DELTA®-NOVAFLEXX als Luft- und Dampfsperre

Luftdichtheit am Dach – Was bedeutet das eigentlich?

Draught-proofing a roof – what does that imply?

Talking about roofs, you often heat it said that particular importance should be attached to good draught-proofing. But what does that mean, really? A building material, a building element, or a building is called draught-proof if it allows little or no air to pass. This means that draught-proofing that is well planned and executed will prevent uncontrollable heat loss through ventilation, ensure cosiness, and prevent inadmissibly high precipitation of condensate caused by convection. 

The last-named item especially represents one of the most frequent causes of damage in converted pitched roofs. The reason may be explained quickly: if warm, humid air from the interior flows uncontrolled through a roof structure in the cold season, water vapour will condense in the insulation. As the function of a heat insulation may be considerably impaired by condensate which, in addition, enhances the risk of mould forming, the heat insulation of converted pitched roofs must at all events be protected from moisture by a draught-proofing layer.

To comply with the Energy Conservation Regulation, therefore, roofs should not only be insulated but also carefully protected from uncontrolled air currents if they are to remain free from damage and ventilation-related heat losses are to be limited in the long run.

What is the difference between a wind-proofing and a draught-proofing layer?

A well-made wind and draught-proofing envelope around a building basically works like a skiing jacket. There is an outer and an inner functional layer with varying tasks and requirements, and in between there is the lining or heat insulation.

Wind-proofing layer
(= the outer layer)

The wind-proofing layer is laid out on the outside of the heat insulation (e.g. mineral fibre panels), possibly consisting of DELTA® sarking membranes with glued seams and butt joints. It reduces the flow of air from outside to the interior. In Germany, it is only recommended but not a standard requirement. However, it offers a variety of benefits, such as improved rain-proofing and more efficient heat insulation.



DELTA®-MAXX PLUS - Unterdeckbahn (winddichte Ebene) zoom

Draught-proofing layer
(= the inner layer)

The draught-proofing layer (e.g. a DELTA® draught and vapour barrier) is generally installed under the heat insulation towards the interior of the room. Materials must have an adequately low air permeability and may comply with other requirements relating to, for example, the material-specific water vapour diffusion resistance or Sd number. The layer must be made airtight all around, with seams, but joints, penetrations, and flashings sealed with, for example, DELTA® adhesive systems . A draught-proofing layer is demanded by codes, standards, and the EnEV (Energy Conservation Regulation).

DELTA®-NOVAFLEXX - Luft- und Dampfsperre (luftdichte Ebende)zoom
 

6 good reasons for a draught-proof building envelope:

  • Lowers heating energy consumption, avoids uncontrolled heating-energy losses through ventilation, lowers CO2 emissions
  • Freedom from physical building damage through avoiding condensate in the structure
  • No damage to the building, no mould formation
  • Cosiness through draught avoidance
  • Improved quality of the interior air (smells, spores, dust...)
  • Better efficiency of interior ventilation systems


Gebäudehülle
 

Draught-proof buildings: save energy and improve the room climate

There are several reasons why draught-proofing plays a crucial part in building construction, conversion, and renovation next to heat insulation: draught-proof buildings provide a pleasant interior climate and may help to reduce energy costs, thus supporting the protection of the environment. Air leaks in roofs, doors, and windows may considerably reduce not only the comfort but even the quality of an entire residential building and necessarily lead to high energy costs. DELTA® offers optimised products for setting up an airtight building envelope. The climatic conditions prevailing inside the building in winter as well as in summer will be improved, and the interior living comfort will be enhanced. Lastly, damage to the construction of the roof will be avoided.

Draught-proofing a roof with DELTA®

The best solution for draught-proofing is a harmonised comprehensive system that includes the right product for any object-specific application. The perfectly tuned DELTA® system comprising draught and vapour barriers and the matching DELTA® adhesive programme serves to form a draught-proof building envelope, markedly reducing both energy costs and CO2 emissions.

Airtight seams – it is the details that count

Permanently airtight seams are indispensable for the sustainability of a building. This holds true for seams, butt joints, connections, and end seals as well as for penetrations. Leaks in the draught-proofing layer at joints, overlaps, and penetrations should never cause heat loss. Moreover, humid warm air should not be allowed to flow from the interior into the structure of a building. Leaks in the building envelope cause high energy losses, unpleasant draughts, and possibly massive damage to the building by mould, for example. Consequently, it is imperative to carefully draught-proof all critical locations, such as 

  •  overlaps of the vapour barrier,
  •  seams between the vapour barrier and the masonry,
  •  seams around dormer and façade windows,
  •  round and angular penetrations,
  •  seams on floors and pedestals

From a universal adhesive tape for overlaps to a viscous functional coating for optimum detail safety: for any accessory you may need for draught-proof seams, look to the DELTA® adhesive range !

 
Overlaps with the Plus Version
Overlaps with the Plus Version
 

Draught-proofing measurement (blower door test)

To test the draught-proofing of a building, differential pressure measurements as per DIN EN 13829 (popularly known as blower door tests) are carried out. A ventilator pumps air either into a building (overpressure test) or out of it (negative pressure test). This permits measurements to locate leaks in new or existing buildings.


The Energy Conservation Regulation (EnEV) rewards successful draught-proofing tests. These so-called EnEV acceptance tests involve negative and/or overpressure tests to review conformance with specified air exchange rates. The current version of the EnEV (Energy Conservation Regulation) specifies the requirements applying to the draught-proofing of buildings.

BlowerDoor
BlowerDoor
BlowerDoor
BlowerDoor
 
Dörken GmbH & Co. KG
 
 

Dörken GmbH & Co. KG
Wetterstraße 58
D-58313 Herdecke
Germany

Tel          +49 23 30/63-0
Fax         +49 23 30/63-355
E-Mail    membranes@doerken.de

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© Dörken GmbH & Co. KG · A member of DÖRKENGROUP · DELTA® is a registered trademark of Ewald Dörken AG, Herdecke, Germany.

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