Building LCA – Alternative designs resulting in options for single or multiple group elements

Alternative designs – single group elements

When undertaking option appraisal, projects may choose to explore discrete alternative designs that significantly affect only a single group element (either superstructure, substructure, hard landscaping or core building services). For example, a change from external timber cladding to aluminium cladding is a discrete change to the superstructure if it has no significant effect on the substructure, hard landscaping or core building services. This is more likely where the design of other group elements is largely fixed, or where each group element is being designed in relative isolation (e.g. by different designers). This approach is acceptable but is less likely to result in a holistic analysis of the project and may be limited in improving environmental performance.

For this approach, the alternative design forms the basis of an option for the relevant group element section in the Mat 01/02 Results Submission Tool only (note: more than one change can be included per option).

Alternative designs – multiple group elements

Alternative designs that affect more than one group element are acceptable and, being more holistic, are encouraged for options appraisal. They are more likely to result in differences to the overall building design, rather than a discrete aspect of it. As such, greater insight may be gained into the environmental performance of the overall building and how to reduce it – the purpose of building LCA.

However, as more than one group element is affected, the scale of modelling and analysis work is likely to be greater. In addition, to be meaningful, alternative designs of this nature typically require building LCA to start earlier in the design process. Therefore, it is acceptable for the same alternative design to form the basis of options in more than one group element section of the Mat 01/02 Results Submission Tool – providing each option is significantly different from the other options in the same group element section (as per the requirements in the technical manual). This is illustrated below.

Alternative design explored Resulting in significant differences for the following group elements Significantly different change(s) listed in the Mat 01/02 Results Submission Tool

(illustrative only: Not detailed, not exhaustive)

Removal of occupied basement. Addition of extra upper floor Superstructure Building 1 storey taller
Substructure Removal of retaining walls
Core building services Primary plant moved to roof from basement. Changes to distribution layouts
Structural grid changed from 7.5m to 9m Superstructure Relocation and resize of columns and beams
Substructure Relocation and resize of piles
Change from HVAC to natural ventilation Superstructure Floorplate depth reduced from 25m to 15m
Substructure Relocation and resize of piles
Hard landscaping Relocation of surrounding road and paths
Core building services Change from HVAC to natural ventilation
Change from a refrigerant distribution-based system to an air distribution-based system Superstructure Changes to cores and floor-to-floor dimension
Core building services Change from a refrigerant distribution-based system to an air distribution-based system

 

For clarity, where an alternative design affects more than one group element (such as the above examples) and forms the basis of changes listed for different group element options, the link between them should be detailed in the Mat 01/02 Results Submission Tool. This is illustrated below.

β€˜Description of differences between superstructure options’ (sheet name)

Example of an alternative design listed as the sole change (ID 2)

Example of an alternative design change plus another subsequent change (ID 3).

β€˜Description of differences between substructure and hard landscaping options’ (sheet name)

Example of an alternative design listed as the sole change (ID 7).