Owens Corning FOAMULAR 250 XPS insulation board is a closed-cell, moisture-resistant rigid foam solution built to handle a wide range of building needs. If you want reliable, long-lasting warmth with less moisture drama, this is your go-to board for projects from walls to slabs.
Key Features & Design
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Material: Extruded Polystyrene (XPS) insulation with a closed-cell structure for outstanding moisture resistance and durability.
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R-Value by Thickness: ¾" — R4; 1" — R5; 1½" — R7.5; 2" — R10; 2½" — R12.5; 3" — R15; 4" — R20.
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Performance: Excellent long-term stable insulating performance at R-5 per inch; exceptional moisture resistance and durability for below-grade and above-grade applications.
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Ease of Use: Lightweight, easy to handle, and simple to cut or score for clean, snug joints (scored square edge).
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Applications: Slows transmission of water vapor in masonry walls; provides continuous insulation over wood or steel stud framing, insulated concrete sandwich panel walls, masonry cavity walls, or when used with non-penetrating surface-mounted furring systems. Ideal for below-grade perimeter and foundation projects or directly beneath concrete slabs.
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Durability & Weather Barrier: FOAMULAR 250 XPS insulation is resistant to soil components and retains insulating properties even after prolonged exposure to moisture, offering a weather-resistant barrier when joints are sealed.
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Coverage: 32 Sq Ft per board across thicknesses (size varies by thickness).
Technical Details
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Dimensions / Thickness Options: ¾", 1", 1½", 2", 2½", 3", 4"
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R-Value (75°F mean): ¾" — 4.0; 1" — 5.0; 1½" — 7.5; 2" — 10; 2½" — 12.5; 3" — 15; 4" — 20
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LTTR (75°F mean): 1" — 5.0; 1½" — 7.8; 2" — 10.6; 2½" — 13.4; 3" — 16.2; 4" — 22.0
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Compressive Strength: 25 psi (172 kPa)
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Flexural Strength: 75 psi (517 kPa)
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Water Absorption: Maximum 0.10% by volume
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Edge: Scored Square Edge
Note: We cannot ship FOAMULAR 250 XPS insulation to the following states: California, Colorado, Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont, Virginia, and Washington.
| Thickness |
Sq Ft Per Board |
R-Value |
| 3/4" |
32 Sq Ft |
R4 |
| 1" |
32 Sq Ft |
R5 |
| 1.5" |
32 Sq Ft |
R7.5 |
| 2" |
32 Sq Ft |
R10 |
| 2.5" |
32 Sq Ft |
R12.5 |
| 3" |
32 Sq Ft |
R15 |
| 4" |
32 Sq Ft |
R20 |
| Property |
Test Method2
|
Value |
Thermal Resistance3, R-Value (180 days) minimum,
hr·ft2·°F/Btu (RSI, °C·m2/W)
@ 75°F (24°C) mean temperature |
ASTM C518 |
|
| ¾" Thickness |
|
4.0 (0.70) |
| 1" Thickness |
|
5.0 (0.88) |
| 1½" Thickness |
|
7.5 (1.32) |
| 2" Thickness |
|
10 (1.76) |
| 2½" Thickness |
|
12.5 (2.20) |
| 3" Thickness |
|
15 (2.64) |
| 4" Thickness |
|
20 (3.52) |
| @ 40°F (4.4°C) mean temperature |
| ¾" Thickness |
|
4.3 (0.76) |
| 1" Thickness |
|
5.4 (0.95) |
| 1½" Thickness |
|
8.1 (1.43) |
| 2" Thickness |
|
10.8 (1.90) |
| 2½" Thickness |
|
13.5 (2.38) |
| 3" Thickness |
|
16.2 (2.85) |
| 4" Thickness |
|
21.6 (3.80) |
Long Term Thermal Resistance, LTTR-Value3, minimum
hr·ft2·°F/Btu (RSI, °C·2/W)
@ 75°F (24°C) mean temperature |
CAN/ULC S770-03 |
|
| ¾" Thickness |
|
N/A |
| 1" Thickness |
|
5.0 (0.88) |
| 1½" Thickness |
|
7.8 (1.37) |
| 2" Thickness |
|
10.6 (1.87) |
| 2½" Thickness |
|
13.4 (2.36) |
| 3" Thickness |
|
16.2 (2.85) |
| 4" Thickness |
|
22.0 (3.87) |
| Compressive Strength, minimum psi (kPa) |
ASTM D1621 |
25 (172) |
| Flexural Strength, minimum psi (kPa) |
ASTM C203 |
75 (517) |
| Water Absorption, maximum % by volume |
ASTM C272 |
0.10 |
| Water Vapor Permeance, maximum perm (ng/Pa·s·m2) |
ASTM E96 |
1.5 (86) |
| Dimensional Stability, maximum % linear change |
ASTM D2126 |
2.0 |
| Flame Spread |
ASTM E84 |
5 |
| Smoke Developed |
ASTM E84 |
45-175 |
| Oxygen Index, minimum % by volume |
ASTM D2863 |
24 |
| Service Temperature, maximum °F (°C) |
|
165 (74) |
| Linear Coefficient of Thermal Expansion, in/in/°F (m/m°C) |
ASTM E228 |
3.5 x 10-5 (6.3 x 10-5) |
