Vapour barriers for roofs, walls and ceilings
The vapour barrier goes on the warm side of the insulation — facing the room. It is the airtight layer of the building.
A vapour barrier (or vapour retarder) is a membrane on the inside of the roof, wall or ceiling. It stops air from the rooms passing through the insulation and reduces the vapour that enters the structure.
The membrane only works if it is taped: the overlaps, the joints with the walls and every penetration for cables and pipes are sealed with tapes and grommets. Why this matters so much is explained on the “The system” page.
How much vapour the membrane lets through is shown by its Sd value: the higher it is, the tighter the membrane is to vapour. With AIRSTOP DIVA and DIVA+ the Sd value changes between 0.5 and 30 m depending on humidity — which is why they are called vapour barriers with a variable Sd value.
Where a vapour barrier goes
| New roof or timber frame wall | AIRSTOP vapour barrier on the inside, with the overlaps and penetrations taped. |
|---|---|
| Insulation above the rafters | naturheld ADB 5 or OMEGA SD10 on the sheathing above the rafters, below the boards. |
| CLT wall or roof | naturheld ADB 5 on the CLT panel, below the insulation, with tapes. |
| Roof renovation from outside, without opening up the inside | No vapour barrier goes on the inside — naturheld LDB 0.02 is laid outside over and between the rafters, with a board ≥ 35 mm. |
| Masonry wall, external insulation | No membrane needed. |
The vapour barriers at a glance
The data come from the manufacturers’ technical data sheets; prices include VAT and are the same as on each product page.
| Product | Use | Sd value | Weight | Fire class | Price |
|---|---|---|---|---|---|
| naturheld ADB 5 | Vapour retarder below the insulation | 5 m | 160 g/m² | E (EN 13501-1), B2 (DIN 4102-1) | €4.12/m² incl. VAT |
| OMEGA SD10 | Vapour barrier for above-rafter insulation | 10 (-5 / +8) m | 175 (± 5) g/m² | E | from €3.32/m² incl. VAT |
| AIRSTOP DIVA | Vapour barrier with variable Sd value | 0.5–30 m | 86 (± 5 %) g/m² | — | from €4.75/m² incl. VAT |
| AIRSTOP DIVA+ | Vapour barrier with variable Sd value, reinforced | 0.5–30 m | 110 (± 5 %) g/m² | E | from €5.14/m² incl. VAT |
| FH FORTE | Non-woven fabric vapour barrier | 2 (± 1) m | 120 g/m² | E | from €2.30/m² incl. VAT |
| AIRSTOP ÖKO Natur | Kraft paper vapour barrier | 6.45 m | 175 g/m² | E | from €2.68/m² incl. VAT |
| TIMBERTEX | Vapour barrier for timber construction | 10 (+3) m | 100 g/m² | E | from €2.17/m² incl. VAT |
| AIRSTOP SD18 | Vapour barrier | 18 m | 90 (± 10) g/m² | E | from €2.77/m² incl. VAT |
| AIRSTOP SOLID SD23 | Vapour barrier, reinforced | 23 m | 100 g/m² | E | from €2.74/m² incl. VAT |
| AIRSTOP SD50 | Vapour barrier | 50 m | 95 g/m² | E | €1.73/m² incl. VAT |
| AIRSTOP VAP | Polyethylene vapour barrier | > 100 m | 180 g/m² | E | from €1.98/m² incl. VAT |
| AIRSTOP 1500 | Vapour-tight membrane | 1500 m | 270 g/m² | E | €5.92/m² incl. VAT |
All vapour barriers
OMEGA SD10
Weather-resistant, non-slip three-layer vapour barrier for laying beneath the thermal insulation in above-rafter systems. Also supplied pre-welded to size.
from €3.32 / m² incl. VAT →AIRSTOP DIVA
Vapour barrier with variable diffusion resistance for the airtight layer — with a high potential for the construction to dry out again.
from €4.75 / m² incl. VAT →AIRSTOP DIVA+
Thread-reinforced vapour barrier with variable diffusion resistance for the airtight layer — very tear-resistant, with a high potential for drying out again.
from €5.14 / m² incl. VAT →FH FORTE
Soft, close-fitting vapour barrier with a moderate effect for roofs, ceilings and walls that are vapour-permeable on the outside.
from €2.30 / m² incl. VAT →AIRSTOP ÖKO Natur
Vapour barrier and airtight layer made of two layers of kraft paper with a strong integrated mesh — for walls, roofs, ceilings and floors.
from €2.68 / m² incl. VAT →TIMBERTEX
Tear-resistant vapour barrier and airtight layer for roofs and walls, with an appearance designed for timber construction.
from €2.17 / m² incl. VAT →AIRSTOP SD18
Transparent, extremely tear-resistant vapour barrier and airtight layer for tighter wall, ceiling and roof constructions.
from €2.77 / m² incl. VAT →AIRSTOP SOLID SD23
Mesh-reinforced, extremely tear-resistant vapour barrier for the airtight layer in roofs and walls.
from €2.74 / m² incl. VAT →AIRSTOP SD50
Universal and economical vapour barrier for roofs and walls that are vapour-permeable on the outside.
from €1.73 / m² incl. VAT →AIRSTOP VAP
High-quality flame-retardant polyethylene vapour barrier film for tighter wall and roof constructions — folded for convenient transport.
from €1.98 / m² incl. VAT →AIRSTOP 1500
Extremely strong vapour-tight membrane — completely impermeable to water vapour even under extreme moisture load.
from €5.92 / m² incl. VAT →Isocell photos and technical data: ISOCELL GmbH & Co KG.
See also
- The system: insulation, vapour barrier and tapes
- Adhesive tapes and sealants
- Grommets and penetrations
- Airtightness and the Blower Door test
- Roofing underlays
- All membranes and accessories
A quote for membranes and tapes
Send us the area and the construction — we reply with a quote for the membrane, the tapes and the quantities.