentration (oCill)
House
No.
NM-26
NM-41
Style
Salt box
Colonial
(Yr")
(84)
(SU87)
(F87)
(84)
(86)
Mitigation
Technique
Sealing, air circulation adjustment
As above
As above
Sealing
As above
Before
6.7
6.7
6.7
4.8
4.8
After
4 1
1.6
9.3
2.6
2.6
Percent
Reduction
39
78
-39
46
46
"F = Fall, SU = Summer, W = Winter.
-------
Table 3. Assess Previously Installed Techniques
Summary of Heat-Recovery Ventilation Results
Integrated Radon Concentration (pCi/l)
House
No.
NM-16
NM-19
NM-28
NM-29
NM-51
NM-56
Style
Contemporary
Victorian
Farm house
Bi-level
Underground
Colonial
Mitigation
(Yr*) Technique
(84) 80 CFM" Whole house HRV on 1/2 time
(88) As above
(84) 150 CFM basement HRV on 1/6 time
(88) As above
(84) 150 CFM basement HRV on full time
(SU87) As above
(FS7) As above
(W88) As above
(84) 150 CFM whole house HRV on 1/4 time
(SU87) HRV off
(F87) HRV on 1/4 time
(W88) As above
(84) Dram sealing, 150 CFM wholehouse HRV
controlled by RH~"
(SU87) As above
(F87) As above
(W87) As above
(84) 80 CFM Basement HRV on full time
(SU87) As above
(F87) As above
(W87) As above
Before
2.4
2.4
19.9
19.9
9.3
9.3
9.3
9.3
7.4
7.4
7.4
7.4
1.9
1.9
1.9
1.9
4.0
4.0
4.0
4.0
After
2.4
2.3
12.1
19.3
4.8
2.5
5.1
6.5
2.3
0.2
7.4
12.5
1.0
0.9
1.9
2.1
1.9
1.1
1.9
2.4
Percent
Reduction
0
4
39
3
48
73
45
30
69
97
0
-69
47
53
0
-11
53
73
53
40
"F = Fall, SU = Summer, W = Winter.
"1 cfm = 0.000472 m3/s
"~RH = Relative humidity
Table 4. Assess Previously Installed Techniques
Summary of Sub-Slab Depressurization Results
Intearated Radon Concentration (oCill)
House
No.
NM-02
NM-05
NM-12
NM-21
NM-31
NM-37
Style Phase
Bi-level 1
1
2
Contemporary 1
1
2
Colonial 1
1
2
Colonial 1
1
2
Bi-level 1
2
Colonial 1
1
2
Mitigation
(Yr) Technique
(84) Sealing, SSD with 20W axial fan
(87) As above, leak in vent pipe
(88) More sealing, SSD with 20W centrifugal
fan
(84) Sealing, SSD with 20W axial fan, vent
craw/space with 20W axial fan
(86) As above, SSD vent blocked with
condensation water
(88) More sealing, SSD and crawlspace
venting with 40W centrifugal fan
(84) Sealing, SSD with 20W axial fan, vent
crawlspace
(86) As above, cracks in slab
(88) More sealing, SSD with 20W centrifugal
fan, vent crawlspace
(84) Sealing, SSD with 30W axial fan
(86) As above
(88) More sealing, 30W axial fan replaced
(84) Two SSD systems with two 20W axial fans
(88) Two SSD systems with two 20W
centrifugal fans
(84) Sealing, SSD with 20W axial fans
(87) As above
(88) More sealing, SSD w/ttj 20W centrifugal
fan
Before
9.0
9.0
9.0
16.2
16.2
16.2
18.3
18.3
18.3
49.8
49.8
49.8
15.5
15.5
28.3
28.3
28.3
After
3.5
7.7
1.4
3.0
23.0
5.4
2.9
4.7
1.8
1.4
2.9
0.2
1.3
1.3
8.1
11.3
2.7
Percent
Reduction
61
14
84
81
-42
67
84
74
90
97
94
100
92
92
71
60
90
-------
sealed, this was probably because the
variations in radon levels due to
environmental changes (including pres-
sure differences and natural ventilation)
overwhelmed the radon reductions due to
increased ventilation from the HRV. Com-
paring results from the two monitoring
periods is therefore very difficult in these
houses.
Radon reductions in the houses during
the heating season were moderate, ac-
tually negative in two of the houses (NM-
29 and NM-51). In houses NM-28, NM-
29, NM-51, and NM-56, where summer
data are available, reductions of radon
were greater in the summer than during
the heating season. In houses NM-28 and
NM-56, which had the HRVs on full time,
radon reduction was more consistent
through the different seasons.
