How to set lifespans
Purpose
Section titled “Purpose”Specify how often a building product is replaced over the assessment period (module B4).
Prerequisites
Section titled “Prerequisites”The building product has been added to a construction in the building model.
- Find the building product in the building model tree, and see the Lifespan column.
- If the lifespan isn’t already set from the library, enter it in years (RSL: reference service life).
- If the value falls outside the lifespan table’s normal range, the app shows a warning: check the value.
Result
Section titled “Result”The building product is replaced every time its lifespan runs out within the assessment period. If the lifespan runs out exactly when the period ends, that does not count as a replacement. The number of replacements in module B4 is therefore:
With an assessment period of 50 years:
| Lifespan | 50 / lifespan | Replacements | Replaced in year |
|---|---|---|---|
| 20 years | 2.5 | 2 | 20 and 40 |
| 25 years | 2 | 1 | 25 |
| 30 years | 1.7 | 1 | 30 |
| 50 years | 1 | 0 | None |
If the lifespan is missing entirely, replacement is left out of the calculation, not the same as setting lifespan to 0.
Lifespan 0 is a different thing from a missing lifespan. Lifespan 0 resets all impacts on the building product, but only in calculation mode BR18 (2023). Don’t confuse the two.
BUILD’s lifespan table
Section titled “BUILD’s lifespan table”BUILD’s lifespan table is used to set lifespans for building products in an LCA, as described in section 297(7) of the building regulations. The table distinguishes between an average lifespan for the building element and material-specific lifespans:
| Value | What it describes |
|---|---|
| Average lifespan | The building element’s functional lifespan regardless of the specific material. |
| Material-specific lifespan | The building element’s lifespan when it is made with the selected material type. |
Choose the material-specific lifespan when the building product matches a material type in the table. Otherwise, use the average lifespan. Enter the selected value in years in the Lifespan column.
If you open the lifespan table from a building product, it is pre-filtered to the building elements the product can belong to, so you find the right row faster.