top of page

Comparative Facts About Structural Insulated Panels (SIPs)

See how we compare to our competitors

Building an Energy-Efficient House or Structure:

An energy-efficient house or structure has many different components: foundation, exterior walls, floor, roof, insulation, windows, doors, mechanical systems, and lighting which all play important roles in the way energy is consumed. However, the core of any energy-efficient structure is the design of the building envelope (foundation, floor, walls, and roof). Yes, there are many different techniques used by architects, designers, and building contractors in designing and constructing the building envelope. Some designs, while performing well, are quite expensive to construct and may take several years before realizing any payback. Other designs are cheap to construct, but they don’t perform as promised. The only design that gives the ultimate quality of comfort while reducing energy consumption for the maximum $$ of energy savings, is a design that uses Structural Insulated Panels (SIPs), which is a composite building product, consisting of an insulating layer of rigid foam sandwiched between two layers of structural sub-straights aka, skins. 

What you might like to know about SIPs that you haven't yet found on the internet:

As the owner and founder of R-Valued Homes, I spent hundreds of hours searching the internet and calling different SIP companies for information as I pursued my desire to become a SIP builder. As a result, I understand why you may have more questions and concerns about building your new house with SIPs. Now, I’m assuming that you have spent hours on the internet researching different websites, including mine, in your endeavor to learn more about SIP construction. I’m also assuming that you have talked to building contractors for their opinions about using SIPs for your new home and probably were told that it would cost substantially more than conventional stick framing. Unfortunately, there are too many uneducated builders and therefore this is the answer most often heard. In fact, building with SIPs is on par with stick-framing when all costs are considered; I have even worked with some builders that told me it costs them less to build with SIPs than it does to use conventional stick-framing. By now you may be wondering what is truth and what is just plain old fluff - something I can totally understand having been there myself many years ago as I pursued my desire to become a SIP builder.


As you discovered during your internet search there are basically two types of foam, expanded polystyrene (EPS) or polyurethane (PUR) used in the manufacturing of SIPs.  You probably also discovered that there are far more sites promoting expanded polystyrene than polyurethane SIPs. Just remember: quantity does not equal quality.


Unfortunately, what you did not learn from the internet is the fact that not all of those companies are reputable and/or manufacturers of SIPs. Many are jobbers or wholesalers and you have no idea where or how they get their SIPs. There are some companies promoting their product as “SIPs” that are nothing more than a 2x framed panel with foam board inserts between the studs. These so-called SIPs don’t even come close to meeting the code requirements of a SIP per the International Residential Code (IRC) section R613. You also don’t know what experience they have, if any, about the challenges of building in Alaska. Their credibility depends solely on whether or not you trust and believe their salesperson. I, on the other hand, have been a builder, distributor, and now a manufacturer and fabricator of polyurethane foam SIPs in Alaska since 1998. This experience has allowed me to witness firsthand the good, bad, and ugly truths regarding the performance of both polyurethane & EPS SIPs.

The difference between our PUR SIP and our competitor's ESP SIP:

The technology and thermal performance between a PUR SIP, and an EPS SIP is like comparing night and day.  Let’s compare mathematically, the annual fuel savings in dollars strictly based just on the insulating R-value of these two different SIPs. For the sake of argument, let’s assume that a house built using Alaska Insulated Panels’ R-44 5-1/2” PUR SIP wall panels will consume $500.00 of fuel annually, that same house built with a competitor’s R-24.5 5-1/2” EPS SIP wall panels would consume $898.00 of fuel annually - an increase of 79.6%. This is assuming that the EPS foam remains dry; once water vapors intrude, condense, and saturate the EPS foam, the fuel consumption will increase substantially.


To further clarify the difference between these two types of SIPs I offer the following facts:

SIP house diagram


(Polyurethane (PUR) Foam Core SIPs):

  1. Made in the USA: AIP is an Alaska owned company located in Wasilla, Alaska and is registered as a “Made in Alaska” (permit number is 6919). We manufacture and fabricate SIPs for all types of residential and light commercial structures. We have a track record of success and know how to coordinate the logistics and the challenges associated with building in harsh environments. You can talk face to face with us or visit and tour our facility where you can witness firsthand our professionalism and the quality of our SIPs - something I believe is unequaled in the industry. 

