Ensolite IG1 vs IV1: What's the difference?
July 16, 2026
Armacell’s Ensolite IG1 and IV1 are commonly used products for gasketing and sealing in HVAC, power distribution, automotive, and industrial equipment. They are both soft, low-density foams with excellent flammability properties, making them ideal in automotive, general industrial, as well as aerospace applications.
The IV1 product was actually developed by Rubatex, a former sponge rubber manufacturer that was acquired by Armacell many years ago. IG1 was an existing Armacell Ensolite product with very similar characteristics and intended use, so IV1 was somewhat redundant. However, many drawings and customer specifications call for IV1, so it was maintained. Over time, the IG1 product has grown in use, due to a lower price point and greater availability, has become the default material displacing IV1 in most new applications.
In order to understand the subtle differences between the two, it is helpful to review the prevailing American Society for Testing Materials (ASTM) D 1056 specification that defines how flexible cellular materials, such as sponge (open cell) and expanded (closed cell) rubber foams are categorized. ASTM D 1056 is the go-to standard for foam materials used in sealing, insulating, gasketing, vibration control, cushioning and similar applications.
ASTM D 1056 Classifications Explained
1) Types (Cell Structure)
- Type 1 – Open-cell rubber (sponge)
- Type 2 – Closed-cell rubber (expanded foam)
2) Classes (Environmental/Resistance)
- Class A – Non oil-resistant (eg. EPDM or SBR)
- Class B – Oil resistant, low swell (eg. nitrile)
- Class C – Oil resistant, medium swell (eg. neoprene)
- Class D – Extreme temperature resistance (eg. silicone)
3) Grades (Firmness/Compression)
Grade Compression Deflection (How “firm” the foam is in psi)
- 0 0-2 (very soft)
- 1 2-5
- 2 5-9
- 3 9-13
- 4 13-17
- 5 17-25 (very firm)
Both of Armacell’s IV1 and IG1 are specified as “2A1/2C1,” meaning that they will meet the requirements of any print calling out Classes A or C. Only IG1, however, is also rated 2B1, meeting any print calling out the most stringent Class B oil resistance. Since both of these foams are NBR/PVC/CR “blends,” and the classes are not mutually exclusive, it is an important distinction.
There are other subtle differences in density, compression set, and elongation, although they are so negligible that they would not be detectible absent testing. Unless a print or material specification calls out these specific properties, the materials would generally be considered interchangeable in many, if not most applications.
Both meet the commonly cited UL94 HF-1 and UL 94V-0 standards and most other properties are identical.
So why choose one over the other? The decision often comes down to availability and oil resistance. Some distributors or fabricators may stock only one (or more of one than the other), typically because of its predominant use for specific customers or applications. InsulFab stocks both, although it often finds that IG1 is a more prominent, lower cost, and available product. Learn more about both Ensolite products here.
And, if any of this seems confusing, rest assured that InsulFab’s engineering team deals with material selection on a daily basis. Whether it is IG1, IV1, or perhaps a different cellular product. let us help you determine you the best material based on price, MOQ, availability and lead time.