Since year-long living-area radon con-
centrations appear to be below the 4.0
pCi/l guideline in these houses, further
mitigation is probably not required,
except to provide for more natural ven-
tilation during the non-heating season. In
all but two houses (NM-28 and NM-56),
further reductions in radon could be
achieved during the heating season by
operating the HRV longer. (However,
there would be an added electrical and
thermal energy penalty.) If more dramatic
reductions of radon were required, simple
sub-slab depressurization systems could
be installed in all these houses except
NM-19 and NM-28. These two houses
were over 100 years old and had stone
foundation walls which would require
extensive sealing before sub-foundation
depressurization would be expected to
work.
Sub-Slab Depressurization
Sub-slab depressurization systems
were installed in 6 of the 14 houses (NM-
02, NM-05, NM-12, NM-21, NM-31, and
NM-37, see Table 4). Sealing was also
used in most of these houses to
maximize the sub-slab depressurization
field. The sealing requirements in most of
the houses and the need for venting
unpaved crawl spaces in two of the
houses, meant that (1984) material and
installation costs varied widely; from $150
for the simplest system to $1250 for the
most elaborate. These systems provided
the greatest potential for reduction of
radon. Unfortunately because of the lack
of experience in installing these systems
they were also the most problem prone.
The most serious problem occurred in
house NM-05 when the sub-slab depres-
surization system vent pipe, next to an
sideways-S-shaped bend, filled with
condensation water because the drain
hose became blocked with debris. This
completely blocked air movement to the
outdoors. The problem was exacerbated
by poor quality caulk used around the
connection between the fan and vent
pipe. Thus radon drawn from the sump
was forced to travel into the basement,
through openings between the fan and
vent pipe. This increased the radon
concentration in the basement beyond
the original concentrations before the
system was installed. To solve this prob-
lem the vent pipe was re-routed to avoid
bends that may collect condensation
water and reduce air flow.
The poor quality caulk used in two of
the six sub-slab depressurization installa-
tions (houses NM-05 and NM-21) caused
leakage of radon into the basement when
the openings were on the positive
pressure side of the fan relative to the
basement. On the negative pressure side
of the fan, if openings were large enough,
short circuiting will occur, where
basement air is drawn directly into the
sub-slab ventilation system, reducing the
magnitude of the negative pressure in the
suction pipe and reducing the extent of
the sub-slab depressurization field.
Similar short circuiting will occur if there
is inadequate sealing of openings in the
basement floor and wall (especially large
openings close to the depressurization
fan). To overcome this problem, the low-
quality butyl caulk was replaced, where
possible, by high quality polyurethane
caulk which was originally used on four of
the six sub-slab depressurization
installations and appeared to hold-up
very well from 1984 to the present (early
1988).
A third problem in the sub-slab depres-
surization systems was the use of axial
fans to provide depressurization. Axial
fans are designed to move relatively
large quantities of air when there is no
static pressure, for example, to vent
electrical equipment and machines. The
ideal sub-slab depressurization fan, on
the other hand, should provide a large
static pressure to a large tightly enclosed
space (the sub-slab cavity) while venting
very little air. Axial fans are therefore not
well suited for sub-slab depressurization,
they do not induce the large static
pressures required, and they do not last
as long as they would if operating in free
air. In fact, one of the fans failed (in
house NM-31) after only 3 years. To
solve this problem all axial fans (except
the larger axial fan in house NM-21) were
replaced with in-line centrifugal fans
which are more suited to conditions of
large static pressure.
Outside vent openings also causei
problems for two of the sub-slal
depressurization installations. The outsidi
vent opening of house NM-37 face
directly into the prevailing winds, and ha
movable louvers which remained close
when the wind blew. This vent openin
was replaced by a screened opening wit
rain cover. For house NM-21 the outsid
vent opening consisted of a 6 in. (15 err
elbow facing downward with no screen.
was discovered that children had place
pieces of wood into the openinc
restricting the flow of air. This ver
opening was replaced by a screene
opening with fixed-open louvers.
The sub-slab depressurization systerr
in this study had fans located inside tr
house, so that if any openings develope
on the positive pressure side of the fa
radon could leak into the house. Th
happened in house NM-05 after tr
exhaust pipe was blocked with coi
densation water (as mentioned abov
and radon leakage may have cause
problems in house NM-02. Ideally, fai
should be installed outdoors, or as clo:
to the outdoors as possible; and all insi<
exhaust pipes should be carefully seal*
and checked with smoke sticks and/
tracer gas.
