Foam Roofing
From Roofing, Solar Power, and Spray Foam Insulation Wiki
Although SPF Roofing systems have existed for over forty years there is still a substantial lack of knowledge about such systems among roofing professionals.
Spray Polyurethane Foam Roofing
A Spray Polyurethane Foam (SPF) roofing system consists of two heated liquid components which are combined and sprayed onto a prepared substrate. The mixture instantly bonds to the surface and expands to form a rigid foam closed cell structure. The two heated components expand to many times their original size, which can be used to alter the roof slope, build up low areas, or improve drainage. Within a few minutes, the sprayed foam hardens to form a durable lightweight monolithic waterproofing barrier. Generally, foam is spray to a depth of 1" to 1.5" inches. Sprayed Foam has an excellent R-Value and generally 1" of Foam represents about 4" of fiberglass in terms of insulation. Walking on the hard and durable foam roof surface feels somewhat like walking on a concrete sidewalk. Spray Polyurethane Foam (SPF) is vulnerable to to ultraviolet rays, and must be protected by an elastomeric coating layer. Usually white coating (acrylic, polyurethane, or silicone based) is used to provide a reflective surface.
The Best Insulator
By nature, SPF Foam Roofs are water resistant because the structure is based on millions of tiny closed cells. This closed cell structure also makes the foam an excellent insulator, giving SPF foam an incredible R-Value of 7 per inch. R-Value represents thermal resistance; the higher an R-Value, the more effective an insulator. Foam is the highest R-Value insulator on the market. It's no surprise Sprayed Polyurethane Foam has often been used to insulate the external fuel tanks of NASA space shuttles to keep them super-cold. In addition to insulation and water resistant properties Foam has additional benefits. A monolithic Foam roof can prevent moisture vapor transmission or be used to improve the appearance or aesthetics of a roof. Lightweight SPF foam can also relieve structural stresses replacing heavy substrates such as tar and gravel.
Meets And Exceeds Building Code Requirements
In addition to excellent thermal resistance, SPF Foam is very fire resistant. Polyurethane Sprayed Foam meets or exceeds all building code standards, and is approved by all national building codes, including International Code Council (ICC), the International Building Code (IBC). Overall, SPF Foam is an incredibly efficient product, and because of high R-Value and insulation properties, a Foam Roof can eventually pay for itself in energy cost savings. With the steep rise in energy costs during the past few decades, a Foam Roof may provide a substantial cost savings on gas and electric heating and cooling bills. Whether a structure is a massive warehouse or a small Eichler flat roof home, the energy cost savings provided by an SPF Foam Roof are substantial.
Foam Roofing is Energy Star Approved
SPF Foam Roofing is an Energy Star approved product as well. Energy Star is an international standard for energy efficient consumer products. First created as a United States government program in 1992, Australia, Canada, Japan, New Zealand, Taiwan and the European Union have adopted the program. Foam Roofing meets or exceeds Energy Star standards in energy efficiency and reliability, such as solar reflectivity and roof life.
How Long Does an SPF Foam Roof Last
Surveys conducted by Dr. Dean Kashiwagi of the Del E. Web School of Construction at Arizona State University and Dr. Rene Dupuis of the National Roofing Foundation revealed that SPF shows little sign of deterioration even after 30 years. Dr. Kashiwagi is the pioneer of the “Performance Based Procurement System” for buying best performing services/facility systems. Between 1983 and 1996, he surveyed the performance of more than 1600 SPF roofing systems, the oldest of which were more than 26 years old. Of the roofs surveyed, 97.6% did not leak and 93% had less than 1% deterioration. These are impressive numbers considering 55% of those roofs were never maintained.
In the most comprehensive roof survey ever performed by the National Roofing Foundation, Dr. Dupuis evaluated 160 SPF roofing systems in California, Texas, Wisconsin, Illinois, New Jersey, and New York. In presenting his findings, Dr. Dupuis concluded that SPF roofing systems appear to have a very high degree of sustainability with an indefinite life expectancy when properly maintained with periodic recoating. Both Kashiwagi and Dupuis also noted the physical properties of SPF did not diminish over time, and more than 70% of the roofs were applied over existing roofing systems.
These findings indicate a properly maintained SPF Foam Roof can be expected to last the lifetime of the property.
How Often Should an SPF Foam Roof Be Inspected
An SPF roofing system should be inspected after a natural disaster such as a hurricane, tornado, or massive hail storm. Otherwise, a professional inspections is recommended every five years. When the surface membrane has substantially thinned due to UV damage or weathering a recoat of an acrylic or silicone based elastomeric coating will be required. The following maintenance schedule is recommended:
* Year 0 - Install SPF Foam Roof * Year 5 - Apply First Recoat * Year 10 - Roof Inspection * Year 15 - Roof Inspection * Year 20 - Roof Inspection * Year 25 - Apply Second Recoat * Year 30 - Roof Inspection * Year 35 - Roof Inspection * Year 40 - Roof Inspection * Year 45 - Apply Third Recoat * Year 50 - Roof Inspection * Year 55 - Roof Inspection * Year 60 - Roof Inspection * Year 65 - Apply Fourth Recoat * Year 70 - Roof Inspection * Year 75 - Roof Inspection * Year 80 - Roof Inspection * Year 85 - Apply Fifth Recoat * Year 90 - Roof Inspection * Year 95 - Roof Inspection * Year 100 - Roof Inspection
Generally, minor damage can be repaired with elastomeric coating and caulking type sealants. In some cases, extensive damage due to neglect or other circumstances may require additional SPF and coating.
When Should SPF Foam Roofing be Applied?
