Exteriors & external wall insulation

Applications & Solutions Guide: FIBRANxps MAESTRO

Last updated: 9 October 2026

Double-skin walls, pitched tiled roof, internal insulation: three areas where the insulation must withstand loads and moisture. And which board to use for each.

The system at a glance

Solutions & Applications · XPS

FIBRANxps MAESTRO is not ‘just another insulation product’. It is the choice for areas where insulation must simultaneously bear loads and resist moisture — cavity walls, pitched roofs, and internal retrofit insulation. Where other materials gradually lose their performance, the closed microcellular structure of XPS maintains it.

The Three Main Areas of Application

A. Cavity Wall Core

The method of laying bricks between two facing bricks is the most common method in traditional Greek construction.

Why this is the case: it does not absorb the moisture trapped within the cavity — its insulating capacity remains stable over decades.
Crucial: the slabs must be laid tightly against one another. Any gap acts as a thermal bridge.

B. Pitched Tiled Roofs & Pitched Roofs

It is installed beneath the roof tiles or on top of the flat roof slab, bearing the weight of the superstructure.

Why here: it withstands the load of roof battens and tiles without sagging — the roof does not ‘lose’ its insulation after years of compression.
Crucial: for installation between battens, select the MAESTRO M version, with longitudinal grooves and a cut-out. The complete roof system is described in the solution ‘Thermal insulation and waterproofing of pitched tiled roofs’.

C. Internal Thermal Insulation with Plasterboard

In refurbishments where external work is not feasible, the board is bonded internally before the plasterboard cladding is fitted.

Why this: high performance with a thin profile — it ‘takes up’ less usable space in the room whilst achieving the same thermal performance.
Key point: for faster installation, the FIBRANxps GP composite is available — an XPS board with a 12.5 mm plasterboard panel already bonded to it.

Technical Specifications

Property	Price
Moisture absorption	< 0.7% — practically zero
Thermal conductivity λ	0.033 – 0.035 W/mK
Compressive strength	Very high — suitable for loads
Service life	50+ years
Structure	Closed-cell, waterproof
Standards	EN 13164 & EN 13172 · CE marking

Guidelines for Correct Installation

Strong bonding: CERESIT CT 84 polyurethane foam — quick to apply and excellent adhesion to brick and concrete.
Mechanical fixing: on vertical surfaces, secure using KLIMAS LTX10 plugs, at a rate of 6–8 per m².
Sealing gaps: any small gaps between the panels are filled with polyurethane foam to prevent heat transfer.
Flatness check: before fixing, ensure that the slabs are laid without distortion — localised curvature creates a gap behind the slab.

The #1 Mistake in the Field

Slabs laid with gaps between them. Any joint that is not watertight acts as a linear thermal bridge and locally negates the insulation — regardless of how good the material is or how thick it is.

Which FIBRANxps Panel for Which Application

Application	Product	Feature
Double-skin masonry, timber flooring, general use	MAESTRO	Smooth surface on both sides
Pitched tiled roof, between rafters	MAESTRO M	Grooves & cutting marks
Internal retrofit insulation	FIBRANxps GP	Composite with 12.5 mm plasterboard
External Wall Insulation (ETICS)	ETICS GF	Grooves for mortar adhesion
Flat roof, inverted & green roof	FIBRANxps 300	High mechanical strength
Creating drainage gradients	FIBRANxps INCLINE	Slope 0.5 per cent–3 per cent
Cold rooms	FIBRANxps 500	Maximum load-bearing capacity

ARGYNET Note

The choice of thickness is not a matter of ‘rough estimates’. It is determined by the region of the country, the type of structural element and the target U-value of the design — and in retrofit insulation projects, the position of the dew point must also be checked.

At ARGYNET, we specify the appropriate slab for each structural element and calculate materials per m².