United States
Environmental Protection
Agency
Research and Development
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
EPA/600/S8-91/200 Feb. 1992
sir EPA Project Summary
Parametric Analysis of the
Installation and Operating
Costs of Active Soil
Depressurization Systems for
Residential Radon Mitigation
D. Bruce Henschel
Recent analysis has shown that cost-
effective indoor radon reduction tech-
nology is required for houses having
initial radon concentrations below 148
Bq/m3, because 78-86% of the national
lung cancer risk due to indoor radon is
associated with those houses. Active
soil depressurization (ASD) is a very
effective, widely applicable, and well
demonstrated radon reduction technol-
ogy. However, many homeowners hav-
ing pre-mftigation levels above 148 Bq/
m3 have not installed an ASD system;
application of ASD by homeowners be-
low 148 Bo/m3 is insignificant. In part,
this limited voluntary use of ASD sys-
tems is likely due to their installation
costs (typically $800-$1,500) and oper-
ating costs. Thus, a comprehensive
cost analysis was conducted to deter-
mine if EPA might be able to reduce
ASD installation and operating costs
enough to significantly increase volun-
tary use of this effective technology,
especially among homeowners having
low initial radon concentrations.
The analysis showed that various
modifications to ASD system designs
offer potential for reducing installation
costs by up to several hundred dollars,
but would not reduce total installed
costs much below $800-$1,500. Be-
cause the price/demand curve is
thought to be relatively inelastic, cost
reductions of this magnitude would
probably not be sufficient to dramati-
cally increase voluntary use of ASD
technology, especially not among
homeowners having only marginally el-
evated pre-mitigation levels. Thus, to
reduce the 78-86% of the national risk
associated with houses below 148 Bq/
m3, some innovative, inexpensive miti-
gation approaches) would appear to
be necessary, in addition to ASD. Even
if such innovative alternative ap-
proaches provided lower radon reduc-
tions than did ASD in a given house,
they could provide a much greater re-
duction in the national health risk, if
their low costs resulted in very wide
utilization. EPA's radon mitigation R&D
program is currently focused on the
development of such innovative, low-
cost approaches.
Decreased ASD fan capacity and in-
creased sealing might reduce ASD op-
erating costs (for fan electricity and
house heating/cooling) by roughly $7.50
per month. This amount would not likely
be a deciding factor for most home-
owners.
This Project Summary was developed
by EPA's Air and Energy Engineering
Research Laboratory, Research Tri-
angle Park, NC, to announce key find-
ings of the research project that is fully
documented in a separate report of the
same title (see Project Report ordering
Information at back).
Introduction
Active soil depressurization (ASD) tech-
niques have been proven to be the most
widely used indoor radon reduction tech-
nique for houses, due to their effective-
ness in reducing radon levels under a
wide variety of conditions, their reliability,
and their moderate installation cost. These
techniques use a suction fan to draw the
Printed on Recycled Paper
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radon-containing soil gas out from beneath
the house, and exhaust it outdoors before
H can enter the house. Variations of the
ASD technique include: sub-slab depres-
surization (SSD), where suction is drawn
on individual suction pipes that are in-
serted beneath the concrete slab in base-
ment and slab-on-grade houses; drain-tile
dapressurization (DTD), commonly imple-
mented by drawing suction on an existing
sump connecting to drain tiles beneath
the slab; and sub-membrane depressur-
ization (SMD) in crawl-space houses,
where suction is drawn beneath a mem-
brane (usually plastic sheeting) placed over
the earthen or gravel-covered crawl-space
iloor.
EPA estimates that thousands of lung
cancer deaths result in the U.S. each year
as a result of exposure to indoor radon.
EPA also estimates that only a few houses
with elevated indoor radon concentrations
have installed radon reduction systems. If
there is to be a significant reduction in the
number of radon-induced lung cancer
deaths, it will be necessary for effective
radon reduction systems to be installed in
a large number of U.S. houses. Based
upon the estimated distribution of indoor
radon levels in the U.S., EPA has calcu-
lated that even houses having pre-mitiga-
tion concentrations below the initial guide-
line of 148 Bq/m3 would have to receive
radon reduction systems if the estimated
death rate is to be reduced by more than
about 14 to 33%.
While a number of factors contribute to
the low response by homeowners in in-
stalling remediation systems, such as pub-
lic perception of the risks involved, one of
these factors is likely to be the cost of the
systems. Typical ASD systems installed
by a commercial radon mitigator cost in
the range of $800 to $1,500.
The objective of this cost analysis was
to identify those ASD design and operat-
ing parameters which have the greatest
impact on system installation and operat-
ing costs. Those parameters could then
be considered as possible targets for EPA-
sponsored research, development, and
demonstration (R,D & D) efforts, to im-
prove guidance to the mitigation commu-
nity concerning the most effective meth-
ods for reducing costs. Reduced costs
might result in increased voluntary utiliza-
tion of ASD technology by homeowners.
Since the price/ demand curve for mitiga-
tion systems is thought to be relatively
inelastic, the cost reduction would prob-
ably have to be substantial in order to
significantly increase demand.
The question underlying this study was,
What will be the relative role of highly
efficient, well-demonstrated ASD technol-
ogy in reducing the national health risk
due to radon, compared to the role(s) of
as-yet undeveloped, innovative, low-cost,
moderate-reduction technique(s)? Through
appropriate R.D&D, can ASD costs be
reduced sufficiently to achieve more wide-
spread voluntary utilization, thus helping
ASD play a greater role in reducing na-
tional risk?
Approach
Installation Costs
The effect of 14 ASD design param-
eters on system installation costs was as-
sessed by obtaining installation cost esti-
mates from five mitigation firms represent-
ing different major mitigation markets
across the country. Initially, each mitigator
developed cost estimates for baseline miti-
gation systems in eight different houses.
The eight houses represented three house
design/construction parameters (substruc-
ture type, number of stories, and degree
of basement finish). Two other house de-
sign/construction variables — presence/
absence of a sump, and nature of sub-
slab communication — were also ad-
dressed, but were handled as mitigation
design variables (sub-slab vs. drain-tile
depressurization, number/location of suc-
tion pipes).
The baseline mitigation system for the
eight houses consisted of selected values
for the 14 system design parameters. The
baseline values for the 14 parameters
are listed in Table 1.
The parametric analysis was then con-
ducted by asking each mitigator to esti-
mate the incremental impact on the
baseline installation cost (and on labor
hour and material cost requirements) as
each of the 14 design parameters was
varied in turn, through a range of logical
values.
In addition to the baseline values for
the 14 system design parameters, each
mitigator was also required to include, in
the baseline cost estimates, certain key
elements, to help ensure consistency. All
of the mitigators included the following in
the baseline:
a) a pre-mitigation visual inspection.