To summarize, sub-slab depressuriz
tion systems were by far the most <
fective systems in consistently reduci
radon levels. However, the early syster
that were installed in this study, wh
there was very little experience in tl
area, developed some problems which,
hindsight, could easily have be
avoided. To learn from mistakes, it
most important to perform long-term tei
and continually evaluate the effectives
of radon mitigation systems.
Demonstrate Radon-Resistant
Construction Techniques in
New Houses
In this task (which is less than \
completed) radon-resistant construct
techniques are to be applied to 15 n
houses, with simultaneous monitor
(and previous baseline monitoring) ir
control houses. Emphasis is to be plat
on the development of cost-effective p
sive methods of radon-resistant c
struction with potential applicability
building codes.
Housing site selection is critical to
success of this task because of the n
to presume high radon levels in hou
not yet built. Ideally, subdivisions req
the following characteristics:
-------
1. Geologic features indicative of high
radon availability.
2, Occupied new houses with high
radon levels near undeveloped
homesites.
3. Substructure types representative of
standard construction.
4. A high annual rate of construction
and sales so that test houses are
likely to be occupied during the
1987-88 heating season.
5. A homebuilder/developer interested
in participating in the project.
A study of 210 houses by Onondaga
County Health Department identified a
band of bedrock with high radon levels,
which included the following formations:
Marcellus shale, Onondaga limestone,
Manlius limestone, Camillus formation,
and Syracuse formation. Within this band
of bedrock the distribution of radon levels
were: 77% above 4 pCi/l, 22% above 20
pCi/l, and 1% above 100 pCi/l. The high-
est levels were over Onondaga limestone
and Marcellus shale.
Based on this information, several
housing subdivisions in Onondaga Coun-
ty were identified as possible candidates
for this task, situated either on Onondaga
limestone or Marcellus shale and where
nearby houses had radon levels above 20
pCi/l. These sites were visited by a
geologist and staff from the New York
State Department of Health who collected
information on depth of soil to bedrock,
bedrock faults, fractures and joints, soil
gas radon, soil and bedrock radium, and
soil gas permeability. Homebuilders/
developers of the subdivisions were also
contacted to ascertain interest and infor-
mation on the rate of construction. This
narrowed the potential housing sub-
divisions down to three. At two of these
subdivisions, two control houses for each
subdivision (four total) were monitored
with charcoal canisters. All four houses
had basement radon levels above 10
pCi/l. A fifth house, that had previously
been measured to have basement radon
levels between 10 and 20 pCi/l, was
chosen as the control house in the third
subdivision. These control houses are
dentified as ON-01 and ON-02 from the
irst subdivision; ON-04 and ON-05 from
he second subdivision; and ON-03 from
he third subdivision.
Houses ON-06, ON-07, ON-08, ON-09,
DN-10, ON-11, ON-12, and ON-13 were
he first houses to be constructed to
•esist radon entry.
Among the mitigation techniques in-
tailed in these houses were:
• Continuous airtight polyethylene film
installed over aggregate before slab
is poured to foundation wall.
-- Plastic film tears, penetrations, or
joints sealed with builder's tape.
~ Plastic film fastened to top of foot-
ings with bituminous caulk.
~ Perimeter edge of slab tooled and
filled with polyurethane caulk.
• Continuous layer of surface bonding
cement installed around exterior
foundation wall and footing.
• Course of termite blocks installed on
top of foundation wall.
• Interior and/or exterior footing drains
discharged to daylight or to a sump
airtight to the basement and vented
to the outside.
Provisions were made to actively vent
the interior and/or exterior footing drains,
if passive venting is not sufficient to keep
radon levels below 4 pCi/l.
Preliminary integrated radon concen-
trations are only available for houses ON-
06, ON-08, ON-09, and ON-10. House
ON-09 has radon levels only slightly
above EPA guidelines (5.5, 8.0, and 6.7
pCi/l in the basement, 4.4 pCi/l on the
first floor, and 4.7 pCi/l on the second
floor). The remaining houses monitored
so far all have radon levels below the
EPA guideline of 4 pCi/l.
•&U. S. GOVERNMENT PRINTING OfFICE: 1989/748-012/07188
-------
Ian Nitschke is with W.S. Fleming and Associates, Inc., Syracuse, NY 13057.
Michael C. Osborne is the EPA Project Officer (see below).
The complete report, entitled "Radon Reduction and Radon Resistant
Construction Demonstrations in New York," (Order No. PB 89-151 476/AS;
Cost: $28.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park NC 27711
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
0 .35 =Ji
EPA/600/S8-89/001
------- |