The life cycle of a building or building product covers every phase of its existence: from extraction of the raw material, through manufacture, construction, use and maintenance, to demolition and processing of the material released. Looking only at build cost, or only at energy use, shows just one slice of that whole.
The concept matters in construction because many decisions are a shift rather than an improvement: extra insulation costs material and manufacturing energy but saves energy in use. Only by looking at the whole cycle can you tell whether the net result is a gain.
The phases in the European system
The European standards for environmental assessment of buildings and building products (EN 15978 for buildings, EN 15804 for products) divide the life cycle into modules:
- A1–A3 — product stage: raw material extraction, transport to the factory and manufacture.
- A4–A5 — construction stage: transport to site and the construction work itself, including construction waste.
- B1–B7 — use stage: use, maintenance, repair, replacement, refurbishment and energy and water use.
- C1–C4 — end of life stage: demolition, transport, waste processing and disposal.
- D — beyond the system boundary: the expected benefits and loads from reuse, recovery and recycling.
That division is what makes comparison possible: two products can only be compared fairly if they have been calculated over the same modules.
Life cycle assessment and EPDs
A life cycle assessment (LCA) quantifies the environmental impacts across those phases. For a building product this is recorded in an Environmental Product Declaration (EPD), published to a common set of rules so that figures are comparable.
The results feed into what is often called whole life carbon: the sum of embodied carbon (modules A, B1–B5 and C) and operational carbon (B6–B7). Increasingly, planning policy, funding schemes and certification systems require this to be reported. Which requirement applies where changes regularly — always check the current rules with the relevant authority or scheme.
Life cycle costing
Alongside environmental impact you can look at cost across the life cycle (life cycle costing, LCC, or total cost of ownership): purchase, energy, maintenance, replacement and eventual demolition. This regularly leads to different decisions from simply chasing the lowest tender price. A window that costs 20 per cent more but lasts twice as long and needs less upkeep is usually cheaper over forty years.
Applying it in practice
- Ask for EPDs, not marketing claims. A declaration states which modules were included.
- Watch the replacement cycle. Materials replaced every 15 years weigh heavily in the use stage.
- Design for disassembly. Reversible connections (screws instead of adhesive and sealant) raise the residual value in module D.
- Compare like with like. A cradle-to-gate assessment (A1–A3 only) is not a cradle-to-grave assessment (A through C).
- Maintenance is a design decision. A detail you cannot reach will not be maintained — and that shortens its life.
Related terms
- Sustainable building
- Circular economy
- External durability
- Durability class
- Building costs
- Reuse
Want to know more about building terms? Take a look at our knowledge base on fredsdiyplans.com.