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Application

Cavity Wall Insulation

A double-leaf masonry wall has an air cavity between the leaves that is doing very little thermal work, while mortar droppings bridge it and wall ties conduct through it. Cavity insulation fills that void with a fire-retardant EPS element that keys into the mortar courses, lifting the wall's thermal resistance and cutting HVAC load without changing the wall footprint or the bricklaying sequence. Important scope note: under SANS 10400-XA a double-skin (cavity) masonry wall is already DEEMED-TO-SATISFY, so this is not a compliance rescue for masonry — it is a performance upgrade (comfort, running cost, rational-design/energy-model route) and a compliance route only for lightweight or otherwise non-qualifying walls.

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What it must achieve

Performance targets

External wall — deemed-to-satisfy route
Double-skin (cavity) masonry, or a plastered single leaf >= 140 mm, satisfies the wall requirement as-built
SANS 10400-XA
No added insulation is REQUIRED on a masonry cavity wall to comply. Do not present PolyKey as a compliance necessity here — it is performance above the minimum, or an input to a rational-design / energy-model submission.
External wall — lightweight / non-qualifying construction
Minimum total R >= 0.35 m2K/W External walls with a SURFACE DENSITY LIGHTER THAN 270 kg/m2 (light steel frame, timber frame, drywall, sandwich panel) must reach a minimum TOTAL R-value of 2.2 m2K/W in energy zones 1, 2, 6 and 7, and 1.9 m2K/W in zones 3, 4, 5 and 5H (SANS 10400-XA:2021, ch.3). And any walling with metal sheet, metal studs, metal tracks or metal battens fixed to each other SHALL have a thermal break. The 0.35 m2K/W figure applies to MASONRY types not covered by the standard provisions - it is NOT the lightweight-wall bar.
SANS 10400-XA
This is the only wall R-value the standard actually mandates, and it applies to walls that do NOT qualify under the deemed-to-satisfy route (e.g. lightweight framed walls). Any EPS insulation layer clears it easily.
Roof / ceiling total R (context — a separate requirement)
3.7 m2K/W in all zones; Zone 5 humid-coastal may use 2.7 m2K/W with roof ventilation
SANS 10400-XA:2021
Cavity wall insulation does NOT contribute to the roof/ceiling R-value. XA:2011 was zone-specific (1:3.7, 2:3.2, 3:2.7, 4:3.7, 5:2.7, 6:3.5); confirm which edition the local authority is enforcing.
Reaction to fire of the EPS element
B-s1,d0
SANS 53501-1 (Euroclass)
Reaction-to-fire only. It is NOT a fire-resistance (REI / minutes) rating, and no fire-resistance rating exists for the element — in this application it is encapsulated between two masonry leaves. All EPS is combustible (fire-retardant treated).
The cavity wall build-up, layer by layer
The same build-up, in the order it goes together. Generated from the assembly data this page lists below, so the drawing and the words cannot disagree.
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Where it goes

The assembly

Section through the cavity wall assembly
  1. External finish
  2. Outer masonry leaf
  3. Residual drainage gap (recommended)
  4. PolyKey FRCel EPS cavity element
  5. Wall ties
  6. Inner masonry leaf
  7. Internal finish

Layers listed outside → inside. The section is drawn to show the ORDER of the layers and where the Technopol product sits in it; the band widths are not to scale.

What each layer is doing — 7 layers, full detail
  1. External finish — Face brick, or plaster and paint on the outer leaf. Not part of the insulation design; keep the outer leaf's drainage function intact.
  2. Outer masonry leaf — Typically 90-110 mm brick/block. Weep holes and cavity DPC/trays must remain clear and continuous — insulating the cavity must not turn it into a water trap.
  3. Residual drainage gap (recommended) — Keep a clear air gap against the back of the outer leaf so water penetrating the outer leaf drains to the weep holes. The element sits on the inner-leaf side of the cavity, not tight against the wet outer leaf.
  4. PolyKey FRCel EPS cavity element — Interlocking tongue-and-groove EPS element, 340 x 1200 mm face, 60/40 mm stepped profile, moulded at 20 kg/m3 (HD/20DV). The T&G edges key into the mortar courses, tying the leaves and blocking mortar drop into the cavity.
  5. Wall ties — Ties remain a thermal bridge through the insulation. If the project needs a defensible U-value, model the tie bridging with the free 2D FEM psi-value tool rather than assuming the clear-wall R applies.
  6. Inner masonry leaf — Typically 90-110 mm brick/block, laid in the same course cycle as the outer leaf so the element beds into both.
  7. Internal finish — Plaster / skim and paint, or dry-lining. Provides the internal lining over a combustible core — the EPS is never left exposed.
Which products, and why

