OverviewOur range of Wraptite external air barriers solve the problem of reliably achieving airtightness in buildings, with a robust two component solution. This new approach saves on both the labour and material costs associated with meeting the demands of modern energy efficiency requirements in both commercial and residential buildings. Moving the air barrier to the outside of the building, away from the 'services zone' means there are far fewer potential penetrations to the air barrier and that there is no requirement for expensive specialist components such as airtight junction boxes, light switches or downlighter hoods. Wraptite-SA is a unique external airtight solution, which is not only highly vapour permeable, yet airtight – but also self-adhered to ensure a consistent airtight external seal.
Potton Passivhaus Showhouse - 0.5 Air Changes Per Hour
The Passivhaus standard must be demonstrated by means of an airtightness test. The air change rate must be less than or equal to 0.60ac/h (air changes per hour), under test conditions, to meet Passivhaus levels. At a recent Self Build Live event on the 4th March 2016, Potton managed to improve on their target of 0.60 ac/h (air changes per hour), to 0.5 ac/h!
As anyone who's ever failed an air tightness test knows, forming a continuous internal air barrier is a time consuming & costly process. The multitude of components required with the internal approach regularly includes expensive speciality airtightness products such as airtight electrical boxes, downlighters, light switches & extractor fans, as well as an airtight VCL, butyl sealing tape & plenty of silicone mastic. Internal air barrier solutions:
External air barriers, which are commonly specified in North America, offer excellent reliability & consistency. Window, door & pipe penetrations are made airtight in a straightforward manner with our Wraptite Tape. Wraptite-SA was recently used on a Kingspan Potton airtight construction, where an air permeability test result of 0.5m3/m2/hr was achieved, with no expensive remedial work required. External air barrier solutions:
A self-adhesive vapour permeable air tightness membrane installed outside the services zone. Assists in achieving good air tightness testing results.
Air tightness tape, tear resistant with high vapour permeability for internal and external applications. Fully bonds to all standard substrates.
The Zero Bills Home - ZEDfactory
Wraptite-SA airtight membrane has been selected by the Zero Bills Home Company and RIBA award winning development pioneers ZEDfactory in their latest innovative solution to deliver zero carbon housing. The Zero Bills Home has been built at the world-renowned BRE Innovation Park in Watford.
The Zero Bills Home concept, is said to offer a fresh approach to the significant challenges faced by the housing market, and offers a pre designed, engineered, and costed housing solution with an option for customisation. The intelligent design seeks to minimise energy requirements, make home energy bills a thing of the past and offer a truly sustainable solution to the demand for more housing.
Wraptite-SA, the only self-adhering vapour permeable air barrier certified by the BBA, was installed as part of the OSB panel construction of the home. The use of Wraptite-SA in the construction makes a significant contribution to a building’s thermal performance by preventing lateral air movement. It also provides high vapour permeability in a continuously sealed, self-adhered, airtight membrane.
Unlike internal air barriers, which can be complex and costly to install due to the need to accommodate building services such as electrical, lighting, heating and drainage systems, Wraptite-SA was applied externally, quickly and easily to the OSB boards in continuous pieces. The membrane fully bonds to virtually any substrate, requiring no mechanical attachment to suppress air leakage around junctions or penetrations. On the Zero Bills Home project the results for airtightness were exemplary, achieving on the first test 1.3 ac/h at 50 pascals.
Another key benefit of the system is that Wraptite-SA’s high vapour permeability allows damp sheathing to dry quickly and moisture vapour to escape. This ensures good indoor air quality and reduces the likelihood of mould, mildew, condensation, timber distortion and metal corrosion.
Alongside Wraptite, an additional product selected from the A. Proctor portfolio was Roofshield, the unique air and vapour permeable pitched roof underlay, which has long been recognised as one of the highest performing roofing membrane solutions and the preferred choice of architects, developers and contractors.
The Zero Bills Home has been developed as a patented system and as a prototype for future building developments. The house is set to be one of the first homes assessed under BRE’s new Home Quality Mark, which provides a star rating system on the quality and sustainability of new homes. It is also awaiting planning permission for use on the next development of 94 new homes in Newport Essex for the Sir Arthur Ellis Trust.
