Mar
In the last article we discussed the different (most-common) types of sheathing for SIPs, but just as there are different sheathings there are also different foam cores. In this article we’ll look at the three main cores there are in the structural insulated panel industry: polyurethane, expanded polystyrene (EPS), and extruded polystyrene (XPS).
Polyurethane: With 6 to 6.8, this foam core has the highest R-value per inch of the three I’ve mentioned. Another advantage is its high melting point; in a fire, it would be the last thing standing. However, polyurethane foam is expensive at nearly 40 cents per square inch of panel, Also, the hot wire burners that are used for on-site adjustments can’t be used because of the melting point.
Expanded Polystyrene (EPS):EPS is the most common type of foam core for SIPs. It is cheap, widely available, and most installers are acquainted with it. However, like many readily available things, there are trade-offs. It has the lowest R-value and melting point.
Extruded Polystyrene (XPS): XPS is a nice in-between when compared to the above two foams. It has a high R-value (5 per inch of panel) while still having a rather low melting point so on-site tweaks can still be made. Something this good has to have a bad point though, and this is no exception: XPS is expensive and hard to find.