Irrespective of the circumstances the complexities of choosing the correct roofing material can be broken down ad expressed as the optimum balance of design, requirements, longevity, sustainability as well as cost.
Environmental impact and sustainability
Of the five main materials PVC is widely acknowledge to be the most long lived and durable. At time of writing over 80% of all the single ply roofing material in the UK is PVC based, which says much about its utility. However, it is considered the least environmentally sound because of the presence of chlorine and other substances. Conversely, if it were substituted properly many of its components can be recycled and converted to other applications in alternative single ply roofing systems.
A substance known as EPDM which is the mainstay of domestic roofing systems cannot be recycled and can only be reused if it is originally set down in mechanically fixed loose layers. Having a roof constructed in this way would clearly defeat the whole point of the exercise. A polymer known as TPO is as durable as PVC but does not contain chlorine or plasticising substances and can be itself recycled and made from recycled materials.
However, it can only be installed after cleaning with solvents. This last factor brought forward the necessity for the alternative TPE. From an environmental point of view PIB with its ISO 14040 standard is the most environmentally sound single-ply roofing material.
Cost of materials
Clearly, there is a strong element of completion and an onus on the end user to play the market and secure for themselves the best possible deal. It must be remembered that although cost is “a” factor it is rarely “the” factor, the performance of the materials of which the roofing sheet is made will often over ride pure cost considerations. In General Terms EPDM is likely to be the cheapest material and PIB the most expensive, with PVC, TPO and TPE situated somewhere in the middle.
Longevity of materials
The quality of materials is always evolving, such that new products are always coming on stream and innovations to existing materials continually present themselves. Overall, PIB will last for between 30 and 50 years, which partly explain its cost. The useful life of PVC sheet depends on its chemical composition but a quality product will last for between 25 and 45 years.
The relatively recent TPO and TPE will last for a minimum of 40 years but as with PVC the potential costs in sound reusing and recycling methods must be factored in to the decision to use them. Furthermore, the actual projected lifespan of the building its self and whether or not the roofing project is a new build or refurbishment must be considered. Finally, the end user is advised to check the credentials of both the product and the contractor installing it.
As can be seen a clear and definite trade-off between several of intertwined factors exists. There are no clear cut boundaries and so the buyer must evaluate all variables in their own individual context.