Usually, a Flat Roof or Low Slope roof benefit the most from an SPF roof. The following conditions are good examples of roofs which can greatly benefit from a Foam Roofing System:
* Ponding or drainage problems need correction * Roof substrate has multiple existing leaks * Lightweight roofing materials needed * Current roof or home insulation is insufficient * Roof area subject to extreme high winds * Roof deck has a strange or unusual configuration * Severe temperatures on roof * Heating & cooling costs need reduction
SPF Foam Roof Systems adhere well to most flat or low slope roofing substrates including metal, wood, concrete and BUR. Foam is extremely lightweight and can often be applied over an existing roof system, after the existing system has been properly prepared. In some cases, a professional inspection reveals an existing roof covering must be torn off before an SPF roofing system may be applied.
Limitations of SPF Roofing Systems
SPF foam roofing system installations require an experienced crew with high technical knowledge and experience. The existing body of knowledgeable experienced SPF contractors and professionals has slowly been growing over time, and some suppliers offer training courses. To get the maximum benefit of an SPF Foam Roof system it's important to have it installed by experienced professionals. A key sign of an incorrect installation is the interlaminar blistering of SPF layers, which indicates poor substrate preparation, equipment problems, sub-optimal installation environment (humidity or other issues), or improper installation procedures.
SPF Installation Environmental Conditions
Manufacturers recommend installation should not proceed when humidity is within five degrees of the dewpoint, or during extreme cold weather. A warm dry day with low winds provides an optimal application environment. Extreme High winds are not optimal, but installation can proceed. For example, a barrier can be used to prevent overspray. A SPF Foam roof system should never be applied under any the following environmental conditions:
* Ice, Frost or extreme Cold * Humidity is within 5 degrees of dewpoint * Moisture is visible on roof substrate
Generally, SPF foam is applied with the use of an internally heated hose to assure optimum application temperatures are reached. However, if there's ice or dew on the ground, most likely, it's not a good or optimal time to install. A wet or moist surface will prevent foam from properly adhering to the roof substrate, and can eventually cause roof blistering.
SPF Installation Requires Technical Knowledge
Since technical knowledge, experience, and proper installation procedures are critical it is important to choose a contractor with a solid track record of positive performance. Also keep in mind, Sprayed Polyurethane foam is ultra light-weight, and can easily be carried by winds a few hundred (or a few thousand feet) depending on the stories of the installation property. Responsible contractors have procedures in place to either cover overspray vulnerable areas, or use some type of barrier to prevent overspray from being blown away from the roof area.
Completion Time
Generally SPF foam cures within minutes. However, coating may take hours or longer to occur, depending on a few factors including: the number of coats, the thickness of each coat in mils, present temperature and humidity levels, and type(s) and colors of coatings applied to the SPF substrate. Some coatings may also emit strong fumes while curing and it may be best to cover or close vents and turn off AC units, or other air-handling types of equipment if there are building occupants during installation.
SPF Roof System Cost
The cost of SPF roof systems depends on several factors including the size of the roof, required foam thickness, the type and thickness of coating or covering, and labor or materials requirements for substrate preparation. Some other factors to consider might be location: is it out of the way or difficult to reach the property, or is it in a busy area in a city where installation can be slowed down or difficult due to traffic, OSHA regulations (such as protective equipment for multiple story buildings). Even more factors may be the number or competitiveness of contractors in the region, local variations in materials or labor costs (e.g. labor in New York will cost substantially more than labor in North Dakota). Substrate preparation varies; for example, a new construction roof (lower preparation costs) may require staples and rolled roofing material to cover bare wood, which would incur minimal materials costs and labor hours vs an older roof with several old re-roofed layers which must all be torn off (consider disposal costs, labor hours, etc).
Are SPF Roof Systems Green Construction?
Properlly installed SPF roof systems can easily last 20 years or longer without any maintenance. In fact, properly maintained SPF Foam Roof sytems can last the life of a property. A related study was performed in 2004 by Michelsen Technologies. This involved a an SPF roofing system life-cycle analysis in five climate areas of the United States. Analysis of evidence led to the conclusion that the average SPF roofing system costs 15 to 50% less to install and maintain than a conventional membrane roof system over a thirty year time period. The study reported costs based on 6-year, 10-year, and 15-year recoat schedules.
At the 1996 Sustainable Low-Slope Roofing Seminar, Oak Ridge National Laboratories described green construction roofing systems: [these are]"roofing systems that have a long life, low maintenance, save energy, add durability to buildings, control moisture in buildings, and contribute very little to the waste stream.” Foam roof systems meet every requirement of the definition of green roofing provided by Oak Ridge National Laboratories. Foam roofs provide excellent insulation which cuts energy usage, which lowers fossil fuel consumption, ozone depletion, and prevents global warming. Often light-weight foam can be applied over an existing roof-membrane (i.e. the original membrane can be re-used), which prevents landfill waste. Landfill waste is a significant issue with roofing. According to a 1999 survey by the National Roofing Contractors Association (NRCA), more than 68.5 percent of the $11.3-billion low-slope re-roofing market includes tear-off and replacement of the existing roof membrane. Foam roofing is also renewable; after installation, proper maintenance only requires periodic recoats, which can allow the Foam Roof System to last the life of the building.
Conclusions
To reap the full benefits of an SPF foam roof system, a knowledgeable and experienced contractor should be hired, preferably one with a good track record. Some of those SPF roofing system benefits are: long lasting roof life, sustainability, and green construction. SPF roof systems are are optimal for flat roofs or low slope roof substrates, and are best applied in a warm, dry climate in low wind conditions. With proper preparation, installation, and maintenance, an SPF Foam Roofing system can potentially last as long as the property.