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Spray foam is a chemical product created by two materials,
isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...
and
polyol In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, thr ...
resin, which react when mixed with each other and expand up to 30-60 times its liquid volume after it is sprayed in place. This expansion makes it useful as a specialty packing material which forms to the shape of the product being packaged and produces a high thermal insulating value with virtually no air infiltration.


History

Otto Bayer Otto Bayer (4 November 1902 – 1 August 1982) was a German industrial chemist at IG Farben who was head of the research group that in 1937 discovered the polyaddition for the synthesis of polyurethanes out of poly- isocyanate and polyol. ...
(1902–1982) is credited with the invention of
polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...
in 1937. He succeeded in synthesizing polyurethane foam by exploring his basic idea that mixing small volumes of chemical substances could create dry foam materials. Polyurethane was further developed for different applications, ranging from shoe soles and cushions to industrial uses. In the 1940s rigid foam was applied to airplanes, and in 1979 polyurethane began being used as building insulation.


Properties


Thermal resistance

R-value is the term given to thermal resistance to heat flow. The higher the R-value of an insulation product, the more effective the insulation properties. Spray polyurethane foam comes in a range of densities and cell structure. Low density foams are referred to as open cell SPF while higher density foams are referred to as closed cell foam. 1.8-2 pound polyurethane foam has the highest R-value of readily available spray foam insulation used in homes and buildings. Polyurethane is a closed-cell foam insulation material that initially contains a low-conductivity gas in its cells. As a result of the high thermal resistance of the gas, spray polyurethane insulation typically has an initial R-value around R-3.4 to R-6.7 per inch. In comparison,
glass wool Glass wool is an insulating material made from glass fiber arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation pro ...
typically has an R-Value of only R-3 to R-4 per inch. Foam insulation blocks all three forms of heat transfer: ;Conductive heat transfer:The flow of thermal energy through a substance from a higher to a lower temperature region. Foam thermoset plastics reduce
conductive heat transfer Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its ''thermal conductivity'', and is denoted . Heat spontaneously flows along a tem ...
due in part to having very loose molecular bonds; In addition the cells of the installed spray foam are either filled with air in the case of open cell foam or HFC's ( 365mfc, 227ea, 245fa) or H(C)FO's ( 1336mzz(Z), 1233zd(E)) in closed cell foam. ;Radiant heat transfer: The process by which heat energy in the form of light (usually IR unless the substrate is hot enough to glow in the visible range) is emitted more strongly by warm surfaces and absorbed by other materials especially those of low IR reflectivity (think matte black finish). Radiant heat transfer does not require a medium. Foam insulation materials, such as spray foam insulation, are opaque to thermal radiation, like most solid materials. ;Convective heat transfer: Heat which is created elsewhere that is transported by means of a fluid, such as water or in our case air. Spray foam insulation's most important attribute is the ability to air seal creating a custom airtight envelope within the building structure. The added benefit to air sealing is the ability to block
convective heat transfer Convection (or convective heat transfer) is the transfer of heat from one place to another due to the movement of fluid. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combined processes o ...
from interior to exterior during heating months and vice versa during cooling months, as the heat cannot escape through gaps in the buildings envelope without the aid of air movement from infiltration as a means of transport.


Applications


Packaging applications

Spray foam is a very specialized packing material, often required for use in shipping valuable
fragile Fragile or The Fragile may refer to: Film and television * ''Fragile'' (film), a 2005 film by Jaume Balagueró * "Fragile" (''Smallville''), a television episode Literature * ''Fragile'' (manga), a 2016 Japanese series by Bin Kusamizu and Sab ...
items. Engineered packaging principles are designed to protect sculptures, vases, large fossils, lamp bases, busts, computers, furniture, chandeliers and other objects of unusual shape. By virtue of the liquid foam expanding by up to 30-60 times the volume of its liquid state, it efficiently protects almost any size, form and weight. The custom fit of the molds, top and bottom, securely and uniformly cushions the object. There are many types of alternative materials that can be used to handle more specific needs.


