Reflective insulation systems, marketed under names like Thermo-Sim, are designed to cut heat transfer through a building envelope using a thin, lightweight, foil-faced layer rather than the thick batts or boards typical of conventional insulation.
How reflective insulation differs from bulk insulation
Traditional bulk insulation (fiberglass, mineral wool, expanded polystyrene) works mainly by trapping air and slowing conductive heat flow. Reflective systems add a different mechanism: a low-emissivity foil surface that reflects radiant heat rather than absorbing and re-emitting it. In practice, most commercial reflective products combine both approaches, sandwiching a thin insulating core (often closed-cell foam) between two foil facings.
The practical appeal is thickness and weight. A reflective panel measured in millimeters can perform close to a bulk material measured in centimeters, which matters in retrofits where wall cavities, roof structures, or load limits do not allow for thick insulation.
Where these systems get used
Reflective heat-protection layers are commonly installed under roofing, inside wall cavities, around ductwork, and in floor assemblies. They are also used in specialized applications such as thermal wrapping for pipework and equipment, and in prefabricated panel systems where minimizing overall assembly thickness matters as much as thermal performance.
What to check before specifying a product
- Thermal conductivity (lambda value). Lower is better; this is the figure that determines how much heat passes through a given thickness.
- Fire classification. Reflective foam-core products vary widely in fire behavior; check the product's certified fire rating (such as Euroclass or an equivalent national standard) before use near flues, chimneys, or high-heat sources.
- Vapor and moisture behavior. Foil facings can act as a vapor barrier, which is beneficial in some assemblies and problematic in others if it traps moisture on the wrong side of the wall.
- Independent test data. Manufacturer efficiency claims (percentage heat-loss reduction, equivalence to a given thickness of bulk insulation) should be backed by recognized third-party testing, not marketing copy alone.
- Installation method. Reflective insulation only performs as rated when installed with the correct air gap facing the reflective surface; compressing it against another material can significantly reduce its effectiveness.
The bottom line
Reflective, foil-faced insulation systems are a legitimate and increasingly common category, valuable specifically where space and weight constraints rule out thick bulk insulation. As with any insulation purchase, the deciding factors should be certified thermal and fire performance data and correct installation, not headline efficiency percentages alone.
Typical technical profile of a reflective system
Products in this category are usually described by a handful of core specifications: a low thermal conductivity figure, an overall assembly thickness in the range of a few centimeters, a density far lower than mineral wool or rigid foam board, and a foil facing rated to a specific fire classification. Installers should request the technical data sheet directly from the manufacturer and compare it against the building code requirements for the specific application, roof, wall, or floor, rather than relying on generic marketing claims about equivalence to a given thickness of traditional insulation. Where a product is being used near a chimney, flue, or other high-temperature source, an installer should confirm the required clearance distances separately, since reflective foam-core products are not universally rated for direct high-heat proximity even when their general fire classification looks favorable on paper.