(No pre-mitigation sub-slab commu-
nication tests were included in the
baseline.)
b) post-mitigation follow-up, including
suction measurements in the sys-
tem piping, and an indoor radon
measurement. (There were some
differences in how the post-mitiga-
tion measurements were made.)
c) a warranty that the house would be
reduced below 148 Bq/m3 for a year
or longer. The exact nature of the
warranty varied from mitigator to
mitigator.
d) meeting all applicable building codes.
e) travel time for the work crews to and
from the job site.
Despite the steps listed above to en-
sure the comparability of the estimates,
the estimates still varied as a result of
inherent differences between the five
mitigators. Among these inherent differ-
ences were:
a) direct labor, fringe benefit, and over-
head/profit rates.
b) differences in system design details,
such as whether exhaust stacks are
boxed in inside or outside the house,
whether interior stacks can be in-
stalled in existing utility chases,
whether exterior stacks penetrate or
jut around the roof overhang, or
whether membranes installed in
crawl spaces must be attached to
the perimeter wall using a wooden
furring strip or fastened to the wall
using a bead of caulk.
c) differences in experiences between
mitigators. For example, some
mitigators provided significantly dif-
ferent estimates for the cost impact
of installing an ASD stack inside the
house, depending upon, e.g., the fa-
miliarity of their crews with such in-
terior installations, the expectations
of local homeowners,; and perhaps
the amenability of the local house
construction characteristics to inte-
rior stacks.
No attempt was made to correct for
variations created by such inherent differ-
ences. These inherent differences reflect
the natural variations between mitigators
across the county, and provide a mean-
ingful measure of the range of cost im-
pacts that would be encountered if one
were to apply one of these parametric
variations on a nationwide basis.
Operating Costs
Four elements can contribute to the
on-going costs that homeowners experi-
ence in operating ASD systems: 1) the
cost of electricity to run the fan; 2) the
heating and cooling penalty resulting from
the exhaust by the system of some treated
house air; 3) the cost of system mainte-
nance, primarily fan repair/replacement,
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Table 1. Summary of the Baseline ASD Mitigation Systems Utilized in Parametric Analysis of ASD Installation Costs
ASD Design Variable
Baseline Value
1. Variation of ASD technology
- basement houses
- slab-on-grade houses
- crawl-space houses
2. Number and
3. Location of SSD/SMD pipes
- basement houses
- slab-on-grade houses
- crawl-space houses
4. Pipe diameter (all houses)
5. Type of pipe (all houses)
6. Nature of slab/membrane
hole
7. Exhaust piping configuration
- basement houses
- slab-on-grade houses
- crawl-space houses
8. Location of fan
- basement houses
- slab-on-grade houses
- crawl-space houses
9. Type of fan (all houses)
10. Degree of slab and
membrane sealing (all houses)
11. SMD membrane design
(crawl-space houses)
12. Nature of gauge/alarm
13. Pre-mitigation diagnostics
14. Post-mitigation diagnostics
Sub-slab depressurization (SSD).
Sub-slab depressurization (SSD).
Sub-membrane depressurization (SMD).
One pipe, 3 m (horizontally) from point where piping
penetrates band joist to outdoors.
One pipe, inside house, directly under point where piping
penetrates ceiling into attic and then through roof.
One pipe, penetrating SMD membrane in center.
10cm.
Thin-walled polyvinyl chloride (PVC).
10- to 13-cm hole cored through slab (or cut through
SMD membrane); no excavation under slab or membrane
at point where hole penetrates.
Vertical stack above eaves, rising outside house.
Through ceiling to fan in attic, exhaust through roof.
Through a foundation vent to a vertical stack above
eaves, rising outside house.
Immediately outside basement, at grade level.
In attic.
Immediately outside crawl space, at grade level.
90-VV in-line duct fan with 15-cm couplings, capable of
moving 127 Us at zero static pressure, and about 52 Us
at 250 Pa static pressure.
No sealing, other than around pipe penetration through
slab or membrane.
Membrane covers crawl-space floor everywhere. No
sealing of membrane anywhere, suction system is one
pipe through center of membrane, as indicated previously.
Dwyer Magnehelic
Visual inspection only: no sub-slab communication testing.
Estimates should include cost penalty based upon experience,
reflecting subsequent system modifications and call backs
resulting from decision to bypass pre-mitigation sub-slab
measurements.
Suction/flow measurements in piping after installation.
Post-mitigation indoor radon measurement, using
technique consistent with mitigator's normal practice.
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plus some effort to re-cement/re-caulk bro-
ken piping joint seals or slab caulking;
and 4) the cost of any periodic re-mea-
surements of indoor radon levels. This
report focusses primarily on fan electricity
and the heating/cooling penalty, since
these elements can be addressed most
quantitatively, and impacted most readily
by additional R & D.
The obvious method for reducing both
the electricity cost and the heating/cooling
penalty is to use a smaller (lower-wattage,
lower-flow) fan, or to operate a larger fan
at reduced capacity using a controller. But
in addition to reducing operating costs,
use of reduced fan capacity will often re-
sult in some degradation in the radon re-
duction performance of the system, even
if indoor levels remain below 148 Bq/m3.
Since the data base is so limited in
defining the effect of reduced fan capacity
on indoor radon levels, the calculations
here do not attempt to quantify the tradeoff
between reduced operating costs and re-
sulting increased health risk from higher
radon levels. Rather, the calculations ad-
dress only the operating cost reductions
that can be achieved with alternative re-
ductions In fan capacity. If the cost reduc-
tions appear to be high, they could war-
rant further R&D to determine the condi-
tions under which such reductions in ca-
pacity might be acceptable, including con-
sideration of the tradeoffs with increased
health risk.
Another method for potentially reducing
the heating/cooling penalty would be to
seal slab cracks and openings, to reduce
the amount of treated house air exhausted
by the system. Again, there are very little
data defining to what degree the flow of
house air into the system can be reduced
by such slab sealing efforts. Tracer gas
studies by various investigators have indi-
cated that between 10 and 90% of the air
in ASD exhausts can be drawn from in-
side the house. For the calculations here,
to obtain a rough estimate of the operat-
ing cost penalty, it was assumed that an
average of 50% of the exhaust was house
air prior to any slab sealing, and that slab
sealing reduced this to 30% (the lower
end of the range most commonly ob-
served). It was also assumed that the
increase in house ventilation rate caused
by the ASD system is exactly equal to the
amount of house air in the ASD exhaust;
this assumption is not necessarily accu-
rate.
The calculations make various assump-
tions regarding fan power consumption,
electricity and fuel costs, the nature of the
furnace and air conditioning system, and
the climate. These assumptions are all
specified in the complete report.
