Cladding life cycle calculator

This Issue This is a part of the Building envelope feature

By - , Build 114

The BRANZ website has an updated tool to compare the life cycle costs of various common wall claddings. Environmental impacts can be combined with the cost data to arrive at an overall score for different claddings.

Figure 1: Menu of the BRANZ wall claddings life cycle analysis tool.
Figure 2: Using the wall cladding tool with 70% weighting to life cycle costs, as in Figure 1, has clay brick as the preferred material.
Figure 3: Life cycle costs have been reduced to 10% weighting and sustainability factors increased to 30% each. The discount rate remains at 5%. Timber weatherboard is now the preferred material.

Developed for designers, the updated 2009 version of the BRANZ wall claddings life cycle analysis tool provides data on environmental impacts of common wall claddings used in domestic buildings in New Zealand. Both the initial and life cycle costs of the claddings are provided.

The calculator tool can compare up to five claddings at one time, and the discount rate can be changed, which affects the life cycle costs. A high discount rate reduces future maintenance costs and hence penalises claddings with low on-going maintenance requirements

The tool is an Excel spreadsheet that can be downloaded free. Figure 1 shows the menu.

Sustainability also considered

There is no right answer for the choice of a cladding material – people have different priorities of costs and sustainability impacts. The calculator allows factors other than costs to be included in the cladding choice. Embodied energy and CO2 emissions in the manufacture and maintenance of the cladding can be included, as well as the recyclability of the material.

Users choose what matters

Each cladding is rated, within the software, on its characteristics – cost, embodied energy, CO2 emissions and recyclability. Users cannot change these parameters, but can select how important each is in their cladding choice. For example, a user may decide that life cycle costs have a 70% weighting and the other three factors share the other 30% weighting.

Figure 1: Menu of the BRANZ wall claddings life cycle analysis tool.

A typical set of results is shown in Figures 2 and 3. In Figure 2, clay brick is the preferred material of the four selected. When the weights are altered more to sustainability characteristics and less to costs, the material rankings change (see Figure 3). Previously, clay brick ranked best but now timber weatherboard becomes the preferred material.

Other considerations, such as aesthetics, are also likely to influence the decision, but the tool does not allow for this. Scoring materials on the basis of appearance is subjective, whereas data is available for costs, embodied energy and CO2 emissions, and approximate quantitative assessment has been made by BRANZ on the recyclability of materials.

Figure 2: Using the wall cladding tool with 70% weighting to life cycle costs, as in Figure 1, has clay brick as the preferred material.
Figure 3: Life cycle costs have been reduced to 10% weighting and sustainability factors increased to 30% each. The discount rate remains at 5%. Timber weatherboard is now the preferred material.

For more

To use the tool, go to www.branz.co.nz/wall_claddings_tool and download the Excel spreadsheet to your computer.

Download the PDF

Articles are correct at the time of publication but may have since become outdated.

Figure 1: Menu of the BRANZ wall claddings life cycle analysis tool.
Figure 2: Using the wall cladding tool with 70% weighting to life cycle costs, as in Figure 1, has clay brick as the preferred material.
Figure 3: Life cycle costs have been reduced to 10% weighting and sustainability factors increased to 30% each. The discount rate remains at 5%. Timber weatherboard is now the preferred material.

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