VAPOUR PERMEABLE CONSTRUCTION FABRICS. Healthy buildings control condensation

Transcription

1 VAPOUR PERMEABLE CONSTRUCTION FABRICS Healthy buildings control condensation

2 VAPOUR PERMEABLE LET YOUR BUILDING BREATHE The Bradford ProctorWrap range of construction fabrics represent the latest in moisture control, vapour permeable water tight membranes. These products are designed to reduce the risk of condensation forming on surfaces within the building envelope where it is undesirable. While allowing moisture to pass outward from the inside of the building, these sophisticated membranes prevent the ingress of water and dust from the outside environment both during and after construction. Benefits during construction Protects the frame and roof structure from the elements prior to the application of external cladding. Improves on-site work flow efficiency by allowing internal trades to commence work before the external cladding is applied. Benefits AFTER construction Forms a condensation management surface beyond the building frame, reducing the risk of moisture and mould related issues compromising the structural integrity and health of the occupants. Satisfies the BCA Part 2.2 objective. EXTERIOR Protection and Permeability Representative of Proctor RW INTERIOR Improves air tightness which in turn improves energy efficiency, but still allows vapour to escape without condensing on the inside of the building frame. Protects the interior of the building from moisture and dust ingress from the outside environment. The problem of moisture in buildings is often perceived to be negligible in Australia due to our warmer climate, construction methods and history of damage. That perception is wrong and places the parties responsible for the design and delivery of a building at risk of liability and the owner and occupiers at risk of financial loss and compromised health. Traditionally our buildings were not airtight and had little or no insulation. However, as a result of changing occupant practices (such as closing windows to exclude external noise or retain conditioned air) and the introduction of mandatory energy efficiency and enhanced bushfire construction requirements, building practices are changing, requiring a change in detailing so that moisture related problems are adequately managed. Australian Building Codes Board (ABCB), Condensation In Buildings, Bradford Proctorwrap

3 UNDERSTANDING CONDENSATION RISK Long perceived to be immune from condensation problems, Australia has seen an increase in the occurrence and severity of condensation problems across dissimilar climate zones due to changes in building design and increases in energy efficiency targets. Energy efficient construction increases condensation risk The drive for energy efficient buildings has resulted in higher levels of insulation in the roof space and walls, as well as reduced air leakage due to modern energy conscious building practices. As a result, this has dramatically changed the temperature and moisture balance within buildings, which has changed the location and frequency of where and when condensation is likely to form. When the surface where condensation wants to form shifts from outside the building to inside the building, condensation can potentially cause damage to the building frame, cladding and insulation, whilst allowing mould to grow. Insulation, whilst keeping some surfaces warm, also keeps other surfaces cold. Sealing up the building can also prevent the safe passage of water vapour, resulting in potentially damaging condensation forming on these cold impermeable surfaces. ABCB, Condensation In Buildings, 2011 The possible consequences of condensation and the subsequent high humidity environment include; Health Risks: Unseen mould growth behind wall linings and external cladding can be a health risk to the occupants, particularly the young or elderly. Visual Deterioration: Deflection or staining of plasterboard linings as a result of moisture trapped behind the linings can cause ugly stains and swelling of standard plasterboard. Structural Decay: Moisture trapped within the structure can result in long term corrosion of metal structures, timber rot, loosening of nails as timber swells, and cladding rot or swelling which can result in costly rectification work. Energy Efficiency: A reduction in the buildings energy efficiency can occur due to moisture saturation of the insulation, which can result in loss of thermal performance. Where condensation forms in the building In an energy efficient airtight building with a conditioned internal environment, moisture is added to the air by the occupants who are showering, cooking and breathing (we all expel CO 2 which contains moisture). This creates an internal environment with a higher vapour pressure than the outside environment which forces or drives the water vapour in the air outward in every direction looking for equilibrium. As this vapour drive occurs and forces moisture toward the cold outer surfaces of the building structure, impermeable materials such as glass, steel, plastic and traditional aluminium sarking materials cannot allow it to escape. As a result, there is a risk that condensation can form on the inside of the building, just as mist or droplets of condensation form on the inside of a window on a cold night. To minimise this risk, the ProctorWrap membranes allow moisture to easily pass through the sarking with minimal resistance, allowing any condensation formation to occur on the outside of the building as shown in Figure 1. Water ingress from outside is shielded by ProctorWrap Gyprock Plasterboard Vented external cavity Bradford Gold Insulation ProctorWrap Water vapour from inside the home passes through the Gyprock Plasterboard, Bradford Gold insulation and ProctorWrap where it can safely form on the cladding or be removed by ventilation or drainage Figure 1: Moisture passes through the ProctorWrap membrane Bradford Proctorwrap 3

