1 · Substrate prep

Existing internal plaster removed back to masonry. Loose pointing made good. Any salt-affected brick treated. Old gloss paint mechanically abraded. The substrate condition matters more than the insulation specification — a damp brick wall hidden behind aerogel becomes a more expensive damp brick wall.

2 · Salt and damp survey

Listed and pre-1919 stock often has hidden salt loading at low level from historic rising damp episodes. We test for hygroscopic salts before fixing the WL boards. Affected areas may need a salt-neutralising render system at low level before WL goes up — quoted separately based on the survey findings.

3 · Adhesive bed

Gypsum or cement-based adhesive applied to the back of each board, full-coverage on uneven substrates. Boards pressed into the bed, plumbed, levelled, butted close at joints. The adhesive sets within hours; mechanical fixing follows.

4 · Mechanical fixings

Polymer plug-and-pin fixings drilled through the board face into the masonry beyond — typically 4–6 per board depending on board orientation and wall condition. Fixings are flush-set into the magnesium silicate face and disappear under the plaster skim.

5 · Joint reinforcement

Self-adhesive scrim tape over every butt joint and at the perimeter where the WL meets the original wall plane. The scrim and the magnesium silicate face together give the plasterer a continuous, paper-faced surface to skim.

6 · Plaster finish

Standard gypsum plaster skim (Thistle Multi-Finish) or a vapour-open lime plaster where conservation requirements specify. Both bond directly to the magnesium silicate carrier. Finished thickness 2–3 mm. Decorate as normal wall — paper, paint, panel mouldings reinstated.

Aspen Aerogels Spaceloft blanket

The aerogel component is Aspen Aerogels' Spaceloft — a flexible aerogel blanket originally developed for industrial process insulation. Aspen has been making aerogel blanket commercially since the early 2000s; the technology is mature, not experimental. Proctor Group licenses Spaceloft for the wall-liner laminate.

Silica nanoparticle matrix

The aerogel structure is amorphous silicon dioxide arranged in nanoscale strands enclosing pore sizes of 20–40 nanometres. Each pore is smaller than the mean free path of an air molecule (~70 nm at room temperature), which is why convection inside the matrix is effectively zero.

Hydrophobic surface treatment

The aerogel is surface-treated to reject liquid water while remaining vapour-open. Raw silica aerogel is naturally hydrophilic; the treatment is what makes Spaceloft viable in a building envelope where condensation and accidental wetting are part of normal service.

Magnesium silicate carrier · 3 mm

The carrier board is a magnesium silicate composite — alkaline, non-organic, mould-resistant, and dimensionally stable. Cuts with a fine-tooth blade. Takes plaster directly. The alkaline chemistry means no microbial food source, which matters in unheated heritage rooms with intermittent occupation.

Lamination bond

The aerogel blanket is mechanically and adhesively bonded to the magnesium silicate carrier at the factory. The bond is permanent and continuous — no air-gap, no delamination over time. Boards arrive on site as finished WL assemblies ready to cut and fix.

Fire: Class C (board) / Bs1-d0 (system)

Spacetherm WL Wall Liner is Euroclass C as a board. When installed behind plaster as a complete internal wall system, the assembly tests Bs1-d0 — the plaster face is what's exposed to the room. Suitable for buildings under 11 m external wall height. For higher buildings, Proctor Group's Spacetherm Slentex variant (Euroclass A2) is the route.

25 year design life

Proctor Group publishes a 25-year design life for Spacetherm WL in standard internal wall service. The aerogel matrix is chemically stable silica — it doesn't degrade, off-gas, or shed fibres over time. The magnesium silicate carrier is similarly stable. In normal service, the assembly should outlive the next two redecorations and several boiler replacements.

Decorate as a normal wall

Once plastered, the wall behaves like any plastered wall. Paint, wallpaper, hung pictures, fixed shelving — all supported, all reversible. Heavy fixings (full shelving units, kitchen wall cabinets) need fixings through the aerogel into the masonry beyond, same way as any plaster-on-brick wall.

No annual service required

No moving part, no electrical component, no filter, and no consumable. Standard plastered-wall maintenance only — touch up dents and paint marks, replace decoration on the homeowner's normal cycle. The aerogel core needs nothing.

Reveal and soffit cold-bridge strip

A wall-plane IWI scope without insulated reveals fails its U-value calculation around windows. Spacetherm CBS (Cold Bridge Strip) wraps reveals, soffits, and lintels with a thinner aerogel detail to break the bridge. Without it, condensation appears around windows on cold mornings — exactly the symptom the IWI scope was supposed to fix.

Salt and damp baseline

Hidden salt loading at low level on pre-1919 stock is the single biggest cause of IWI failure in heritage retrofit. We run a salt-and-damp survey before fixing any boards; affected areas get a salt-neutralising render at low level before the WL goes up. Skip this step and the IWI traps the salt cycle behind a sealed face.

Heating system rebalance

An IWI'd room loses heat far more slowly than it did before. The existing radiator (sized for the pre-insulation heat loss) is now oversized; the room overheats. We rebalance the heating system on completion — typically a quick valve adjustment, occasionally a radiator downsize. Included for one-room scopes; quoted separately for whole-floor scope.