Radon Resistant New Construction (RRNC) Efficiency Testing
January 2005 through February 2005
Brian R. Hanson
Kansas Radon Program
133 Ward Hall
Kansas State University
Manhattan, KS 66506

Funding provided by the State Indoor Radon Grant (SIRG) program through the Kansas
Department of Health & Environment and the Environmental Protection Agency (EPA).
Work performed by the Kansas Industrial Extension Service at Kansas State University
with the assistance of the Manhattan Municipal Code Department at the City of
Manhattan.

Abstract
The Kansas Radon Program performed a follow-up round of efficiency testing of
homes built with Radon Resistant New Construction (RRNC) techniques in Manhattan,
Kansas. The project was designed to review performance and identify whether defects
identified during the November 2002-January 2003 testing program (performed in
conjunction with the National Environmental Health Association (NEHA), the EPA and
the City of Manhattan), were being reduced or eliminated. Eleven homes volunteered to
undergo efficiency testing as per the EPA RRNC efficiency testing protocol. Of the 11
homes, 4 homes (36%) exhibited elevated radon levels (average radon value of 4.0 pCi/L
or higher) during the operational phase of the testing. The average observed percent
reduction in the RRNC systems was 36.6%. Construction errors similar to those
identified during the November 2002 testing period were found, including: 1) unsealed
sump pit foundation penetrations, 2) excessive horizontal pipe runs, and 3) inadequate
attic bracing on horizontal pipe runs.
Introduction
Radon gas is a radioactive element that can collect in homes, sometimes in fairly
high airborne concentrations. Studies have shown that radon gas is the second leading
cause of lung cancer, behind tobacco smoke. As such, exposure to elevated levels of
radon in the home can increase the risk for individuals regarding the development of lung
cancer.
As of February 2001, all new single-family and two-family homes in Manhattan,
Kansas, have been required to be built with radon resistant new construction (RRNC)
building techniques due to the adoption of the RRNC appendix to the International
Building Code (IBC 2003). The goal of RRNC construction is to control indoor radon

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concentrations, with the stated concentrations to be maintained below 4.0 pCi/L, which is
the EPA’s recommended action level.
Three primary elements exist with RRNC construction. First, a porous fill is used
to level the future foundation of the house. Gravel fill is ideal as it provides the least
resistance to airflow. Sand fill can be used as long as corrugated drain tile is looped
through the fill. Second, a polyethylene sheet is used to separate the fill from the
concrete. The sheet acts as a barrier to radon gas, which aids in keeping the radon from
penetrating the concrete foundation. Third, a minimum three inch diameter plastic vent
stack is ran from the fill, through the foundation and up through the roof of the house.
The vent stack provides a means of escape for the radon from under the foundation and
the polyethylene sheet and acts to vent the radon into the atmosphere. However, since
RRNC techniques are designed to control radon passively, without the use of a fan to
induce suction, there is no guarantee that indoor radon levels will be maintained below
the 4.0 pCi/L action level.
In order to examine the efficiency of RRNC construction, NEHA and the EPA
partnered to provide funds to municipalities to test homes built to RRNC specifications.
The City of Manhattan, Kansas, along with the Kansas State University Research and
Extension Service, was one of the award grantees.
Nine homes agreed to participate in the first RRNC efficiency testing procedure.
One of the nine homes was eliminated from testing due to construction features of the
roof, which would have made the capping/uncapping process unnecessarily dangerous.
A second of the nine homes was disqualified when additional examination of the RRNC
vent stack revealed that it had been exited through the side of the house at ground level
rather than vented through the roof as required by the RRNC protocol. Seven homes
were successfully tested using the EPA RRNC efficiency protocol, the results of which
are listed in Table 1.
Table 1. EPA RRNC Test Protocol Houses - First Round - November 2002
Preliminary Test House
Zip
House Non# Code
Operational operational Percent Reduction
2.3
1 66502
2.4
1.9
N/A
4.4
2 66502
3.8
4.6
17.4%
66502
5.2
3
4.1
7.0
41.4%
66502
5.2
4
4.8
5.7
15.8%
6.1
5 66502
4.8
7.9
39.2%
6.1
6 66502
6.1
11.1
45.0%
10.1
7 66502
N/A
12.1
7.7
Five of the seven homes tested exhibited a drop in radon levels when the RRNC
system was operational, with the average radon reduction being approximately 31%.
House #1 indicated that a window in an upstairs bedroom had inadvertently been opened.
House #7 indicated that the HVAC system for the house had been turned off and that
there was one evening during the testing period where two windows were inadvertently
opened on the upper floor but not in the basement where the test kits were located.

