1 · Concrete foundation

Standard reinforced concrete foundation or strip footing per the structural engineer's design. The Perinsul course doesn't change the foundation specification — it sits above the concrete, in the masonry course that would otherwise be the first brick or block course of the plinth.

2 · DPM (damp-proof membrane)

Standard DPM laid over the foundation as the building's primary damp barrier. The DPM continues across the slab edge and out under the wall plate. Perinsul sits above the DPM in the wall course — the cellular glass adds a secondary water barrier at the plinth, but the DPM is still the design-life damp control.

3 · Perinsul HL course

Foamglas Perinsul HL blocks bedded on standard mortar — same way a brick or block course goes in. Bricklayer-friendly install; no specialist trade or fixing equipment required. Standard block dimensions are 365 × 115 × 115 mm — sized to match common UK masonry coursing. Joint width and mortar mix per the manufacturer's specification.

4 · Masonry wall above

Standard brick or block wall built up on top of the Perinsul course. The wall sits on the thermal break course; the rest of the build proceeds normally. EWI, IWI, cavity insulation, render finish — all the wall-above scopes work the same way they would without Perinsul, because the wall is the same wall.

5 · DPC at the wall

Standard DPC bedded in the mortar joint above the Perinsul course. The DPC sits at the conventional level — typically 150 mm above external ground level. The Perinsul course sits below the DPC, in the plinth band where the wall meets the ground.

6 · External render or finish

The Perinsul course is visible at the external face of the plinth — typically painted, rendered, or covered by a plinth detail (engineering brick course, stone band, render with a different colour). CleverBloom's standard detail uses a render-over solution that hides the Perinsul block visually while preserving the thermal-break function.

Cellular glass

Pure glass foam — silica, soda lime, and minor mineral additives, melted at ~1,200°C and foamed under controlled conditions to create a closed-cell structure. The cells are sealed, dimensionally stable, and chemically inert. The material is rigid mineral glass, end of bill of materials.

60% recycled glass

A substantial proportion of the feedstock is post-consumer recycled glass — bottle and window glass that would otherwise enter the landfill or low-grade aggregate stream. Each m³ of Foamglas Perinsul HL incorporates around 100 kg of recycled glass. EPD published; specifiable into BREEAM and LEED.

High-load grade (HL suffix)

Owens Corning manufactures Perinsul in two density grades: standard Perinsul (lower compressive strength, lighter wall loads) and Perinsul HL (1.6 MPa, residential masonry walls, mid-rise commercial, structural loads). HL is the CleverBloom default for UK residential plinth applications.

Sealed-cell water resistance

Zero water absorption through the bulk material — the closed-cell structure has no continuous pore network for water to penetrate. Surface water runs off; capillary uptake is zero. The reason cellular glass is the right specification at ground level where below-DPM water exposure is part of normal service.

A1 core fire classification

Pure mineral glass, non-combustible. Euroclass A1 core fire class — the highest non-combustibility category. No 11 m external wall height restriction, no fire-engineering compensating measure. Plinth-course thermal break that doesn't introduce a fire-class discontinuity into the wall section.

Made in Belgium by Owens Corning

Foamglas is Owens Corning's cellular glass insulation brand, manufactured at facilities in Belgium and the Czech Republic. The chemistry has 80+ years of European industrial and architectural service history — originally developed for petrochemical pipe insulation; the Perinsul construction grade is the modern architectural application.

100-year design life

Owens Corning publishes a 100-year design life for Foamglas in standard service. Cellular glass is chemically inert mineral — no degradation in the bedded plinth course environment. The Perinsul course performs for the life of the building.

No annual service required

No moving part, no electrical component, no consumable. The course sits as masonry-equivalent for the building's life. Standard plinth inspection cadence applies — visual review of the rendered or pointed plinth band every 10–15 years, same as any plinth course in the wall.

Doesn't lose performance when wet

Cellular glass is unique among insulation materials in having zero water absorption. Saturation events (flooded site, prolonged surface-water ingress, failed DPM elsewhere in the building) don't degrade Perinsul's thermal performance — the material can't absorb water, so its λ value is unchanged after exposure.

Structural engineer approval

The Perinsul course is a structural element — it carries the wall above. Specification must reference the SE's approved load calculation; CleverBloom doesn't substitute Perinsul grades or omit the course on the bricklayer's discretion. Every project's SE signs off on the specification before fixing.

DPM continuity

The DPM is the primary damp-proof barrier; Perinsul is a thermal break with secondary water-resistance benefit but not a DPM substitute. Where the DPM detailing is poor or the membrane has been damaged at the slab edge, Perinsul doesn't fix it — the DPM detail comes first, Perinsul sits in the masonry course above.

EWI returns to the plinth

For a properly closed thermal envelope, the wall EWI (Gutex Thermowall, STO Therm Mineral K) needs to return down to or below the Perinsul course at the external face. A plinth thermal break with an un-extended EWI line above leaves a residual cold bridge at the wall-to-plinth transition. CleverBloom details this junction at design stage; the EWI returns 100–150 mm below the Perinsul course.