ISO-ACO-04 — Habitable attic with exposed rafters — Gold in cavities
1. Subject and scope of application
This specification sets out the technical requirements for quality, execution and acceptance for the build-up “Habitable attic with exposed rafters — Gold in cavities”, in accordance with Isoflect construction detail ISO-ACO-04. Variant A · the rafters above the timber boarding are already installed · Reflectiva Gold in cavities or Reflectiva Multistrat in two layers · Isoflect Wolle 15 cm.
The specification covers the supply and installation of the Isoflect products in the build-up: Reflectiva Gold, Reflectiva Multistrat, Reflectiva Roof Pro, Reflectiva Roof Optim, Isoflect Wolle P800/P1500/P2100 and Isoflect Power Tape. It applies to new constructions and renovations where the design provides for this build-up, and is to be read together with the CAD detail and the technical data sheets of the products.
2. Build-up
Sequence of layers, as per the CAD detail: habitable attic → exterior.
| No. | Layer |
|---|---|
| 1 | Exposed rafters — visible in the habitable attic, sloping ceiling up to the ridge |
| 2 | Tongue-and-groove boarding nailed over the rafters, on top of them |
| 3 | Reflectiva Gold in the recesses between rafters — run down the sides of the rafters, strips butt-jointed, fixed with 14–16 mm staples or 1,5 cm wood screws; alternatively: Reflectiva Multistrat in two layers |
| 4 | Rafters above the boarding (already installed) + Isoflect Wolle 15 cm — P800 5 cm + P1500 or P2100 10 cm, in any order; recommended clear spacing between rafters: approx. 59–60 cm (the board is 61 cm wide) |
| 5 | Roof boarding — optional, as per design; with Reflectiva Roof Pro it can be omitted if the roof pitch is greater than 15 degrees |
| 6 | Reflectiva Roof Pro or Reflectiva Roof Optim — diffusion membrane, rolls laid parallel to the eaves, installed starting from the eaves |
| 7 | Vertical batten 5 cm |
| 8 | Horizontal batten and roof covering |
3. Materials and required characteristics
Reflectiva Gold
| Characteristic | Value | Standard |
|---|---|---|
| Build-up | Two pure aluminium faces; core of air-bubble film and expanded polyethylene | |
| Total thickness | 10 mm (±1) | EN 823 |
| Mass per unit area | 460 g/m² | EN 1850-2 |
| Roll dimensions | 1,20 m × 10 m — 12 m² | EN 1848-2 |
| Roll weight | 5,52 kg | |
| Reflectivity of thermal radiation | 95–97 % | |
| Emissivity | 0,05 | prEN 15976 |
| Water vapour diffusion resistance, Sd | 190 m | EN 13859-1 |
| Tensile strength (longitudinal / transverse) | 261 / 205 N/50 mm | EN 12311-1 |
| Elongation at break (longitudinal / transverse) | 21,6 % / 17,1 % | EN 12311-1 |
| Tear resistance (longitudinal / transverse) | 154 / 199 N | EN 12310-1 |
| Resistance to water penetration | Class W1 | EN 1928 / EN 13859-1 |
| Reaction to fire | Class F | SR EN 13501-1+A1:2010 |
| Volatile organic compounds (VOC) | None |
Reflectiva Multistrat
| Characteristic | Value | Standard |
|---|---|---|
| Build-up | Bubble film of 110 µm; on the bubble cap side, 24 µm pure aluminium film (7 µm aluminium + 17 µm lamination layer); on the opposite side, expanded polyethylene film | |
| Total thickness | 5 mm (±1) | EN 823 |
| Mass per unit area | 175 g/m² | EN 1850-2 |
| Roll dimensions | 1200 mm × 25 m (±3 %) — 30 m² | EN 1848-2 |
| Roll weight | 5,25 kg | |
| Reflectivity of thermal radiation | 95–97 % | |
| Emissivity | 0,05 | prEN 15976 |
| Water vapour diffusion resistance, Sd | 190 m | EN 13859-1 |
| Resistance to water penetration | Class W1 | EN 13859-1 |
| Reaction to fire | Class F | SR EN 13501-1+A1:2010 |
| Service temperature range | −40 … +80 °C | |
| Shelf life | 24 months from delivery |
Reflectiva Roof Pro
| Characteristic | Value | Standard |