4 CONTROLLING CONDENSATION RISK The condensation solution let your building breathe Unlike traditional foil faced sarking materials, the high water vapour permeability of the Bradford ProctorWrap range of vapour permeable membranes allow for the controlled escape of moisture from within a building structure whilst restricting the ingress of liquid water and dust from the outside environment. Controlling condensation is not necessarily about stopping condensation formation on cold surfaces, it s about controlling where on the building envelope it forms. Ideally condensation should form on the outside of the building structure but as insulation becomes more effective at keeping the warmth inside the building envelope, the position of this condensation surface is changing. ProctorWrap membranes allow the condensation surface to be designed into the building envelope and controlled. Positioned on the external side of the building frame, with the cladding spaced from the membrane to allow a drainage path for moisture, ProctorWrap membranes position the condensation surface beyond the building frame and insulation. With exceptionally high levels of vapour permeability combined with high water hold-out when joints are taped and lapped, the ProctorWrap range allows moisture inside the building to escape without compromising airtight designs. Measuring vapour permeability Vapour permeability is measured as micrograms of water vapour that can pass through 1m² of material under 1 Newton of vapour pressure differential in 1 second, expressed in units of measure as μg/ns. The higher the value, the greater the amount of moisture that can migrate through the membrane. A good quality vapour permeable membrane should also be classified as a high water barrier according to AS/NZS :1994 in order to function as a sarking material. Beware of unclassified products or those that do not clearly state compliance to AS/NZS :1994, particularly if the product is required to function as a sarking that is a vapour permeable membrane and a water barrier. Vapour Permeability of sarkings (μg/ns)* Vapour permeable foil faced foam (6.5mm) Wall Breather Thermakraft Cover Up Tyvek Homewrap ProctorWrap BL ProctorWrap HT-R ProctorWrap CW ProctorWrap RW *In accordance with AS Bradford Proctorwrap

5 SELECTING THE RIGHT PRODUCT If you need additional information or assistance in selecting the right material for your project please contact CSR Bradford on APPLICATION roof Commercial and residential PRODUCT High tensile roof (HT-R) ProctorWrap HT-R is a highly durable, UV stabilised high water hold-out vapour permeable roof underlay for use in residential or commercial tiled, slate and metal roof applications. It has been designed to meet the compulsory and stringent AS/NZS requirement for classification as a medium duty membrane for use under tiled and metal roofs. wall Residential Residential wall (RW) ProctorWrap Residential Wall (RW) is a light duty * vapour permeable wall wrap designed for use in residential timber and steel frame wall construction. ProctorWrap (RW) is a durable and lightweight textile membrane with a soft construction designed to reduce noise when exposed to the wind, even when exposed to coastal regions. wall commercial Commercial wall (CW) ProctorWrap Commercial Wall (CW) is a light duty *, triple layer construction, vapour permeable wall wrap designed for use in commercial steel and timber frame wall construction behind claddings that are not water tight and allow ingress of wind driven rain. ProctorWrap CW can be left exposed for up to 2 months during construction, offering temporary rain screen protection to allow other trades to continue work whilst the external cladding is applied. exposed joint wall and roof commercial and residential black label (bl-it) ProctorWrap Black Label (BL-IT) is a high water hold-out, vapour permeable membrane with a unique functional coating that offers excellent resistance against UV and high temperatures up to 120ºC. Developed primarily as a vapour permeable underlay for use under solar panels and behind open joint rain screen facades, ProctorWrap BL-IT offers a combination of durability and high water holdout without compromising vapour permeability. Note: This product is supplied with integrated tape (IT) already installed for fast and secure taping of lap joints. High Performance Adhesive Tapes High Performance Adhesive Tapes The range of ProctorWrap tapes are designed to complement the ProctorWrap products by offering high initial tack and excellent long term adhesion properties. Where required and specified in the product Installation Guide, it is always recommended that only ProctorWrap tapes are used with ProctorWrap products. * Light duty: Based on burst strength criteria set out in AS Bradford Proctorwrap 5