Results and Discussion
Installation Costs
Table 2 presents the average of the
total installation costs for baseline sys-
tems in the eight houses. The figures in
the table are the arithmetic mean of the
estimates from the five mitigators. Tables
3, 4, and 5 indicate the average incre-
mental increases or decreases in those
baseline costs caused by the variations to
the 14 system design variables. Table 3
presents those parametric variations hav-
ing a cost impact near to, or greater than,
$100 (relative to the baseline system);
these are the parameters for which addi-
tional R&D would be expected to offer the
greatest potential for installation cost re-
ductions. Parametric variations having an
impact between $50 and $100 are listed
in Table 4, and parametric variations hav-
ing cost impacts less than $50 are listed
in Table 5. While the parameters in Table
5, taken together, can have a noticeable
combined effect on the total cost, the cost
impact of any one of them alone is prob-
ably lost within the uncertainty level of the
cost estimates that mitigators provide to
prospective clients.
Parametric variations having a cost im-
pact of about $100 or greater (Table 3).
Three of the parametric variations having
significant cost impact deal with houses
having poor sub-slab communication,
which is not surprising. Adding additional
suction pipes in basements and slabs on
grade (Item 1 in Table 3), jackhammering
a 0.6- by 0.6-m hole in the slab to enable
excavation of a large pit beneath the suc-
tion pipe (Item 2), and conducting pre-
mitigation sub- slab communication test-
ing (Item 7), are all steps for addressing
poor-communication houses. Each addi-
tional suction pipe adds about $135 to
$274 to the total installation cost, depend-
ing upon house characteristics; each
jackhammered hole adds roughly $200,
with a broad standard deviation; and the
pre-mitigation sub-slab communication
testing adds about $200, where these di-
agnostics require a separate trip to the
house. Whether sub-slab diagnostics are
conducted during a separate trip, or on
the morning that the crew arrives to install
the system, depends upon the particular
situation and the practices of an individual
mitigator. As shown in Table 5, the cost of
these diagnostics decreases significantly
when the communication testing and the
installation can be conducted during the
same visit.
To reduce the need for additional suc-
tion pipes (Item 1) or for large sub-slab
pits (Item 2), R&D would have to identify
inexpensive methods for: a) improving the
communication; and/or b) improving the
performance of a one-pipe SSD system
without improving the communication. An
example of means for improving commu-
nication is the use of high- pressure air or
water jets under the slab to create chan-
nels between the bottom of the slab and
the underlying soil. Examples of ap-
proaches for improvmg performance with-
out improving communication might include
improved pre-mitigation diagnostics and
higher- performance fans. At the present
time, EPA's R&D program is addressing
only one of the above possibilities, in a
relatively limited manner; this possibility is
improved pre-mitigation diagnostics, which
should result from improved fundamental
understanding resulting from the on-going
fundamental/innovative research effort.
Other investigators are conducting some
Table 2. Total Installation Costs for Baseline Mitigation Systems1
Baseline Installation Costs2 ($)
House
No.
1
2
3
4
5
6
7
8
House Description
Basement (unfinished) - one story
Basement (unfinished) - two stories
Slab on grade - one story
Slab on grade - two stories
Crawl space - one story
Crawl space - two stories
Basement (finished) - one story
Basement (finished) - two stories
Range Mean
790- ,383 ,080
833- ,576 ,168
760- ,343 ,048
852- ,504 ,167
966- ,852 ,418
977- ,716 ,317
790-1,510 ,147
833-1,704 1,239
Estimated
Standard Deviation
268
326
275
291
320
308
312
370
1 The baseline mitigation systems are defined in Table 1.
2 The installation cost range, mean, and estimated standard deviation are derived from the
estimates of five mitigators. Costs are expressed in U. S. dollars.
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studies on the use of sub-slab air and
water jets, and on improving fan perfor-
mance. Any re- direction of the EPA R&D
program would have to be preceded by
an appropriate planning effort.
In evaluating possible R&D to reduce
system costs in poor-communication
houses, consideration must be given to
the fact that — to be cost-effective — the
methods developed for improving commu-
nication, or for improving the performance
of a one-pipe SSD system without im-
proving communication, must be commer-
cially applicable at a cost significantly lower
than the cost of the alternatives. That is,
they must add less to the total installation
cost than the roughly $200 required to
add another suction pipe or to excavate a
large pit.
It is doubtful that R&D can reduce the
cost of conducting added pre-mrtigation
diagnostics in poor-communication houses,
where a separate trip to the house is
required (Item 7 in Table 3). Improved
diagnostics would not reduce the travel
time, nor the time to actually perform the
diagnostics. (The time to conduct the im-
proved diagnostics might even increase,
compared to the current sub-slab commu-
nication test methods.) However, if R&D
ultimately results in diagnostics which per-
mit more effective SSD system designs,
the cost of the sub-slab diagnostics might
be at least partially offset by cost reduc-
tions resulting from the need for fewer
suction pipes, or from avoiding the need
for sub- slab excavations.
Note that the baseline installation costs
(averaging $1,000 to $1,200 for SSD sys-
tems, as shown in Table 2) assume
houses having relatively good communi-
cation, requiring only one suction pipe, no
sub-slab excavation, and no communica-
tion testing. Thus, if the R&D discussed
.above were successful in reducing the
number of pipes or excavations in poor-
communication houses, or in making the
diagnostics more efficient, this R&D would
not reduce average installation costs be-
low $1,000-$1,200. Rather, it would only
prevent installation costs in poor-commu-
nication houses from increasing so signifi-
cantly above these baseline costs.
In addition to means for addressing
poor-communication houses, another vari-
able shown as having a potentially signifi-
cant cost impact is the configuration of
the exhaust (Item 3 in Table 3). Exhaust-
ing at grade level (eliminating the exterior
stack) reduces costs by $93 to $169, de-
pending primarily on the number of sto-
ries. Locating the stack in the adjoining
garage rather than outside the house in-
creases costs by $96. Locating the stack
inside the house, rather than outdoors,
can result in either a significant cost in-
crease ($91-$T55) or some cost reduction
($38-$61), depending upon the estimator;
whether the interior stack is more or less
expensive appears to depend at least in
part upon the degree of experience that
the particular mitigator has with interior
stacks.
It is doubtful that any R&D that EPA
could perform would significantly impact
the cost of interior vs. exterior stacks, or
of stacks in the garage vs. outdoors. To
the extent that lack of experience is in fact
responsible for the higher estimates from
some m'rtigators for interior stacks, reduc-
ing the cost of interior stacks by those
mitigators would appear to reflect a po-
tential need for improved training, improved
technology transfer, and increased mar-
ket demand for interior stacks, rather than
a need for R&D.
