an aerial view of sip construction panels installed on a house foundation with nothing else there yet

The introduction of structural insulated panels (SIPs) has revolutionized modern construction techniques. SIPs are energy-efficient, sustainable, cost-effective, and robust building materials. 

However, despite their apparent advantages, SIPs panels are often misunderstood or misused.

This article will provide an overview of how structural insulated panels are made, how they work, and why they are beneficial for construction projects.

So, let’s get into it!

What Are Structural Insulated Panels?

SIPs are composed of an insulation layer sandwiched between an Oriented Strand Board (OSB) or other skins. They are used to improve energy efficiency in residential and commercial construction. Additionally, SIPs allow for enhanced structural integrity and load-bearing capabilities. 

How Are SIPs Made?

Structural insulated panels are made by placing aluminum frames between two OSB boards, which are then stacked in a hydraulic press. A two-part resin is injected through a hole in the frame. This process allows the insulating foam layer to bond to the OSB as the resin cures and hardens.

a stack of sip panels in a factory showing the OSB outer wood layer and the styrofoam interior

Some manufacturers do not stack the frames on top of each other into a hydraulic press. Instead, they run the frames through a conveyor belt, which applies consistent pressure to the boards. Regardless of the method the manufacturer uses to apply pressure, it is an essential part of the resin’s curing process. 

The two parts of the resin mix with each other when pressed into the aluminum frame. The pressure from the hydraulic press accelerates the curing process and allows the resin to fill holes in the OSB, effectively creating a skin around the insulating layer. 

What Is the R-Value of Structural Insulated Panels?

The typical R-value of SIPs is between R-15 and R-67. The exact number depends on various factors, including the thickness of the insulating layer and the type of insulation used. Different sizes, thicknesses, and R-values are usually available from the different manufacturers.

Building codes set the minimum R-value for the construction of residential and commercial buildings. The R-value measures how well the insulation can resist a flow of heat through it.   

In other words, it is a measure of thermal resistance. It’s best to consult your local building code to determine the minimum R-value for your specific construction project. 

SIPs do not lose R-value over time, and the combined thermal resistance of a constructed wall is not the same as the thermal resistance within a single panel—it’s why even green home builders in cold areas like Canada use structural insulated panels. 

Can You Make Your Own SIPs?

You can make your own structural insulated panels, but you probably can’t get a permit for their use in construction. Additionally, making structural insulated panels on your own is a complex process. SIPs are manufactured in fully accredited and regulated factories. 

EPS foam SIPs can be made by building a frame to mix the foam with water and covering it in a vacuum for curing. However, PU-type panels are more challenging because you must apply pressure on the frame.

Polystyrene blocks used for container home insulation stacked in a warehouse
EPS is a material commonly used for SIPs

Making your own structural insulated panels may sound like a great way to save money, but it’s not recommended. If you decide to make your own, the result may be less effective than professionally manufactured panels.

The R-value determines their effectiveness. Unfortunately, DIY methods lack the precision to create a panel with an R-value equal to commercially-made ones. Furthermore, the structural integrity of self-assembled panels can also suffer due to incorrect assembly techniques or inadequate materials used during DIY fabrication.

Can SIPs Be Load-Bearing?

Structural insulated panels can withstand considerable loads. Load-bearing panels are engineered with enhanced structural integrity, allowing them to carry loads in construction. As a result, SIPs provide a robust and durable alternative to traditional wood frame construction with the added benefit of energy efficiency.

When constructed properly, these panels can bear heavy loads without additional support. They may be lightweight, but structural insulated panels are designed with airtight insulating foam that allows them to distribute considerable loads evenly. 

The high load-bearing capacity of structural insulated panels makes them an excellent choice for constructing roofs and walls. 

Are SIPs Fire-Resistant?

Structural insulated panels are fire-resistant and are even considered self-extinguishing. The insulating layer is commercially treated with flame retardants, which prevent fire from spreading. More importantly, the gypsum board layers that sandwich the insulation layer are highly effective flame barriers.

