So now that we have discussed the major components that make up a SIP we would like to get into the specifics of how exactly SIPs work.  There are two levels on which SIPs work. First they are structural and can replace the majority of the lumber required to frame a building in a conventional manner and second they create a super insulated wall system.

SIPs are similar to steel I-beams with the skins acting as the flange and the foam core the web. This configuration is incredibly strong and virtually eliminates the need for any additional lumber for structural support. In the instances where there is need for support for point loads an LSL or dimensional lumber is added into the wall system. With Earthcore SIPs any additionally required support is placed in the wall system at the factory, eliminating the need for job-site modification. Earthcore also gains additional strength from the type of foam that it uses. Instead of a

polystyrene foam, Earthcore uses polyurethane with has structural integrity on its own, plus, because polyurethane foams are an adhesive, and a secondary adhesive is not required to make our SIPs, the final unit is bonded together to form one cohesive unit. Eliminating the wood framing in a wall has several advantages. Obviously, using less wood is a better environmental choice, particularly, as mentioned in our article on OSB, the wood content in a SIP is from fast growth forests and 98% of the tree is used. SIP panels are formed in a controlled environment and made with engineered products so that walls are straighter and less susceptible to warping and bowing. The largest advantage, though, is that with less wood there is more room for insulation.

As you can see in the example to the left, eliminating the wood within the wall allows for continuous insulation from top to bottom and side to side. This increases the performance of the wall by eliminating the thermal breaks caused by the wood members of a conventionally framed wall. In other words, in a conventional framed wall, at every 16″ on center, the insulation of that wall is broken. This not only allows areas for the air outside of the house to penetrate into the “conditioned” space of the house, but decreases the R-Value of the wall at every point where there is wood. Wood has an R-value of .5 for every inch so in a wood framed house you decrease the R-value at these points from R-19 in a 2 x6 framed wall to R-2.8. In comparison, in an equivalently thick Earthcore SIP structure you have a continuous R-42.

There is also the issue of air infiltration to which we eluted to previously. The wood studs in a conventionally framed house break the continuity of the insulation which could lead to gaps in the insulation as well as points where air can penetrate in the conditioned living space. With Earthcore’s foam core there are no points of air penetration and with the foam spline and the application of foam at all connection points a SIPs house can be the “tightest” house available of all the building methods in practice today. This is accomplished, too, because SIPs can panelize larger portions of the building creating a wall system as opposed to components being cobbled together in sections. As an example, Sustainably Built, a Boulder, CO energy modeling company, recently tested a home built with SIPs that measured 1 natural air change per every 23-24 hours. Todays energy codes only require one natural air change every 3.5 hours. This increased “tightness” helps reduce wasted energy to heat and cool a structure and also allows for greater control of the indoor air quality which produces a healthier environment in which to live and work.

To help the public understand Earthcore SIPs and it’s products we are posting informational blogs that discuss in-depth the various aspects of our SIPs. In the first segment of this series we discussed the OSB skins that Earthcore uses. One significant point that was left out of the last blog is that Earthcore uses an OSB engineered specifically for the SIPs industry.

In today’s segment we would like to concentrate on the foam core that Earthcore uses in it’s products. Both the the OSB and foam core in a SIP work together to form a high strength system. So the foam is an equal contributor to the structural value of the panel as is the OSB. This structural value is unique to polyurethane SIPs. While polystyrene adhered to two “skins” works in tandem to create structure, only polyurethane foam has structural value independent of it’s “skins” Another difference to note is that polystyrene has a separate adhesive applied in order to create the bond between the foam and the “skins”. In a polyurethane SIP the foam has adherence properties that bond to the OSB creating a single unit.

While adding some structural value to the SIP diaphragm the foam is meant to primarily create high insulation values. In general polyurethane SIPs have an R-value of  7.5 per inch. This translates into a total panel R-value of 42 in a 6 1/2″ panel. But- R-value is not very useful if the there is a high level of air infiltration into your building. With polyurethane being a continuous insulation system there are no areas for air to infiltrate once the panels are installed. With a very low “air exchange rate” your building is not only cheaper to heat, but is very comfortable as well.

Earthcore took great care in selecting the foam that it uses in its products. Our foams are completely HFC, CFC and VOC free. It meets the Kyoto and Montreal protocols and has no Global Warming Potential (GWP) or Ozone Depleting Potential (ODP).

