Extreme Heat: Climate-Resilient Housing for Low-Income Women in Indonesia

For years, Tati Mulyati relied on electric fans day and night to get through the heat in her home in one of Jakarta’s informal neighborhoods. The living room was stuffy, and the nights were hot. “It just didn’t feel comfortable,” she says.

Tati’s experience is common. For billions of people worldwide, home does not provide an escape from extreme heat.

Heat is more than discomfort. According to the World Health Organization, approximately 489,000 heat-related deaths occur every year worldwide. Heat also puts additional stress on the heart and kidneys, worsening existing health conditions.

Many heat adaptation solutions focus on outdoor spaces. But billions of people spend the hottest hours of the day at home, and most of them are women: running home-based businesses, caring for children and older relatives, with no option to leave when temperatures peak.

The conditions inside a home impact how people experience heat every day. Ventilation, insulation, shade, roofing and building materials all play a role.

At Build Change, we are working to make practical heat adaptation solutions more accessible to the people who need them most.

THE CHALLENGE

Low-income families in Indonesia—especially women living on less than $5 per day—are on the frontlines of climate change. Extreme heat threatens their health and productivity, yet they lack the capital and expertise to adapt their homes.

Heat, Housing & Health

WHO research shows that informal housing often traps heat instead of providing shelter. Due to poor insulation and materials like galvanized steel, indoor temperatures can soar 4–5°C higher than outdoors. This lack of “thermal comfort” leads to heat exhaustion, kidney stress, and severe respiratory or cardiovascular complications.

Heat Threatens Livelihoods

Chronic heat actively drains a family’s long-term potential:

• Stalled Education: Global research links rising temperatures to significant learning loss. Without a cool place to sleep or study, children in these homes face severe cognitive deficits.
• Eroded Incomes: For women running home-based micro-enterprises, heatwaves are economic crises. Extreme heat can slash daily earnings by up to 40% due to physical exhaustion and sleep deprivation.

THE SOLUTION

With institutional support from the Global Innovation Fund and follow-on funding from the ClimateWorks Foundation, we partnered with KOMIDA, a leading Indonesian microfinance institution (MFI), to pioneer a scalable model for heat adaptation. The initiative drives impact through three pillars:

• Innovative Financing: We developed an Incremental Climate Adaptation Loan (ICAL) that allows low-income women to invest in critical home upgrades to improve climate resilience, health and wellbeing. 
• Tech-Driven Scale: We are training KOMIDA loan officers to use BCtap, a digital technical assistance platform that streamlines the assessment, planning, and implementation of climate-resilient construction.
• Low-Cost, High-Impact Interventions: We design and refine a menu of affordable solutions (averaging $150–$600 per home)—including reflective roof coatings, insulation, and enhanced ventilation—specifically engineered to reduce indoor temperatures.

For Tati, the process started with a renovation loan from KOMIDA. When she learned about ICAL’s heat adaptation options, she decided to try them. Working with Build Change and the KOMIDA team, she used the PENEDUH climate-adaptation loan to improve ventilation and roof insulation, while the renovation also included new windows and wall strengthening. That was especially important in the kitchen, where the old wooden roof structure had been deteriorating.

“When I was cooking, I’d often look up and think, ‘Oh no, what if it falls?'” she says. “Now, I don’t. I feel at ease.”

IMPACT AND FINDINGS

Launched in May 2025, the ICAL loan product has proved the viability of climate resilience financing for low-income women. The impact of the project’s first phase includes:

• Impressive Scale & Growth: From its initial launch, the product expanded to 90 branches across three provinces, reaching 289 members.
• Direct Impact: 246 members fully completed their home upgrades, improving indoor living conditions for 960 people (48% women).
• Proven Thermal Performance: 90% of measured houses showed cooler indoor environments. At peak hours, indoor spaces became nearly 2°C cooler relative to outdoor conditions, leading to 73% of users reporting improved thermal comfort.
• Lower Energy Costs & Consumption: 85% of measured ICAL users experienced reduced monthly electricity consumption and costs, achieving an average reduction of 12%.
• Socio-Economic & Health Returns: The reduction in indoor heat actively improved lives, with 26.5% of those surveyed reporting improved household health and 22.3% reporting a reduction in work challenges and heat-related absenteeism.

For Tati, the results are simple. “I used to use an electric fan in our bedroom, but not anymore,” she says. “It used to be very hot at night, but now it isn’t. It’s comfortable.”

MOVING BEYOND PILOT

In the next phase of the program, funded by ClimateWorks, we are replicating this model in the Philippines and, in Indonesia, scaling ICAL intervention packages for extreme heat adaptation for at least 1,000 beneficiaries in 150 KOMIDA branches, expanding solutions for up to 3-story houses, with the aim of generating a sustainable ICAL business product line for KOMIDA and other MFIs.