Navy Study on Elastomeric Coatings
- Summary of NCEL Technical Note N-1815
- “INVESTIGATION OF SPRAY-APPLIED POLYURETHANE FOAM ROOFING SYSTEMS-II”
- Naval Civil Engineering Laboratory—Port Hueneme, California
- Sponsored by Naval Facilities Engineering Command
- Conducted by: R.L. Alumbaugh, E.F. Humm, and John R. Keaton
- July 1976–January 1986
Background: This study was initiated by the NCEL at the request of NAVFAC in a continuing effort to reduce maintenance and repair costs of the roofs at Naval installations. This study was limited to Spayed Polyurethane Foam (SPF) and Coating roofs, and was intended to generate data that provides guidelines for coating systems to protect SPF materials used in the roof.
The principal objectives of this investigation were to determine how long the candidate SPF roof perform satisfactorily when exposed to the weather and which of the candidate roofs were superior. The SPF roofs were exposed to 3 different climatic conditions: A seashore site at Port Hueneme, CA, a desert site at China Lake, and a mountain site at Pickle Meadows in the high Sierras.
Their experience had shown that if the SPF is properly applied to a suitably prepared substrate, the performance of the roof is primarily dependent on the performance of the protective elastomeric coating system. That is, with a high quality foam, if the coating performs well, the SPF roof as a whole can generally be expected to perform well.
The performance of the coated SPF panels at the 3 sites was monitored periodically. The performance characteristics of the various systems were determined at periodic intervals by visual inspections and ratings. The characteristics considered related primarily to the coatings and included adhesion, blistering, checking, cohesion, cracking, flaking, peeling, pinholing, and hail and bird damage. All of these factors were then considered in assigning an overall performance rating as follows:
- 10=Excellent: The system is performing without any noticeable deterioration.
- 9=Very good: Only very minor deterioration of the system.
- 8–9=Good: Although the system shows some deterioration, it is not yet serious.
- 7=Poor: System deterioration is becoming serious. Remedial action will be required in the near future.
- 6–0=Failed: Deterioration of the system has advanced to the point of requiring immediate maintenance.
Results of Field Investigations
Of the 54 systems tested, only 11 were rated Very Good (9) or Excellent (10) at all 3 sites. There were 2 Silicone systems, 5 Acrylics, 3 Urethanes and 1 Urethane-Silicone. (Tables 12,13) Of those we have extracted the following for comparison: (Note: All three of these systems were set out at the same time in December of 1978. The results recorded here were observed in January of 1986. total exposure time was 7 yr. 11 months at that time.)
Silicones: Moisture-Cured-System 2G
Dow Corning #3-5000 construction Coating, Gray Base and White Top Coat with Granules over CPR Upjohn 485-2 foam was rated Excellent (10, 10, 10) at all three sites. (Note: the other 2 Dow Silicone systems (2, 2A) in the study without granules were downgraded due to cracking, checking, bird pecking.)
System 6G: United Coatings “Diathon” with granules over CPR Upjohn 485-2 foam. At all 3 sites was rated Excellent (10, 10, 10), At the seashore site, minor blistering caused slight downgrade. The other two Diathon systems (6,6A) without granules were both rated lower due to pinholing, checking, cracking and bird pecking.
SYSTEM 24G:SWD URETHANE COMPANY’S “1929F” WITH GRANULES OVER SWD 525-2.5 FOAM. RATED EXCELLENT (10, 10, 10) AT ALL 3 SITES. THERE WAS NO DETERIORATION.
A Comparison of Conventional and SPF Roofs—A Texas A&M Study
- Sam Cohen—Project Management Supervisor
- Engineering Design Services
- Physical Plant Department
- Texas A&M University
In 1974, dissatisfied with the performance of traditional tar and gravel built-up roofs (BUR), the Physical Plant Department began looking for viable roofing alternatives. The BUR roofs were constantly leaking, and because of the nature of BUR, leak detection was virtually impossible.
As the Physical Plant Department began soliciting information from various roofing sources and checking references, sprayed polyurethane foam (SPF) roofs exhibited advantages that seemed to fit the criteria of the University. The Physical Plant Department found the following:
- Seams are one of the major sources of leaks in roofs, and SPF roofs are totally seamless.
- Water does not travel laterally in SPF roofs as it can in BUR or single-ply roofs. The water from a leak in the top membrane of a BUR or single-ply roof will spread, saturating the insulation and causing multiple interior leaks. With SPF, even if a hole is punched through the entire two-inch membrane, water movement will be restricted to the hole. In most cases, repairs can be made with a tube of caulk.
- Because the SPF roof is lightweight, permeable, and fully adhered, the old roof normally does not need to be removed to apply a new one. If underlying areas of saturated insulation are found, minimal tear-off may be required.
- SPF roofing is less disruptive to students and faculty since tear-off is minimal. Also, projects are accomplished faster because the application is quieter, quicker, and requires far fewer laborers.
- Roof-mounted units, penetrations, curbs, and parapets can receive a seamless monolithic application because SPF is spray applied. BUR and single-ply roofs require flashing materials with sealants that frequently result in leaks.
In 1974–75, convinced the proceeding advantages warranted taking a look at this relatively new roof, the Physical Plant Department issued contracts for the reroofing of several buildings. One of the earliest roofs was Davis-Gary dorm. After 17 years, this roof has not leaked and requires minimal maintenance.
