Structural Insulated Panels

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HOW DO SIPs COMPARE IN R-VALUES??? R-Value is a measurement of a materials ability to restrict heat flow. The higher the R-Value is of a material the better its insulating qualities, in theory. However, in practice, there is a lot more than R-Value that determines the performance of a building and is one of the most commonly misunderstood topics in construction today. At Heavy Timber Truss and Frame we have been in construction for years have worked with all kinds of insulation and manufacturers. The following is some of the key factors:

Not all insulating materials provide constant performance during changing conditions of heat, humidity and time. The R-Value of fiberglass batt insulation declines in proportion to increases in humidity, they also "settle" from the fully fluffed installation due to gravity and collect air borne dust and dirt. All these reduce the R-Value. The SIP foam cores used by Heavy Timber Truss and Frame are expanded polystyrene (EPS). The R-Value of EPS is very stable and actually increases somewhat as temperatures decline. They also do not off-gas any harmful emissions.

HOW DOES EPS FOAM COMPARE WITH OTHER FOAM PRODUCTS??? Some foam plastic insulation materials (polyisocyanurate and polyurethane) use blowing agents (in manufacturing) that have high resistance to heat flow. This causes the material to have an abnormally high R-Value at the time of manufacture. As the blowing agents diffuse from the cellular structure of the foam over its lifetime, the R-Value of the material is reduced by up to 30%. EPS is stable at the time of manufacture and its cellular structure does not change as time elapses.

WHAT IS NEOPOR ??? Neopor is the next advancement in EPS product developed by BASF. This product has been in wide use in Europe and is being introduced in North America by BASF. Graphite is added the manufacturing of EPS. Neopor - EPS foam cores have nearly 20% greater R-Value than panels made from standard EPS.

EPS Foam Core
Neopor EPS Foam Core
4 1/2" SIP
6 1/2" SIP
8 1/4" SIP
10 1/4" SIP
12 1/4" SIP











Heavy Timber Truss & Frames uses Neopor SIPs for our wall and roof panels. This progressive use of the best possible insulating product is in keeping with Heavy Timber Truss & Frames core philosophy of using the best components.

WHAT REALLY MATTERS??? R-Value has long been the measure of performance. It is one of many important factors. As building science has progressed so has our understanding of why certain structures thermally perform better than others. R-Value is important but we have learned that there are diminishing returns from just more R-Value. Increasingly it is understood that thermal short-circuits, air infiltration and poor construction methods are the keys to making higher R-Value work. Thermal shortcuts occur when there is wood to wood construction that transmits cold through the envelope. Stick type construction typically has this type construction every 16". Air infiltration occurs every place there is a joint that is not properly caulked or where loose batt or blown-in type insulation has gaps from installation or settling. Poor construction methods allow for air infiltration, perhaps the largest contributor to poor thermal performance of all.

HEAVY TIMBER TRUSS & FRAME management's years of experience understands the building science and is one of the primary reasons we have chosen SIPs: high R-Value, no thermal short cut connections and low to no air infiltration. We ensure this performance through our experienced installation crew's understanding of their importance and dedication to properly install SIPs efficiently and effectively.

At Heavy Timber Truss and Frame it starts with choosing the best components. Structural Insulated Panels (SIP) s are the choice that work best to create the most energy efficient envelope with timber framing. At Heavy Timber Truss and Frame we have worked with a variety of insulations and firms. We have chosen to use Neopor SIP panels because they offer a number of advantages. The following will give some basic information on SIPs.


SIPs are high performance building panels used in floors, walls and roofs for residential and light commercial buildings. SIPs are made with an expanded polystyrene (EPS) rigid foam core sandwiched between two structural skins of 7/16" oriented strand board (OSB). Panels are manufactured in standard thickness of 4 1/2", 6 1/2", 8 1/4", 10 1/4", and 12 1/4". Panels are manufactured in a standard dimensions of 8' x 24'.


Heavy Timber Truss and Frame designs custom panels to exactly fit your home. These are called Ready-to-Assemble panels. The dimensions are taken right from the architectural plans and are factory machine cut to precise sizes. The panels foam cores are relieved for spline connections and top and bottom plates. Dimensional lumber is factory installed around window cut outs, wall corners and roof perimeters. Wire chases built into the panel at 16" and 44" from all factory edges. All window cut-outs and other scrap is recycled at the factory to eliminate site waste and disposal.

Heavy Timber Truss and Frame coordinates the delivery to your site just as the foundation is completed, your first floor deck on, timber frame up and ready to begin the panel enclosure. Just-in-time keeps your site clean and orderly! All panel installation materials are shipped with the dimensional lumber, specialty SIP fasteners, splines and a foam-compatible adhesive. Wall systems are shipped together and are usually followed by the roof panel delivery 3 days later depending on the size of the home. While every home is different a rule of thumb is that assembly of the entire enclosure takes about 1/3rd the time the same home would take to stick frame. The stick frame home still then needs to be insulated whereas the panel is completely insulated. The difference is on site... TIME and as the old saying goes... "Time is Money"... and in this case it is yours!!