Building applications

Spray foam insulation or spray polyurethane foam (SPF) is an alternative to traditional building insulation such as
fiberglass Fiberglass ( American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cl ...
. A two-component mixture composed of
isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...
and
polyol In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, thr ...
resin comes together at the tip of a gun, and forms an expanding foam that is sprayed onto roof tiles, concrete slabs, into wall cavities, or through holes drilled in into a cavity of a finished wall. "Spray foam" is also an informal term used to refer to various plastic foam materials that are used in building construction to provide
thermal insulation Thermal insulation is the reduction of heat transfer (i.e., the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with ...
and minimize
air infiltration Infiltration is the unintentional or accidental introduction of outside air into a building, typically through cracks in the building envelope and through use of doors for passage. Infiltration is sometimes called air leakage. The leakage of room ...
.
Polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...
and
polyisocyanurate Polyisocyanurate (), also referred to as PIR, polyiso, or ISO, is a thermoset plastic typically produced as a foam and used as rigid thermal insulation. The starting materials are similar to those used in polyurethane (PUR) except that the propor ...
are two types of foam used in this application.


Types

Spray polyurethane foam (SPF) insulation can be categorized into two different types: light-density open-cell spray foam insulation and medium-density closed-cell spray foam insulation. Both types of SPF are thermoset cellular plastics comprising millions of small cells. Open cell insulation can be crushed in your hand and has a lower insulation value. Closed cell is rigid to the touch and each air cell is completely sealed. While closed cell foam has a higher R-value, it is more costly to buy. Medium-density closed-cell spray foam (ccSPF) Medium-density closed-cell foam insulation is often referred to as two pound (2 lb) foam. It is a rigid insulating material with a Long Term Thermal Resistance (LTTR) R-value that ranges between 5.1 and 6 per inch When the required minimum thickness of 50 mm is installed, ccSPF is both a vapour barrier and an air barrier. In Canada, the National Building Code references two standards that apply to the manufacturing and installation of ccSPF: the CAN/ULC S705.1 Material Standard and the CAN/ULC S705.2 National Application Standard. The installation standard requires that all installers of ccSPF in Canada be licensed and carry a photo ID card. Typically the foam's natural colour is yellow, however in Canada all ccSPF that have CCMC listings are required to have a unique colour for field identification. Light-density open-cell spray foam (ocSPF) Light-density open-cell SPF is commonly known as half-pound foam. It is a semi-rigid material with a sponge-like appearance that expands during installation and creates small, open cells that are filled with carbon dioxide. Due to its ability to expand during the application process, it fills cracks, crevices and voids and adheres to irregular surfaces or substrates to form an air sealing insulation. While the R value will vary, most ocSPF products have an R value of around 3.8 per inch. Unlike medium-density closed-cell SPF, thinner layers of ocSPF are not particularly effective as vapour barrier because the air infiltrates through the open cell structure. However, when installed at 5.5 inches or more, ocSPF does act as an air barrier. It is often used for interior walls because it provides sound reduction by blocking and absorbing air leakage. It is usually only recommended for indoor applications.


Application methods


=Asia

= A type of use quite familiar in South East Asian countries is applying the foam by spraying it against the bottom of roof tiles under high pressure with a spray gun. A hard but flexible layer of rigid foam is then created and seals all the tiles to each other and to the steel structure. This spraying method, especially very popular in Thailand, is used not only against heavy leaks but helps also as insulation against the enormous heat the roofs constantly face. This tropical heat causes the steel substructure that supports many roofs in that part of the world, to continuously expand and contract, changing slightly the position of the tiles resting on top of them. This displacement eventually creates small openings between the tiles and the substructure, through which rainwater can seep, creating leaks that can damage the plastered ceilings, electric wiring, and other components of the building supporting the roof.


=Europe

= Some 150,000 properties have been treated with polyurethane foam insulation in the UK. There are systems which have British Board of Agreement approval for use in existing and new build applications and can show compliance to Building Regulations. However, if applied incorrectly or in damp spaces, spray foam insulation can trap moisture and destroy the
roof A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of t ...
. As a result, very few mortgage lenders in the UK will offer a loan to buy or to refinance any home that has any spray foam insulation, especially the closed-cell type.


=North America

= The Canadian National Building Code references the CAN/ULC S705.2 National Application Standard which must be followed during all installations of 2lb medium density closed cell polyurethane foam. Every installer of CAN/ULC-S705.1 compliant medium density, spray applied foam must be licensed in order to spray foam and hold valid photo ID issued by their Quality Assurance Program (QAP) provider showing their license is in good standing. The United States has adapted to using sprayfoam insulation and a new technology called Wall Injection to retrofit existing wall construction by drilling small holes between wall studs in the structures framing and filling the void with a less aggressive expanding water-based foam. This allows existing home and business owners to conserve energy by creating a thermal envelope in their existing structure.