Closeup on the corner of a stack of gypsum boards

Although gypsum boards might look lightweight and the paper exterior can catch fire quickly, they are used in construction because they provide exceptional resistance to fire—a gypsum board’s flame barrier provides structural integrity during a fire, giving responders enough time to enter and exit a building.

Are Structural Insulated Panels Flammable?

Most SIPs panels are flammable, but they will resist spreading a fire for at least an hour. This characteristic is because they contain an insulating layer made of expanded polystyrene (EPS), a fire-resistant material incapable of spreading fire.

Because of their one-hour fire rating, structural insulated panels are safe for use in fire-prone regions and areas that face the threat of wildfires. Builders can increase the fire resistance of SIPs by using gypsum boards on top of them.

Can Structural Insulated Panels Get Wet?

SIPs can get wet during the construction phase. However, they must be allowed to dry off to preserve their structural integrity. Continued exposure to water damages the panel’s insulating layer. Additionally, the OSB may rot if it does not dry off. 

Most experts recommend covering SIPs during the construction phase because they can be difficult to dry off after prolonged exposure to water. This is one disadvantage of using SIPs, which is why some contractors choose ICF instead.

Closeup on the internal composition of an ICF block before the concrete is poured
ICF is a popular SIPs alternative

Can You Get a Mortgage on a SIPs-Constructed House?

You can get a mortgage on a structural insulated panel house in most Western countries. SIP houses are considered fully mortgageable because this type of construction has become wildly popular. However, non-standard mortgages on SIPs-constructed homes are easier to attain.

For most banks, standard mortgages are out of the question for those who don’t own a property built from bricks, concrete or similar materials. SIPs homes are usually only covered by non-standard mortgages, as they are constructed from wood panels filled with an insulating foam core. 

However, there’s no need to worry about the term non-standard mortgage. A non-standard mortgage means the bank will lend you the money using a different payment plan. 

Most banks will want detailed information about your construction plans. Additionally, they might release the loan in stages depending on your construction phase. This arrangement is called a stage payment mortgage.

There are several benefits to taking a stage payment mortgage out on your home, especially if you’re a first-time homeowner. For one, you would only need to pay interest on the money you receive, not the entire amount. In addition, if you stop construction at any point, you won’t spend as much on interest.  

Can You Use SIPs as Flooring? 

Structural insulated panels can replace traditional flooring, providing insulation, a structural frame, and even an air barrier. They are considered a more efficient choice for floor construction because they combine all three features in one material. Modular homes frequently use SIPs in their flooring. 

Nowadays, many new homes are primarily built using structural insulated panel construction. Floor SIPs are an improved flooring system that is more efficient and easier to install than their traditional counterparts. 

The panels are lightweight yet durable and designed for quick installation with minimal effort. These features make them a great alternative to other flooring systems, as they can be built in hours rather than days. 

On the other hand, if you own an older home and wish to extend or convert the flooring in some rooms, you may use SIPs. Make sure you have a competent architect to draw up the construction plans to ensure that the structural insulated panel flooring is adequately strong. 

Can You Screw Into SIPs?

You can screw into structural insulated panels made with 0.75-inch (two-centimeter) OSB boards as long as you use short screws and the OSB is not soaked in water. Reasonable loads for OSB boards include decorations, frames, mounted TV sets, etc.

A worker screwing an SIP to the ceiling in a home under construction

Avoid drilling through the OSB board and into the insulating foam because doing so would affect the panel’s structural integrity. Do not drill into SIPs for plumbing or wiring, as that would be too deep, increasing the likelihood that you will reach the insulating layer. 

If you’re unsure about the length of your screws, it’s best not to screw them into the panels. Before working with SIPs, you must ensure you have the correct size screw for each job. Measure carefully before purchasing screws and double-check their size against what is needed for your project.

Final Thoughts

Structural insulated panel homes are quickly becoming the new standard for residential and commercial construction. These energy-efficient structures are constructed from prefabricated panels with an insulation core sandwiched between two OSBs or other structural skins. 

SIPs offer superior insulation capabilities, lower costs, and faster construction times than traditional building methods. 

First-time homeowners are highly encouraged to choose the SIP construction method because it offers many advantages in terms of cost savings and durability.

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