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A statistical examination of the results (see Table 2) indicated an average radon
value of 5.4 pCi/L with RRNC systems operational and 6.6 pCi/L with the systems nonoperational. A Student’s T-Test indicates that there is no significant difference between
the operational and non-operational sample sets (t=0.4, p<0.05). This result indicates that
the absolute radon values between the two sample sets are not statistically different.
However, the observed average percent reduction of 31% in radon between the sample
sets is a better indicator of system efficiency due to the low n-value of homes used in the
statistical evaluation.
Table 2. Statistical Results – First Round – November 2002
House Operational House Non-operational
5.4
6.6
Mean
3.1
2.9
Standard Deviation
Student's T-Test
0.4
A follow-up round of testing was proposed for the winter in the Kansas Radon
Program’s work plan for the State Indoor Radon Grant (SIRG) Year 15 funding period.
A total of 149 homes constructed since the testing period began in November 2002 were
contacted to participated in the new round of RRNC efficiency testing. Fifty-three letters
were returned as undeliverable, indicating that those homes were as yet unoccupied or
still under construction. Eleven homes volunteered to undergo the testing procedure.
Results
Eleven homes were tested during the operational phase of the efficiency testing
protocol. The average exhibited radon value was 3.4 pCi/L with a standard deviation of
2.4 (See Table 3). Four homes (36%) exhibited operational phase radon concentrations
of 4.0 pCi/L or greater. Home number 2 was eliminated from the non-operational phase
due to safety concerns related to roof design and the placement of the radon vent pipe.
The average exhibited radon value during the non-operational phase was 4.8 pCi/L with
a standard deviation of 3.4. The average percent reduction across the 8 homes that
exhibited differential radon values was 36.6%.
Table 3. EPA RRNC Test Protocol Houses - Second Round - January 2005
# Zip Code House Operational
1 66502
2 66502
3 66502
4 66502
5 66502
6 66502
7 66502
8 66502

House Non-operational Percent Reduction

0.8
3.7
0.8
6.9
3.7
5.4
1.9
1.3

1.5
Not Tested
1.0
11
5.8
7.6
4.0
2.0

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46.7%
N/A
20%
37.3%
37.9%
28.9%
52.5%
35%

9 66502
10 66502
11 66502

7.4
1.3
4.4

6.9
1.1
6.7

N/A
N/A
34.3%

As noted above, home number 2 was eliminated from the non-operational testing
phase due to safety concerns. The vent pipe on home number 9 was found to have fallen
into the home’s attic when Kansas Radon Program personnel boarded the roof to place
the cap on the vent pipe. When the pipe was reinserted through the roof and a proper
drainage level for the pipe was achieved, it was noted that there was water trapped in the
pipe, making it non-functional during the operational testing phase. The system in home
number 10 was examined, but no identifiable flaws were located. The lack of significant
change in radon values between the operational and non-operational phases indicates that
the RRNC system is having little to no effect on the homes radon gas concentrations.
A Student’s T-Test indicates that there is no significant difference between the
operational and non-operational sample sets (t=0.3, p<0.05). This result indicates that
the absolute radon values between the two sample sets are not statistically different.
However, the observed average percent reduction of 36.6% in radon between the sample
sets is a better indicator of system efficiency due to the low n-value of homes used in the
statistical evaluation. The statistical results are essentially unchanged from the
November 2002 testing program results.

Table 4. Statistical Results - Second Round - January 2005
House Operational House Non-operational
3.4
4.8
Mean
2.4
3.4
Standard Deviation
Student's T-Test
0.3

Discussion
The current study examined the efficiency of RRNC construction techniques for
the control of indoor radon concentrations, with the state goal being to maintain radon
concentrations below the EPA’s action level of 4.0 pCi/L. Homes were tested in
Manhattan, Kansas. The homes tested were all approximately 1 year of age or less. The
testing regimen was used to identify whether or not previous construction errors
identified during the November 2002 testing period had been corrected by area home
builders.
An examination of the initial test results, 36% of the 11 homes tested exhibited an
average indoor radon value of 4.0 pCi/L or higher during winter testing (January 2005).
These results compare to 54% of the 24 homes screened in November 2002. As with the
November 2002 testing period, statistical evaluation of the samples during operational
and non-operational phases indicated no significant difference in radon reduction.
However, an examination of the percent reduction indicated an average 36.6% radon
reduction across the houses between the operational and non-operation phases, compared

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with an average 31% reduction in November 2002. This observed reduction indicates
that while the RRNC passive systems are not always meeting the 4.0 pCi/L goal, the
systems are reducing indoor radon concentrations.
As was the case with the group of homes tested during the November 2002
program, several construction errors were identified. Several homes had covered but
unsealed/caulked sump pits. Multiple homes exhibited horizontal pipe runs, either in the
level where the pipe entered the foundation or in the attics. One home was found to have
the radon vent pipe fallen into the attic due the installation of upside-down J-hooks being
used to support a horizontal run. Another home had the pipe exit through the attic
portion over the garage, outside the heated envelope of the home.
These construction flaws contribute to the loss of radon reduction value from the
RRNC construction. Long horizontal runs reduce the vent stack’s ability to draw radon
through it by increasing airflow resistance. Garage-mounted vent stacks also reduce
stack effect induced venting suction by placing the stack outside the heated area of the
home. Non-sealed sump pits provide areas of escape for radon gas from the vent stack
itself.
Two items need to be noted concerning the results of this study. One, RRNC
construction techniques do reduce the amount of indoor radon gas. As noted above, the
average percent reduction across the eight houses was slightly more than 36%. Given
the possible lung cancer risk factors associated with long-term radon exposure, any
reduction in the radon concentration is desirable. Two, errors in following the protocols
for installation of RRNC passive control systems deteriorate the overall efficiency of
those systems.
However, there is no blame to be given in the observed construction faults. There
is a learning curve associated with any new technique, and it is the purpose of this type of
research to identify flaws and offer recommendations on corrective measures. Once
identified, a design fault can be corrected, and the information gained here will assist in
correcting those faults in the future.
References:
U. S. Environmental Protection Agency. 1999. Design for a program to measure the
effectiveness of passive radon-resistant new construction. Indoor Environments
Division, Washington DC.

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