雅思阅读 125: Roofs That Breathe（会呼吸的屋顶）

改编自 European Commission Environment / MDPI Atmosphere（2026年）。雅思阅读 Section 3 难度，约 1050 词。 素材来源：https://environment.ec.europa.eu/news/how-green-roofs-improve-urban-life-boost-climate-resilience-2026-06-01_en

Reading Passage

A. On a summer afternoon, the asphalt and concrete roofs of a dense city absorb solar radiation until their surfaces reach temperatures that can exceed sixty degrees Celsius. That stored heat is radiated back out through the evening, keeping city air several degrees warmer than surrounding rural land — the phenomenon known as the urban heat island effect. As climate change makes heatwaves longer and more frequent, the heat island is no longer a seasonal discomfort but a public-health emergency: excess heat now kills more urban residents in Europe than any other weather-related hazard. In response, planners have turned to an old idea with a new urgency — covering roofs with living plants. Green roofs, long treated as a boutique architectural feature, are increasingly seen not as decoration but as infrastructure: a passive cooling technology that uses vegetation and soil to shade, insulate and evaporate moisture, replacing the thermal behaviour of a black membrane with that of a meadow. The idea is not new — ancient Persian and Roman buildings used planted roofs for insulation — but it is now being deployed at a scale that can move the urban temperature needle.

B. The physics of how a green roof works is simpler than it looks. A conventional roof is designed to shed water quickly and reflect what little radiation its pale surface can. A green roof reverses the principle: a layer of growing medium, typically fifteen to twenty centimetres deep, supports grasses, sedums or even small shrubs, and the plants intercept sunlight before it reaches the waterproof membrane beneath. Two cooling mechanisms dominate. First, evapotranspiration — the combined evaporation from soil and transpiration from leaves — consumes heat as water turns to vapour, exactly as human sweating does. Second, the soil layer acts as thermal mass, delaying the passage of heat into the building until night, when the roof can cool. The difference in surface temperature can be dramatic: a Polish study measured one extensive green roof at 57 degrees Celsius cooler than an adjacent bituminous membrane on a hot summer day. Moss-based systems trialled in 2025 reduced daytime rooftop surface temperature by six to ten degrees on average, while retaining a modest 1.5 to 2.5 degrees of warmth overnight.

C. The benefits extend well beyond the roof itself. Because rooftops occupy as much as 27.8 per cent of all impermeable surfaces in a typical built-up area, converting even a fraction of them can shift the city's thermal balance at neighbourhood scale. The European Union's LIFE-myBUILDINGisGREEN programme, which installed green roofs on schools across Spain and Portugal, measured indoor temperatures four to six degrees lower in summer and an 11 per cent drop in electricity use for cooling — a saving that matters both for household budgets and for grid stress during heatwaves. Stormwater management is the secondary dividend: the growing medium absorbs rainfall that would otherwise rush instantly into overloaded municipal drains, reducing flash-flood risk after intense downpours. A 2025 simulation of a dense Chinese neighbourhood found that combining cool roofs and rooftop greenery could reduce local heat-island intensity by up to 0.175 degrees at community scale, with the largest gains on flat roofs where installation is cheapest.

D. Not all green roofs are equal, and the distinction matters for cost. Extensive roofs use shallow substrate — as little as eight centimetres — planted with hardy, drought-tolerant sedums that need no irrigation, no fertiliser and almost no maintenance. They are light enough to retrofit on most existing buildings without structural reinforcement. Intensive roofs, by contrast, resemble rooftop gardens: deeper soil supporting shrubs and even trees, requiring regular watering and heavier structural load. They are usually built into new construction rather than retrofitted. The choice between them is not merely aesthetic. A 2025 review of Polish installations found that the thermal performance of different extensive green-roof compositions was remarkably similar regardless of plant species or substrate mix — the cooling came mostly from the soil layer itself, not from any particular plant. This is encouraging for mass deployment: it means builders need not chase exotic species or bespoke designs to capture most of the cooling benefit, and local, hardy vegetation will do the job. Recent trials with moss-based systems in semi-arid climates have also shown that even extremely shallow, drought-resistant coverings can reduce rooftop surface temperatures by six to ten degrees during the day while retaining modest thermal buffering at night, opening the technique to regions where water for irrigation is scarce.

E. Despite these advantages, green roofs have spread slowly. The reasons are economic and institutional rather than technical. The upfront cost of a green roof — waterproofing, root-barrier protection, growing medium and plants — is two to three times that of a conventional membrane, and the building owner who pays the cost does not always capture the public benefits: cooler neighbourhood air, reduced stormwater runoff, lower heat-related mortality. In cities where the financial case is strongest — Singapore, Tokyo, Toronto — municipal subsidies and mandatory green-roof policies have closed that gap. Singapore's Skyrise Greenery Incentive Scheme, for example, co-funds up to half the installation cost, and the result is a dense canopy of rooftop vegetation that the city credits with measurable local cooling. As heatwaves intensify, more cities are weighing whether to follow suit. The question is no longer whether green roofs work — the evidence is now robust — but whether regulators can design subsidy schemes that make the long-term, public-good case outweigh the short-term, private cost for enough building owners to move the urban temperature needle at scale. Toronto's mandatory green-roof bylaw, which requires new commercial buildings to allocate a percentage of rooftop space to vegetation, offers a model that other North American cities are now watching closely.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. How plants and soil cool a roof physically ii. The history of asphalt manufacturing iii. Wider benefits beyond the building itself iv. Extensive versus intensive green roofs v. Why adoption has been slow — and what might accelerate it vi. How to waterproof a conventional membrane vii. The cost of air conditioning in 2025

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. By how much did one Polish study measure a green roof cooler than a bituminous membrane? A. 6-10 degrees Celsius. B. 4-6 degrees Celsius. C. 57 degrees Celsius. D. 1.5-2.5 degrees Celsius.

6. What was the cooling electricity reduction found in the EU school programme? A. About 6 per cent. B. About 11 per cent. C. About 28 per cent. D. About 46 per cent.

7. What did the Polish review find about different green-roof compositions? A. Exotic plant species produced significantly better cooling. B. Shallow substrates never worked. C. Thermal performance was similar regardless of species or mix. D. Intensive roofs always outperformed extensive ones.

8. According to the passage, why have green roofs spread slowly? A. The technology does not work in hot climates. B. Upfront costs are high and public benefits are not captured by the building owner. C. No city has yet allowed them. D. They increase stormwater runoff.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Rooftops can account for nearly 28 per cent of impermeable urban surfaces.
10. Evapotranspiration is one of the two main cooling mechanisms of a green roof.
11. Intensive green roofs are always cheaper to install than extensive ones.
12. Singapore mandates green roofs without any financial support.
13. Green roofs can help reduce flash-flood risk after heavy rain.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

Green roofs cool buildings through two mechanisms: (14) __________ and the insulating effect of the soil layer. While (15) __________ roofs are lightweight and low-maintenance, intensive roofs support deeper vegetation but require more structural support.

答案与解析

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