Design for sustainability practice questions.

A kettle manufacturer reduces the mass of polymer in its packaging by 20 per cent but changes nothing about the kettle, its supply chain or what happens to it at the end of its life. Which term best describes this approach?

• Sustainable design, because the full life cycle has been re-evaluated
• Green design, a single-issue improvement to an existing product
• Design for disassembly, because fewer parts have to be separated
• Circular design, because the packaging returns to the producer

Answer: Green design, a single-issue improvement to an existing product

Green design tackles one measurable issue on a product that otherwise stays as it is, whereas sustainable design reworks the whole system of materials, use and end of life against social and economic criteria as well. Reducing one input is a useful step but does not make the design sustainable.

A furniture workshop is deciding whether to buy its oak from a local estate or from an overseas supplier. Which consideration belongs to the social pillar of sustainability rather than the environmental or economic pillar?

• The transport distance from the forest to the workshop
• The purchase price per cubic metre of the sawn boards
• The working conditions of the people who fell and saw the timber
• The rate at which the woodland regenerates after each felling cycle

Answer: The working conditions of the people who fell and saw the timber

The social pillar covers the people affected by a design decision: labour conditions, health, skills and community impact. Transport distance and regrowth rate are environmental measures and price is economic, which is why a decision can score well on one pillar and badly on another.

After a town fits low-energy lamps that use one fifth of the electricity of the old ones, residents leave more lamps on for longer and the measured electricity saving is far smaller than predicted. Which concept explains this outcome?

• Planned obsolescence, where a shorter service life is designed in
• Greenwashing, where an environmental claim cannot be supported by evidence
• Dematerialisation, where the same service is delivered with less material
• The rebound effect, where efficiency gains are offset by greater use

Answer: The rebound effect, where efficiency gains are offset by greater use

Efficiency lowers the cost of a service, and cheaper services tend to be consumed in greater quantity, so part of the technical saving is spent again by the user. This is why a designer cannot convert an efficiency figure straight into a predicted environmental saving.

A phone case is re-released each season in new colours while the mould, the material and the protection it gives stay unchanged, and retailers stop stocking the earlier colours. Which form of obsolescence is being used?

• Aesthetic obsolescence, driven by fashion rather than function
• Functional obsolescence, because the product no longer works and cannot be repaired
• Technological obsolescence, because a newer technology has superseded it
• Economic obsolescence, driven by repair costing more than replacement

Answer: Aesthetic obsolescence, driven by fashion rather than function

Nothing about the product's performance has changed, so the older case is discarded only because it looks dated; that is style or aesthetic obsolescence. Functional obsolescence means the product has stopped working or its parts are no longer available, and technological obsolescence means a newer technology has overtaken it.

A council specifies oak benches for a park and wants written assurance that felling in the source forest does not exceed regrowth. Which requirement in the specification delivers that assurance?

• Timber that has been kiln dried to a moisture content below 12 per cent
• Timber treated with a preservative to resist fungal attack outdoors
• Timber from an independently certified sustainably managed forest
• Timber cut from a fast-growing softwood rather than a tropical hardwood

Answer: Timber from an independently certified sustainably managed forest

Only third-party certification of the forest links the delivered board back to a documented management regime; the other requirements describe the condition or species of the timber, not how the source is managed. A renewable material is not automatically a sustainably sourced one.

A canteen has already removed every takeaway container it can do without and now ranks what to do with the containers it still needs. Which pair of measures is ordered correctly from higher to lower in the waste hierarchy?

• Washing and refilling the containers, then granulating them into new mouldings
• Granulating the containers into new mouldings, then washing and refilling them
• Burning the containers with heat capture, then granulating them into new mouldings
• Sending the containers to landfill, then burning them with heat capture

Answer: Washing and refilling the containers, then granulating them into new mouldings

Below prevention the order runs reuse, then recycling, then recovery, then disposal, so refilling an intact container outranks reprocessing its material and heat capture outranks landfill. Each of the other three pairs inverts one of those steps.