  2. Panel skins:  AIP uses ½” CDX plywood exclusively for its durability. Due to the plywood manufacture’s size limitation and AIPs equipment limitation, we produce panels 4 feet wide and up to 12 feet long; the most common lengths being 8, 9, and 10 feet. 12-foot plywood needs to be custom ordered, have minimum order quantities, and longer lead times.

  3. Wall & Header Panels: We can fabricate wall panels up to 16’ tall and custom headers up to 24’ wide.

  4. Insulating Foam: Two-part polyurethane mixture, closed-cell insulating foam.

  5. Density: 2.3 pounds nominal per cubic foot.

  6. Chemical Resistance: PUR foam is not affected by oil or most solvents.

  7. Thermal Resistance: R-value 8.0 r’s per inch @ 20°F (ATSM 518), one of the highest R-values of all the insulating foams available.

  8. Manufacturing Process: In a controlled environment, using a specially designed mold to hold the plywood skins apart, then placed in a hydraulic press where a two-part polyurethane mixture is injected into the cavity and compressed until fully cured, resulting in a thermoset plastic composite panel. 

  9. Curing Process: The chemical reaction created after injecting the polyurethane's two-component mixture causes the foam to expand over 50 times its volume in about 8 seconds and becomes tack free in about 2 minutes. The foam generates pressures of 15 psi and temperatures of 350°F that impregnate into the plywood fibers resulting in a closed-cell structural insulated foam panel of tremendous strength (6 times stronger than conventional stick framing). Once cured it becomes a thermoset plastic that will not change.

  10. Water Vapor Permeance: Polyurethane foam is impervious to water absorption and as such maintains a constant R-value. AIP SIPs have a perm rating of less than 1 which qualifies it, by code, as the vapor barrier.

  11. Flammability: UL Class 1 Fire rated PUR foam will not melt and will only burn when exposed to a continuous open flame in excess of 800°F, and will only char at lower temperatures. To meet federal fire regulations, tris(1-chloro-2-propyl) phosphate (TCPP) flame retardant has been added.

  12. Fabrication: AIP SIPs are custom fabricated according to specific shop drawings including the installation of framing members for window bucks & door trimers, wall end fills, as well as point loads. Window & door headers are custom fabricated and vertical electrical chases and box cutouts are installed. Once fabricated, panels are then assembled and dry fit on a racking wall where they are quality checked for accuracy.

  13. Energy Ratings: AIP has over 600 SIP constructed homes throughout Alaska that have documented AkWarm Energy Ratings of 5 stars, 5 star-plus, and 6 stars (the highest possible rating). 



(Expanded Polystyrene (EPS) Foam Core SIPs):


  1. Made where?: All EPS SIP manufacturers are located outside of Alaska and very few have representatives in the state; mainly located on the internet and only contacted by phone or email.  Their SIPs may be made in the USA or imported from a foreign country; a word of caution, very few of these companies manufacture their own SIPs. Most of them are jobbers/wholesalers and you have no idea where the SIPs they sell are manufactured. Very few have ever been to Alaska, let alone know anything about the logistics, the environment, or the challenges of building in Alaska.

  2. Panel Skins: 7/16” Oriented Strand Board (OSB) is the skin of choice for almost all SIP manufacturers and used exclusively by EPS SIP manufacturers. OSB is cheaper than plywood, however cut edges are easily saturated by moisture causing it to expand, thereby making SIPs difficult to assemble on site. Once water gets into OSB it is very slow to leave, and the longer that water remains within OSB the more likely it is to rot.

  3. Insulating Foam: Expanded Polystyrene (EPS) foam is structurally an open-celled beadboard.

  4. Density: Typically 0.95 pounds per cubic foot. 

  5. Chemical Resistance: EPS foam is highly susceptible to oil and solvents and will melt when they come in contact with each other.

  6. Thermal Resistance: R-value up to 4.08 per inch @ 45°F - one of the lowest R-values of all the insulating foams, thereby reducing the amount of energy saving. As the EPS foam absorbs moisture, the effective R-value decreases substantially.

