In the tropics, thermal comfort has always been a challenge. With rapid urbanization and rural to urban migration, air-conditioning has become almost a default solution for comfort for households who can afford it.
Over the last few years, we have seen a gradual shift of consumer preferences from fixed speed air-conditioners to inverter air-conditioners. This change is driven by strong marketing from manufacturers and positive word of mouth from early adopters who experience real cost savings.
However, awareness and a shift in purchasing decision-making around green buildings is limited. There has not been enough communication about the benefits, associated with green buildings and the market does not yet have enough green buildings for early adopters to champion and influence wider consumer perception.
Working with international organisations including the UN Economic and Social Commission for Asia and the Pacific (ESCAP) and the United Nations Environment Programme (UNEP) within the framework of the Cool Coalition, with support from the Institute of Technology of Cambodia, contributed to the vital success of the Passive Cooling Strategies (PCS) Demonstration Project at Borey Chankiri and was an incredibly enriching experience for the Urbanland team.
We’ve always tried to incorporate passive cooling measures alongside an emphasis on natural light and ventilation in our buildings, but previously we were operating on a first principles basis, with no way to track and measure the effectiveness of our strategies.
The PCS Demonstration Project introduced us to a more science-based approach using simulations and field measurements to validate different passive cooling strategies.
The demonstration project also brought together many different participants, including consultants, academic experts, and other private actors through the Passive Cooling Community of Practice in Cambodia. Learning from this diverse group was extremely enriching. The encouragement and involvement of ESCAP, UNEP and Cool Coalition partners gave the programme strong credibility and encouraged broader private sector participation.
At Urbanland, our decision to integrate passive cooling strategies into Borey Chankiri’s latest designs comes from a simple goal: creating homes that feel naturally comfortable while reducing energy use. Global studies, including UNEP’s Global Cooling Watch, show that passive-first and low-energy strategies account for nearly two-thirds of the potential emissions reductions in sustainable cooling pathways and offer low-cost ways to improve thermal comfort in hot climates.
Building on these insights and leveraging the learnings from the analysis of our first- and second-generation home designs, we were able to take a more strategic approach to the design of our third-generation homes. We improved the thermal performance of the building envelope and reduced construction costs, while maintaining good natural light, and ventilation, all while maintaining the thoughtfully designed architecture and interiors that are a hallmark of Urbanland projects. In doing so, we were able to offer our customers greater value, at even more competitive prices.
We are aware that buildings and the activities they encompass account for 37% of annual global greenhouse gas emissions. As part of the ISI Group, with operations across several sectors, we at Urbanland see passive cooling as a critical area that supports energy efficiency and complements active cooling, behaviour change and renewable energy in the transition to net zero. Through these efforts, we aim to deliver homes that are not only sustainable but also healthier and climate resilient.
Many materials and technologies for improving thermal performance of building envelopes are already available. The real challenge in an emerging market like Cambodia is balancing these measures with affordability, given the price sensitivity of homeowners. At Urbanland, we address this by making strategic design choices such as optimizing building orientation and window-to-wall ratios, and by using accessible materials like composite roofs with integrated insultation. This allows us to build homes that are thermally efficient, cost-effective and visually appealing.
However, cost considerations currently prevent us from deploying the entire spectrum of technologies and material available to us, such as low-e or double-glazing, or the use of AAC blocks. While AAC blocks offer productivity gains and better thermal performance, they require special surface treatments because of their higher porosity compared to clay bricks. This adds complexity and cost, with a local workforce not yet familiar with these installation techniques, create additional execution risks. Similarly, cooling materials like reflective paints and cool tiles remain expensive or unavailable locally because of low demand and high import tariffs.
These factors highlight that while many passive cooling measures are cost-efficient and easy to implement, some advanced materials and technologies remain limited by supply, cost, or local expertise. Addressing these challenges will be key to scaling passive cooling strategies across the market.
In our first generation of homes, we focused on making sure our homes had enough natural light and ventilation because we felt that those two elements were paramount to the experience of a comfortable and healthy interior environment. We made sure that there were overhangs over openings, and some vertical fins for additional shading.
However, once residents moved in, we learned that too much heat was also entering the homes, which made it difficult to stay comfortable without air conditioning.
In our second-generation homes, we adjusted the orientation of the buildings in the masterplan to maximise north-south facing units and reduced the window-to-wall ratios of the homes, calibrating it such that there was still a reasonable amount of natural light and ventilation entering the interiors of the houses.
Simulations on the demonstration houses showed around a 20 percent improvement in thermal performance between the first- and second-generation homes. With these simulated results, and after testing passive cooling measures such as cool paints, composite roofs and solar films, we were able to make deliberate improvements to the design and specifications of our third-generation homes. The showhouses already demonstrate noticeable improvements in thermal comfort due to better shading, controlled window-to-wall ratios, and the integration of an overhanging composite steel roof with integrated insulation.
Although we could not implement every PCS measure at handover, we continue to encourage homeowners to adopt additional low-cost measures, such as installing solar films and planting trees for shading and microclimate benefits.
As a private sector actor that believes passive cooling in buildings is essential for both net zero transition and building good homes for people, we feel it is our responsibility to develop robust, well designed and thermally efficient homes that are comfortable, energy efficient and affordable. By reducing dependence on air conditioning, households can save money and live more comfortably, while also contributing to reduced energy demand and lower emissions. If more developers adopt this approach, the broader transition to energy efficient and climate-friendly buildings will accelerate.
For a mid-sized private sector developer, global platforms like the Global Cooling Pledge can sometimes feel broad and distant from day-to-day operations.
Yet, they play an important role by raising awareness, setting direction for policymakers and signalling that sustainable cooling is a global priority. Strong policy and market signals can eventually help reduce costs, improve supply chains and create an enabling environment for companies like ours to scale passive cooling solutions more easily.
For developers like Urbanland, these platforms reaffirm that our efforts are part of a wider international momentum, and they motivate us to keep aligning our projects with global climate goals. Above all, they remind us that meaningful progress emerges when ambition is shared, and when actors across borders collaborate, and choose to move forward together.