The products that do this job

Product

LiteCel Cavity & Drainage System

The drained-cavity element, and the newer of the two cavity boards: a 35 mm moulded EPS board whose knobs hold a clear 25 mm cavity against the outer leaf, so water that penetrates the face brick runs down the channels to the DPC and out through the weep holes instead of being bridged across. 425 x 1240 mm — the 425 mm height is five brick courses, which is also the wall-tie spacing. Where PolyKey fills the cavity, LiteCel CD insulates it and drains it.

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Product

Polykey Cavity Insulation

The cavity-fill element: interlocking fire-retardant FRCel EPS cavity insulation, T&G edges keying into the mortar courses of a double-leaf masonry wall, 340 x 1200 x 60/40 mm.

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Product

Bulk Insulation Products

Plain cut-to-size FRCel EPS sheet as an alternative cavity fill where the interlocking PolyKey profile is not wanted, or where a non-standard cavity width must be filled.

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Product

LiteCore Bricks

Alternative wall system, not a cavity insert: the LiteCore Building System is the only Technopol product with an Agrement SA certificate (2020/609), and only as a NON-LOAD-BEARING wall. Consider where the design is not a traditional double-leaf masonry cavity wall.

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Product

LiteClad Steel Profiles

Alternative route when the cavity is unavailable (solid or existing wall): a separate continuous external EPS layer on top-hat rails, weather-skinned with bare 0.5 mm roll-formed PPGL/PPGI LiteClad profiles. LiteClad is a steel weatherskin only — NOT a composite or insulated panel — and adds negligible R on its own.

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The numbers

Performance data

Every test report and certificate behind these figures is held by Technopol and is available on request.

8 figures, full data
PropertyValueStandard
Thermal conductivity (lambda, k @10 degC)<= 0.035 W/m.KEPS grade datasheet value for HD/20DV (20 kg/m3)
Thermal resistance R of the 60/40 mm element (tested with wall ties)2.0 m2K/WGuarded hot-box test
Nominal density / grade20 (HD / 20DV) kg/m3EPS grade datasheet
Compressive stress at 10% deformation>= 110 kPaEPS grade datasheet (grade-dependent)
Element size (H x L x thickness, T&G profile)340 x 1200 x 60/40 mmProduct geometry
Reaction-to-fire classification (EPS FRCel 20DV, 60 mm)B-s1,d0SANS 53501-1 (Euroclass)
Fire-resistance (REI) rating of the elementNone — no fire-resistance rating exists for an EPS cavity elementSANS 10177-2
Quality management system (company credential)ISO 9001:2015 certifiedISO 9001:2015
Size it

SANS 10400-XA compliance checker

Enter the climatic zone and wall build-up. For a double-skin masonry wall it will confirm you are already deemed-to-satisfy; use it to see what cavity insulation buys you above the minimum, or to size a lightweight wall to the R >= 0.35 m2K/W floor. Then run ../../technical/thermal-bridge/ for the wall-tie psi-value before quoting any assembly U-value, and ../../technical/spec-writer/ for the clause text. External walls with a SURFACE DENSITY LIGHTER THAN 270 kg/m2 (light steel frame, timber frame, drywall, sandwich panel) must reach a minimum TOTAL R-value of 2.2 m2K/W in energy zones 1, 2, 6 and 7, and 1.9 m2K/W in zones 3, 4, 5 and 5H (SANS 10400-XA:2021, ch.3). And any walling with metal sheet, metal studs, metal tracks or metal battens fixed to each other SHALL have a thermal break. The 0.35 m2K/W figure applies to MASONRY types not covered by the standard provisions - it is NOT the lightweight-wall bar.

