When a building envelope comes to the end of its current life there are a number of options available to the building owner, designed to either extend its life further or ensure it is disposed of safely and with minimum impact both economically and environmentally, writes Corus.
The sustainability of a building in terms of its material usage, construction, occupation and end of life is becoming an ever more important consideration. This is driven by the need to provide a better quality of life for people and protect the needs of future generations. Many construction companies use the term “environmentally friendly” to describe their offering without providing any quantitative information or credible research to substantiate such claims. Whilst some information might be available to explain how the products are manufactured sustainably, few companies address what happens to the products at the end of their life. There are several options available to either extend a building’s life or ensure it is disposed of safely.
- Refurbishment – Refurbishing buildings offers a sustainable approach to achieving new facilities without the full cost of new build, effectively extending the useful life of the building and so minimising the impact of the resources used.
Refurbishment may be undertaken for purely aesthetic reasons, in which case it results in an improvement in the working and social environment, or for functional reasons, such as to upgrade insulation. In all cases, effective use is made of still-functioning aspects of the building, only replacing those which have gone beyond their useful life, and thereby minimising both the work carried out and the use of resources. Buildings using pre-finished steel cladding systems are ideally suited to refurbishment – whether it be for aesthetic or functional reasons. There are a number of refurbishment options available including overpainting, overcladding and recladding of damaged areas.
- Re-use – Where building materials are to be disposed of, re-use is generally the lowest impact option, both financially and environmentally. With careful dismantling and removal it is possible to re-use some of the materials used in the original construction. The European Commission Life Cycle assessment for steel construction1 states that while around 10% of total construction steel is re-used, 15% of the cladding sheets removed from buildings during the demolition process enter the market for re-use.
For a number of years, the agricultural sector has provided a market for the re-use of pre-finished steel clad buildings, particularly for portal frame sheds. By contrast, the re-use of roof and wall cladding systems within the commercial and industrial sector is less common. This is mainly because of aesthetic problems with second hand cladding, the impact of different panel lengths and purlin spacing and the limited likelihood of achieving full regulatory approval where re-used materials are used extensively.
- Recycling – Wherever possible, if construction waste cannot be re-used, as much as possible of it should be recycled to re-enter the supply chain at the manufacture stage.
Research suggests that overall 84% of construction steel is recycled while only 6% of steel cladding enters landfill. The means and costs of recycling and disposal for built-up and composite cladding systems vary significantly. However, in each case, the main aim is to recycle as much as possible, which requires effective separation of the steel components from the remainder of the system.
The recycling of built-up systems is relatively straight forward. The two key elements to consider are the pre-finished steel outer and inner sheets and the mineral wool or glass fibre insulation. These two elements are readily separated during the demolition process so that the steel can be recycled without further processing. The positive value of the steel scrap more than offsets the costs of disposal of insulation, giving a marginally positive overall value to the operation.
Steel scrap recycling
The steel industry has been operating steel scrap recycling on a large scale for more than 150 years. Recycling of steel scrap has always had economic as well as environmental advantages for the steel industry, saving resources and energy.
The steel recycling infrastructure is very efficient and all the steel in collected end of life products is recycled. Products that are easy to disassemble, with easy to separate steel parts, such as pre-finished steel from built-up systems, have a greater potential to be recycled. The steel can be recycled indefinitely without any downgrading.
Recycling of factory insulated foam filled composite panels
Increasing pressure to develop environmentally robust and cost effective recycling routes is expected over the next five years as significant amounts of buildings constructed using factory insulated foam filled composite panels reach the end of their life.
By their very nature, composite panels present a greater challenge at end of life than built-up systems, since the components are adhesively bonded together. To achieve the optimum solution for disposal, the foam core and steel sheets need separation, but the presence of gases known as blowing agents in the core can complicate this, depending on the blowing agents used. Due to their relative bulk in comparison with their weight, whole factory insulated foam filled composite panels are not suitable for charging directly to the steel-making processes. Manually separating the outer sheets from the foam core and recycling the steel and foam separately is not generally a viable option due to the level of manual labour involved and the potential release of blowing agent gases.
Legislation on the disposal of foams blown with Ozone Depleting Substances (ODS) states that where practicable, the ODS gases should be collected and disposed of safely. This legislation has had a significant effect on the disposal of fridges, but is equally applicable to foam filled composite panels produced before 2004, since these blowing agents have been banned. It should be noted that if the blowing agents used in the panels are unknown then the panels must be treated as if they contain ODS. For this reason it is important that good quality records are kept in all cases. As a result, factory insulated foam filled composite panels in buildings reaching the end of their lives require a different approach to recycling and disposal than built-up systems. This also needs to take into account the type of blowing agents used in the manufacture of the foam.
The options for consideration are:
- Fragmentation /shredding.
- Fridge recycling.
- High temperature incineration.
Recycling of factory insulated mineral wool composite panels
The amount of mineral wool composite panels used for cladding, predominantly on walls, has risen in recent years. Two methods of recycling these panels are currently available, steel scrap recycling and fragmentation. Steel scrap recycling would involve manually separating the outer and inner sheets and recovering the steel scrap for recycling. The mineral core would be landfilled or returned to the mineral wool manufacturer for recycling. The practicalities of this manual process for end of life disposal would only lend itself to the treatment of relatively small volume of factory insulated mineral wool composite panels.
Fragmentation would involve using the shredder route is more appropriate for larger volumes of mineral wool panels. As the mineral wool panels contain no blowing agents, they can safely be handled through the fragmentation route. The steel could be recycled effectively and the mineral wool landfilled along with the other automotive shredder waste. Any future requirement for recycling of the mineral wool core could potentially be accommodated by dedicated shredding facilities if volumes of the panels for recycling were sufficient. Additionally, mineral fibres recovered from fibre-cored composite panels are generally clean and so suitable for recycling themselves.
1. The European Commission, 2002, Life cycle assessment for steel construction Report EUR 20570 EN.