RetroFoam: The Non-Combustible Injection Solution
RetroFoam is not a spray polyurethane foam; it is a resin-based tripolymer foam injected as a shaving-cream-like substance that cures into a solid thermal barrier. Because it is typically used to fill the cores of concrete blocks or the cavities behind existing brick/drywall, its fire-resistive properties are among the best in the insulation industry.
1. Fire Resistance & Safety Ratings
RetroFoam is often selected specifically for projects where high fire-load materials (like standard spray foam) are restricted.
- Non-Flammable: RetroFoam will not support a flame. If exposed to intense heat, it will simply char and eventually dissipate without contributing fuel to the fire.
- ASTM E84 Results: Typically achieves a Flame Spread of 0 and a Smoke Developed index of 5.
- UL Listed Assemblies: It is frequently used in 2-hour and 4-hour fire-rated concrete block (CMU) assemblies to enhance thermal performance without voiding the wall’s fire rating.
2. The Injection Process (The “Hidden” Seal)
RetroFoam provides an “automatic” smoke seal within wall cavities that other insulations cannot reach:
- Access: Small holes are drilled into mortar joints (exterior) or drywall (interior).
- Injection: The foam is pumped under low pressure, flowing around wires, pipes, and electrical boxes.
- Compaction: As the foam fills the cavity, it creates a tight air seal that prevents the “chimney effect,” stopping smoke and hot gases from traveling laterally through the wall.
3. RetroFoam vs. Spray Foam: The Fire Safety Difference
| Feature | RetroFoam (Tripolymer) | Spray Foam (Polyurethane) |
| Combustibility | Non-combustible / Will not burn. | Combustible (Requires thermal barrier). |
| Smoke Development | Near Zero (<5). | Moderate (≤450). |
| Heat Release | Does not add heat to a fire. | Exothermic; adds fuel if ignited. |
| Application | Injected into closed cavities. | Sprayed into open cavities. |
Export to Sheets
Frequently Asked Questions (FAQ)
Is RetroFoam a fireblock?
While RetroFoam is non-combustible and excellent at stopping air movement, it is technically an insulator. In many jurisdictions, it can serve as a “fireblock” within a wall cavity because it prevents the passage of flame and gases, but you should always verify with your local Fire Marshal for specific “Firestop” assembly credits.
Does RetroFoam emit toxic fumes during a fire?
One of RetroFoam’s greatest safety advantages is its extremely low smoke-developed index. Because it is a water-based tripolymer, it does not contain the oils or chemicals found in traditional plastics that produce thick, black, toxic smoke.
Can I inject RetroFoam around electrical wires?
Yes. RetroFoam is non-flammable and non-conductive. It is commonly used to “fire-seal” the gaps around outlet boxes and wiring inside existing walls, which are often the primary pathways for fire to spread between rooms.
Does it require a 15-minute thermal barrier (drywall)?
Because RetroFoam has a Flame Spread of 0, it often has fewer restrictive requirements than polyurethane spray foam. However, since it is almost always injected behind existing drywall or masonry, it is inherently protected by a thermal barrier.
Can RetroFoam be used as a through-penetration firestop?
No. If a new pipe is installed through a wall already filled with RetroFoam, you must still use a UL-listed firestop sealant or collar at the point of penetration. RetroFoam provides the cavity seal, but the “breach” itself must be handled by a dedicated firestop product.
Why Choose Firestopping.com for RetroFoam Projects?
We specialize in the technical side of wall-cavity safety. We provide the UL assembly data for masonry infill and the ASTM test results needed to prove to inspectors that your insulation isn’t just saving energy—it’s adding a layer of fire protection to the building.