|---|---|---|
| Build-up | Micro-perforated pure aluminium + microporous polypropylene film, heat-bonded, mesh-reinforced structure | |
| Roll dimensions | 1,50 m × 50 m — 75 m²; 17,5 kg | EN 1848-2 |
| Mass per unit area | 230 g/m² | EN 1849-2 |
| Reflectivity of thermal radiation | 95–97 % | |
| Emissivity (before / after ageing) | 0,05 / 0,05 | prEN 15976 |
| Water vapour diffusion resistance, Sd | 0,045 m (±0,015) | EN 12572 |
| Resistance to water penetration | Class W1, including after artificial ageing | EN 1928 / EN 13859-1, Annex C |
| Tensile strength (MD / CMD) | 350 / 225 N/50 mm | EN 12311-1 |
| Tensile strength after ageing (MD / CMD) | 330 / 175 N/50 mm | EN 13859-1, Annex C |
| Elongation (MD / CMD) | 30 % / 70 % | EN 12311-1 |
| Tear resistance | 200 / 200 N | EN 12310-1 |
| Dimensional stability | < 2 % | EN 1107-2 |
| Flexibility at low temperatures | −30 °C | EN 1109 |
| Service temperature range | −40 … +80 °C | |
| Reaction to fire | Class E | SR EN 13501-1 |
| Visible defects | No visible defects | EN 1850-2 |
| Estimated service life | 50 years |
Reflectiva Roof Optim
| Characteristic | Value | Standard |
|---|---|---|
| Build-up | 4 layers: outer micro-perforated aluminised foil + three layers of microporous polypropylene film; two integrated self-adhesive strips along the full length | |
| Roll dimensions | 1,50 m × 50 m — 75 m²; 12 kg | EN 1848-2 |
| Mass per unit area | 155 g/m² | EN 1849-2 |
| Emissivity (before / after ageing) | 0,18 / 0,18 | prEN 15976 |
| Water vapour diffusion resistance, Sd | 0,07 m (±0,02) | EN 12572 |
| Resistance to water penetration | Class W1, including after artificial ageing | EN 1928 / EN 13859-1, Annex C |
| Tensile strength (MD / CMD) | 330 / 230 N/50 mm; after ageing 280 / 195 | EN 12311-1 |
| Elongation (MD / CMD) | 40 % / 20 %; after ageing 30 % / 10 % | EN 12311-1 |
| Tear resistance | 130 / 140 N | EN 12310-1 |
| Dimensional stability | < 2 % | EN 1107-2 |
| Flexibility at low temperatures | −20 °C | EN 1109 |
| Service temperature range | −40 … +80 °C | |
| Reaction to fire | Class E | SR EN 13501-1 / EN ISO 11925-2 |
| Estimated service life | 30 years |
Isoflect Wolle
| Characteristic | P800 | P1500 | P2100 | Standard |
|---|---|---|---|---|
| Thickness | 50 mm | 100 mm | 100 mm | |
| Board dimensions | 1200 × 610 × 50 mm | 1200 × 610 × 100 mm | 1200 × 610 × 100 mm | |
| Mass per unit area | 800 g/m² | 1500 g/m² | 2100 g/m² | |
| Pack contents | 16 boards — 11.712 m² | 8 boards — 5.856 m² | 8 boards — 5.856 m² | |
| Thermal conductivity, λ₁₀ | 0,038 W/mK | 0,038 W/mK | 0,035 W/mK | SR EN 12667:2002 |
| Thermal resistance of the layer, R | 1,32 m²K/W | 2,63 m²K/W | 2,86 m²K/W | SR EN 12667:2002 |
| Characteristic | Value | Standard |
|---|---|---|
| Material | Thermal insulation fibre made of recycled PET, without binders, formaldehyde or phenol | |
| Reaction to fire | C-s2,d0 | EN 13501-1 |
| German classification | B1 | DIN 4102 |
| Behaviour in the presence of moisture | Fully hydrophobic | |
| Long-term stability | No settlement | |
| Technical approval (Agrément) | AT 001SB-03/1039-2024 — INCD URBAN-INCERC, INCERC Bucharest Branch; favourably endorsed by CTPC on 29.01.2025 (Minutes No. 18014); valid until 29.01.2028 |
Isoflect Power Tape
| Characteristic | Value | Standard |
|---|---|---|
| Width | 10 cm | |
| Roll length | 50 m | |
| Service temperature range | −60 … +140 °C | |
| Required for Floor Pro | One roll for each roll of Floor Pro (40 m²) |
The declared values refer to the product, not to the build-up in which it is installed; the performance of the system is determined by a hygrothermal calculation for each case. The current revision of the technical data sheet shall always apply.
