SIP Panel Primer – Your Affordable Mass Produced House

Let’s start by describing what a SIP Panel is and why they are called SIP Panels in the first place.

The SIP Panel is actually an ingenious combination of three things; two panels and a core. One panel serves as an exterior skin, the core is a block of construction foam, and a second panel serves as an outer skin. These three items are bonded together to create a strong Structural Insulated Panel.

Sip panels with skinsThe skins of the panels are typically conventional sheeting material like Orient Strand Board (OSB), plywood, metal, drywall, and cement type boards. Because these construction materials are already used to create interior and exterior walls for conventional construction, they are readily available and accepted. The core is usually one of two materials; polyurethane foam or expanded polystyrene foam. There are advantages to each which we’ll describe below.

The idea behind the development of structural insulated panels sips started in the 1950’s when people tried to figure out how to build houses faster than was traditionally being built using timber frame construction. Since SIP Panels are panels, they make for simple, fast, and efficient construction. Placing one panel that alrady has the exterior wall, the interior wall, and the insulation combined AND serve as the load bearing structural members of the building, is many times faster to assemble than cutting each framing member, nailing it all together, then adding layers of interior and exterior wall material (stick built construction).

There are even significant time savings in developing countries where mass construction of houses are usually completed using brick and mortar or concrete. Unlike in the United States where the brick is typically a veneer, much of the construction in developing countries, especially in rural areas rely on brick and mortar since getting the forms and concrete trucks to remote areas would be impossible.

From a financial perspective; many SIP Panel manufacturing companies are capitalizing on the Green Building and Sustainable Development phenomena and have inflated their products value which jeopardizes their broader use as a general purpose, mass produced building material. This premium perspective tends to slow the interest and investigation as a solution to the global affordable housing shortage.

As a matter of fact, our experience shows that SIP Panels are indeed the right product, at the right time and will play a significant role in affordable mass-produced housing, especially in developing countries where housing demand is unbelievable high.

SIPs have become extremely popular in the US, Canada, and Europe and are now used as an alternative construction material for homes and other buildings. Many Composite Panel building systems have been developed over the years but  SIPs now usually refers to panels made from a thick layer of foam (polystyrene or polyurethane) sandwiched between two layers of Oriented Strand Board (OSB), plywood or fiber-cement. 

But don’t take our word for it:  According to the US Department of Energy

“The basic design concept for SIPs is elegant in its simplicity, and offers several advantages for constructing walls and roofs. Bonding the foam core to the stiff outer skins creates a web-and-flange structural strength (along the same principal as an I-beam) across the length and breadth of the panel. With the capacity to handle axial, bending, racking, and shear loads, properly designed and assembled SIPs not only replace conventional framing, but will withstand high wind, and seismic forces.”

This article will help identify what drives SIP Panel costs, limitations, and hindrances and explain why the IADDIC SIP Panel System offers superior opportunities to build SIP Panel structures in overwhelming volume. 

SIP Panel Homes

SIP Panel HouseMany of the frequently asked question about SIP Panels involve their appropriateness for use in homes. The Sip Homes, like any home, must be a comfortable and secure place for living, raising a family and in some instances earning a living.

Early on, SIP Panels were prone to failures due to the process of laminating the sheeting to the core. Those issues, along with standards for building materials solved many problems a long time ago and hundreds of millions of square feet of buildings have been constructed using SIP Panels over the years.

The modern view of SIP Panels is that SIP’s offer the best opportunity to build an Energy Efficient Home . Buzz words in the construction industry including LEEN, and Net Zero Homes often rely on the use of SIP Panels.

There is no doubt that today’s SIP Panels are unlike the ones constructed in the early days where delamination was a concern. Rather, today, they are perceived as a premium building material. I think that is unfortunate since the material costs are very low and the construction speed is very high.  

Typically, manufactured wall panels are 4 feet to 24 feet wide, and 8feet or 9 feet. high.  They are made to standard thicknesses of 4 ½ ” to 6 ½” to coincide with construction lumber dimensions. The core is usually recessed from the edge to allow the panel to accept 2×4 top and bottom plates. Thicknesses of up to 12 inches are possible and are used for roof panels where greater R-value is required. 