Technical Data

		HCFC-141b	HFC-245fa	Pentane iC5	Pentane nC5	Pentane cC5	HCFC-134a	HCFC-22	365 mfc / 227ea (93/7%)
MW	60	117	134	72	72	70	102	86.5	150
BPt, C	32	32.2	10	28	36	49	-26.2	-40.8	30
lambda	10.7	10	12	14	14	11	14	11	10.7
Flash Pt, C	-32	None	None	-51	-49	-37	None	None	None
Sp. Gr.	0.982	1.24	1.32	0.624	0.63	0.75	1.22	1.19	1.28
ODP	0	0.11	0	0	0	0	0	0.055	0
GWP	0	700	900	11	11	11	1300	1700	820
VOC	Exempt	Exempt	Exempt	Yes	Yes	Yes	Exempt	Exempt	N/A
Kyoto Compliant	Yes	No	No	Yes	Yes	Yes	No	No	No
Montreal Compliant	Yes	No	Yes	Yes	Yes	Yes	Yes	No	Yes
Vapor Pressure @ 25°C [mmHg]	476 mmHg @ 20°C	590 mmHg @ 25°C	923 mmHg @ 20°C	580 mmHg @ 20°C	426 mmHg @ 20°C	338 mmHg @ 20°C	4432 mmHg @ 20°C	7033 mmHg @ 20°C	600 mmHg @ 20°C
Flammability LEL	5%	7.6%	None	1.4%	1.50%	1.10%	None	None	3.8

• Available for use in the U.S.A.
• Phased out per Montreal Protocal

As many people may already know SIPs are made up of two basic components, a rigid foam core and a skin, that are adhered together to form one strong wall system. To help create a greater understanding of what to expect when purchasing an Earthcore SIP we have decided to post several articles explaining the properties our SIPs components. This article will concentrate on the “skins” of the SIPs and attempt to answer most of the common questions surrounding this product..

Earthcore primarily uses oriented strand board (OSB) for it’s skins. Depending upon the engineering requirements of a project and whether the panel is being used as a wall panel or a roof panel, Earthcore will typically supply panels with either 7/16″ or 15/32″ thick skins.

OSB was introduced in 1978 and since that time has been accepted as a common building material throughout the world. “OSB sheathing panels can be used to create horizontal diaphragms and shearwalls in order to brace buildings for wind and seismic loads.”(OSB Guide™) This part of the OSB adds to the overall strength of our SIPs. In the future we will discuss how the strength of the OSB and the foam come together to form a super strong wall. “The ASCE Standard ASCE 16 “LRFD Design of Engineered Wood Construction” is referenced in the model U.S. building codes.” (OSB Guide™)

Frequently, questions as to the environmentally friendliness of OSB arise. What type of wood is used in OSB?, Does OSB off gas?, What type of adhesives are used?

“OSB panels can be manufactured from a wide range of fast-growing species and from relatively small trees. The production process utilizes a maximum amount of wood fiber from each tree that is harvested, and because the process is very highly automated the yield of finished product is very high.” (APA) New growth trees, managed forests, a highly efficient manufacturing process and a long life cycle make OSB one of the more sustainable products on the market. This coupled with  far less embodied energy to create than either steel or concrete make OSB the preferable building product to use.

Off gassing in OSB is not significant, either naturally or from the adhesives that are used to bond the stands of wood together. TECO, a testing facility dedicated to testing wood and building products issued a report in May of 2009 concerning the specifics of formaldehyde off gassing in OSB. This report also explains the type of adhesives used in OSB.

One final issue that I would like to refer to, is our specific supply of OSB. Currently we obtain our OSB from within a 500 mile radius of our manufacturing facilities and the OSB itself is manufactured within that 500 mile radius as well.

Earthcore SIPs strives to be the most environmentally responsible SIP manufacturer it can. Using OSB is just one part of  this mission. Our next topic will discuss Earthcore’s foam and its properties.

Well we finally did it. We finally got our website up and running. Our dedication to quality runs deep throughout and we would appreciate any feedback from all of you out there, not only about our site, but how we are servicing our customers with this exciting product. We look forward to hearing from many of you and are eager to work with you on any projects that you may have.  Happy green building.