Polyurethane vs. EPS (SIPs)

With Thermocore, it all starts with the foam.

Most structural insulated panels (SIPs) on the market today use two types of foam - polyurethane or expanded polystyrene (EPS). Because of the advantages of polyurethane over EPS foam – especially when it comes to the highest R-value, fire safety and moisture absorption, Thermocore chooses to only manufacture polyurethane foam core panels. We use the best because you deserve the best.

Do you know the difference?

  Thermocore EPS Panels
Foam Used Polyurethane Expanded Polystyrene
Color Yellow White
R-value (per inch) 82% Better
6.9 per inch
3.8 per inch
Thermal Drift OSB skins prevent thermal drift in Thermocore panels. Thermocore panels tested by BASF that were over 3 years old showed no loss of R-value. Stable unless exposed to moisture. Due to EPS high perm rating, moisture absorption can cause loss of R-value.
Density / Strength
Higher density = higher strength
2.2 lb. minimum 1.0 lb.
Fire Resistance
(Exposure to Flame)
Self-extinguishing (not a fuel source).
Thermocore pays for a fire retardant to be added to our foam.
Fuel for fire
Exposure to Heat Will never melt.
Polyurethane is a thermoset plastic. It cannot be melted or reshaped.
Not recommended for temperatures above 180 degrees due to softening (can be cut with a hot knife)

Vapor Barrier
(Moisture Resistance)

Serves as its own vapor barrier.
Permeance rating of 1.2

Vapor barrier needed
Permeance rating of 2.0 to 5.0
Chemical Resistance Polyurethane is resistant to petrochemicals and other common household chemicals. EPS is highly susceptible to petroleum-based products, oils, and solvents, which can cause EPS to melt when brought in contact.
Manufacturing Polyurethane bonds to the OSB skins in three ways. Adhesion, chemical and mechanical. It creates the strongest bond in the industry. Thermocore panels carry a limited lifetime warranty against delamination. EPS panels use a poly-based adhesive to bond EPS to the OSB. The glue is the only bond to the EPS. Most companies only offer a 15-year warranty.
Cost Thermocore panels are often equal or lower costs when compared to EPS while providing more standard features than any EPS company. With Thermocore there are no added costs associated with lumber/lumber install or any upcharge from your electrician to wire your panels. We take care of the electrical at our plant. EPS panels do not typically come with door and window bucks included. It is an added charge. You will also have to pay a significant upcharge to have your electrical run as EPS companies DO NOT include electrical boxes and conduit, installed custom, as part of their package.
¾ Conduit Included Drilled Case (avg $5/ft)
4x4 Electrical Boxes Included Electrician added in field
Door & Window Cut Out Included with CNC Avg $200/window
Windows & Doors Framed 2x4’s Included Avg $75/frame
Roof Ridge Plum Cut Included Avg $6/ft
Sub Fascia in Place Included Avg $3.50/ft
Molded Foam Spline Included Avg $4.50/ft
Sill Plate Included Owner Supplied
Top Plates, Corners & Nails Included Extra
Beam Pockets & Column Supports Included Avg $250/pocket

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