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[Sustainable products] Revisions to Part L have caused a surge in products concerned with airtightness, says Sandy Patience

Some of the more important products at this year’s Ecobuild were to be found on the stands of manufacturers producing the membranes, tapes, sealants and other accessories that address the problems associated with ensuring airtightness.

Building regulations now require an air permeability ceiling as low as 5m³/hm² (@ 50 Pa) and, if this isn’t enough, the popular Passivhaus standard requires an even more onerous equivalent of less than 1m³/hm² (@ 50 Pa).

The design response to the new standards has been to introduce the idea of the continuous airtightness barrier system. Though simple in conception (the barrier is often represented in drawings by a single continuous red line), in practice the system can be challenged by any number of junction conditions between elements and penetration by openings and services.

A technology of materials and products has grown to match the evolving needs. Tape in particular has developed well beyond the eponymous ‘duct tape’ of old, with material and adhesives specially designed to deal with specific sealing issues such as jointing membranes, junctions between different materials and to form complex internal moisture permeable seals around window openings. Passage of pipes and wiring through the airtightness barrier are addressed by sleeves and grommets that seal penetrations of different diameters while backing receptacles have been designed to receive electrical sockets and recessed downlights.

Where previously a degree of detailing around openings and at junctions was necessary to ensure good aesthetic and weather-tight performance - the interpretation of which was often at the constructor’s discretion - the introduction of airtightness as an explicit requirement has changed the game. Now the designer needs to work carefully with the construction team to ensure that the detailed application of airtightness materials is carried out around those same openings and at junctions as well as a host of other points at which the airtightness barrier becomes vulnerable.


Astro Fra

Astro Fra

Designed for application in voids behind plasterboard, the Astro Fra’s primary function is fire protection. Equally, it is a proven method of reducing air leakage. The covers are pre-formed to fit the boxes and can be fixed mechanically without the need of screws or adhesives.

Product Astro Fra Socket Box Cover Intumescent Fire & Acoustic Socket Box
Type Leak-reducing socket box
Manufacturer Astroflame
Materials Mineral fibre and organic fibre with intercalated graphite and organic (latex) binder plus clay
Fireresistance 120 minutes to BS476 part 20
Sizes Single and double
Countryof manufacture UK
Supplier Astroflame




Corvum is a single-sided high performance tape that provides a solution for easy, quick and permanently airtight sealing of door and window frames on the inside. The tape is invisible behind the cladding because it is precisely prefolded.

Product Corvum 12/48
Type Sealing tape for angular penetrations
Manufacturer Siga
Material PE coated paper coated with a modified acrylic-based pressure sensitive adhesive, covered by a double-side siliconised release liner
Temperatureresistance -40°C to +100°C
Country of manufacture Switzerland
Supplier Eco Building Systems




Sprayed as a liquid, the insulation foam is suitable for a number of applications including timber frame stud walling, pitched roofs and suspended timber ground floors, and for internal work on masonry walls. As it expands it seals cracks, electrical boxes and other service penetrations.

Product Icynene
Type Spray applied, low-density, open-cell, soft insulation foam
Manufacturer Icynene
Materials Water-blown isocyanate-polyol foam
Thermalconductivity 0.039 Wm-1K-1
Installation By approved installers
Warranty 25 years
Approvals BBA, ETA
Waterabsorption 0.57% by volume
Lifeexpectancy Lifetime of the structure
Country of manufacture Canada
Supplier Airseal Insulation




Sealing grommet made of strong and highly flexible EPDM. Ideally suited for rapid and permanent airtight feed-throughs for cables and pipes through the airtight sealing layer. Roflex can also be used outdoors, e.g. for sub-roofs and for refurbishment vapour check.

Product Roflex and Kaflex
Type Airtightness grommet for cables and small pipes
Manufacturer Pro Clima
Material EPDM
Temperatureresistance -40°C to +120°C
Lifeexpectancy 60 years or longer
Country of manufacture Germany
Supplier Ecological Building Systems


Tremco Illbruck

Tremco Illbruck

The product has a specially designed reactive membrane-water vapour permeability changes depending on the humidity inside the joint. This allows the product to perform as an intelligent seal for airtight internal joints, and weather tight breathable external joints.

Product Duo Flexible Window Membrane E
Type Intelligent seal for airtight internal and weathertight external joints
Manufacturer Tremco Illbruck
Material Polyethylene copolymer film with woven fleece fabric and acrylic self-adhesive and butyl adhesive strips for location to frame and wall
Airtightness 0.04m3/m2.h
Temperatureresistance -40°C to +100°C
Country of manufacture Germany
Supplier Trermco Illbruck




The airtight seal of the door is maintained by means of a prestressed spring, which ensures that the door remains airtight, even when a blower door test is carried out. The gap between the door and the hatch is sealed with a rubber gasket.

Product Loft hatch
Manufacturer Wellhofer
Materials Casing:MultifunctionBoard; trapdoor: chipboard laminate; Twin-wallsealing: TPV-profile; insulation: polyethylenethermodeck
Size Length 1,200mm, width 600mm, height 250mm
Attic ladders Available on request
Fire resistance 30 mins and 90 mins
U-value 1.1W/m2K
Airtightness 0.03m3/m2.h
Country of manufacture Germany
Supplier Ecological Building Systems


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