However, the mitigators are in general
agreement that eliminating a stack releas-
ing the exhaust immediately beside the
house, could result in a potentially signifi-
cant reduction in cost. EPA's current rec-
ommendation is that the exhaust should
be released above the eave; i.e., that a
stack is desirable. In view of the potential
cost reductions from eliminating the stack,
R&D would appear justified to determine
under what conditions grade- level ex-
haust might be acceptable (e.g., exhaust
radon concentration, exhaust velocity, ex-
haust configuration, and house and
weather characteristics). Such R&D could
include tracer gas studies to assess re-
entrainment of the exhaust back into the
house, and to identify "plume effects" in
the yards of the homeowners and their
neighbors. In addition to reducing costs,
elimination of the stack might also increase
homeowner acceptance of SSD systems
by eliminating the aesthetic impact of
stacks.
Sealing the slab also has a significant
impact on installation costs in basement
houses (Item 5 in Table 3). This cost is
especially pronounced when a perimeter
channel drain (French drain) is present
($326-$470). The range of the costs shown
in the table for sealing the wall/floor joint
or for closing the French drain results
because the one-story house has a much
larger footprint than the two-story, thus a
longer perimeter joint to seal. Some R&D
(involving demonstration testing in houses
having SSD systems) might be warranted
to assess the impact of crack and French
drain sealing on the radon reduction per-
formance of the systems and on the heat-
ing/cooling penalty, to enable a better
judgement of the cost-effectiveness of slab
sealing. However, the effects of slab seal-
ing are likely to be so site- specific, that it
is not clear that a reasonably-sized dem-
onstration effort would answer these ques-
tions definitively.
Sealing the membrane for crawl-space
SMD systems (Item 5 in Table 3), can
have a significant impact in crawl-space
houses. This cost impact is especially large
($456-$620) if a complete sealing job is
necessary, including careful perimeter seal-
ing, which would require wrapping the edge
of the membrane around a 2.5- by 10-cm
furring strip and nailing/caulking the strip
to the foundation wall. By comparison, if
the membrane can simply be attached to
the foundation wall with a bead of caulk
— clearly a less rigorous approach — the
cost of the complete sealing would fall to
$102-$248. If perimeter sealing can be
eliminated altogether, since the suction
pipe is at a central location some distance
from the perimeter, and if only the seams
between sheets are caulked, the cost in-
crease would drop to $66-$117. (Again,
these ranges result because of the differ-
ences in crawl-space floor area between
one- and two-story houses.)
The completeness of the membrane
sealing effort required depends upon how
significantly the leakage of crawl-space
air into the SMD system degrades radon
reduction performance, and how signifi-
cantly it increases the heating/cooling pen-
alty in the house. Some field testing re-
sults suggest that little membrane sealing
is required in some cases, except in the
immediate vicinity where the suction pipe
penetrates the membrane. However, test-
ing in crawl-space houses has been quite
limited, relative to that in basements and
slabs on grade. As a result, EPA cannot
give rigorous guidance regarding what de-
gree of membrane sealing is cost-effec-
tive. In view of the significant additional
cost that careful sealing requires, further
R&D in crawl-space houses appears de-
sirable in order to define the conditions
under which alternative degrees of mem-
brane sealing are required, and the per-
formance and operating cost penalties that
will result under the various conditions if
the sealing" is not performed (or if it de-
grades over time, as may occur if the
membrane is simply caulked to the foun-
dation wall). Both field demonstration test-
ing and more fundamental studies would
appear to be warranted.
Modifications to the design configura-
tion of crawl-space SMD systems (Item 6
in Table 3) can also have a significant
impact on cost. The one alternative con-
figuration which offers potential for reduc-
ing costs is the approach of leaving "diffi-
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Table 3. Parametric Variations Resulting in an Installation Cost Impact of About $100 or More
Mean
Cost
Impact1
($)
Estimated
Standard
Deviation1
($)
1. Adding SSO suction pipes to basement and slab-on-grade houses,
beyond the one pipe assumed for the baseline system (Variables
2 and 3):
• unfinished basements (increase per pipe added)
- finished basements (increase per pipe added)
- one-story slabs on grade (increase per pipe added)
- two-story slabs on grade (increase per pipe added)
2. Jackhammering one 0.6- by 0.6-m hole in the slab to enable exca-
vation of a large sub-slab pit in basements and slabs on grade
to improve suction field extension, rather than the baseline
case of simply coring a hole through the slab (Variable 6):
3. Modifications to the SSD exhaust configuration in basements
and craw) spaces, compared to the baseline exterior stack
discharging above the eaves (Variable 7):
- elimination of stack (grade-level exhaust)
— one-story houses
— two-story houses
- locating stack inside the house rather than outdoors
— mitigators less familiar with interior stacks
— one-story houses
— two-story houses
— mitigators more familiar with interior stacks
— one-story houses
— two-story houses
- routing stack up through adjoining slab-on-grade garage
4. Locating fan on roof (above exterior stack) rather than at
grade level outdoors, below the stack (Variable 8):
5. Increasing the degree of sealing of the slab or membrane,
compared to the baseline case where no slab or membrane
sealing is performed (Variable 10):
- sealing the accessible wall/floor joint in an unfinished
basement, where that joint is nor a perimeter channel drain
— one-story house (54-m perimeter)
— two-story house (39-m perimeter)
5. Increased degree of sealing, Variable 10 (continued)
- sealing the accessible wall/floor joint in an unfinished
basement, where that joint is a perimeter channel drain
— one-story house
— two-story house
- sealing the seams between membrane sheets in a crawl-space
SMD system
— one-story house
— two-story house
- completely sealing the SMD membrane, including the perimeter
and the seams between sheets
— membrane perimeter simply caulked to foundation wall
— one-story house
— two-story house
— membrane perimeter attached using furring strip
nailed to wall
— one-story house
— two-story house
+135
+221
+226
+274
+206
44
90
S3
95
208
-93
-169
+91
+155
-38
-61
+96
+235
37
84
10
91
35
74
59
35
+164
+108
+470
+326
+117
+66
+248
+102
+620
+456
127
91
262
184
46
45
113
70
160
71
Table 3. Continued
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Table 3. Continued
Mean
Cost
Impact1
($)
Estimated
Standard
Deviation1
($)
6. Modification of the baseline SMD design configuration (Variable 11):
- leaving a portion of crawl-space floor uncovered
- perforated piping loop around perimeter, membrane perimeter
sealed using furring strip
- perforated piping under central membrane, no sealing
7. Increasing the baseline pre-mitigation diagnostics (visual
inspection only) to include sub-slab communication measurements,
where the sub-slab diagnostics require an extra trip
to the house (Variable 13):
-100 (approx.)2
+500 (approx.)2
+100 (approx.'2
+208
46
The arithmetic mean increases (+) or decreases (-) in installation costs, relative to the baselines,
are calculated from the estimates from the five mitigators contributing to this study. The estimat-
ed standard deviations reflect the range covered by the five estimates.