Benefits

Spray foam insulation, like other insulation, saves on energy costs and lowers utility bills. Studies by the
US Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United States. ...
show that 40% of a home's energy is lost as the result of air
infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...
through walls, windows and doorways. Buildings treated with spray foam insulation insulate as much as 50% better than traditional insulation products. Insulation properly deployed can be part of a system designed to protect against
moisture Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial products. Moisture also refers to the amount of water vapo ...
, which provides the benefit of reducing the chance of harmful
mold A mold () or mould () is one of the structures certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not ...
,
mildew Mildew is a form of fungus. It is distinguished from its closely related counterpart, mould, largely by its colour: moulds appear in shades of black, blue, red, and green, whereas mildew is white. It appears as a thin, superficial growth consi ...
and rotting of wood. In addition to building
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
and moisture control, spray foam insulation is often used to reduce noise. Foam insulation serves as a
barrier A barrier or barricade is a physical structure which blocks or impedes something. Barrier may also refer to: Places * Barrier, Kentucky, a community in the United States * Barrier, Voerendaal, a place in the municipality of Voerendaal, Netherl ...
to airborne sounds, and reduces
airborne sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
transfer through a building's roof, floor and walls compared an uninsulated structure. In the United States, homes treated with spray foam insulation often qualify for state and federal tax deductions. Insulation of all types stops a good deal of energy loss. Some types including spray foams also seal air leaks. Insulation can also save energy in hot climates by reducing air conditioning use.


Blowing agent climate impact

Most closed-cell spray foam is now formed using
hydrofluorocarbon Hydrofluorocarbons (HFCs) are man-made organic compounds that contain fluorine and hydrogen atoms, and are the most common type of organofluorine compounds. Most are gases at room temperature and pressure. They are frequently used in air condi ...
(HFC)
blowing agent A blowing agent is a substance which is capable of producing a cellular structure via a foaming process in a variety of materials that undergo hardening or phase transition, such as polymers, plastics, and metals. They are typically applied wh ...
s that have high
global warming potential Global warming potential (GWP) is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide (). GWP is 1 for . For other gases it depends on the gas and the time ...
, partially or completely offsetting the climate benefits of the energy savings they can offer. In the United States, HFCs are scheduled to be phased out by January, 2021. A few spray foam suppliers have started supplying spray foam blown with
hydrofluoroolefin Hydrofluoroolefins (HFOs) are unsaturated organic compounds composed of hydrogen, fluorine and carbon. These organofluorine compound are of interest as refrigerants. Unlike traditional hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs), whic ...
(HFO) blowing agents without this problem as of early 2017.


Health effects

Spray foam insulation is typically
non-toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...
only after it has cured. While curing, spray foam emits a gas that causes blurred vision and trouble breathing. Using full face and respiratory protection while applying the product is recommended. Isocyanates are powerful irritants to the eyes and gastrointestinal as well as the respiratory tracts. Direct skin contact with isocyanates can also cause marked inflammation. Some people say that their eyes feel like they have sand in them at the onset of problems. Some break out in a rash on their arms, chest, and neck. Overexposure to isocyanates can sensitize workers, making them subject to asthma attacks if they are exposed again. Respiratory irritation may progress to a chemical bronchitis. Additional exposures can make the onset easier with less isocyanate necessary to start the attack. Sporadic cases of hypersensitivity pneumonitis (HP) have also been reported in workers exposed to isocyanates. The symptoms may seem like the flu, with fever, muscle aches, and headaches. Other symptoms may include a dry cough, chest tightness, and difficult breathing. Individuals with chronic HP often experience progressively more difficult breathing, fatigue, and weight loss. Individuals with acute HP typically develop symptoms 4–6 hours after exposure.


See also

*
Building insulation materials Building insulation materials are the building materials which form the thermal envelope of a building or otherwise reduce heat transfer. Insulation may be categorized by its composition (natural or synthetic materials), form (batts, blankets, loo ...
* Insulation (list of insulation material) *
R-value (insulation) In the context of construction, the R-value is a measure of how well a two-dimensional barrier, such as a layer of insulation, a window or a complete wall or ceiling, resists the conductive flow of heat. R-value is the temperature difference pe ...


References


External links

* {{Cite web , url=https://tspace.library.utoronto.ca/bitstream/1807/69303/3/Khazabi_Mustafa_201506_PhD_thesis.pdf , title=Investigation of Biopolyol Spray Foam Insulation Midified with Natural Fibers , last=Khazabi , first=Mustafa , date=23 July 2015 , publisher=
University of Toronto The University of Toronto (UToronto or U of T) is a public research university in Toronto, Ontario, Canada, located on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution ...
, access-date=4 January 2021 Building materials Building insulation materials Sustainable building Thermal protection Energy conservation Heat transfer Packaging