Airtightness vs. Insulation
Compliance with modern building regulations requires a wholistic approach that includes numerous energy efficiency measures. One area that is often overlooked at the design stage is improving the buildings designed air tightness beyond mandatory minimums. Using Wraptite externally can reduce a building's carbon emissions by 6.7% when keeping the same u-Value, or reduce the amount of insulation required by over 100mm whilst maintaining the same Dwelling Emission Rate. The reliability & consistent performance available with an external air barrier solution allows for:
|Airtightness||PUR Insulation||Insulation Cost||Dwelling Emission Rate|
The Problem - In many constructions, about half of all heat loss is due to air leakage through the building. Given that approximately half of all energy used in the UK is from buildings, it is easy to see that air leakage, or draughts, account for a considerable amount of energy - and therefore cost.
As thermal insulation requirements have increased over the last few years, the proportion of energy lost through air leakage has become more evident. The ever-increasing thermal insulation required will however be rendered largely ineffective unless the airtightness of the structure itself is addressed. Tests indicate that air leakage can reduce the effectiveness of thermal insulation by up to 70%; therefore if energy efficiency is to be improved within buildings, this is the most critical area to focus on.
In addition to improved insulation, energy efficient heating systems will also be ineffective if warm air can escape the building and cold air can seep in. This is reflected in the fact that total space heating costs in an airtight construction may be as much as 40% less than in a leaky one.
Another issue associated with air leakage in buildings is that warm and often moist air can escape to colder parts of the outer construction where it can cool and condense, leading to a build-up of moisture. This in turn can lead to:-Decay of organic materials such as timber frames. Saturation of insulating materials, thus reducing their insulative effect (further increasing heat loss). Corrosion of metal components. Frost damage where moisture has accumulated on the cold side of the insulation.
Air leakage through cracks, holes or gaps causes a significant reduction in the thermal performance and efficiency of a structure. However this can be remedied by careful design and good quality construction practice.
The Solution - Wraptite-SA and Wraptite Tape are effective methods of stopping unwanted air leakage. Wraptite-SA is a self-adhering airtight membrane which consists of a triple layer polypropylene micro-porous film laminate with a proprietary moisture vapour-permeable adhesive, plus a silicon-coated PET release liner. It can be used in full wall applications, on pitched roofs (under metal, tile, slate, wood shingles and clay tile) and for window flashings or other details.
Wraptite-SA combines the best properties of a vapour-permeable membrane and an airtight membrane in one innovative, affordable self-adhering product. It fully bonds (no primer or mechanical attachments required) to almost any substrate for air tightness and ease of installation, negating the requirement for sealants or tapes.
Penetrations in sheet material such as pipes, ducts and electrical work also need to be sealed to ensure compliance with air pressure testing. Wraptite Tape is an air tightness tape that has all the benefits of Wraptite-SA, but with the convenience of a tape. Air tight Wraptite Tape is tear resistant and offers high vapour permeability for internal and external applications. It is also suitable for permanent airtight sealing of membrane overlaps. Detailing is quick and easy, providing an effective, convenient solution to what can be an expensive problem.
Wraptite: All-in-One - Wraptite products do not require a primer and can be installed in temperatures as low as 0°C.Its wide service temperature range means it can be easily installed in all climates. It is very easy to install, with a tough facer laminate that resists rips, punctures and tears. Wraptite is fully bonded, hence fasteners are not required at installation; this prevents lateral air movement, further enhancing the building’s thermal performance, and increasing performance in an air leak test. Being highly water vapour permeable, Wraptite thereby reduces potential for trapped interior moisture and condensation. Wraptite is resistant for up to six weeks of UV and climate exposure.
Wraptite-SA and Wraptite Tape are unsurpassed in performance. Both offering an SD rating of 0.039, Wraptite-SA and Wraptite tape provide a highly vapour-permeable, yet airtight performance for a wide variety of applications and conditions, and offer an optimal solution for achieving excellent results in an air pressure test. They allow damp sheathing to dry quickly and moisture vapour to escape, ensuring good indoor air quality while reducing incidence of mould, mildew, condensation, timber distortion and metal corrosion. The unique characteristics of Wraptite allow the moisture vapour to escape the structure easily, while fully maintaining the integrity of the air-tight building envelope.
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A. Proctor Group Ltd, The Haugh, Blairgowrie, Scotland, PH10 7ER