Calculated independently of the estimates from the five mitigators. Thus, no standard deviation
is shown.
Table 4. Parametric Variations Resulting in an Installation Cost Impact of$50-$100
Mean
Cost
Impact1
($)
Estimated
Standard
Deviation1
($)
1. Increasing the horizontal piping run for the one-pipe SSD system
by 4.5 m in a finished basement, increasing the 3-m horizontal
run in the baseline system to 7.5 m (Variables 2 and 3):
2. Adding a 7.5-m horizontal run in the attic for the one-interior-
pipe SSD system in slab-on-grade houses, relative to the baseline
case where the interior SSD pipe extended straight up through the
ceiling and through the roof (Variables 2 and 3):
3. Adding additional suction pipes through the membrane of the
crawl-space SMD system, beyond the one pipe included in the
baseline (Variables 2 and 3):
- increase per pipe added
4. Upgrading the type of pipe to 10-cm diameter Schedule 40,
compared to the 10-cm thin-walled pipe used in the baseline
systems (Variable 5):
- basement houses
- slab-on-grade houses
- crawl-space houses
5. Upgrading the fan to a 100-W unit having 15- or 20-cm
couplings, compared to the baseline 90-W, 15-cm fan capable
of moving 127 L/s (Variable 9):
- upgrade to 100-W unit with 15-cm couplings, capable of
moving 169 L/s
- upgrade to 100-W unit with 20-cm couplings, capable of
moving 193 L/s
+89
+58
+63
+80
+54
+87
+50 to +7S2
+90 to +1202
69
21
8
29
49
1 The arithmetic mean increases (+) or decreases (-) in installation costs, relative to the baselines,
are calculated from the estimates from the five mitigators contributing to this study. The
estimated standard deviations reflect the range covered by the five estimates.
2 Calculated independently of the estimates from the five mitigators, based upon manufacturers'
quotes and assuming a 50% markup by mitigators for overhead plus profit. Thus, no standard
deviation is shown.
-------
Tablo 5. Parametric Variations Resulting in an Installation Cost Impact of Less Than $50
Mean
Cost
Impact1
($)
Estimated
Standard
Deviation1
($)
1. Utilizing sump/DTD rather than the baseline one-pipe SSD
system, in houses where a sump is present (Variable 1): +33 15
2. Increasing the horizontal piping run for the one-pipe SSD
system by 4.5 m in an unfinished basement, increasing the 3-m
run in the baseline system to 7.5 m (Variables 2 and 3): +33 16
3, Utilizing a one-pipe exteriorSSD system in a slab-on-grade
house (with the suction pipe penetrating horizontally through
the foundation wall from outdoors, with an exterior stack),
rather than the baseline case of one suction pipe vertically
through the slab indoors, with an interior stack (Variables 2
and 3):
- one-story slab on grade +10 34
- two-story slab on grade -25 54
4. Using 7.5-cm diameter piping rather than the baseline thin-
walled 10-cm piping (Variable 4):
- jf thin-walled 7.5-cm pipe and fittings available -212
- if only Schedule 40 7.5-cm pipe and fittings available +362
5. Excavating a small pit beneath the cored hole through the slab
in basement and slab-on-grade houses, compared to the baseline
casa of no pit (Variable 6): +18 18
6. Locating the fan inside the basement or crawl space, compared
to the baseline case where the fan is immediately outside the
house, with an exterior stack (Variable 8): 00
7. Using a smaller fan (50-70 W, 10- to 13-cm diameter couplings),
compared to the baseline 90-W, 15-cm fan (Variable 9): -152
8. Installing a less expensive alarm, rather than a Magnehelic
gauge (Variable 12):
- replace Magnehelic with curved inclined manometer -302
- replace with U-tube manometer or floating-ball device -452
9. Increasing the baseline pre-mitigation diagnostics (visual
Inspection only) to include sub-slab communication measurements,
where the sub-slab diagnostics can be conducted when
the crew arrives to install the system (Variable 13):
- unfinished basement +45 47
- finished basement or slab on grade +1063 3
10. Increasing post-mitigation diagnostics, beyond the suction and
indoor Rn measurements included in the baseline (Variable 14): O4
' The arithmetic mean increases (+) or decreases (-) in installation costs, relative to the baselines,
are calculated from the estimates from the five mitigators contributing to this study. The
estimated standard deviations reflect the range covered by the five estimates.
1 Calculated independently of the estimates from the five mitigators, based upon manufacturers'
quotes and assuming a 50% markup by mitigators for overhead plus profit. Thus, no standard
deviation is shown.
3 Includes estimate from only one mitigator.
4 Any post-mitigation diagnostics will likely result from failure of the initial installation to achieve
148 Bq/m3 arid less, and thus would be conducted under the warranty that most mitigators
offer, resulting in no additional direct cost to the homeowner.
cult" or inaccessible portions of the floor
area uncovered by membrane (rather than
ensuring coverage of the entire floor, as
in the baseline case). Depending upon
how much of the floor area is left uncov-
ered, and upon how inaccessible that area
is (i.e., how much it would have cost to
ensure complete coverage), leaving por-
tions of the floor uncovered could result in
installation cost reductions of $100 or
more. The uncertainty, of course, is how
such incomplete coverage might impact
the radon reduction performance of the
system.
The other SMD modifications consid-
ered involved the use of perforated piping
underneath the membrane in an effort to
improve the distribution of the suction field
under the membrane. These other modifi-
cations either increased costs, or left them
unchanged. The question is whether the
increased costs resulting from drawing
suction on a matrix of perforated piping,
rather than simply inserting a suction pipe
through the plastic, would result in suffi-
ciently improved performance to warrant
the increased cost. If the simple pipe pen-
etration through the complete but unsealed
membrane (the baseline case) is replaced
by suction on a matrix of perforated piping
under a complete but unsealed membrane,
the installation cost increases by about
$100.
If the baseline system is instead re-
placed by a loop of perforated piping
around the crawl- space perimeter, and if
the membrane covers only the perimeter
(from the foundation wall out to a distance
equal to the width of the polyethylene
sheeting), then the effect on costs will
depend upon the amount of membrane
sealing necessary. If this perimeter mem-
brane can be left largely unsealed, then
the cost increase resulting from the mate-
rials cost for the perforated piping is es-
sentially offset by the cost reduction re-
sulting from being able to leave the cen-
tral portion of the crawl-space floor uncov-
ered, and this configuration has a cost
comparable to the baseline. If, on the other
hand, location of the suction around the
perimeter (with this perforated piping loop)
requires careful sealing of the membrane
to the perimeter foundation wall using a
furring strip, whereas suction on a central
pipe penetration (as in the baseline) does
not require such careful sealing, then the
perimeter-loop configuration will be $500
more expensive than the baseline, due to
the expense of careful perimeter sealing,
discussed previously. If careful perimeter
sealing is not necessary with the perim-
eter-loop configuration, and if that con-
figuration gave good radon reductions (as
-------
it has in two study houses), this could
make the SMD approach feasible in
houses where the central area of the crawl-
space floor was inaccessible. Again, an
unanswered question is the relative effec-
tiveness of the two configurations in re-
ducing radon levels.