SIPs typically have higher R values than a conventional wall construction of the same thickness. Thus, thermal performance is improved and produce a very airtight seal reducing unwanted air infiltration, adding to their performance.

 

SIP Panel Cost

So what does a SIP Panel cost? This is a little tougher question to answer. SIP Panels like many products come in many variations. For the moment, let us look at costing concepts rather than actual costs. I’ll get to the actual costs in a moment, but let’s look at what it takes to make and use SIP Panels.

Typically SIP Panels are made in a factory. You send the factory your house plans or select a house plan they offer as standard. The plans are then analyzed and sliced into rectangles, triangles, and other geometric shapes. Each shape represents what will eventually become a panel used to build the SIP Panel Home.

First, however; the panels must be made. The actual making of the panel depends on the core the manufacturer has selected. In either case, the skins of the panel are selected depending on their function and location in the building. Particular attention is given to those that are interior walls or exterior wall panels.

These skins are inserted into a machine and attached to the center core. The machines either glue and press the skins to a polystyrene core or they are fixed to a mold where the center core is filled with liquid polyurethane foam. The polyurethane foam expands and bonds everything together.

IADDIC has chosen to use the polyurethane foam core for our systems. The reason is quite simple, The cost to ship foam cores is expensive; especially if shipping internationally. Secondly, the pressure and heat needed to bond the skins to polystyrene are quite high making a field operable system impractical.

SIP Panel Factory Costing

Some panel manufacturers use lamination machines which automate forming and cutting to the dimensions acquired from digital floor plans or CAD files. Arriving precut to the job site, each panel can be rapidly installed by workers without extensive training. SIPs construction makes it possible to quickly construct an exterior building envelope that is airtight, energy efficient, and strong.

So you see, there has been a need for expensive machines, in many cases a factory, raw material, and laborers. In the developed world it is quite reasonable to expect volume production to be efficient, quality controlled and with enough automation; quite inexpensive to make.

In developing countries,however;  this is not the case. Building a factory in the first place is cost prohibitive and fraught with regulations, tariffs, taxes, fees, and gravitas which act as impediments that make factory construction impractical. This isn’t to say it’s not being done, but you can imagine the difficulties.

To counter the high cost of building a SIP Panel factory IADDIC has developed a suite of field operable SIP Panel Mold Presses (SIP Panel Machines) that make the construction of SIP Panels practical almost anywhere in the world; on the construction site or near to it.

SIP Panel Shipping Costs

can not ship sips truckThe downside to SIP Panels is if they are built in factories they need to be shipped to the construction location. Obviously, the further away the factory from the construction site, the higher the costs. Because SIP Panels are bulky, they consume a lot of shipping container space. Space and distance are premiums and are not governed by the SIP Panel factory but by the logistics companies and the ability to control these costs is minimal.

It should also be obvious that the larger the SIP Panel House or structure, more trucks or shipping containers are needed to get all of the panels to the site.

SIP Construction Costs

SIP Panel HouseNow here is the big winner and cost savings opportunity. Compared to other building methods, SIP Panel Construction can go up 3 or 4 times faster. The economics here have changed over the years. There was a time when construction was performed by highly skilled trades, like carpenters. Today, lower-wage skills are used to cut costs and since many houses are repeated when building a housing development, the same labor becomes accustomed to mass production on the construction site.

Speed of Money Costs

Rarely talked about is the speed of money. This is an important concept to contractors who invest in construction projects before any owners take possession. The faster he can build and sell the house the quicker he gets paid. This may seem trivial, but builders constructing many houses have the interest to pay on the debt used to finance the construction project. Since construction times can be reduced to 1/3rd or 1/4th of the traditional construction time the contractor pays less interest and may lower the price of the home.

To review, the main costs drivers for construction are:

  • Raw Material Costs

  • Factory Costs

  • Shipping Costs

  • Construction Costs

SIP Panel Construction

Building structures using SIP Panels is one of the easiest and fastest building methods available. Because the SIP Panels include interior walls, exterior walls, structural and insulating capabilities; all that is required is to simply set the panels in place and fasten them together (usually using screws).

