{
  "id": 208240,
  "title": "Harvesting rainwater from rooftops could help cities stay cool",
  "url": "https://urgent.news/2026/08/06/harvesting-rainwater-from-rooftops-could-help-cities-stay-cool",
  "topic": "world",
  "section": "World",
  "published": "2026-08-06T05:00:01.000Z",
  "source": {
    "name": "The National UAE",
    "slug": "the-national-uae",
    "url": "https://www.thenationalnews.com/climate/2026/08/06/harvesting-rainwater-from-rooftops-could-help-cities-stay-cool/"
  },
  "original_language": "en",
  "account": "A recent study from the University of Manchester suggests that spraying rainwater collected from rooftops onto buildings during hot weather could help cities combat the effects of heatwaves. By employing sprinklers, rainwater stored in water butts can be utilized to reduce air conditioning usage and consequently lower urban temperatures, according to research published in Earth’s Future. As global temperatures rise, cities face mounting challenges to public health, infrastructure, and energy systems. Europe has witnessed a surge in heatwaves, raising concerns over power generation due to low river levels essential for cooling, while wildfires have approached a nuclear power plant in the UK. Air conditioning's increased reliance exacerbates energy demand and waste heat, potentially intensifying the urban heat island effect. The simulation model employed Tokyo as a case study, revealing that strategic cooling of rooftops could mitigate energy consumption by air conditioning units. The study concluded that this approach could reduce urban temperatures, diminish the frequency of heatwave days, and lessen the severity of extreme heat events. Dr Zhonghua Zheng, the lead author, emphasized that cities worldwide are grappling with escalating heat-related challenges. Air conditioning provides relief but also consumes substantial energy and emits additional heat into the urban environment. The research posits that harvesting rainwater from rooftops and employing it judiciously for cooling could yield a practical solution to curtail energy demand and urban temperatures. Particularly noteworthy is that the benefits amplify during hotter years, underscoring the growing importance of this strategy amidst climate change. While rooftop cooling systems hold promise, there is no universal remedy, as each system must be assessed in terms of cost, water availability, and local regulations. The precise timing of sprinkler activation proved more crucial than the tank's size or water volume. Moreover, the study discovered that larger tanks did not significantly enhance energy savings and extreme heat reduction. Dr Zheng illustrated that the optimal temperature threshold for triggering sprinklers in Tokyo's case settled between 35°C and 40°C, recognizing that this value is site-specific due to variations in local climate and building characteristics. The researchers' AI-powered framework can aid in determining this optimal temperature for any given location. PhD researcher Junjie Yu highlighted the rainwater tank as a \"natural solution to natural challenges,\" leveraging rainwater as a resource to mitigate thermal stress and hydrological extremes.",
  "summary": "Spraying buildings with water collected from rooftops could help cities reduce the impact of heatwaves, a study has found. Using sprinklers in hot weather to distribute rainwater stored in water butts could cut air conditioning use and lower urban temperatures, according to research from the University of Manchester. Rising temperatures globally are putting pressure on public health,…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}