Because of the limited data base on
crawl-space houses, EPA is not able to
give guidance regarding the ability to re-
duce SMD costs by leaving a portion of
the floor uncovered, or regarding the cost-
effectiveness of using perforated piping to
improve system performance and to ex-
tend SMD applicability to houses where
portions of the crawl-space floor are inac-
cessible. As discussed previously, in con-
nection with the need to seal the mem-
brane, further R&D would be valuable in
crawl-space houses, in order to better de-
fine the tradeoffs between the cost sav-
ings (or cost increases) obtainable through
these SMD design modification, and the
reductions (or improvements) in radon re-
duction performance that might result.
The one other parametric variation listed
in Table 3 as having a significant cost
impact — locating the fan on the roof,
above the exterior stack (Item 4 in the
table) — increases the installation cost by
about $235, due primarily to the increased
cost of the roof-mountable fan itself. No
R&D is warranted to address this param-
eter. Roof mounting clearly offers no po-
tential for cost savings. There could be
some advantages in roof mounting (e.g.,
ice built up inside the piping in cold weather
could not fall into the fan blades, as could
happen when the fan is mounted at grade
level, at the bottom of the stack). How-
ever, there are also disadvantages, in-
cluding increased difficulty in performing
maintenance. Mitigators generally do not
mount fans on the roof at this time, and
there does not appear to be any technical
or cost justification to warrant encourage-
ment of that practice.
Parametric variations having a cost im-
pact between $50 and $100 (Table 4).
Among the parametric variations creating
an intermediate cost impact are increased
lengths of horizontal piping runs in fin-
ished basements (+ $89) and in the attics
of slab-on-grade houses (+ $58) (Items 1
and 2 in Table 4). The need for such
horizontal runs is usually determined by
site-specific considerations, involving the
degree of finish or other obstructions in
the house, and logical exit routes for the
exhaust piping. No R&D specifically ad-
dressing this parameter would appear war-
ranted.
Another parametric variation in this cat-
egory is the addition of suction pipes pen-
etrating the membrane in crawl-space SMD
systems (increasing costs by about $63
per additional pipe). Multiple SMD pipes
have been found to be helpful in a few
R&D study houses having large crawl
spaces and poor soil permeability, although
it does not appear that many m'rtigators
have used such multi-pipe systems com-
mercially. In the R&D recommended pre-
viously for crawl-space houses, it could
be of value to investigate whether multiple
pipes, or a sub-membrane matrix of perfo-
rated piping, or perhaps a layer of fiber
matting beneath "the membrane, or per-
haps more careful sealing of the mem-
brane, would be the preferred approach
when a single central suction pipe through
a complete, unsealed membrane (the
baseline system) appears insufficient.
Upgrading the type of pipe used, from
10-cm diameter thin-walled PVC piping to
heavier, 10-cm Schedule 40 piping (Item
4), would increase installation cost by $54-
$87, depending upon the length of piping
and the number of fittings required in the
system. Most mitigators consistently use
the thin-walled pipe, on the basis that it
provides sufficient strength for this appli-
cation, so that the increased material and
labor cost involved with the heavier pipe
is not warranted. The primary concern with
the thin-walled pipe is inadequate resis-
tance to ultraviolet (UV) radiation where
used outdoors. Some mitigators paint thin-
walled pipe installed outdoors, for UV pro-
tection (as well as aesthetics). There does
not appear to be any significant potential
for reducing installation costs through R&D
addressing this variable.
Upgrading the system fan to a 100-W
unit (with either 15- or 20-cm couplings)
increases the total installation cost by
about $50-$120 relative to the baseline
90-W, 15-cm fan, assuming a 50% over-
head/profit burden rate (Item 5 in Table
4). The larger fans would also increase
the operating cosl. Most residential instal-
lations do not require such a large fan,
and the 100-W fans are usually consid-
ered only in cases involving unusually high
flows. Such large fans appear to be
needed so infrequently in residential ap-
plications, that R&D to define more pre-
cisely when they are cost-effective would
appear to be of only secondary priority.
Parametric variations having a cost im-
pact of less than $50 (Table 5). Most of
the parametric variations in this category,
offering less potential for significant instal-
lation cost reductions, probably could not
be influenced by additional R&D. The use
of sump/ DTD rather than SSD (Item 1 in
Table 5) will usually be determined by
whether a sump is present in the base-
ment, and will be the preferred approach
in that case regardless of the marginal,
$33 average cost increase that results.
Increased horizontal piping runs in unfin-
ished basements (Item 2), or use of an
exterior rather than interior SSD system in
slab- on-grade houses (Item 3), will gen-
erally be determined by practical, site-spe-
cific considerations; it is unlikely that addi-
tional R&D addressing these parameters
would reduce system costs.
Most mitigators use of 7.5-cm instead
of 10-cm diameter piping (Item 4) only in
low-flow cases where there is some physi-
cal constraint (such as the need to fit
inside a stud wall) requiring the smaller
pipe. Since most mitigators stock only 10-
cm pipe, use of 7.5-cm pipe would often
result in increased complexity and in-
creased cost (beyond the -$21 to +$36
indicated in Table 5) due to the additional
planning required to obtain the needed
7.5-cm piping. Excavation of a small pit
beneath cored slab holes (Item 5) is a
step that many mitigators always take,
because it is either easy (where aggre-
gate is present) or is known (without fur-
ther research) to be required (where no
aggregate is present). Location of the fan
inside the basement or crawl space gen-
erally has no cost impact relative to mount-
ing immediately outside the house shell;
since interior mounting of the fan is against
EPA's recommendations , research on this
issue is not necessary.
Further R&D might be warranted for
smaller fans (Item 7 in Table 5), to better
define the conditions under which the use
of the smaller fan would offer benefits
(reduced material cost, reduced operating
cost) that would offset any reductions in
radon mitigation performance. However,
the potential reductions in the cost of the
fan itself are minor (about $10). As dis-
cussed under Operating Costs, below, the
reductions in operating cost will be rela-
tively small as well, except when consid-
ered in terms of energy consumption na-
tionwide by tens of thousands of installa-
tions. In addition, results to date suggest
that such reductions in fan capacity will
usually result in some increase in indoor
radon level, even if levels remain below
148 Bq/m3; hence, there will usually be
some increase in health risk resulting from
installing a smaller fan on a given system.
