TIMBER TALK
REALISING THE TRUE U-VALUE OF YOUR TIMBER FRAME The aluminium foil forms a radiant barrier when facing a ≥20mm air space (≥13mm in roofs) creating a low emissivity cavity which significantly reduces heat loss. Protect VC Foil Ultra raises the thermal resistance of the airspace from 0.18m2K/W to 0.78m2K/W in the wall (0.53m2K/W in the roof) when fixed as per standard timber frame practice/stud and rafter centres. This provides a significant thermal improvement to the construction without adding to the wall/roof thickness. The installation success of any AVCL is in the sealing of laps and junctions, not just the integrity of the membrane itself. Protect VC Foil Ultra is also available with integral “lap and seal” technology to ensure a full proof seal at the laps. It is now widely accepted that insulation plays a vital role in modern properties, in simple terms, improved levels of insulation and airtightness mean that more heat is retained within the building for longer at less cost – subject of course to good construction methods. Matt McAndry, Director of Technical at Building Product Design Ltd (of which Protect Membranes is a division) explains more. Design U-values can often be very different to those achieved ‘as built’. Research has shown that convection paths or gaps through the building construction can lead to significant heat loss as well as mass moisture vapour migration with the associated risk of harmful condensation forming. Therefore, to truly gain the best performance from any insulant, the aim is to deliver an air and vapour control layer/barrier on the warm side. Timber frame has been traditionally designed with an integral air and vapour layer (AVCL) in the form of the polythene sheet on the warm side of the insulation. The need to maintain the integrity of the AVCL to prevent it being compromised by penetrations has led to the widespread use of a service cavity between this layer and the internal lining boards. Protect VC Foil Ultra, an air and vapour control membrane, with its high purity, solid aluminium foil facing and tough nonwoven spunbond core, combines the necessary AVCL qualities with low emissivity technology
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Protect Membranes have also applied their low emissivity reflective technology to the breather membrane, Protect TF200 Thermo, which is fitted on the outer face of the sheathing board and provides a similar thermal improvement to the external air cavity. This combined Protect membrane solution can achieve an increase of up to 25% thermal efficiency, the equivalent of up to 60mm of 0.035 W/mK insulation to the wall U-value without adding to its overall thickness, thereby maximising the available floor area internally.
Both Protect VC Foil Ultra and TF200 Thermo are independently certified by BMTRADA through their Q Mark certification scheme. The Protect membrane solution is completed with a complementary range of high tack, untearable adhesive tapes. The “lap and seal” range ensures that junctions between walls and floors/ceilings are fully sealed, providing a cost effective solution to seal any necessary service entry penetrations or repair any accidental site damage. The key advantages of flexible air and vapour control membranes to the developer are ease and speed of installation, as well as the ability to facilitate a first fix air pressure test in order to provide an assurance of airtightness prior to the application of the internal lining. To the owner/occupier, the long term integrity of the air and vapour control layer and breather membrane will ensure that the full design benefits of a thermally efficient envelope and heating system are achieved. The reflective technology of both the Protect VC Foil Ultra and TF200 Thermo further enhances this benefit. As the industry looks forward to further regulations and standards targets to limit air leakage, we must also look more closely at our methods of construction. The designed air spaces available within timber frame construction provide developers with a rare opportunity to not only meet these requirements but to far exceed them without affecting their normal construction processes or significantly increasing costs. For more information: visit: www.protectmembranes.com info@protectmembranes.com Tel: 0161 905 5700
STRUC TUR AL TIMBER MAG A ZINE | ISSUE 05 | AUTUMN 2015