C578 Type VIII
ASTM C578 Type VIII is an intermediate-density molded EPS, pre-expanded to about 19 kg/m³, sitting between Type I and Type II with a thermal conductivity near 0.036 W/m·K.
Reference datasheet — C578 Type VIII is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the FR condition
C578 Type VIII grades and fills
C578 Type VIII is supplied in 4 conditions, soft to hard. FR is the default FabDigit quotes; the values on this page are for it.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
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 | — |
Supply forms, finishes and certifications
Ways C578 Type VIII is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
FACED | Facer-laminated | Coating |
What is C578 Type VIII?
ASTM C578 Type VIII is an intermediate-density molded EPS, pre-expanded to about 19 kg/m³, sitting between Type I and Type II with a thermal conductivity near 0.036 W/m·K. It is used where moderate compressive load and predictable low weight are both needed, and is supplied as molded block, hot-wire-cut board, geofoam blocks and faced panels in FR and non-FR bead. Like all EPS it is solvent-, bitumen- and UV-sensitive and requires a code-compliant thermal barrier indoors. Type IX is the next step up when bearing capacity governs. C578 Type VIII 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). C578 Type VIII has a tensile strength of 0.2 MPa (0.029 ksi), weaker than 96% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0 GPa (6.53×10⁻⁴ Msi).
What is C578 Type VIII used for?
- Geofoam fill
- Insulated concrete forms
- Roof insulation
Advantages
- Lightweight — 0.02 g/cm³ (6.86×10⁻⁴ lb/in³), better than 99% of polymer grades
- Easy to machine — 85/100, better than 88% of polymer grades
Limitations
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0208 BTU/hr·ft·°F), 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
- Limited ductility — 2.5%, worse than 89% of polymer grades
C578 Type VIII properties
Typical room-temperature values for C578 Type VIII-FR; bars are the position among polymer grades.
Physical4
C578 Type VIII 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 has a tensile strength of 0.2 MPa (0.029 ksi), weaker than 96% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0 GPa (6.53×10⁻⁴ Msi).
Thermal9
C578 Type VIII is rated for continuous service to 75°C (167 °F). It conducts heat at 0.04 W/m·K (0.0208 BTU/hr·ft·°F), worse than 92% of polymer grades. Thermal expansion is 65 µm/m·K (36.1 µin/in·°F).
Electrical4
C578 Type VIII has an electrical resistivity of 1×10¹⁴ 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 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's machinability is excellent (85/100, better than 88% of polymer grades); weldability poor (20/100); formability poor (15/100).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the polymer family
Yield strength against density for every polymer grade FabDigit runs. C578 Type VIII is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type VIII
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.
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) | — |
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.
How much does C578 Type VIII cost?
C578 Type VIII is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C578 Type VIII — frequently asked
What is C578 Type VIII used for?
C578 Type VIII is typically used for geofoam fill, insulated concrete forms and roof insulation. In short: between Type I and II; common geofoam density; moderate-load EPS board.
What is the tensile strength of C578 Type VIII?
C578 Type VIII has a typical tensile strength of 0.2 MPa (0.029 ksi) — weaker than 96% of polymer grades. Strength varies by condition: see the 4 listed tempers.
Is C578 Type VIII easy to machine?
Yes — machinability is rated excellent (85/100, better than 88% of polymer grades). Hot-wire, hot-knife or fine-tooth band saw cuts cleanly; routing/CNC milling works with sharp tools, high rpm and vacuum extraction of beads.
Can C578 Type VIII be welded?
Not readily — weldability is rated poor (20/100). No structural welding — join with EPS-safe (water-based or solvent-free) adhesives, steam fusion in block molding, or mechanical fasteners/plates.
What surface finishes work on C578 Type VIII?
Coat with cementitious base coat/EIFS mesh, acrylic render or foil facers; never use solvent-based paints, adhesives or hot bitumen, and always shield from UV and from thermal barrier code requirements.
Can C578 Type VIII be formed, bent or molded?
Shaped by steam pre-expansion of beads to ~19 kg/m³ then block or shape molding at ~0.8–1.1 bar steam; blocks must age 2–5 days before cutting to stabilize dimensions.
What is the maximum service temperature of C578 Type VIII?
C578 Type VIII is rated for continuous use to about 75°C (167 °F), and briefly to 95°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C578 Type VIII cost?
C578 Type VIII is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
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; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.