SIP Panel houses and buildings can qualify for Energy Efficient ratings. To do so particular attention needs to be paid to the joint between two SIP Panels. For non-energy rated buildings, it is likely that standard dimensional lumber will be used. This, however, creates what is known as a thermal bridge which allows heat to pass through the walls at the joint. The use of insulated splines ( thinner SIP Panels cut into strips) prevents thermal bridging yet provide the strength necessary to hold the panels together without compromising structural integrity.

Other strategies like adding adhesives and caulks as a sealant add strength to the bond and additional sealing capabilities.  

There are several dozen SIP Panel manufacturers shipping SIP products throughout the US.  Some of the manufacturers have their own construction crews but most use general contractors to build the structures.   Maybe the largest implementation concern is in regard to the roof.  Some shingle manufacturers will not warrant shingles if placed on SIP’s without ventilation channels.  alternatively, metal roofs are extremely popular.  In one instance a roof in Alaska showed signs of deterioration because of a lack of ventilation.  It should be noted that the Structural Insulated Panel Association (SIPA) asserts that standard SIPs panels will not deteriorate if properly installed.

To capitalize on the highly insulated walls and roof, care must be taken to seal all joints properly.  Spray polyurethane foam is sometimes used to fill any seam gaps. We’ve provided a “best practice” connection diagrams for typical joints and details.

Construction Details

SIP Panel Detail - Roof Connection Ridge CapTo make things a little complicated, SIP Panel manufacturers modify panels in unique ways suggesting these modifications add value. Sometimes they do and sometimes they don’t. For example, some manufacturers embedded a locking mechanism along the edges of the panel. These locking mechanisms do speed up assembly, but they make the panels unique and add costs. Others manufacturers use routers to taper the edges of the panels in mats that create male and female cross-sections suggesting these create better joints. This may or may not be true in a given application.

Because IADDIC is interested in the rapid construction of affordable housing our systems uses a traditional square cut routed edge. This allows for the insertion of square or rectangle splice materials that are readily available.

For an overview of roofing panels, wall panels and floor panels and how they assemble please click this link for a complete set of technical SIP Panel detail drawings showing the various joint fastening strategies.

Home Kits

656 sq ft sip panel houseWhy might you consider a SIP Panel House Kit? For starters if you are looking for some of the strongest building technologies and great energy efficiency then these are at the top of the list. If you want to build very quickly then you will find nothing else quite like them.

Some specialty manufacturers make home kits available. Be certain to check what is in the kit as many are just providing the envelope (exterior walls and roof), splices, and screws. All other items need to be purchased separately and installed.

It is also important to know if the manufacturer is providing all of the cutouts for windows and doors or will you need to cut them out yourself. If you must cut your own openings, you will need panel saws and tools to remove the core material where a framing member is installed to hold the window or door.

IADDIC Provides Panel Saws and SIP Panel tools.

An option is to purchase SIP Panels in stock sizes and plan to fit them yourself. There is nothing particularly hard about this if you are handy with tools and have a way to lift the panels into place.

SIP Panel Home Kits Prices

There are a number of SIP Panel manufacturers who make custom designed homes as well as offer a variety of standard home plans. It is fairly easy to locate a manufacturer near you and learn what they offer. You may find that the manufacturers near you do not offer exactly what you are looking for. If this is the case you can choose SIP Panel manufactures further away, however; shipping costs increase the farther away the manufacturer is from the build site.

So, what does all this add up to? The round about average comes out to be about $22.00 USD to $27.00 USD per square foot under roof for the building shell; plus shipping costs which can be in the thousands of dollars.

SIP Panel Sizes

SIP Panel sizes are dictated by two factors. The first is the availability of sheeting sizes. For example, OSB sheeting come in lengths as long as 24′. Some SIP Panel Home manufacturers will create as large a panel as possible to improve energy efficiency, strength and speed construction time.

However; more common sizes of SIP Panels follow the generally available stock OSB sizes of 4′ X 8′ and 4′ X 10′.

Thickness

Of particular importance is the thickness of the panels. The thickness will add r-value to the panel making them more energy efficient. Here too, the thicknesses tend to conform to standard lumber sizes. In the US, for example, the standard core thickness (dimension between the skins) would be 3.5”, 5.5”, or 7.5” to conform with standard dimensional construction lumber.

r-value

I mentioned above that there are increasing levels of insulating capabilities with SIP Panels. The thicker the SIP Panel, the higher the r-value. Although polyurethane foam has a higher r-value than polystyrene, unless you need exact figures, a general rule of thumb is that the r value will be about r 6 to r 6.5 per inch regardless of the type of foam used for the core.

