The Passive House concept is founded on five basic principles for good design.
- Thermal Insulation
- Thermal Bridge Free Design
- Ventilation and Heat Recovery
- Passive House Windows
These five simple ideas, properly applied in a well constructed dwelling, facilitate a dramatic reduction in the energy required for space heating. This is achieved by maximising solar gains and harvesting waste heat, whilst minimising all mechanisms of heat loss from the envelope.
These are by no means new ideas, but todays increasing focus on both housing quality and energy consciousness serves to reiterate their importance.
With innovative solutions to simplify reducing air leakage rates and control cold bridging, the Proctor Passive range of solutions allows specifiers to adhere to these guiding principles without compromising in other areas. This ensures the delivery of best practice performance with the least impact on costs and timescales.
External Airtight Membranes - an Introduction
Why are airtight membranes needed?
Air leakage through cracks, gaps, holes and improperly sealed elements such as doors and windows can cause a significant reduction in the performance of even thermally insulated building envelopes. Housebuilders have a key role to play in the installation of effective air barrier systems which have become essential in achieving the most effective means of controlling and reducing air leaks.
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. Air leakage greatly reduces the effect of thermal insulation; therefore if energy efficiency is to be improved within buildings, this is the most critical area to focus on.
The two main ways to achieve airtightness in the building envelope are internally or externally, or in other terms, “inside of the services zone’ or ‘outside of the services zone’. For the housebuilder, the use of traditional internal air barriers can be more complex and costly to install, due to the need to accommodate building services such as electrical, lighting, heating and drainage systems. An internal air barrier is only as good as it’s installation. If all the service penetrations are not adequately sealed, performance will be compromised.
For many years, external air barriers have been commonly used in North American building design and construction. By moving the air barrier to the external side of the structural frame, external air barrier systems such as Wraptite® allow for an almost penetration-free airtight layer, which can be installed faster and more robustly. This offers an effective but simple system comprising a self-adhesive vapour permeable air barrier membrane, plus vapour permeable sealing tape, Wraptite Corners and Wraptite Liquid Flashing, and provides effective secondary weather protection while preventing trapped moisture and air leakage. Far simpler than internal options an external air barrier system like Wraptite will maintain the envelope’s integrity, with less building services and structural penetrations to be sealed, and less room for error.
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 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:
Wraptite is a unique patented external airtight and vapour permeable, self-adhered membrane which solves the problem of reliably achieving airtightness in buildings. Applying Wraptite to the outside of the building will mean there are fewer penetrations for services therefore the likelihood of expensive remedial work is greatly reduced. Wraptite is lightweight, easy to install and fully bonds to virtually any substrate, with a key benefit being its speed and ease of installation, negating any requirement for sealants or tapes. 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.
Wraptite has received BBA certification for use in roofs, walls and modular floor construction making it an ideal choice for commercial projects with large uninterrupted façades. Its unique patented technology means it is the only self-adhering vapour permeable air barrier certified by the BBA. Wraptite is compliant with Part B regulation changes and also has BRE acceptance for use in the external wall systems of buildings over 18m in height, both as a continuous layer on sheathing board, behind fire classified insulation, and for use to tape joints in insulation behind rainscreen.
Wraptite Liquid Flashing
Wraptite Liquid Flashing is a high-quality, gunable, elastomeric, polyether, liquid applied flashing and detailing membrane. It bonds to most construction materials, such as aluminium, brick, concrete, wood, vinyl, and exterior sheathing boards. Wraptite Liquid Flashing is compatible with our entire range of vapour permeable products for joint detailing in exterior sheathing panels.
Wraptite Liquid Flashing is ideal for use in complex details. It can also be used to protect the leading edge of the Wraptite membrane or tape from water penetration if the edge cannot be protected by overlapping in a shingle fashion.
A useful way of stopping unnecessary air leakage around openings and overlaps is to use Wraptite Tape, an airtight, tear resistant tape with high vapour permeability for internal and external applications. Wraptite Tape’s flexibility facilitates ease of application and detailing, while its resilient composition resists punctures and tears during construction. It can be left exposed for up to 120 days during construction and has a wide operating temperature range (-40°C to +100°C). Wraptite Tape is also available with a split release liner for ease of installation.
It fully bonds to all standard substrates, with no primer required, suppressing air leakage around joints, openings and penetrations. It is also suitable for permanent airtight sealing of membrane overlaps and for taping insulation joints. Wraptite Tape’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. Wraptite Tape contains no VOC’s.
Wraptite Preformed Airtight Corners have been developed for the difficult areas around doors and windows where maintaining good air barrier continuity is difficult and time consuming. Wraptite Corners’ simple design and installation process makes sealing openings against air leakage simple, just peel off the release liner, stick the corners in place, then install the Wraptite membrane as normal. This helps achieve the best possible results in the shortest possible time.
Once installed, the corner sections provide the same vapour permeable air barrier performance as the Wraptite membrane itself, ensuring air leakage and water ingress are minimised without trapping construction moisture or causing condensation.
Procheck Adapt® is a high performance variable-permeability vapour control layer for use in a variety of commercial and residential applications. It is designed to protect the building fabric from potential risks of condensation and it will also act as an airtight barrier. Its variable permeability adapts to changes in humidity levels becoming more resistant in Winter and more permeable in Summer. This means the building fabric is protected from damaging moisture levels during cold, wet months of the year and it will allow the fabric to dry out effectively in warmer, drier months. Procheck Adapts’ translucent structure eases fixing to structural frames and in conjunction with its integral tape allows for a fast installation time.
Spacetherm can be supplied on its own and cut to size or laminated to a number of facings to suit your individual requirements. Its remarkable performance is achieved through the use of flexible aerogel blankets. The insulation used in Spacetherm is material derived from silica gel.
With a thermal conductivity of 0.019 W/mK, Spacetherm SLENTEX® A2’s performance, coupled with its superior fire performance, qualify it as one of the best insulation materials available worldwide. Engineered for space-critical applications, the product offers low thermal conductivity, plus breathability allied to hydrophobic characteristics. Its flexibility and ease of use has proven it as the insulation material of choice in many applications and for a wide variety of clients.
Reflectashield TF 0.81
Reflectashield is a vapour permeable low emissivity membrane for use externally on timber frame buildings. Once Reflectashield TF 0.81 is applied to the walls, the primary wall covering should be installed within 3 months.
The A. Proctor Group are constantly reviewing their product portfolio to keep up with current legislation. The A. Proctor Group have re-tested Reflectashield TF 0.81 at the National Physics Laboratory (NPL) resulting in an uplift of the claimed thermal performance to an R-Value of 0.81m2K/W.
Reflectashield TF 0.81 complies with the vapour resistance requirements set out by BS 4016, TRADA and the NHBC.
Reflectatherm Premier is a reflective vapour control layer with integrated tape for ease of installation. Reflectatherm Premier is for internal walls, ceilings and floors, specifically designed to enhance the thermal performance when placed on the warm side of the insulation.
The integrated tape, which is a key feature of Reflectatherm Premier, ensures an efficient, consistent, continuous and well sealed membrane to protect the structure from vapour and air movement.