Purpose of the Challenge


The Kigali Cooling Efficiency Programme (K-CEP) is a philanthropic programme to support the Kigali Amendment to the Montreal Protocol by focusing on improving the energy efficiency of cooling in tandem with the F-gas transition.

The Kigali Amendment outlines a timetable to phasedown production and consumption of HFCs - coolant gases that have replaced CFCs in cooling systems as they are less harmful for the ozone layer, but which are powerful greenhouse gases. The amendment also opened the door to improving the energy efficiency of cooling, an increasingly urgent issue as global temperatures increase and deadly heat waves become more common.

One of K-CEP’s four focus areas (‘windows’) is ‘Access to Cooling’. This aims to promote sustainable cooling solutions in the developing world in order to support the Kigali Amendment as well as the Paris Agreement on climate change and the Sustainable Development Goals. K-CEP has partnered with the Global Cool Cities Alliance, Nesta’s Challenge Prize Centre and Sustainable Energy for All to deliver the Million Cool Roofs Challenge, a $2 million, two year competition to rapidly scale up the use of highly solar reflective ‘cool’ roofs in countries with the greatest need, with the ultimate goal of closing the cooling access gap globally.

The need for ‘cool roofs’

Cooling is an essential component of modern life, fundamental to the supply and storage of food, medicine and vaccines, and for ensuring the quality of life and productivity of citizens. Yet around the world millions of people die every year from causes related to a lack of access to cooling.

Sustainable Energy for All and the Kigali Cooling Efficiency Programme recently produced a report on global cooling access, Chilling Prospects: Providing Sustainable Cooling for All, linking the cooling access gap to the Sustainable Development Goals, the Paris Agreement and the Kigali Amendment.

The report’s authors estimated that there are 1.1 billion people facing access to cooling risks. This includes 630 million slum dwellers living in hotter-climate urban areas where electricity services do not exist, are intermittent, or are too expensive. In addition, the report identified 2.3 billion people in developing countries who are increasingly able to purchase air conditioners, but are likely to only be able to buy the most inefficient and thus energy-intensive models, associated with higher greenhouse gas emissions and greater usage costs.

The rise in global temperatures and associated higher frequency of heat waves is increasing the risks associated with lack of cooling access. Increasing use of unsustainable cooling systems will further exacerbate climate change, requiring more cooling and creating a vicious cycle. Expanding access to sustainable cooling is thus fundamental for directly tackling, and mitigating the effects of, climate change, as well as achieving the Sustainable Development Goals around health, food security, work and economic growth and sustainable cities and communities.

One proven approach to increasing access to sustainable cooling in developing countries at risk of heat stress is the use of highly solar reflective ‘cool’ roofs. This involves applying coatings and materials to increase the solar reflectivity of roofs to maximise the amount of incident solar radiation that is reflected, and the amount of absorbed radiation that is emitted back into the atmosphere. This prevents absorbed solar radiation being conducted to the building below as heat. Cool roof materials are often white, and simply painting the roof white goes a long way towards increasing the roofs’ reflectivity, though a range of materials exist in a variety of colours and with different levels of reflectivity, emissivity and durability.

Studies have shown that in a building without air conditioning, replacing a dark roof with a white roof can cool the top floor of the building by 2 to 3 degrees Celsius and that the net annual energy use for a one-story building with air conditioning is reduced by up to 20 percent upon raising the solar reflectance of the roof from 10 to 20 percent to 60 percent. Additionally, concentrated deployment of cool roofs in a single area is associated with community-wide benefits, reducing the average external ambient temperature through a reduction in the ‘urban heat island’ effect.

Cool roofs have grown in prominence in recent years, notably in the US, including high profile initiatives in New York and California, but they are only just beginning to be used in low income countries, where there is arguably the greatest need. Rapidly scaling up the use of cool roofs in low income countries is a significant challenge requiring the cooperation of multiple stakeholders, and activities that can raise awareness and show the benefits of cool roofs to citizens, policy makers and building owners. Some of the key barriers to greater use of cool roofs in low income countries include:

  • Lack of awareness of cool roofs - on the part of individuals, community groups, construction companies and governments

  • Lack of locally relevant data - particularly data around existing roof materials and the benefits of cool roof deployments

  • Lack of financing – there is a gap for early stage demonstrations and action planning for cool roof initiatives, that once in place can attract further investment from development banks, aid agencies, and industry to continue to grow cool roof deployments

  • Lack of heat mitigation policies and implementation frameworks – there are multiple policy pathways to implementing cool roofs but there are so far only a few example frameworks and limited understanding of best practices and their applicability in different contexts

  • Underdeveloped markets for cool surface products - there needs to be greater awareness of the benefits of cool roofs in order to drive demand, and incentives for the seeding of local capacity for implementation and development of materials

  • Cost effective quality cool coatings - many of the most effective products are still on the higher-cost end of the spectrum and there is a need for more cost-effective, highquality and easy to apply cool coatings

Scaling cool roofs

The Million Cool Roofs Challenge is looking for the most impactful proposals to improve access to sustainable cooling through the rapid scaling of cool roofs in countries with large numbers of people facing heat stress risks. The winning project will have demonstrated an effective, sustainable and scalable model for stimulating rapid deployment of cool roofs, overcoming the major barriers to adoption.

These projects will respond to local needs and contexts, embed cool roof capacity and best practice locally, and provide a compelling case study for further scaling of cool roofs, both in the country of deployment and beyond. Efficacy will be judged according to the judging criteria, of which scale of deployment achieved is one important factor.

Projects may include, but are not limited to, one or more of the following activities:

  • Demonstrator projects

  • Training programmes

  • Policy change (e.g. building codes)

  • Awareness raising and communication campaigns

  • Volunteer programmes

  • Novel approaches to financing and fundraising

  • Stakeholder coordination

  • Building up of local supply chains

  • Data gathering and impact measurement

  • New business models for companies selling cool coatings

The programme objective is to improve access to cooling, and so it is expected that projects will include application of cool roof materials to buildings that do not currently have air conditioning, for example houses in informal settlements in low-income neighbourhoods.

However, in order to seed change and embed the approach, projects may also include buildings that have air conditioning and can reduce their energy consumption through the use of cool roofs, providing a stronger financial incentive for the owners and a more sustainable business model that can enable cool roof ecosystems to develop develop locally. The objective is to benefit individuals and communities and so only buildings that are regularly occupied by people may be included, but there is no formal restriction on the type or main use of the building beyond this.

Applying to the Challenge

If you’re interested in applying to the Challenge, visit the Apply page for everything you need to know, including details of the prize fund, eligibility and judging criteria, and the application process.