Open the tool → Write the spec clause

On site

Installation

The full installation sequence — 9 steps
  1. Confirm cavity width and wall-tie type/spacing with the structural engineer before ordering — the 60/40 mm element assumes a conventional double-leaf cavity, and the tie layout dictates how the elements thread on.
  2. Keep the cavity DPC, cavity trays and weep holes fully functional. Do not bed the element hard against the back of the outer leaf where it could bridge water across to the inner leaf; maintain the residual drainage gap.
  3. Lay the elements course-by-course with the bricklayers, not as a retrofit stuff-in: the tongue-and-groove edges are designed to bed into the mortar courses of both leaves as the wall rises.
  4. Butt the T&G joints tightly and stagger vertical joints between courses. An open joint is a direct convective/thermal bypass and the wall's delivered R will fall well short of the element R.
  5. Keep the cavity clean of mortar droppings below the elements; the mortar-drop function only protects the courses already laid.
  6. Do not leave EPS exposed to sunlight on site. Store and stage under cover — UV degrades the surface of unprotected EPS.
  7. Keep the element clear of chimneys, flue penetrations, boiler/heater flues and any hot service. Provide non-combustible sleeving and the required clearance at every penetration through the cavity.
  8. Use only EPS-compatible (water-based / EPS-approved) adhesives, sealants and primers, and separate PVC-sheathed cables from the EPS.
  9. Complete the internal plaster/lining. The EPS must be encapsulated between the masonry leaves and finished; it is not a permitted exposed surface.
The limits

Where not to use this

A material specified for the wrong job fails you, then us.

Where the client only needs to pass SANS 10400-XA on a normal double-skin masonry or >= 140 mm plastered wall
That wall is already deemed-to-satisfy under XA. Presenting cavity insulation as a compliance requirement there is false — the standard demands nothing extra.
→ Say so plainly and reframe as comfort / HVAC-load / running-cost, or as input to a rational-design energy model. Spend the budget on the roof/ceiling instead, where a real 3.7 m2K/W total R is mandated (2.7 in Zone 5 humid-coastal with roof ventilation).
Adjacent to chimneys, flues, boiler or heater vents, or any surface hot in service
All EPS is combustible (fire-retardant treated). B-s1,d0 is a reaction-to-fire class, not a fire-resistance rating, and EPS softens and shrinks far below flame temperatures.
→ Non-combustible mineral-wool cavity insulation, or a mortar/masonry-only zone with the specified clearance at every hot penetration.
Anywhere a fire-resistance (REI / minutes) rating is required of the insulation, or in a fire-rated separating wall relying on the cavity
No fire-resistance test covers an EPS cavity element, and plain EPS-core assemblies have failed SANS 10177-2 (e.g. FTC 16-162). The nearest fire-resistance result in the range is FT 24-003 — NuClad LiteCore LSF wall, FR60 load-bearing (E/I/R 60) — a different assembly.
→ Use the tested LiteCore/plaster system, mineral-wool-cored construction, or design the rating into the masonry leaves.
In a cavity that is also the wall's drainage path, in a persistently wet or flood-prone zone, or below DPC / in ground contact
EPS is not a drainage layer, and a cavity blocked or bridged by insulation can carry water to the inner leaf. Long-term moisture uptake also degrades the effective lambda — the <= 0.035 W/m.K figure is a dry grade-datasheet value.
→ Keep the residual drainage gap with functioning trays and weeps, or move the insulation outboard as a continuous external layer (EIFS render or LiteClad build-up) so the cavity stays a pure drainage cavity.
In contact with solvent-based products — solvent adhesives, bitumen primers, some sealants, PVC cable sheathing
EPS is attacked and dissolved by aromatic and chlorinated solvents and by plasticiser migration from PVC. The element loses section silently inside the cavity where nobody can inspect it.
→ Specify EPS-compatible (water-based / EPS-approved) adhesives, primers and sealants; sleeve or separate PVC-sheathed cables from the EPS.
Where the wall transfers load through the cavity, or the element is expected to carry structural or sustained load
The >= 110 kPa figure is compressive stress at 10% DEFORMATION — a strength index measured at destruction-level strain, not a working load. Sustained EPS design load is creep-governed and limited to roughly the 1% strain level, far below the 10% figure.
→ Load must pass through the masonry leaves. Where EPS genuinely carries load (fill, under-slab), specify geofoam and size it with the geofoam design checker.
As a retrofit blown or stuffed fill into an existing, already-built cavity
The element is a T&G unit designed to bed into the mortar courses as the wall is laid. Post-hoc insertion cannot key the joints, cannot dodge the wall ties and cannot guarantee the residual drainage gap — the delivered R will not resemble the element R.
→ Insulate externally: a continuous EPS layer finished with a Terraco render system, or clad with LiteClad steel profiles on top-hat rails over that EPS layer.
As an exposed or long-term UV-exposed layer, or left uncovered on site
Unprotected EPS degrades under UV and is combustible while exposed; it has no facing in this application.
→ Encapsulate between the masonry leaves and finish the wall; store under cover on site.
Where it has been used

