C578 Type IV
ASTM C578 Type IV is the baseline closed-cell extruded polystyrene (XPS) board in the ASTM C578 family, foamed by continuous extrusion with an injected blowing agent.
Reference datasheet — C578 Type IV 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.
C578 Type IV grades and fills
C578 Type IV is supplied in 3 conditions, soft to hard.
Compare all 3 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Thin (6–13 mm) scored fanfold underlayment bundles | Thin Type IV-class sheet used as siding underlayment / re-side board where only a small added R-value and a flat plane are needed. | 0.28 | 0.32 | 3 | — |
High recycled-content (post-industrial/post-consumer PS) board | Specified for green-building credits; property spread is slightly wider than virgin-resin board. | 0.3 | 0.35 | 2.5 | — |
HBCD-free polymeric brominated flame-retardant formulation | Current standard chemistry for markets restricting HBCD (EU POP, GB 8624 B1 class); same thermal and mechanical performance. | 0.35 | 0.4 | 3 | — |
Supply forms, finishes and certifications
Ways C578 Type IV is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
DRAIN | Grooved / channelled drainage board for foundation walls | Surface finish |
FACED | Factory-laminated facer | Coating |
PLANED | Skinless / planed surface for plaster and adhesive bond | Coating |
TG | T&G | Coating |
STDDefault | Standard unfaced board with extrusion skin, square edge | Standard supply |
What is C578 Type IV?
ASTM C578 Type IV is the baseline closed-cell extruded polystyrene (XPS) board in the ASTM C578 family, foamed by continuous extrusion with an injected blowing agent. Nominal density is 0.029 g/cm³ (29 kg/m³) with a thermal conductivity of 0.029 W/m·K, and stock forms include plain and planed board, tongue-and-groove, drainage-grooved, faced, fanfold, flame-retardant polymer and recycled-content versions. Low moisture absorption makes it the default choice for below-grade walls, foundations and roofs. Maximum service temperature is 74 °C; it is not weldable and degrades under UV and solvents, and Type VI or VII should be used where compressive load is higher. C578 Type IV has a density of 0.03 g/cm³ (0.001 lb/in³), lighter than 95% of polymer grades. Its glass-transition temperature is 100°C (212 °F). C578 Type IV has a tensile strength of 0.4 MPa (0.058 ksi), weaker than 91% of polymer grades. The elastic modulus is 0.01 GPa (0.0019 Msi).
What is C578 Type IV used for?
- Below-grade wall insulation
- Roof insulation
- Foundation insulation
Advantages
- Lightweight — 0.03 g/cm³ (0.001 lb/in³), better than 95% of polymer grades
- Easy to machine — 90/100, better than 95% of polymer grades
- Low moisture uptake — 0.1%, better than 77% of polymer grades
Limitations
- Hard to polish — 5/100, worse than 99% of polymer grades
- Poor heat conductor — 0.03 W/m·K (0.0168 BTU/hr·ft·°F), worse than 98% of polymer grades
- Degrades in UV without stabilisers — 15/100, worse than 95% of polymer grades
- Low stiffness — 0.01 GPa (0.0019 Msi), worse than 78% of polymer grades
C578 Type IV properties
Typical room-temperature values; bars are the position among polymer grades.
Physical4
C578 Type IV has a density of 0.03 g/cm³ (0.001 lb/in³), lighter than 95% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical7
C578 Type IV has a tensile strength of 0.4 MPa (0.058 ksi), weaker than 91% of polymer grades. The elastic modulus is 0.01 GPa (0.0019 Msi).
Thermal7
C578 Type IV is rated for continuous service to 74°C (165 °F). It conducts heat at 0.03 W/m·K (0.0168 BTU/hr·ft·°F), worse than 98% of polymer grades. Thermal expansion is 70 µm/m·K (38.9 µin/in·°F).
Electrical4
C578 Type IV has an electrical resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (85/100), better than 65% of polymer grades. UV resistance is poor.
Sustainability3
Producing a kilogram of C578 Type IV takes about 105 MJ of energy and emits 5.5 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 15%.
Manufacturability4
C578 Type IV's machinability is excellent (90/100, better than 95% of polymer grades); weldability poor (20/100); formability poor (30/100).
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 IV is highlighted; hover a dot for its name, or open the interactive family chart.
Working with C578 Type IV
Is C578 Type IV easy to machine?
Cut with hot wire, serrated knife or a sharp router bit at high rpm/low feed; vacuum chip extraction is essential because dust is static-charged.
Can C578 Type IV be welded?
Not thermally welded in practice — panels are joined with T&G edges, low-VOC foam adhesive or mechanical plate anchors.
Can C578 Type IV be formed, bent or molded?
Produced by continuous extrusion with direct gas injection through a slot die and calibrated by cooling plates; boards can be kerf-bent but not thermoformed.
C578 Type IV 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 |
|---|---|---|
| blowing agent (HFO-1234ze / CO2 / isobutlegacy grades used HCFC-142b/HFC-134a | 1 – 5 | 3 |
| brominated flame retardant (polymeric bu | 0.5 – 2 | 1 |
| talc / nucleating agentcell-size control | 0.1 – 1 | 0.4 |
| pigment (blue/pink/green identification) | 0 – 0.5 | 0.2 |
| polystyrene (GPPS resin)virgin + recycled PS matrix | ≥ 92 (balance) | — |
What surface finishes work on C578 Type IV?
Skin must be planed or roughened before cementitious render; protect from UV and from solvent-based mastics, and always cover with a code-required thermal/fire barrier.
How much does C578 Type IV cost?
C578 Type IV is a standard-cost polymer ($$), cheaper than about 71% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
C578 Type IV — frequently asked
What is C578 Type IV used for?
C578 Type IV is typically used for below-grade wall insulation, roof insulation and foundation insulation. In short: baseline below-grade XPS; low moisture absorption; widest stock form range.
What is the tensile strength of C578 Type IV?
C578 Type IV has a typical tensile strength of 0.4 MPa (0.058 ksi) — weaker than 91% of polymer grades. Strength varies by condition: see the 3 listed tempers.
Is C578 Type IV easy to machine?
Yes — machinability is rated excellent (90/100, better than 95% of polymer grades). Cut with hot wire, serrated knife or a sharp router bit at high rpm/low feed; vacuum chip extraction is essential because dust is static-charged.
Can C578 Type IV be welded?
Not readily — weldability is rated poor (20/100). Not thermally welded in practice — panels are joined with T&G edges, low-VOC foam adhesive or mechanical plate anchors.
What surface finishes work on C578 Type IV?
Skin must be planed or roughened before cementitious render; protect from UV and from solvent-based mastics, and always cover with a code-required thermal/fire barrier.
Can C578 Type IV be formed, bent or molded?
Produced by continuous extrusion with direct gas injection through a slot die and calibrated by cooling plates; boards can be kerf-bent but not thermoformed.
What is the maximum service temperature of C578 Type IV?
C578 Type IV is rated for continuous use to about 74°C (165 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does C578 Type IV cost?
C578 Type IV is a standard-cost polymer ($$), 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)
- FOAMULAR 250 Extruded Polystyrene Insulation product data — Owens Corning (2023)
- STYROFOAM Brand Extruded Polystyrene Insulation technical data — DuPont Performance Building Solutions (2022)
- ASM Engineered Materials Handbook Vol. 2 — Engineering Plastics (polystyrene foams) — ASM International (1988)
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.