The Sustainability of PVC

General

The two major systems used for domestic roofline and cladding application are timber and cellular PVC.  No assessment of the environmental credentials of PVC can be done outside the context of product and system comparisons between these materials.

In many applications timber is an excellent material that gives us elegant, functional and long lasting products that enhance our living environment. However there is a tendency within construction to uncritically assume that timber must be an environmentally excellent material for all applications to which it is currently put, because it is ‘natural’ and ‘renewable’.

This way of thinking diverts us from considering just how unsuitable and unsustainable low grade timber systems are for meteorologically exposed and physically inaccessible locations around the home.

At present it is not possible to prove conclusively superior sustainability credentials for either system. However we can say that in the context of resistance to the elements and the requirement for maintenance, there is a very strong case for Cellular PVC given that it lasts the longest, requires the least maintenance, costs the least over its lifetime, and has the most potential for recycling. Cellular PVC is therefore the most resource efficient.

Longevity

The Building Research Establishment (BRE) currently quotes a minimum reference service life of 35 years for PVC roofline products and windows. This has been determined by examining early window and roofline installations completed in the 1970’s.

The evidence shows that non-PVC components (eg. handles, hinges etc which are used on all windows and doors) are the main limitation on the life of units and not the PVC itself. In fact the PVC in the window frames and rooflines demonstrated no material change in performance after 35 years.

The case for a much extended service life for PVC rooflines, where there are no limiting non PVC components, is clear.

In the spring of 2006 Swish Building Products undertook an audit of some of its cellular PVC products that were installed over thirty years ago. None of the profiles surveyed had lost its protective functionality and all remained completely impervious to water.

Swish Building Products believes that the condition of these products, which are essentially made of PVC alone, is such that they could be expected to last many more decades before replacement becomes an issue.

In particular it is likely that the PVC rooflines will last longer than the 60 year service life used for the BRE’s Green Guide assessment. This will result in a much improved Green Guide rating.

Maintenance

Timber requires regular maintenance to combat the elements but is unlikely to receive the necessary attention for two major reasons:

Paint Systems -The majority of contract quality gloss paint systems currently available are unable to cope with the expansion and contraction characteristics of softwood for more than 3 years without losing their integrity, even when applied in the sequence and according to the method recommended by the manufacturer.

Microporous paint systems, which are more able to accommodate the daily movement of timber and the expression of water vapour that accompanies it, are expensive and detrimental to the contractor's bottom line. In addition, these paints must be applied from new and refurbished in the same materials in order to be effective in the long term.

Access - The roofline is not properly accessible via a standard roofer’s ladder system which is designed to allow work to take place on TOP of the pitched surface. Neither is it safe to employ traditional ladders when working in this area as the soffit overhang encourages the worker to lean away from the building and to put himself in jeopardy.

Safe access will therefore often require scaffolding or specialist cantilevered access decking. Without safe stable access, a painter cannot hope to fully protect the most vulnerable areas of the roofline, i.e. around and above the gutter brackets.

Lifetime Costs

The initial installed costs for PVC roofline are roughly comparable with those for timber. (Installed costs include materials, paint and labour). Where PVC scores heavily is in the minimal maintenance costs incurred during its service life.

For reasons already outlined above, timber must be regularly maintained to keep its looks and retain its integrity. If one assumes a regular four yearly maintenance cycle, then within the BRE minimum service life for PVC of 35 years, timber will have been repainted at least seven times.

Where social housing and privately rented accommodation is involved the landlord will be seeking to minimise maintenance costs and these ongoing charges will be unwelcome.

In reality it is rare that a landlord or indeed private house holder will keep up a strict maintenance regime. Even with an 8-year refurbishment cycle the lifetime costs for timber are high.

With an extended maintenance cycle the degradation of the timber is likely to take place sooner than otherwise expected and so a replacement of the substrate will need to be factored in a lot sooner.

Finally it is worth remembering that 35 years is the “reference” life expectancy for PVC roofline. The real expectation from Swish Building Products is that their products will last much longer.

Emissions

PVC products are inert and once manufacturing is complete they do not generate greenhouse gasses during their life time.

However timber inevitably requires the assistance of preservative coatings to avoid degeneration. The production and application of paint strippers, heat guns, primers, undercoats, gloss paints, and the manufacture of glass paper, paint brushes and a number of other accessories all contribute to CO₂ emissions during the maintenance cycle for timber.

Further greenhouse gasses are also produced in the transportation of labour and materials to and from site.

PVC is 100% recyclable

Manufacturing Waste

Within Swish Building Products, considerable investment has taken place to identify and recycle all production waste including start-up waste, damages and even saw dust from inline saws. Everything that can be recycled is recycled, and only under unusual circumstances is any material sent to land fill. On average, Swish cellular PVC products contain 8% recycled material.

Within the PVC construction products sector generally, recycling rates for production waste are high. A study conducted by AJI Europe in 2005 found that within the EU15, production waste from window and door manufacturers, represented less than 10% of their total output and 96% of that waste was recycled onsite.

Swish is part of a large building products group that owns a recycling facility which currently recycles approximately 18000 tonnes of off cuts from window and door per annum.

Post Consumer

Post Consumer recycling of PVC roofline and cladding systems is relatively simple. The only non-PVC components that require removal are stainless steel nails and screws. The boards can then be ground and pulverised in the same way that production waste is recycled..

The longevity of Swish cellular PVC roofline and cladding products has meant that to date there has not been any significant volume of post consumer material that has become available for recycling. Swish is part of the Epwin group of companies that owns PVC recycling facilities, and plans are in place to identify and attract this waste stream when eventually it begins to flow.

The European PVC Industry is currently funding several approaches to developing the infrastructure for post consumer recycling. These cover all types and qualities of PVC. Of most relevance to the construction industry is the Recovinyl scheme. It brings together recyclers and demolition/construction companies, providing a strong financial incentive to all parties to take part in the process rather than resort to land fill. The Recovinyl scheme has met all its growth targets to date and is firmly on track to meet the recycling targets made by the PVC industry in the Vinyl 2010 commitment.

Timber Recycling

Treated and rotted timber cannot be recycled but must be sent to land fill where it degrades and eventually gives up its ‘carbon store’.

This aspect of timber specification can easily be overlooked in the desire to embrace what is a natural material, and a renewable material, but is by no means the most sustainable material for this application.

Treated timber is classified as hazardous waste because of the chemical content of the preservatives used. It therefore requires special handling and disposal.