Windtight and airtight systems

Windtight and airtight systems

Draughts are banned.



Besides cellulose insulation, ISOCELL has proved itself to be a competent and innovative trouble-shooter in the field of airtightness for both craftsmen and installers. Since 1995 roof underlays, wind seals, vapour barriers and adhesive systems have been developed and distributed under the brand names AIRSTOP and OMEGA. Over 600 airtight measurements a year on building sites at home and abroad provide comprehensive data and new knowledge.

Air and wind-tightness are decisive factors for efficient thermal insulation. Through non-airtight sections – so-called leakage – in the building’s envelope, warm indoor air can flow freely to the outside and is replaced by cold air from outdoors. This cold air must be warmed again by the heating system. Research has shown that even when houses are well insulated, the proportion of thermal loss through non-airtight areas and thermal bridges can be up to 60 % of the total loss. Direct results of leakage in the envelope of the building are damage from condensation, reduced performance of acoustic insulation, dry room air and cold floors on the ground floor.

How much the insulating effect of a building component is diminished has been measured at the Institute for Building Physics in Stuttgart: a component (typical for use in prefabricated housing), with outer measurement 1 m x 1 m and 14 cm thick has a U-value 0.3 W/m²K when tight. If there is a 1 mm wide continuous gap of only 1mm, the U-value is reduced to 1.44 W/m²K.

Adhesive tapes and sealing compounds – energy loss lies in small details
The increasing demand for even more airtight building envelopes in the low and passive house sector, calls for complex solutions. Due to intensive cooperation with the installation trade, the main focus is, besides the highest standard of quality, above all on rational and easy handling of products. Laboratory tests are carried out before the product is launched on the market and tested by partner companies for suitability, in practice as well as in outdoor trials. Special products such as airtight tapes for sealing the threshold area or sleeves for pipe and cable penetration points are very popular with planners and installers. In the production of adhesive tapes pure acrylate adhesives without the addition of resins are used, and which are guaranteed to be resistant to aging for 30 years (Certificate from Kassel University).

Windtight level (= outer envelope)
Intended to protect the building component from rain and wind. Wind causes a permanent pressure-suction strain on the building. Without a windtight layer, that ISOCELL’s windtight system effectively provides, the component is flushed with air from outside and the thermal insulating properties of the construction are reduced. Moisture entry can result in damage to the construction as well as reduction of acoustic protection.

Airtight level (= inner layer)
On the outside, the construction must be protected from the weather. Inside, it is a question of preventing moisture from inside from penetrating into the structure and into the insulation. The airtight layer is always the so-called warm side of the outer building component.

Saving energy and costs
Even in well-insulated houses, leakage in the building’s envelope causes energy loss of up to 60 %. Through these gaps and cracks cold air forces its way in and needs to be re-heated by the heating system. When an airtight level has been carried out properly, the cold stays outside.

Improved thermal insulation
A correctly installed building’s airtight envelope protects not only from cold in winter but also from heat in summer. Gaps in outer construction components impair the insulation’s effect considerably. Here an example: for a building component with outer measurement 1 m x 1 m and 14 cm thick, the U-value deteriorates from 0.3 W/m²K to 1.44 W/m²K if there is a 1mm wide continuous gap. 

Protection from condensation
Condensation in the construction leads to obvious deterioration in the U-value. An even greater problem is, however, the serious subsequent damage to the construction if moisture cannot dry out quickly. It is estimated that two thirds of all damage from moisture in the construction sector can be traced back to lack of airtightness.

A ban on draughts entering
The proverbial ‘tornado from the socket’ has a considerably negative impact on the comfort of living space. Everyone has experienced cold feet – caused by air drawn into in the building’s envelope through untight areas. As this cold air is heavier it moves to the lowest point in the room, to the floor. Then, when air from outside enters through cracks, even the best insulation value is no use.

Improved air quality
Untight areas in inner walls have a negative impact on the indoor climate as dust and fibres from insulation permeate into the air. Walls sealed with ISOCELL products ensure good quality of room climate (provided there is a functioning air-conditioning system or adequate ventilation).

Optimum functioning of air-conditioning systems
Where air-conditioning systems are used, a building must be particularly airtight. The maximum permitted value for airtightness of the building envelope is in accordance with DIN 4108-2. That is twice as high as for buildings without ‘enforced ventilation’.

Noise stays outside
Even with good acoustic insulation of building components surrounding a room the sound level can increase due to gaps in the building’s envelope. Noise enters through even the smallest cracks. With ISOCELL airtight systems annoying sounds simply stay where they belong: outside.