6 PRODUCT FEATURES OVERVIEW Please refer to the individual product Data Sheets or contact CSR Bradford for more detailed technical information. features Compliant: Meets or exceeds Australian Standards & the Building Code of Australia Low Flammability Index 5: Suitable for use in Bushfire zones and BCA building projects High UV resistance: Specifically designed for Australian conditions and able to withstand exposure to UV during construction * High vapour permeability: Allows moisture to easily escape from inside the building High water resistance: Prevents water and dust from entering from outside the building Durable construction: Flexible spun bonded polyolefin membranes Quality: Manufactured in Europe to specifically meet Australian Standards Full range of complementary tape products benefits AS/NZS compliant solutions for wide range of roof and wall construction types. No greater than 5 (when tested to AS1530:2) which permits the application of these products in almost all bush fire attack levels (BALs) in accordance with AS3959: Prevents damage or degradation of the membrane when left exposed to UV light during construction, even in the harsh Australian climate. Refer to the table below for individual product performance. Vapour permeability of over 2.5μg/N.s (vapour resistance of no greater than 0.4 MNs/g) when tested in accordance with AS Water resistance equivalent to over a 2m hydrostatic head. Designed to protect insulation and the building structure from wind-driven rain and dust during and after construction. Manufactured in conformity with EN :2 under ISO 9001 and ISO approved quality, safety and environmental management systems. A full range of high tack ProctorWrap adhesive tapes are available for taping lap joints and penetrations or repairs. * Excludes ProctorWrap RW which is 1 month maximum exposure. technical product overview Description Test Method Unit Residential Wall Commercial Wall High Tensile Roof Black Label Duty classification Water barrier AS/NZS AS AS/NZS AS Light * Light * Medium Light * High High High High Vapour permeability ASTM E96 μg/n.s Vapour resistance ASTM E96 MN.s/g Burst strength AS N >200 >250 >500 >480 Shrinkage AS/NZS % <0.5% <0.5% <0.5% <0.5% Flammability index AS Low 5 Low 5 Low 5 Low 5^ UV exposure prior to cladding Manufacturers recommendation 1 month 2 months 2 months 4 months * Duty classification is based on burst strength ^ Sections of membrane without integrated tape 6 Bradford Proctorwrap

7 Insulation and ventilation R-Value Contribution of Membranes verse Reflective Sarking Like most sarking membranes, the ProctorWrap membranes are thin materials that do not contribute any material R-value to the construction. Reflective foil laminate materials that promote an R-Value, rely upon a still air cavity (an air void in the structural building frame) to create an R-Value that relates to the specific thickness of the air gap as part of the total wall or ceiling system. is filled with bulk insulation, as there is no loss in R-Value in comparison with an assembly using a reflective foil sarking in the same location. Where the frame is filled with bulk insulation and there is no air gap between the sarking and the insulation it should be noted that there is no opportunity for either reflective sarking or vapour permeable membrane to contribute a reflective space R-Value. In walls where light weight cladding is directly fixed to the frame or where a single sided reflective foil laminate is used there is no difference in R-Value whether using a reflective sarking or non-reflective membrane such as ProctorWrap. The same applies when the frame ventilation of roof spaces is part of the Condensation solution Whilst vapour permeable membranes provide a path for the transfer of moisture, buildings must be adequately ventilated in order to allow effective carriage of the moist air from inside the structure to outside. The type and location of ventilation can be a complex issue requiring consideration of both the ventilation of the interior space and building cavities. Interior Ventilation: Occupant comfort is a key consideration for interior ventilation and the level of interior ventilation can influence the relative humidity of the interior environment. Without specific ventilation to manage this humidity inside the building, the water vapour generated as a result is then likely to enter the building envelope through the various gaps and leaks in the building structure. Building Cavity Ventilation: Wall and ceiling cavities into which humid, moist air from the interior leaks into then become the most likely areas within the building structure where condensation will form. Natural and mechanical ventilation within wall cavities and the roof space can reduce condensation risk and aid in the drying of any moisture that potentially does form. To assist in condensation control in ceiling cavities, CSR Bradford recommend the use of Edmonds Windmaster or SupaVent, natural wind powered ventilators for residential applications and natural powered Hurricane or hybrid powered ecopower ventilators for commercial applications. Wall cavity ventilation can be effectively managed by battening the external cladding away from the building structure which provides a drainage and drying passage for any condensation that does form on the outside of the vapour permeable membrane. For more information on CSR Edmonds ventilators, visit roof sheet gets cold heat moisture Condensation control in roofs Bradford Proctorwrap 7

8 HOW TO SPECIFY ENVIROSEAL PROCTORWRAP How to specify ProctorWrap The vapour permeable membrane shall be Bradford ProctorWrap (specify product type, eg commercial wall = CW) having a vapour permeability of μg/n.s (specify permeability as μg/n.s) and duty classification of (specify duty classification) as tested in accordance with AS/NZS :1994. TECHNICAL SUPPORT CSR Bradford offer a range of technical services including condensation modelling for project or climate specific applications, as well as general product and project technical support. For more information please contact CSR Bradford on or bradfordwebenq@csr.com.au bradford construction fabrics check out our other products thermoseal Residential and Commercial vapour barrier products. For more information call or visit CSR Bradford Locked Bag 1345 North Ryde BC NSW 1670 Telephone Facsimile (02) CSR Bradford is a business division of CSR Building Products Limited ABN The contents of this brochure are copyright protected and may not be reproduced in any form without prior written consent of CSR Bradford. Recommendations and advice regarding the use of the products described in this brochure are to be taken as a guide only, and are given without liability on the part of the company or its employees. We reserve the right to change product specifications without prior notification, please refer to the CSR Bradford website for the latest revision of this document. The purchaser should independently determine the suitability of the product for the intended use and application. Publish date: 07/13 Doc Ref: B0033