Materials in the build-up that are not Isoflect products (timber, boards, metal profiles, roof coverings, waterproofing, screeds, finishes) shall be specified by the designer, in accordance with the applicable product standards and the manufacturers' documentation.
4. Delivery, storage, handling
The products are delivered in their original, labelled packaging, accompanied by the quality documents and, where issued, the declaration of performance. On receipt, the product designation, the roll dimensions or the contents of the package, and the integrity of the packaging are checked.
The Reflectiva Gold and Reflectiva Multistrat rolls are stored horizontally, on a clean and level surface, protected from direct solar radiation and from moisture.
The shelf life of Reflectiva Multistrat is 24 months from delivery.
The Reflectiva Roof Pro and Reflectiva Roof Optim rolls are stored horizontally, on a clean and level surface, protected from the sun.
Isoflect Wolle packages are stored in covered areas, protected from moisture and from direct solar radiation. Handling and cutting do not require conventional protective equipment; the fibre is not irritating.
Isoflect Power Tape is kept in its original packaging, in covered areas, protected from moisture and from direct solar radiation.
The membranes are handled so that the aluminium faces are not perforated or damaged; damaged areas are repaired before the layer is closed.
5. Execution conditions and sequence
Execution begins only after the load-bearing structure has been completed and checked, and the installation surfaces are clean and dry. The layers are executed in the build-up order shown in detail ISO-ACO-04; each layer that is to be covered is checked before being covered. Isoflect products are installed in accordance with the technical data sheets in force.
Orientation of the aluminium faces: the aluminium is always oriented towards the adjacent air gap, as indicated in the build-up. A membrane bonded directly to a wall or ceiling is installed with the aluminium facing inwards, that is, likewise towards the air gap.
Reflectiva Gold is installed in the position indicated in the detail — in standard build-ups beneath the rafters, from the inside, over the bulk insulation. Joints and overlaps are hermetically sealed with Isoflect Power Tape, to ensure the continuity of the radiant barrier and of the vapour barrier.
Reflectiva Gold is brought down the sides of the rafters, in strips butt-jointed, fixed with 14–16 mm staples or 1.5 cm wood screws; the joints are sealed with Isoflect Power Tape. Alternatively, in accordance with the detail, Reflectiva Multistrat is used in two layers.
Reflectiva Multistrat is installed in the position and with the orientation indicated in the detail. Where OSB is installed over the insulation between the rafters, the orientation is reversed: aluminium facing inwards. All joints are hermetically sealed with Isoflect Power Tape.
Isoflect Wolle is installed between the structural elements, in full boards or boards cut to the width of the cavity, without compression and without open joints. The boards are cut with the Wolle Sword knife.
Reflectiva Roof Pro and Reflectiva Roof Optim: fixing is carried out with corrosion-resistant nails or flat-head staples. The strips overlap by approximately 10 cm, so that the integrated self-adhesive strips overlap one another rather than lying side by side. Direct exposure until covering is a maximum of 90 days. The membrane is not installed on surfaces with a temperature above 80 °C. On the roof, the membrane is installed horizontally, across the slope, starting from the eaves; the adhesive strip on the inner face is oriented downwards, towards the eaves, and the one on the aluminised face upwards, towards the ridge. Ventilation is provided above the membrane, through the counter-battens and battens — the ventilation layer is mandatory; no ventilation space is provided beneath the membrane.