  7. Manufacturing Process (3 components): Small foam beads are placed in a mold and exposed to steam. This process causes the beads to expand and stick together creating interconnected voids between the beads to form an open-celled beadboard. This molded beadboard is then cut with a hot knife to the desired panel thickness and glued to OSB skins using a special, formulated glue that will not melt EPS foam.

  8. Curing Process: Depending on the manufacturer, glued panels are placed in a press or vacuum bag and held until the glue has set. It is not uncommon to find EPS SIPs that are not square or plumb across the edges. EPS SIPs are sandwiched panels that are only as strong as its weakest connection - that being the glue bond of the OSB to the EPS beadboard.

  9. Water Vapor Permeance: The open-celled structure (interconnected voids) of EPS foam provides a pathway for water to penetrate and be absorbed by the insulation up to 4.3% by volume or 4.71 gallons of water in a 5-1/2”x4’x8’ SIP Panel.  Any penetration through the vapor barrier and OSB skins (fastening wall coverings, hanging pictures, etc.) allows moisture-laden vapors (a process called perm drive) to be infused and absorbed. At some point, these vapor pockets will reach the dew point (the point at which moisture-laden vapor condensates to water) and it becomes trapped. When EPS foam and the OSB skins become saturated with water, it affects the performance and structural properties of the panel. For example:

    • Water is one of the most efficient conductors of heat transfer (heat goes to cold) and as such greatly reduces the thermal performance and lowers the effective R-value which increases fuel consumption

    • When condensed water freezes and expands, it breaks the glue bond between the OSB and EPS foam causing the panel to delaminate

    • Over time trapped water will also saturate the OSB skins which will decompose and lose its structural integrity, resulting in building failure

  10. Flammability: EPS foam is not fire rated; however, to meet federal fire regulations a brominated fire retardant, HBCD (hexabromocyclododecane) is added to the foam beads. Although this retardant prevents the EPS foam from igniting at temperatures below approximately 700°F, it will melt at temperatures between 180°F and 240°F thereby dropping liquid fuel onto the flames. HBCD fire retardant is banned in the European Union (EU) and is described as being "persistent in the environment, bioaccumulative in biological systems, and toxic" (Source “building green insulation report,used%20in%20polystyrene%20building%20insulation.&text=Restriction%20of%20Chemicals).-,HBCD%20is%20used%20in%20all%20polystyrene%20building%20insulation%2D%2Dboth,and%20expanded%20polystyrene%20(EPS)   

  11. Fabrication:  Some EPS SIP manufacturers/vendors only ship panels and you, the customer, will need to provide and install all required framing components on-site. In Alaska, you could be hundreds of miles from the nearest lumber yard, so dealing with out-of-square and un-plumb panels, or just being short one small piece, can be a time-consuming and costly experience

  12. Energy Ratings:  Unknown

Now, just for those folks who can only compare value in $$$ and think conventional framing is cheaper:

A house, conventionally framed, using 2x6’ studs @ 16” o.c with R-19 fiberglass batt insulation (which has an effective R-value of 15.4) would consume $,1429.00 of fuel annually; that is 1-1/2 times higher than the fuel-consumption of EPS SIPs and 3 times higher than AIP’s PUR SIPs. Additionally, when one is comparing stick framing to building with SIPs, one should also consider all the cost-effective benefits of SIPs such as:

1) reduced labor costs

2) shorter construction time (which also reduces the cost of interest on construction financing)

3) reduced on-site waste

4) fewer sub-contractors to schedule, etc.


When all of these costs are factored in, SIP type construction costs about the same as stick framing (sometimes even less). Also, with fuel costs 3 times higher, and fuel prices that keep increasing year after year, it only makes good sense to build with AIP SIPs.

Alaska Insulated Panels is your best choice. 

Alaska Insulated Panels, Wasilla, Alaska wants to earn your business; however, if you are only looking for the lowest, bottom-line dollar then we may not be the company for you. But, if you are looking for the ultimate value for your money and a SIP building system that has a proven track record of reducing energy consumption by as much as 80 percent, that is made in the United States of America and manufactured in Alaska, then we are the company you will want to use.


In closing I offer a little food for thought; when you are looking for value remember “Nothing cheap is ever good and something good is never cheap”.


RJ Burkhardsmeier


bottom of page