The issue of airtightness on the roof plays a central role when it comes to the physical function of the building. Since not just the protection from the outside, but also tailor-made solutions for airtightness from the inside is one of our core competencies. That is the exact reason why we at the company DÖRKEN have made it our business to develop our own systems for you including airtight membranes and the adequate adhesive accessories. We are at your side with this expertise and also through our sales network as well as our technical support. We do not just offer you standard solutions, by providing you with our expertise for project-related inquiries as well.
Airtightness is the characteristic of a building material, of a component or of a building that air does not flow through it, or only flows through it to a small extent. This means that a well-planned and well-executed airtightness prevents any uncontrolled ventilation heat losses by ensuring comfort and preventing inadmissibly high levels of condensation water losses caused by convection.
Especially the last aspect is one of the most frequent causes of damage in a built-up pitched roof. The reason for this is pretty easy to explain: As soon as warm, moist room air flows uncontrollably through the roof structure in the course of the cold season, the water vapour will condense inside the insulation. Since the condensation can noticeably reduce the function of the thermal insulation by at the same time increasing the risk of mould, every thermal insulation in the built-up pitched roof must be protected from moisture by airtight layers.
Generally speaking, a well-designed airtight and windproof building shell works like a ski jacket: There is an outer and an inner functional layer with different tasks and requirements while the lining and thermal insulation are positioned in between.
Windproof layer (= the outer layer)
The windproof layer is laid on the outside in front of the thermal insulation (for example, mineral fibre insulation), e.g. with DELTA® roofing membranes with bonded seams and joints. It permits the reduction of the air currents coming from the outside to the inside. In Germany the windproof layer is recommended without being standardised. Consequently, it is not a main requirement. However, it offers a number of advantages, such as for example an increased rain resistance and a more efficient thermal insulation.
Airtight layer (= the inner layer)
The airtight layer is usually laid under the thermal insulation on the inside of the room, e.g. for example in combination with the air and vapour barriers of DELTA®. The materials must have a sufficiently low air permeability and can meet other requirements, such as the material-specific water vapour diffusion resistance, the so-called SD value. The airtight layer must be produced as a circumferential airtight surface in which seams, and joints, penetrations and connections are for example sealed by means of DELTA® adhesive systems.
Permanently airtight connections are absolutely required for sustainable construction. This applies to seams and joints, connections, and terminations as well as to penetrations. There shouldn't be any heat loss caused by leaks in the airtight layer at joints, overlaps and penetrations. In addition, no moist, warm air must flow into the structure from the inside of the building. Leaks in the building envelope result in high energy losses, unpleasant drafts and may cause massive structural damage, for example due to mould. For this reason, all critical points are to be carefully glued airtight, for example:
From universal adhesive tape for overlays to pasty functional coatings for ideal detail security: you will find the accessories you require for airtight bonding in the DELTA® adhesive range.