An environmental impact comparison of external wall insulation types

• An LCA comparison of 3 external wall insulation materials: phenolic foam, EPS and rockwool.
• Embodied carbon comparison expanded to also include PIR and woodfibre board.
• Paybacks for each impact category estimated based on a simplified case study.
• Data and comparison provided is useful for retrofit decision making.

A large proportion of existing buildings require thermal efficiency improvements to the building fabric. One method which can be utilised is external wall insulation. It is important for designers to have a good understanding of the materials that they specify and this includes the initial environmental impacts that occur from extraction, processing and manufacture of insulation. This paper quantifies and compares the environmental impact of three insulation materials: expanded polystyrene, phenolic foam and mineral wool insulation. It was found that expanded polystyrene had the lowest environmental impact in fourteen of the sixteen impact categories examined. When applied to a typical dwelling, all three insulation materials demonstrated a net positive benefit over a thirty year life span due to the reduced heating requirements of the building. A study of embodied carbon also included PIR and woodfibre boards. This demonstrated that woodfibre board had the lowest embodied carbon, mainly due to carbon sequestration. Modest savings (e.g. 115 kgCO2eq if EPS is used instead of phenolic foam) can be made from insulation choice for a single house but these savings become much more significant if scaled across the large number of UK homes that would benefit from external wall insulation.