C578 Type VIII GPS (GPS / grey EPS)
Additive grade
Pick when R-value per thickness matters more than price: graphite IR absorber cuts conductivity ~15–20 % at the same 19 kg/m³ density, but boards must be shaded during storage/expansion.
Values for the GPS condition
Other C578 Type VIII grades and fills
C578 Type VIII is listed in 4 conditions; see the grade overview at C578 Type VIII.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
GPSThis page GPS / grey EPS | Pick when R-value per thickness matters more than price: graphite IR absorber cuts conductivity ~15–20 % at the same 19 kg/m³ density, but boards must be shaded during storage/expansion. | — | 0.19 | 2.2 | — |
FRDefault Standard flame-retardant molded board | Default construction-grade board: polymeric brominated FR added so LOI ≥24 % and ASTM E84 Class A is met; use for under-slab, perimeter, EIFS/ICF and panel cores. | — | 0.2 | 2.5 | — |
EPS19 geofoam | Choose for lightweight embankment fill, retaining-wall backfill and slope stabilization where design uses 1 % strain resistance rather than 10 % values. | — | 0.2 | 2.5 | — |
Non-FR | Only for packaging, mould/void fill and non-building uses — cheapest, but LOI is below the C578 requirement so it cannot be certified as Type VIII insulation. | — | 0.2 | 2.5 | — |
What is C578 Type VIII GPS?
C578 Type VIII GPS is C578 Type VIII in the GPS grade — pick when R-value per thickness matters more than price: graphite IR absorber cuts conductivity ~15–20 % at the same 19 kg/m³ density, but boards must be shaded during storage/expansion. C578 Type VIII GPS has a tensile strength of 0.19 MPa (0.0276 ksi), weaker than 97% of polymer grades. Elongation at break is 2.2% and the elastic modulus is 0 GPa (6.53×10⁻⁴ Msi). C578 Type VIII GPS has a density of 0.02 g/cm³ (6.86×10⁻⁴ lb/in³), lighter than 99% of polymer grades. Its glass-transition temperature is 100°C (212 °F). FR is the default condition FabDigit quotes; GPS is available on request or by drawing note.
Advantages
- Lightweight — 0.02 g/cm³ (6.86×10⁻⁴ lb/in³), better than 99% of polymer grades
- Easy to machine — 84/100, better than 86% of polymer grades
Limitations
- Poor heat conductor — 0.03 W/m·K (0.0182 BTU/hr·ft·°F), worse than 96% of polymer grades
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Limited ductility — 2.2%, worse than 92% of polymer grades
- Absorbs moisture — dry before molding — 1.5%, worse than 91% of polymer grades
- Low stiffness — 0 GPa (6.53×10⁻⁴ Msi), worse than 90% of polymer grades
C578 Type VIII GPS properties
Typical room-temperature values for C578 Type VIII GPS; 17 are specific to this condition. Other listed values are C578 Type VIII reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
C578 Type VIII GPS has a density of 0.02 g/cm³ (6.86×10⁻⁴ lb/in³), lighter than 99% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical10
C578 Type VIII GPS has a tensile strength of 0.19 MPa (0.0276 ksi), weaker than 97% of polymer grades. Elongation at break is 2.2% and the elastic modulus is 0 GPa (6.53×10⁻⁴ Msi).
Thermal9
C578 Type VIII GPS is rated for continuous service to 75°C (167 °F). It conducts heat at 0.03 W/m·K (0.0182 BTU/hr·ft·°F), worse than 96% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
C578 Type VIII GPS has an electrical resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 78% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of C578 Type VIII GPS takes about 105 MJ of energy and emits 3.6 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 5%.
Manufacturability4
C578 Type VIII GPS's machinability is very good (84/100, better than 86% of polymer grades); weldability poor (20/100); formability not recommended (14/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C578 Type VIII GPS
Is C578 Type VIII easy to machine?
Hot-wire, hot-knife or fine-tooth band saw cuts cleanly; routing/CNC milling works with sharp tools, high rpm and vacuum extraction of beads.
Can C578 Type VIII be welded?
No structural welding — join with EPS-safe (water-based or solvent-free) adhesives, steam fusion in block molding, or mechanical fasteners/plates.
Can C578 Type VIII be formed, bent or molded?
Shaped by steam pre-expansion of beads to ~19 kg/m³ then block or shape molding at ~0.8–1.1 bar steam; blocks must age 2–5 days before cutting to stabilize dimensions.
What surface finishes work on C578 Type VIII?
Coat with cementitious base coat/EIFS mesh, acrylic render or foil facers; never use solvent-based paints, adhesives or hot bitumen, and always shield from UV and from thermal barrier code requirements.
C578 Type VIII chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| pentane (residual blowing agent)mostly diffused out after aging | 0.1 – 1.5 | 0.6 |
| polymeric brominated flame retardantFR grades only (HBCD-free polymeric FR since ~2015) | 0.4 – 1.2 | 0.8 |
| graphite (IR absorber)GPS/grey EPS variant only, 2–4 % | 0 – 4 | 0 |
| process aids / nucleants / antistatic co | 0 – 0.5 | 0.2 |
| polystyrene (styrene homopolymer)solid-phase basis; foam is ~97–98 vol % air | ≥ 96 (balance) | — |
C578 Type VIII GPS — frequently asked
What is C578 Type VIII GPS used for?
C578 Type VIII GPS is typically used for geofoam fill, insulated concrete forms and roof insulation. In short: between Type I and II; common geofoam density; moderate-load EPS board.
What is the tensile strength of C578 Type VIII GPS?
C578 Type VIII GPS has a typical tensile strength of 0.19 MPa (0.0276 ksi) — weaker than 97% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type VIII GPS easy to machine?
Yes — machinability is rated very good (84/100, better than 86% of polymer grades). Hot-wire, hot-knife or fine-tooth band saw cuts cleanly; routing/CNC milling works with sharp tools, high rpm and vacuum extraction of beads.
Can C578 Type VIII GPS be welded?
Not readily — weldability is rated poor (20/100). No structural welding — join with EPS-safe (water-based or solvent-free) adhesives, steam fusion in block molding, or mechanical fasteners/plates.
What surface finishes work on C578 Type VIII GPS?
Coat with cementitious base coat/EIFS mesh, acrylic render or foil facers; never use solvent-based paints, adhesives or hot bitumen, and always shield from UV and from thermal barrier code requirements.
Can C578 Type VIII GPS be formed, bent or molded?
Shaped by steam pre-expansion of beads to ~19 kg/m³ then block or shape molding at ~0.8–1.1 bar steam; blocks must age 2–5 days before cutting to stabilize dimensions.
What is the maximum service temperature of C578 Type VIII GPS?
C578 Type VIII GPS is rated for continuous use to about 75°C (167 °F), and briefly to 95°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM C578 — Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation — ASTM International (2022)
- ASTM D6817 — Standard Specification for Rigid Cellular Polystyrene Geofoam — ASTM International (2021)
- EPS Industry Alliance technical bulletins (physical properties, chemical compatibility, water absorption) — EPS-IA (2021)
- Insulfoam / ACH Foam Type VIII EPS board data; BASF Neopor grey EPS data — Carlisle / BASF (2023)
- NCHRP Report 529 — Guideline and Recommended Standard for Geofoam Applications — TRB (2004)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.