Isoflect Power Tape is applied on a clean, dry and dust-free surface, pressing firmly along the entire length of the joint. Membrane overlaps are covered completely, so that the vapour barrier is continuous; perimeter junctions, penetrations and openings are sealed with the same tape.
6. Checks during execution and at acceptance
On receipt of the materials, the following are checked: the designation and type of the products, in accordance with the design; the current revision of the technical data sheets; the roll dimensions and the contents of the packages; the integrity of the packaging and of the aluminium faces; the declarations of performance, for products that have them; for Isoflect Wolle, technical approval AT 001SB-03/1039-2024 and the declaration of conformity with the approval.
During execution, the following are checked:
- the orientation of the aluminium faces, in accordance with the detail, and the continuity of the reflective layer; the sealing of all joints, overlaps and junctions with Isoflect Power Tape, without creases, detachments or gaps;
- for Isoflect Wolle: complete filling of the cavities, without compression and without open joints; the layer thickness — the total thickness is not measured; the boards are counted;
- for roof membranes: overlaps of approximately 10 cm, with the self-adhesive strips overlapping and bonded; the fixing; the duration of direct exposure, a maximum of 90 days;
- the presence of the ventilation layer above the roof membrane.
Before each layer is covered (plasterboard, OSB, roof boarding, screed, roof covering), a record of concealed works shall be drawn up in accordance with the regulations in force. Acceptance upon completion of the works shall be based on the records of concealed works, the quality documents of the products and the visual inspection of the accessible layers.
7. Measurement and settlement
The Isoflect membranes (Reflectiva Gold, Reflectiva Multistrat, Reflectiva Roof Pro and Reflectiva Roof Optim) shall be measured in m² of covered area, as developed, without separate inclusion of the overlaps; overlaps, fixings and technological losses are included in the unit price.
Isoflect Wolle shall be measured in m² of insulated area, separately for each board type (P800, P1500, P2100) and for each layer.
Isoflect Power Tape is included in the unit price of the sealed membrane or is measured separately, in rolls of 50 m, as established in the bills of quantities.
The other layers (structure, profiles, boards, roof coverings, waterproofing, screeds, finishes) shall be measured and settled in accordance with the relevant work chapters.
8. Reference documents
- Isoflect construction detail ISO-ACO-04 — PDF, DXF and IFC, from the library for designers.
- Technical data sheet Reflectiva Gold, revision 5, 11.10.2026.
- Technical data sheet Reflectiva Multistrat, revision 4, 13.09.2026.
- Declaration of performance Reflectiva Multistrat.
- Technical data sheet Reflectiva Roof Pro, revision 4, 13.09.2026.
- Declaration of performance Reflectiva Roof Pro.
- Technical data sheet Reflectiva Roof Optim, revision 4, 13.09.2026.
- Declaration of performance Reflectiva Roof Optim.
- Technical data sheet Isoflect Wolle P800, revision 4, 13.09.2026.
- Technical data sheet Isoflect Wolle P1500, revision 4, 13.09.2026.
- Technical data sheet Isoflect Wolle P2100, revision 4, 13.09.2026.
- Declaration of performance Isoflect Wolle P800.
- Declaration of performance Isoflect Wolle P1500.
- Declaration of performance Isoflect Wolle P2100.
- Technical agrément AT 001SB-03/1039-2024 — INCD URBAN-INCERC, INCERC Bucharest Branch; favourably endorsed by CTPC on 29.01.2025 (Minutes No. 18014); valid until 29.01.2028; technical opinion valid until 29.01.2027; declaration of conformity with the technical agrément.
- Technical data sheet Isoflect Power Tape, revision 4, 13.09.2026.
- Test standards cited in the technical data sheets: DIN 4102, EN 1107-2, EN 1109, EN 12310-1, EN 12311-1, EN 12572, EN 13501-1, EN 13859-1, EN 1848-2, EN 1849-2, EN 1850-2, EN 1928, EN 823, EN ISO 11925-2, SR EN 12667:2002, SR EN 13501-1, SR EN 13501-1+A1:2010, prEN 15976.