How do you do whole life costing?
Whole life costing requires the specifier (client) to define what they want from the asset they are asking the delivery team to provide. This means that we need to move towards performance specifications of assets rather than prescriptive specifications.
The design team have a requirement for vertical circulation between 2 floors and have a physical space to accommodate it. The usual solution is for the architect to decide the size and number of lifts, draw the shafts and the quantity surveyor asks the supplier(s) for quotations.
In the WLCF whole life costing methodology the architect defines the physical aspects of the requirement such as the space available on each floor and the floor-to-floor distance. They then detail the performance requirements such as the maximum hourly traffic in one direction of, for example, 500 people per hour, and that the lifts will operate for 18 hours a day, and providing the expected traffic at each hour. Selected suppliers are then asked to deliver their whole life costed solutions.
In an actual example of this type, several solutions were presented, each offering different benefits.
The supplier offered several options for a 25 year life:
2 x 30 people lifts travelling at 0.5m per second at £100k capital and £150k cost in use.
WLC £250 000
3 x 20 people lifts travelling at 0.75 m per second at £120k capital and £150k cost in use.
WLC £270 000
In a traditional, capital focused, project it is likely that Option one, with the lower initial capital cost, would be selected. However, the client required minimum waiting time for the lift users as one of his key KPIs (Key Performance Indicators) and when the cycle times were analysed the 3 x 20 lift was the most suitable.
This is not the end of the story, as the design team were consequently able to work with the lift supplier to optimise the service and maintenance regimes across 3 lifts and reduce the cost in use by £30000 giving a total WLC of £240000.