Project references

LiteCore Bricks

In2food, Benoni

Benoni · Industrial (food processing)

LiteClad Steel Profiles

Our Shack

Residential

LiteClad Steel Profiles

ModuPod 1.0 / 2.0

Modular building

LiteCore Bricks

Hillcrest Campus

Education / campus

Questions

Specifier FAQ

Do I need cavity wall insulation to pass SANS 10400-XA?
On a normal double-skin masonry wall, no. A double-skin (cavity) masonry wall — or a plastered single leaf at least 140 mm thick — is deemed-to-satisfy under XA, so no added wall insulation is required to comply. The only mandated wall R-value (total R >= 0.35 m2K/W) applies to lightweight or otherwise non-qualifying walls. PolyKey is a performance upgrade above the minimum, or a rational-design input — not a compliance rescue. External walls with a SURFACE DENSITY LIGHTER THAN 270 kg/m2 (light steel frame, timber frame, drywall, sandwich panel) must reach a minimum TOTAL R-value of 2.2 m2K/W in energy zones 1, 2, 6 and 7, and 1.9 m2K/W in zones 3, 4, 5 and 5H (SANS 10400-XA:2021, ch.3). And any walling with metal sheet, metal studs, metal tracks or metal battens fixed to each other SHALL have a thermal break. The 0.35 m2K/W figure applies to MASONRY types not covered by the standard provisions - it is NOT the lightweight-wall bar.
What is the R-value of the wall once PolyKey is in the cavity?
The 60/40 mm element has a thermal resistance of 2.0 m2K/W, from a 2025 guarded hot-box test done with the wall ties in place. It is an element figure, not a whole-wall figure: the masonry leaves add resistance and the wall ties subtract it. If your submission needs a defensible whole-wall U-value, model it — use the free thermal-bridge tool for the tie psi-value and the XA checker for the assembly.
Is PolyKey fire-rated?
It has a reaction-to-fire classification of B-s1,d0 to SANS 53501-1, from Ignis Testing report IT 23-08-00009 on EPS FRCel 20DV at 60 mm, valid to August 2028 — that one is VERIFIED. But reaction-to-fire is not fire resistance: it says nothing about how many minutes an assembly survives a furnace. There is no fire-resistance (REI) rating for the EPS element, and all EPS — including fire-retardant grades — is combustible. In a cavity wall the fire resistance comes from the masonry leaves. Keep the element clear of flues and hot services.
Is there an Agrement certificate for cavity wall insulation?
No. Agrement SA certificate 2020/609 covers the LiteCore Building System only, as a non-load-bearing wall. It does not cover PolyKey, LiteSpan, LiteClad, Terraco or geofoam, and a product certificate is not a company credential. Technopol's company-level credential is the ISO 9001:2015 quality management system.
Does the 110 kPa compressive figure mean it can carry load in the wall?
No. 110 kPa is the compressive stress at 10% deformation — a material strength index measured at destruction-level strain, not a working load. Sustained EPS design loading is creep-governed and sits nearer the 1% strain level. In a cavity wall all structural load goes through the masonry leaves; the element carries nothing but itself.
Can I fill an existing cavity with it?
Not properly. The elements are tongue-and-groove units meant to bed into the mortar courses as the leaves are laid, so the joints key and the drainage gap is preserved. For an existing wall, insulate externally instead — a continuous EPS layer finished with a Terraco render system, or clad with LiteClad steel profiles on top-hat rails.
Is LiteClad an insulated panel I could use instead?
No, and the distinction matters. LiteClad profiles are bare 0.5 mm roll-formed PPGL/PPGI steel — a weatherskin, nothing more (IBR Wide 990, Corrugated 990, Standing Seam 282/495, ClipClad 270, DutchClad 293 wall-only). They are laid OVER a separate continuous EPS insulation layer on top-hat rails or battens; they are not factory-laminated to an EPS core and must never be called a composite or insulated panel. The 0.5 mm steel adds negligible R — the EPS thickness behind it is an independent design input. (NuClad is the steel-faced EPS composite board; LiteSpan is the factory-laminated sandwich panel. LiteClad is neither.)

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