Thus the r value for dimensional lumber:

2 x 4 (3.5” thick) 21 to 22.75

2 X 6 (5.5” thick) 33 to 35.75

2 X 8 (7.5” thick) 45 to 48.75

A non-traditional size for a SIP Panel is one that has a 1.5” core. This size allows a 2 X4 to be turned sideways and used as the splice. Thin wall SIP Panels would be perfect for sheds and small structures like Tiny Houses.

Unfortunately; we are unaware of any manufacturer willing to produce this size panel. Thin wall SIP’s, although frequently asked for are not commercially available. However; IADDIC does offer 1.5” thick SIP Panels and or machines are adjustable to manufacture this size panel.

Tiny House

There has been a lot of interest in the tiny house movement. There are many reasons people are attracted to the tiny house movement, not the least being their mobility and low costs. Many Tiny House or Tiny Home builders are “do it yourself” types of people, but a number of companies have started producing tiny houses.

Tiny House builders could benefit significantly by constructing SIP Panel Tiny Houses which would add strength and durability to their structures. It is very important that wind-resistant building techniques be incorporated into the tiny house to keep them from falling apart as they are towed down highways.

The primary advantage that a tiny house would gain from SIP Panels is the incredible racking strength offered by the panels themselves. SIP Panels do not flex in the same way that a stick built home does and are very rigid. So rigidity coupled with racking strength are much higher.

SIP Panel Cost Comparison

Earlier we discussed the general costs associated with SIP Panels. Here we will break the costs down a bit further and look at the cost of the raw material for SIP Panels and compare SIP Panel materials to finished panel costs. As you will see, there is quite a bit of “mark up” to the commercially available SIP Panels.

For convenience, we have developed a SIP Panel COST Calculator for your use.

This is why IADDIC has chosen to offer field operable SIP Panel systems. We believe the contractors across the globe are capable of building their own SIP Panels and save a significant amount of money and time. Thus, they are able to produce better homes for less money. Hence affordable housing.

For Example:

To produce 10,000 4′ by 8′ SIP Panels 3.5” thick with 19/32” OSB skins for both the inside and outside will sell for about 85.00 USD if IADDIC produced the panels using our PBS3000 SIP Panel Building System.

Comparably: To purchase the materials for the same panels would run about $80.00.

The same panel purchased from a SIP Panel manufacturer in the USA will cost as much as $140.00. Of course, you will need to add the shipping costs to this value.

As you can see, most of the SIP Panel costs are in the raw materials and factories charge a premium for the panels.

IADDIC has an SIP Panel Costs online calculator to help you determine the costs using our system. Be sure to check our costs compared to any quotes you receive to determine who is providing the best deal.

DIY SIP Panel Construction

SIP Panel Mold PressWe’ve been manufacturing structures using structural foams and panels for over a decade and DIY SIP panels are possible but not without some limitations. We’ve proven that SIP Panels Machines capable of producing quality panels that can be used in residential and commercial structures is possible using our PBS 3000 Field Operable SIP Panel press. We have manufactured panels in wooden presses made from plywood, but the quality decreases significantly. The problem is that polyurethane foams produce a significant amount os pressure in the press and this must be counteracted by the press structural members. If not the panels will bow and swell as the foam expands.

Even considering the use of pre-cut polystyrene blocks for the core would require even higher pressures plus the addition of heat to bond the skins to the core. We have been unable to solve that challenge and we do not see any shipping advantage especially for our international customers since blocks would consume the same shipping space as panels themselves.

If you are ready to add field built SIP Panels production to your construction process please give us a call. We’ll be happy to develop a full quote for your specific needs. Also, don’t forget we offer engineering and project management assistance for larger projects.

Request A Quote

 

Richard Grabowski
Adequate housing and shelters are more than just products; they provide security, enable sustainable development, unite families, and help establish stable communities. Our focus at IADDIC is to bring the best technology, at the lowest cost, in the highest volume we can to make affordable housing indeed affordable.
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