Christopher
J. Seffrin Jersey
Infrared Consultants
P.O. Box 39
Burlington, NJ 08016
609-386-1281
Abstract
The use of
infrared thermography for flat and low-slope roof inspections
has become increasingly common during the last 20 years. Thermography
is typically used for condition assessment and forensic studies,
as well as quality assurance of new installations. Experience
has shown few facilities willing to incorporate thermography
into a regular maintenance program. This paper illustrates
a six-year case study illustrating how one facility has used
thermography to reduce maintenance costs while extending the
life of their roofing system and improving its performance.
A financial model illustrating savings is also provided.
Introduction
Infrared thermography was first used to detect
moisture entrapment within flat and low slope roofing systems
in the 1970's. Since that time its usage has steadily increased
with millions of square feet now inspected annually worldwide.
Widespread usage of thermography led to the publication of
Standard Practice C-1153 by ASTM in 1990.
Generally, thermography can be applied to
built-up and single-ply roofing systems where either an insulating
roof deck or a layer of insulation is located in direct and
continuous contact with the underside of the roof membrane.
Thermography may be performed from aircraft or ground-based.
With the proper equipment, technique, and training, a thermographer
can detect and document areas of moisture infiltration ranging
from a few square inches to thousands of square feet.
For varied reasons, many facility managers
do not perform routine roof maintenance. Often if the roof
is not leaking, there is no motivation to perform inspections
of any type. Our experience indicates that thermography is
generally used only after a roof has entered failure or as
a quality assurance tool for new installations and retrofits.
In order to assess the effectiveness of thermography
as a maintenance tool, annual infrared inspection reports
covering a five-year period for a large warehouse were studied.
Results were then compared with maintenance costs and building
performance. This paper documents and discusses the results
of that study.
Case
History
The Pennsylvania Liquor Control Board is
a state agency, which operates a 360,000-square-foot warehouse
and distribution center in Philadelphia, Pennsylvania. The
roof comprises a corrugated metal deck covered with wood fiber
insulation, and a coal-tar-built-up membrane covered with
slag. The roof is divided into eight discrete areas on two
elevations.
In 1992, the roof began to experience leaks
in several areas. Faced with a 22 year old roof entering failure,
PLCB management began to investigate the possibility of replacing
or retrofitting the entire roof. Cost estimates for replacement
ranged from 2.5 to over 3 million dollars.
In order to help assess the condition of
the existing system, Jersey Infrared Consultants were engaged
to perform an infrared inspection of the entire roof in September
1992.
Findings
On September 14, 1992, an infrared inspection
was performed using an Inframetrics 522 infrared imaging system.
All work was performed in accordance with ASTM Standard Practice
C-1153. All thermal data were verified with core samples and
correlated moisture-meter readings. All wet areas were outlined
on the roof surface with spray paint.
Our infrared inspection found seven separate
wet areas comprising a total of 1,208 square feet of subsurface
moisture. With less than one percent of the roofing system
requiring replacement, a roofing contractor was hired by the
PLCB to remove the moisture-damaged areas and to make other
necessary repairs. The total cost of the repairs and the infrared
inspection for 1992 totaled $20,705.
In order to verify the 1992 roof repairs
and to re-assess the condition of the entire roof, another
infrared inspection was performed in December 1993. Our 1993
inspection found seven new wet areas comprising a total of
1,399 square feet of subsurface moisture. Once again, less
than one percent of the roofing system required replacement.
A roofing contractor was again hired by the PLCB to remove
the moisture-damaged areas and to make other necessary repairs.
The total cost of repairs and the infrared inspection for
1993 totaled $18,217.
Pleased with improved roof system performance
and repair costs far less than replacement, the PLCB opted
to perform infrared inspections and repairs annually beginning
in 1994. The results of these inspections are listed in Table
1.
Table
1
Year
Number of
Wet Areas
Area of
Damage (sf)
Percent
Damage
Annual
Cost
1992
7
1208
<1
$20,705
1993
7
1399
<1
18,217
1994
3
83
<1
5,865
1995
1
30
<1
4,020
1996
1
144
<1
4,270
1997
5
172
<1
6,224
Total
$59,301
The total cost for infrared inspections and
repairs for the period 1992 through 1997 totaled $59,301.
Of particular note is the annual decrease
in the total area of damage after 1993. For years 1994 and
1995, the total damage is confined to less than 100 square
feet annually and less than 200 square feet in both 1996 and
1997.
Additionally, the overall sizes of the largest
wet areas ranged from 276 to 400 square feet in 1992 and 1993
while the largest wet areas have ranged from 30 to 144 square
feet since 1994. Not surprising is the reduction in annual
maintenance costs. With less damage to repair, annual costs
are reduced.
Discussion
Since the annual infrared inspection and
preventive maintenance program began, no areas of moisture
damage have been detected in the same location from year to
year. This would suggest that effective repair efforts were
accurately directed to the problem areas.
The number of problems detected annually
has decreased and the overall sizes of the wet areas detected
have also decreased since 1992. This would suggest that wet
areas detected after 1993 were being caught in their formative
stages. The proactive approach of combining infrared inspections
with proper repairs has helped to reduce annual maintenance
costs.
Building management also reports an overall
increase in the performance of the building. With fewer leaks
annually and less damage in the roofing system, there is a
greater amount of usable floor space available within the
building. In many instances, the infrared inspections have
detected moisture damage within the roof before corresponding
leaks were experienced within the building.
When thermography was utilized in 1992, a
replacement option for the roof was being considered. The
results from the infrared inspection, combined with effective
repairs, have allowed management to retain the original roof
and avoid the expense associated with replacement or retrofit.
This savings allows the money to be used for other purposes
or invested.
For a privately owned facility of this size,
budgeting a capital outlay of 3 million dollars at an interest
rate of 10%, interest would amount to $300,000 for the first
year alone. Using these figures, the interest for the first
year is more than 5 times the entire proactive costs for a
6-year period!
When calculated for a five-year period, interest
costs for replacement would total $900,000. Subtracting the
total proactive costs of $59,599, we realize a savings of
over $840,000.
It should be noted that neither energy savings
nor the avoided cost of lost product were considered for this
facility. Had they been considered, the actual savings would
have been greater.
Conclusion
By utilizing thermography as a proactive
maintenance tool, it is possible to increase the performance
of the roof while extending its useful service life as well
as reduce overall maintenance costs. The effectiveness of
such a program will depend upon the quality of the data obtained
from the infrared inspection as well as the quality of the
repairs.
While this paper studied only one building,
the implications for similar success on other buildings make
a strong case for this type of proactive maintenance program.
Since the overall success will depend upon the initial condition
of the roof, infrared inspections should be implemented before
the roof begins to leak. Where possible, the roof should be
inspected soon after installation and annually thereafter.
References
ASTM C- 1153 Standard Practice for the Location
of Wet Insulation in Roofing Systems Using Infrared Imaging.