Thus, R&D on this parameter would ap-
pear to be of secondary priority.
The use of alternative alarms (Item 8) is
not an area where further EPA-sponsored
R&D would appear to be warranted.
Regarding increased pre-mitigation di-
agnostics (sub-slab communication test-
ing) where these diagnostics are con-
-------
ducted when the crew arrives to install the
system (Item 9), the situation is the same
as that discussed previously for the more
expensive case where a separate visit is
required to perform the added diagnos-
tics. Improved fundamental under- stand-
ing may lead to improved diagnostic meth-
ods and/or improved ways of interpreting
the diagnostic results. It is unlikely that
this fundamental R&D would reduce the
costs of conducting the diagnostics; in
fact, it might even result in diagnostics
having an increased cost. However, if the
improved diagnostic methods permit more
effective and/or less expensive SSD sys-
tem designs, the cost of these added di-
agnostics might be at least partially off-
set by decreases in installation cost (and/
or in reduced health risk through improved
system performance).
Similarly, fundamental and applied R&D
might improve the additional post-mitiga-
tion diagnostics that are necessary to de-
termine why a system is not performing
as desired (Item 10). Although the costs
of any such troubleshooting diagnostics
would commonly be borne by the m'rtigator
under the warranties that many mitigators
offer, and would thus not directly increase
the installation cost for that specific job,
installation costs do in fact include such
call-back costs, usually in the form of the
overhead/profit burden that is applied to
all jobs. Again, the improved post-mitiga-
tion diagnostics that might result from the
R&D might not be less expensive than
current methods, but hopefully might help
the mitigator solve the particular problem
more efficiently, hence reducing overall
costs.
Summary of discussion of installation
costs. Several radon mitigation system
design parameters have been identified
for which additional R&D might contribute
to reductions in the installation costs for
systems. Among the R&D areas appear-
ing to offer the greatest potential for cost
reductions are:
a) investigation of methods for improv-
ing sub-slab communication in poor-
communication houses, or for im-
proving system performance without
improvements in communication, to
reduce the number of suction pipes
necessary and/or to reduce the need
to excavate a pit beneath the slab.
Maximum potential savings: about
$135 to $274 per suction pipe elimi-
nated, roughly $200 per 0.6- by
0.6-m excavation avoided. If suc-
cessful, such R&D would prevent
SSD installation costs in poor-com-
munication houses from increasing
so significantly above the $1,000-
$1,200 cost for one-pipe SSD sys-
tems in houses having good com-
munication.
b) fundamental and applied R&D ef-
forts to improve pre-mitigation (and
post-mitigation) diagnostics, and to
improve the interpretation of these
diagnostics, with the objective of
achieving net reductions in the total
system installation cost (even if the
costs of performing the diagnostics
themselves do not decrease). Maxi-
mum potential savings: difficult to
define; the $45 to $240 cost of pre-
mitigation diagnostics would be off-
set if the diagnostics eliminated one
SSD suction pipe from the installa-
tion, saving $200.
c) testing to define the conditions un-
der which grade-level exhausts might
be acceptable for ASD systems, so
that the cost of an interior or exterior
stack could be eliminated. Maxi-
mum savings (where grade-level ex-
haust is found to be acceptable):
about $93-$169 if an exterior stack
is eliminated; about $189-$265 if a
stack through an adjoining garage is
eliminated; and about $55-$324 if
an interior stack is eliminated.
d) fundamental and demonstration test-
ing to enable better guidance re-
garding the design of SMD systems
for crawl-space houses, including
identification of the cost-effectiveness
of alternative degrees of membrane
sealing, alternative degrees of floor
coverage by the membrane, and al-
ternative methods for using perfo-
rated piping to aid in suction field
extension under the membrane, un-
der different conditions. Maximum
savings: as great as about $600, if
it is found that careful membrane
sealing is not required. Major ben-
efit of R&D could be improved sys-
tem performance in reducing indoor
radon levels.
It is difficult to predict how successful
R&D addressing those parameters might
be in reducing installation costs. From a
practical standpoint, it is reasonable to
assume that R&D efforts would likely
achieve only a fraction of the maximum
cost savings listed above for the param-
eters offering the greatest potential for
cost reductions. (For example, the method
used to enable the number of suction pipes
to be reduced might cost, say, half as
much as the additional pipes would have
cost, so that the net savings from reduc-
ing the number of pipes would be only
half of the roughly $200/pipe indicated
above.) Thus, realistically, the greatest cost
reductions that might be expected result-
ing from the R&D effort on all of these
parameters would be on the order of sev-
eral hundred dollars (on systems having
baseline installation costs ranging from
$1,000 to $1,400). As discussed in con-
nection with a) above, some of these sav-
ings would likely be achieved only for "dif-
ficult" houses (e.g., houses with poor sub-
slab communication), where the installa-
tion costs would have otherwise been
much greater than the baseline costs
(which were derived for good-communica-
tion houses). Thus, some of these sav-
ings would not reduce the baseline instal-
lation costs below $1,000-$1,400, but
rather, would simply prevent costs for dif-
ficult houses from escalating so signifi-
cantly above this baseline.
In addition to the possible reductions in
installation costs, R&D aimed at reducing
the number of SSD suction pipes or elimi-
nating the exhaust stack would also im-
prove the aesthetics of these systems,
possibly resulting in some incremental in-
crease in voluntary utilization of this tech-
nology by homeowners.
The price/demand curve for ASD sys-
tems, though unknown, is anticipated to
be relatively inelastic, based upon practi-
cal experience. Thus, it is not likely that
cost reductions of several hundred dollars
would be sufficient to create a dramatic
increase in ASD utilization by homeowners,
especially not for houses having only mar-
ginally elevated pre-mitigation radon lev-
els.
Therefore, to reduce the 78-86% of the
national lung cancer risk associated with
houses below 148 Bq/m3, some innova-
tive, simple, low-cost mitigation
approaches) — that will be widely utilized
by homeowners having only marginally-
elevated levels — will be required, in ad-
dition to ASD. If such alternative mitiga-
tion approaches are widely used, they may
provide a greater reduction in national
health risk than will ASD, even if these
alternatives provide less of a radon reduc-
tion in a given house than does ASD.
As one additional consideration, the
prices actually being charged to
homeowners for comparable ASD instal-
lations by the five mitigators participating
in this study vary by more than $500,
reflecting a clear regional variation in the
going market rate for mitigation systems.
