IVL Swedish Environmental Research Institute

The use of chemicals in construction products and risk mitigation is an area that is often attached to material selection. Wood preservatives are used to increase the durability of the wood, so that it can be applied in fields that otherwise would not have been possible. The use of wood preservatives is regulated by the Biocides Products Regulation and requires a national approval from the UK’s Health and Safety Executive (HSE). Concerning the efficacy requirements, so far retention levels for the different wood preservatives have been stipulated by the manufacturer and given as a recommendation to the user. Currently a working group within the Wood Protection Association (WPA) is working on an independent system for data requirement and application procedure for the approval of wood preservatives. This investigation presents a life cycle assessment (LCA) on pressure treated timber according to BS 8417 and using Wolmanit CX-10 . The analysed product category in the case study are two fence designs including pressure treated timber and an alternative post and rail material of plastic, and untreated ‘natural durable’ wooden posts made of UK home grown European larch and Siberian larch (from Siberia). The LCA methodology applied, including the environmental impact indicators, use the requirements prescribed by the Product Category Rules (PCR) for all construction products as defined in EN 15804. This so called Core PCR is used as guideline for environmental product declarations (EPD) and is linked to the construction products regulation (CPR). The purpose of this study is to evaluate how these requirements can be used and to evaluate the environmental performance, with respect to selected and mandatory impact indicators in the EPD. Calculations showed that BS 8417 use class 4 treated timber, with a retention for 15 year service life and 30 year service life, has a better environmental performance, in comparison to the alternative materials used for the assessment. Uncertainties in the choice of service life prediction data exist in relation to plastic posts, but also to some extent to posts of larch. These differences determine the relative ranking between the investigated Siberian larch and respective plastic fences. The study has taken into account all environmental impact categories, which are required to be included in accordance with EN 15804 apart from resource use, since assessment methods for renewable materials is not available. This impact category has therefore been excluded from the study, as it would render a comparison incomplete with respect to the plastic alternative. Consequently we find a need to develop better methods for resource use in the future. Since human toxicity and ecotoxicity are not found among the mandatory environmental impact categories included in the LCA, in accordance with EN 15804, these aspects are not included in the study, and here we also find a need for future developments.

This report is only available in English.