SIPs is an acronym for Structural Insulated Panel. Structural Insulated Panels (SIPs) are a high performance building system for residential and light commercial construction. The panels consist of an insulating rigid foam core sandwiched between two structural facings, typically oriented strand board (OSB). SIPs are manufactured under factory controlled conditions and can be fabricated to fit nearly any building design. The result is a building system that is extremely strong, energy efficient and cost effective.

Types of SIPs

There are three main types of SIPs, although the SIPs themselves can be encased in different outer materials called skins. The inner insulation core is usually made from expandable polystyrene (EPS), polyurethane or polyisocyanurate. Each delivers a strong, light building material with exceptional insulation properties.

Types of SIP skins

Most SIPs feature OSB as the skins that encompass the inner foam insulation core of the

panel. But other skins are available, including:


 Fiber cement

 Fiber reinforced concrete


 Gypsum board

The third component in SIPs is the spline or connector piece between SIP panels. Dimensional lumber is commonly used but creates thermal bridging and lowers insulation values. To maintain higher insulation values through the spline, manufacturers use Insulated Lumber, Composite Splines, Mechanical Locks, Overlapping OSB Panels, or other creative methods. Depending on the method selected, other advantages such as full nailing surfaces or increased structural strength may become available.

SIPs share the same structural properties as an I-beam or I-column. The rigid insulation core of the SIP acts as a web, while the OSB sheathing exhibits the same properties as the flanges. SIPs combine several components of conventional building, such as studs and joists, insulation, vapor barrier and air barrier. They can be used for many different applications, such as exterior wall, roof, floor and foundation systems.


Structural insulated panels (SIPs)are one of the most airtight and well insulated building systems available, making them an inherently green product. An airtight SIP building will use less energy to heat and cool, allow for better control over indoor environmental conditions, and reduce construction waste.

Why you will see SIPs more than ever before!

Firefighting Concerns:

As you have saw from the information above there are several types of SIPs and many types of skins however as mentioned before the most common is Oriented Strand Board (OSB) as the skin and the core made of Expanded Polystyrene Foam. So I am going to focus on concerns with those two materials.

Oriented Strand Board (OSB)

This material begins to break down at relatively low temperatures for fire conditions (about 450 F same as sawn wood) and it is now a major structural component and not just a covering.

The adhesives used in OSB can vary by manufacturer. It appears that the wood components will burn before the adhesives in most cases. The wood will start to burn at about 450 F and the adhesives around 750 F. The manufactures state that the OSB will behave like sawn wood in a fire, which may be true, but it is the thickness (mass) that then becomes the problem, as OSB is usually no more than thick and usually less.

Although the manufactures state that the products of combustion are no worse than natural wood, some of the materials in the adhesives may be extremely toxic, corrosive, or carcinogens.

Expanded Polystyrene (EPS)

  • When heated it melts!
  • Expanded Polystyrene is combustible.
  • It should not be exposed to flame or other ignition sources
  • Flash Point: 600F to 650F
  • Auto-ignition Temperature: 824F – 914F
  • Fire and Explosion Hazards: WILL MELT WHEN EXPOSED TO TEMPERATURES OF 300F TO 500F
  • Unusual Fire and Explosion Hazards: Pentane vapors may be emitted from freshly expanded or processed foam or when product is heated. Hazardous concentrations may accumulate inside a sealed container or within confined areas. If ignited, there may be a very high rate of flame propagation and/or an associated explosion.
  • Hazardous Combustion Products: Burning foam emits a dense, black, irritating smoke with acid gases. Primary combustion products are carbon monoxide, carbon dioxide, and styrene.
  • Special Firefighting Procedures: SCBA & Full PPE

Click the links below to watch a crude parking lot burn test:

sip burn at fishers


Hopefully you have learned something from this post? If so please share it with every firefighter you know.

Stay Safe

Lt. John Shafer


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