What is Spray Polyurethane Foam?

Spray polyurethane foam, commonly referred to as SPF, is a spray-applied insulating foam plastic that is installed as a liquid and then expands to many times its original size. Spray polyurethane foam can be adjusted and have many different physical properties depending on the desired use. For example, the same basic raw materials that can make insulation foam semi-rigid and soft to the touch also creates high density roofing foam that is resistant to foot traffic and water.


What is SPF used for?

Spray polyurethane foam is used in a wide variety of applications, including, but not limited to:

  1. Roofing
  2. Air barriers
  3. Commercial and residential insulation in walls, ceilings, attics and basements
  4. Industrial insulation for pipes and tanks, cold storage facilities, freezers, walk-in coolers, and climate-controlled buildings such as produce storage and clean rooms
  5. Flotation for boats, ships, barges, floating docks, etc.
  6. Higher density spray polyurethane foam has been used to increase the structural strength of wings in airplanes


How is SPF applied?

Specialized equipment is used to apply the spray polyurethane foam and proper technical training is necessary in order to get the best results.


Why choose SPF?

Spray polyurethane foam is the king of building materials for multitasking. For insulation, it can provide high R-Value levels, while providing air barriers and assisting with moisture control. For roofing, spray polyurethane foam insulates and eliminates thermal bridging through fasteners or gaps in decking, while providing a long-lasting roofing system that has a life that can be extended by recoating or recovering on average of every 10 – 15 years.


What are the benefits of SPF?

Spray polyurethane foam is environmentally friendly, contains no formaldehyde or ozone depleting chemicals, saves energy and reduces the use of fossil fuels, thereby reducing global warming gases. It also assists in providing good indoor air quality, requires less energy to produce than the leading insulation, and reduces the amount of energy required to transport and install it. SPF is durable, maintains physical properties over time, contributes little to the waste stream, and in a single product (depending on the formula and project) can take the place of three-four other products, including insulation, air barriers, sealants, vapor retarders, and weather barriers.


  • SPF reduces drafts and increases comfort
  • SPF helps maintain a comfortable, constant, temperature throughout the building, from room to room and floor to floor
  • SPF reduces noise from outside by sealing the building


  • SPF assists in improving indoor air quality
  • SPF reduces the infiltration of outside air pollutants and soil gases
  • SPF can reduce moisture condensation and mold growth within the building walls and roof
  • Closed-cell SPF adds structural strength and glues a building together, thereby making it more resistant to racking events, such as hurricanes and high winds
  • Closed-cell SPF can provide an added barrier against water intrusion


  • Excellent insulation efficiency of SPF can reduce heating and cooling usage dramatically
  • HVAC equipment can be down-sized, thereby reducing construction costs
  • SPF will not sag or settle
  • SPF can eliminate the need for separate house wrap and vapor retarders


  • SPF helps conserve energy, reducing CO2 emissions
  • SPF contributes LEED credits for sustainable, green construction
  • SPF can help reduce structural damage caused by high winds
  • SPF contains no formaldehyde or ozone depleting substances


How does SPF reduce energy use?

SPF reduces energy use in the following ways:

  • Has high R-value per inch (open-cell 3.5 per inch and closed-cell 6.0 per inch)
  • Eliminates air infiltration by providing a continuous air barrier
  • Prevents moisture infiltration
  • Reduces convective currents in walls and attics
  • Eliminates wind washing
  • Provides the correct environment so that the ventilation system performs more efficiently
  • Minimizes dew point problems and condensation
  • Avoids thermal bridging
  • Resists heat movement in all directions


Is Spray Polyurethane Foam Safe?

Yes, cured spray polyurethane foam is relatively inert and studies indicate that SPF does not release toxic gases or leach harmful chemicals into the soil. Applicators and other persons within a close proximity to the spray operation could be exposed to fumes and spills beyond OSHA and NIOSH requirements. Precautions should be made for applicators, helpers and building occupants to be protected from these fumes, mists and spills. Typically, for the applicator, this would include respirator, solvent resistant gloves and protective clothing. The zone where protective equipment is required can vary depending on the amount of open space and free ventilation. For example, on a rooftop the fumes dissipate rapidly outside of a few feet, while in an enclosed room, fumes and mists can build. Each job should be assessed and a safety plan developed specific to the application.


Is SPF a good soundproofing material?

Both low and medium (2lb/cubic/ft.) density SPF effectively reduce noise from outside sources by sealing cracks and gaps that allow sound to travel through the walls, floors and ceilings into the building. They are less effective against noise caused by vibration.


How long does a spray polyurethane foam (SPF) roof last?

The oldest performing SPF roofs are over 30 years old. Because the physical properties of the SPF change little with age, how long the SPF roof system lasts depends primarily on the original application and long-term maintenance.


How is a SPF roof system maintained?

SPF roof systems should be inspected semi-annually and after events that could cause physical damage. Small (less than 3″ diameter) dents, cracks, punctures from dropped tools, and wind driven debris can be repaired with an elastomeric sealant compatible with the SPF and coating system. More extensive damage can be repaired by reapplying SPF. Typically SPF roof systems are re-coated every 10 – 15 years, depending on the type and thickness of coating used and factors specific to the roof, such as wind erosion effects, hail, foot traffic, abuse, etc. Recoating extends the service life of the SPF roof system.


Where can I use an SPF roofing system?

SPF has excellent adhesion to a variety of substrates including, BUR, clay and concrete tile, shingles, metal, wood and concrete. Since they add little weight and can be applied in varying thickness to add slope and fill in low areas, SPF roofing systems are often used to recover over existing roof systems.

SPF roofing systems excel where:

  • Additional insulation is desired
  • The roof substrate has many penetrations
  • The roof deck is an unusual shape or configuration
  • The roof is in a severe weather environment (hurricanes, hail, etc.)
  • Lightweight materials are required
  • Slope must be added to provide positive drainage
  • It is desirable to keep existing roof covering


How do SPF roof systems compare in cost to other roof systems?

SPF roofing systems are cost competitive with other systems. Life Cycle Cost Analysis performed by Michelsen Technologies demonstrated that over a 30 year life span, SPF roof systems cost between 10% and 50% less on average than comparably insulated membrane roof systems. (Averages were based on SPF roof system recoats of every 6, 10 and 15 years. A copy of the Life Cycle report is available from SPFA.)


Why do you need coatings or coverings over SPF?

SPF is water resistant without other coverings; however, the surface of SPF can deteriorate under the sun’s ultraviolet (UV) rays. Typically, elastomeric coatings or aggregate coverings are used to protect the SPF against UV radiation.


How long has SPF been around?

Spray polyurethane foam was first used commercially in the US in the 1960s for cold storage and industrial insulation projects. SPF roofing systems evolved from exterior applications to tanks and pipes in the late 1960s to early 1970s.