Based upon this observation, it would ap-
pear that market forces will have an im-
pact on installation costs that is at least
as great as the possible cost savings re-
sulting from R&D.
10
-------
Operating Costs
Cost of electricity to operate the fan.
The baseline fan is a 90-W in-line duct
fan having 15-cm diameter couplings. As-
suming that this fan draws the full 90-W
(which it likely will not do) for 365 days
per year, and that electricity costs $0.08/
kWh, the cost of electricity to operate this
fan would be $63 per year, or about $5
per month.
Replacing this fan with the smallest fan
considered here (50 W), or assuming that
the 90-W fan was turned down to the
point where it drew only 50 W, would
result in an annual cost of electricity of
$35. The annual savings in the cost of
electricity, relative to the 90-W fan, would
be $28, or about $2 per month.
On the other hand, replacement of the
90-W fan with one of the larger, 100-W
fans would increase the cost of electricity
by $7 per year, or about $0.50 per month.
Heating/cooling penalty. To estimate the
heating/cooling penalty of the ASD sys-
tems, it was assumed that the ASD sys-
tem with the baseline 90-W fan exhausts
75 cfm,* 50% of which is house air (dis-
cussed above under Approach). The house
is assumed to be in a climate representa-
tive of Washington, D. C., with a gas-fired
forced-air furnace and an electric air con-
ditioner.
With these assumptions, for the baseline
90-W fan, the house heating cost increases
by $49 per year, and the cooling cost
increases by $30 per year, for a com-
bined heating/ cooling penalty of $79 per
year, or about $7 per month on average.
Thus, for the 90-W fan, the total operating
cost (the combined cost of electricity and
heating/cooling penalty) is $63 + $79 =
$142 per year, or about $12 per month.
The heating/cooling penalty could be
reduced in two ways. One approach would
be to reduce the capacity of the fan, so
that less air would be exhausted. The
second approach would be to seal cracks/
openings in the slab, to reduce the frac-
tion of the exhaust which is treated house
air.
If the 90-W fan (75 cfm total exhaust)
were replaced with a 50-W fan (assumed
to have a total exhaust rate of about 38
cfm), and if the slab remains unsealed (as
in the baseline), the amount of house air
exhausted would decrease from 50% of
* 1 dm = 0.00047 mfs.
75 cfm (or 38 cfm) to 50% of 38 cfm (or
19 cfm). The corresponding heating/cool-
ing penalty would fall from $79 to $39 per
year. The total operating cost (electricity
plus heating/cooling penalty) would thus
decline from $142 per year with the 90-W
fan, to $35 + $39 = $74 per year with the
50-W fan, a total savings of $68 per year,
or about $5.50 per month, resulting from
the switch to the smaller fan.
To assess the effect of slab sealing, it
is assumed that caulking the wall/floor joint
and other slab sealing steps reduce the
percentage of house air in the exhaust to
30%, rather than 50%. The total exhaust
flow from the ASD system is assumed to
be reduced accordingly, due to the lower
flow from inside the house. With the 90-W
fan, with these assumptions, caulking the
slab would reduce the total system ex-
haust from 75 to 54 cfm, and would re-
duce the amount of house air exhausted
from 50% of 75 cfm (38 cfm) to 30% of 54
cfm (16 cfm). Thus, slab sealing would
decrease the heating/cooling penalty with
the 90-W fan from $79 to $33 per year, a
savings of $46 per year or about $4 per
month. Slab sealing would reduce the to-
tal operating costs for the 90-W fan from
$142 per year to $63 + $33 = $96 per
year.
Combined effect of reduced fan size
and slab sealing. If the reduced heating/
cooling penalty associated with slab seal-
ing is combined with the operating cost
savings associated with switching to a
50-W fan, the result should roughly repre-
sent the greatest reduction in operating
costs that might reasonably be anticipated.
With the slab sealed, the total ASD ex-
haust rate with the 50-W fan would drop
from 38 to 27 cfm. The amount of house
air exhausted by the system would drop
to 30% of 27 cfm (or 8 cfm). At this low
house air exhaust rate, the heating/cool-
ing penalty would fall to $17 per year. The
total operating cost (electricity plus heat-
ing/cooling penalty) for this case (50-W
fan, slab sealed) would thus be $35 + $17
= $52 per year. Comparing this cost to the
$142 per year estimated for the baseline
case (90-W fan, slab unsealed), the cost
savings is $90 per year, or $7.50 per
month.
Summary of discussion of operating
costs. By switching to a small fan and by
sealing the slab, the maximum potential
operating cost savings that can result from
the combined effects of reduced fan elec-
trical consumption and reduced heating/
cooling penalty are $7.50 per month.
These savings might or might not be dis-
tinguishable among the normal variations
that homeowners would see in their
monthly gas and electric bills. The total
savings of $90 per year might be impor-
tant to some homeowners. On a national
scale, the reduction in energy consump-
tion by tens of thousands of installations
could be significant. However, it is doubt-
ful that the incremental operating cost sav-
ings resulting from the use of less electric-
ity and less gas would often play a deter-
mining role in the decision by an indi-
vidual homeowner whether or not to in-
stall an ASD system.
It is re-emphasized that the reduction in
fan capacity will commonly cause some
degradation in the radon reduction perfor-
mance of the ASD system, even if indoor
levels remain below 148 Bq/m3. Thus, the
modest reduction in operating cost would
be achieved at the expense of some in-
crease in health risk. A better understand-
ing of the impacts of reduced fan capacity
on ASD performance — and of any incre-
mental increase in demand for ASD sys-
tems that might result from the reduced
operating costs — would be required in
order to perform a cost-benefit analysis
which could integrate these considerations
(i.e., which could estimate the effect of
the reduced fan capacity on the cost-per-
life-saved).
Additional R&D would be needed to sup-
port such a cost-benefit analysis. This R&D
would include field testing, supported by
fundamental R&D, to more rigorously de-
fine: a) how reductions in fan capacity
influence indoor radon levels under vari-
ous conditions; b) how reductions in fan
capacity influence the amount of house
air exhausted under various conditions; c)
how alternative degrees of slab sealing
influence the amount of house air in the
ASD exhaust; and, if possible d) the ac-
tual impacts of ASD systems on house
ventilation rates (as distinguished from the
amount of house air in the exhausts).
11
•&U.S. GOVERNMENT PRINTING OFFICE: 1992 - 648-080/40146
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D. Bruce Henachel (also the EPA Project Officer see below) is with Air and Energy
Engineering Research Laboratory, Research Triangle Park, NC 27711.
The complete report, entitled "Parametric Analysis of the Installation and Operating
Costs of Active Soil Depressurization Systems for Residential Radon Mitigation,"
(Order No. PB92-116 037/AS; Cost: $26.00, 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
EPA/600/S8-91/200
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