By using Roofshield, a roofing underlay that is both air and vapour permeable, the ventilation comes free as does the cost of buying and installing a vapour control layer.
As Roofshield is accepted by the NHBC without the requirement of ventilation or a VCL, even in cold pitched roof constructions, the choice of underlay becomes simple. Recent independent research shows that the use of Roofshield without ventilation or a VCL is the most economical choice. Things become even simpler when looking for the best vapour permeability, combined with the added benefit of air permeability – Roofshield is the only membrane that meets both these criteria.
For years the debate regarding how to achieve a truly ventilation free cold pitched roof has been held in many offices, committee rooms and building sites, but the industry is rapidly educating themselves about the subtle differences in roofing underlays performance. It is an inconvenient truth that air permeable membranes do significantly reduce condensation risk, because most manufacturers produce air tight membranes. Independent research reaching back to the early 2000’s including the PII (Partners In Innovation) findings by Caledonian University demonstrate the benefits beyond any doubt.
The majority now realise that not all underlays are the same. Roofing underlays come in all manner of different colours, but it’s what you can’t see that does most of the work – the middle layer. Whilst the colour of the top surface or underside is useful for identification, it is irrelevant in terms of performance. This middle layer can be likened to the same robustness as normal kitchen cling film and needs the protection of the sandwich construction to make this suitable and fit for purpose in a pitched roof. Taking a microscopic view of the middle layer clarifies the difference between an air tight and air permeable membrane. Fig.1 shows our Roofshield membrane, Fig.2 shows a typical air tight roofing underlay. The difference between air permeability and air tightness is fundamental to the products performance and use. In a traditional UK cold pitched roof construction, the large cold void above the horizontal insulation requires the quick release of vapour laden air that is reaching its dew point and potentially causing damaging condensation; Roofshield is certified by the BBA and accepted by the NHBC for use without ventilation or a VCL in even these most demanding circumstances. This is particularly advantageous in refurbishment projects where the installation of the VCL can lead to owners or tenants having to move out if a non-ventilated roof strategy is adopted.
When all the above is taken into consideration a sensible question that may be asked is “How do I know these new types of membranes work? “ Clearly this is an acceptable question, especially in a conservative market that can be resistant to change, however Roofshield has been on the market for nearly 20 years and is manufactured to the same exacting standards today as in 1996, a claim that many would not be able to make. A highly skilled technical department with several years’ experience in this field is always on hand to answer queries at any stage in the construction process.
The evidence is clear. If you are looking for a fail-safe roof that saves you money yet enjoys the highest performance in its class there can only be one choice, Roofshield.
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