Between 1975 and 1977 the Physical Plant Department and TAMU Systems Facilities Planning and Construction (FPC) communicated back and forth concerning the monitoring of these roof installations. New BUR roofs were providing the University with a service life of less than 5 years, and many of the BURs were leaking from the onset.
In 1977, the Physical Plant Department foamed over a BUR application that was less than 4 years old. After monitoring the SPF installations, FPC was also convinced, and since 1977, all new roof applications have used SPF roofs.
FPC received numerous complaints stemming from this decision. Few roofing contractors had the financial ability to mobilize spraying foam. Fewer still had the caliber of crews that chemically formulate foam in the field. Though this eliminated potential bidders, it in effect greatly elevated the caliber of roofing contractor performing work at Texas A&M.
Many outside architects working at the University were unfamiliar with the roof, and some of these had a reluctance to learn anything new, but the Physical Plant and FPC were adamant. As time went by, architects and general contractors learned the many advantages of the roof. This caused the proliferation of SPF roofs in surrounding school districts and universities.
Today, over 7 million square feet of SPF roofing has been applied throughout the A&M System. With very few exceptions, these roofs are holding up extremely well. In fact, it is rare that one of these roofs leaks at all. Blister defects, which occasionally occur, do not create leak problems. Most leak problems at the campus occur on the few buildings that still have BUR on them.
More Advantages—Leak Prevention, Reduced Utility Costs
In 1985, the Physical Plant Department found another advantage in using SPF roofs. For a number of years, Mr. Gerald Scott, P.E. was in charge of roofing and energy conservation within the Physical Plant Department. Vendors of the SPF roof always championed the energy-saving characteristics of the roof.
They realized polyurethane was a most effective insulation, but their main concern had always been to prevent roof leaks.
Mr. Scott monitored energy savings on 27 different buildings that had received SPF roofs from 1980 to 1984. The results were astounding. TAMU was able to recover the complete cost of the roof application through energy savings in an average of 4.5 years.
"Without question, SPF roofs have a tremendous edge"
Quoted here is Mr. Scott’s conclusion, which is still shared by today’s Physical Plant Department:
“From the time of construction, and throughout the life of the roof, built-up roofs were major maintenance and repair items. The experience that the Texas A&M University Physical Plant gained since 1974, when they began, indicates that no major problem, and very few minor ones, exist in SPF roofs.
“As a result of this experience, all new construction includes SPF roofing. To date, some 16 new facilities have this roof, totaling nearly 1 million square feet.
“Another major advantage in an SPF roof that does not exist with any other roof, is that SPF is renewable. While BURs and single-plys must be removed and replaced after their usable lives, SPF roofs can be repaired and recoated to offer an indefinite life expectancy.
“Coupled with the energy savings and reduction of in-house maintenance costs, SPF roofs maintain a tremendous long-term cost efficiency advantage over all other commercial roofs. Without question, SPF roofs have a tremendous edge in preventing leaks and in detection and repair when one does occur.”
SPF Roofing Stands up to Hurricane Winds
The NIST (National Institute for Standards and Technology, USA) reports on the impacts on structures from hurricanes Katrina and Rita are very favorable toward spray foam roofing.
3.2.3 Spray Polyurethane Foam (SPF) Roofs Page 69
“A number of spray polyurethane foam (SPF) roofs were observed in the Pascagoula, MS area. Some of these roofs were estimated to be about 20 years old. With one minor exception, all were found to have sustained Hurricane Katrina extremely well, without blow-off of the SPF or damage to flashings.
“In the single case where damage was observed, the SPF had been applied to a wood fiber insulation that had been mechanically fastened to the metal deck with an inadequate number of fasteners. Failure likely occurred when the insulation board delaminated from the deck. The area of the failure was less than 1 percent of the total roof area.”
Louisiana SuperDome Roof Pages 62–63—Chapter 6 | Key Findings and Observations
“Spray foam roofs were the only type of roofs described as having performed ‘extremely well’.”
6.2.2 Roofing Pages 176–177
“A limited number of spray foam (SPF) roofs were observed in the hurricane Katrina damage zone. Such roofing was found, with minor exception, to have sustained the winds extremely well without blow-off of the (SPF) or damage to flashings.”
Sustainability Characteristics of SPF Roofs and Insulation—A Review of Work to Date.
Building owners have used spray polyurethane foam (SPF) as a roofing, insulation and sealing product for many years. Recent research and performance studies on SPF applications demonstrate many sustainable characteristics of the material.
As documented in many studies, SPF roofs:
- Have a long life
- Are renewable
- Save energy
- Add durability to buildings
- Control moisture in buildings
- Contribute very little to the waste stream
The use of SPF roofs can significantly affect the durability and climate control of a building, increase structural strength, provide effective air barriers and control moisture.
Field Performance of SPF Flashings
This study, by structural researcher René M. Dupuis, documents the results of a survey chartered to determine the viability of the SPF material as a flashing material over a wide range of substrates.
The use of SPF and appropriate coatings were observed to work quite well as singular flashings. The use of metal counterflashing was not seen to be required as part of an SPF roof.
SPF as a flashing material in concert with an SPF roof offered the advantages of no seams or joints to allow for water penetration, and no differential movement between materials.