Heatwaves & Buildings: Thailand’s New Thermal Comfort Regulations Explained

As Southeast Asia experiences increasingly frequent and intense heatwaves, the importance of designing buildings that keep occupants comfortable without excessive energy use is more urgent than ever. Thailand, in particular, is taking a proactive step by updating its thermal comfort regulations within its Building Energy Code (BEC) to address this growing challenge. These new standards aim to protect human health, improve energy efficiency, and raise national building performance levels.

For architects, engineers, developers, and building owners, these regulatory changes present both challenges and exciting opportunities. This article explores the why, what, and how of Thailand’s new thermal comfort regulations and their implications for the built environment.

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Why Thermal Comfort Matters in a Changing Climate

Thermal comfort refers to a state where building occupants feel neither too hot nor too cold, a critical factor affecting health, productivity, and overall wellbeing. In hot and humid climates like Thailand’s, achieving thermal comfort is especially challenging. Without proper design, indoor environments can become unbearable, forcing over-reliance on mechanical cooling systems, which drives up energy demand and greenhouse gas emissions.

According to the Thai Meteorological Department, average annual temperatures across Thailand have increased by approximately 1.5°C since 1981. The International Energy Agency (IEA) projects that need cooling energy demand in Southeast Asia could triple by 2040 if no improvements are made to building design and energy efficiency.

“By 2050, 1.6 billion people globally could be regularly exposed to extreme heatwaves—up from 230 million today.” — United Nations Office for Disaster Risk Reduction (UNDRR)

Heatwaves not only stress energy grids but also have serious health implications, increasing risks of heat stroke, dehydration, and mortality, especially among vulnerable populations. Buildings that manage heat effectively are thus vital to climate resilience and public health.

Understanding Thermal Comfort: Key Principles and Metrics

Thermal comfort is governed by multiple factors:

• Air temperature: The temperature of the air surrounding occupants.

• Radiant temperature: Heat emitted from surfaces such as walls, floors, and ceilings.

• Humidity: Moisture content in the air; high humidity makes heat feel more intense.

• Air movement: Gentle airflow can enhance cooling sensations.

• Clothing and activity levels: These personal factors influence how heat or cold is perceived.

Designers often use two key metrics to quantify comfort:

• Predicted Mean Vote (PMV): A scale from -3 (cold) to +3 (hot) that predicts average occupant sensation.

• Percentage of People Dissatisfied (PPD): The estimated percentage of occupants likely to feel uncomfortable.

Meeting thermal comfort means keeping PMV near zero and PPD as low as possible, ideally under 10-15%.

What Do the New Thai Thermal Comfort Regulations Say?

Thailand’s Department of Alternative Energy Development and Efficiency (DEDE), in coordination with the Ministry of Energy, has recently updated the Building Energy Code (BEC) with specific provisions addressing thermal comfort.

Key highlights include:

• Indoor temperature targets: The code sets an optimal indoor temperature range of 24–26°C for air-conditioned spaces to balance comfort and energy use. For naturally ventilated buildings, the guidelines promote adaptive comfort models that consider outdoor climate variations.

• Envelope performance requirements: Roofs and walls must meet higher insulation standards, reducing heat transfer into buildings. Window-to-Wall Ratio (WWR) limits are stricter, minimizing excessive solar heat gain.

• Passive cooling encouragement: Designs must incorporate cross-ventilation paths, external shading devices such as louvers or awnings, and natural ventilation strategies to reduce reliance on air conditioning.

• Climate zoning: Recognizing Thailand’s varied climates, the regulations offer differentiated guidance by region—for example, northern areas with cooler winters can use different comfort parameters than hot central plains.

Initially, these rules target larger buildings (over 2,000 m²), including commercial and mixed-use developments, with gradual application expected for smaller-scale projects.

Practical Strategies to Comply and Go Beyond

To meet and exceed these regulations, building professionals should consider:

1. Climate-Specific Design Approaches

Orient buildings to minimize east and west-facing glazing that receives harsh morning and afternoon sun. Use deep eaves and green roofs to shade and cool roofs. Planting trees for natural shading can also reduce heat loads.

2. Optimize Glazing and Shading

Select high-performance, low-emissivity (low-E) glass with visible light transmittance tuned for daylight needs but reduced solar heat gain. Combine glazing with external shading elements like vertical fins or adjustable louvers for maximum control.

3. Enhance Natural Ventilation

Design floor plans and openings to facilitate cross-ventilation and use the stack effect (warm air rising) to pull fresh air through the building. This can dramatically reduce the need for air conditioning in transitional seasons.

4. Use Advanced Thermal Modeling

Simulate thermal comfort using tools like DesignBuilder, IESVE, or EnergyPlus, applying standards such as ASHRAE 55 or ISO 7730. This enables designers to evaluate PMV and PPD for different design options before construction.

5. Leverage Local Green Building Certifications

Programs like TREES (Thailand’s Rating of Energy and Environmental Sustainability) or IFC’s EDGE provide frameworks aligned with the new code and help demonstrate compliance while boosting market appeal.

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Case Study: Passive Design for a School in Chiang Mai

Prem Tinsulanonda International School in Chiang Mai exemplifies tropical passive design. Its architecture incorporates:

• Cross-ventilation corridors promoting airflow

• Perforated facade walls that shade yet allow light and air

• Earth-coupled flooring using the cooler ground temperature for comfort

These strategies helped maintain an average indoor temperature around 27°C with a PPD below 15%, meeting local comfort benchmarks without mechanical cooling for much of the year.

Source: International WELL Building Institute, Case Studies – Prem Tinsulanonda International School, https://www.wellcertified.com/en/case-studies/prem-tinsulanonda-international-school

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The Broader Impact on Green Building and Finance

For projects pursuing global certifications such as LEED, WELL, or EDGE, aligning with Thailand’s thermal comfort regulations supports credit achievement related to passive design, indoor environmental quality, and energy savings.

Additionally, heat resilience is increasingly a key focus area for lenders and investors. Entities like the International Finance Corporation (IFC) and Asian Development Bank (ADB) are integrating heat adaptation criteria into financing frameworks, which can open new funding sources for compliant developments.

Looking Ahead: Trends and Challenges

• Technology Integration: Use of smart building management systems and IoT sensors for real-time monitoring of indoor conditions is on the rise.

• Material Innovation: New insulation materials and reflective coatings are being developed to optimize building envelopes.

• Education and Training: Designers and contractors will need upskilling to implement passive cooling solutions effectively.

• Urban Heat Island Effect: Managing outdoor heat through urban greening and reflective surfaces is gaining attention alongside building-level solutions.

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Thailand’s updated thermal comfort regulations mark a significant step forward in adapting buildings to a hotter future while controlling energy use. By embracing climate-responsive design, passive cooling, and advanced modeling, the building sector can deliver healthier, more sustainable indoor environments. This not only aligns with national policy but also positions projects for global certification and green finance opportunities.

Professionals who act now to integrate these approaches will future-proof their buildings, enhance occupant wellbeing, and contribute meaningfully to climate resilience.

Sources

• DEDE Thailand, Building Energy Code 2023 Update, https://www.dede.go.th/

• UNDRR, Global Assessment Report on Disaster Risk Reduction 2023, https://www.undrr.org/

• IEA Southeast Asia Energy Outlook 2022, https://www.iea.org/reports/southeast-asia-energy-outlook-2022

• TREES Green Building Institute Thailand, https://www.tgbi.or.th/

• EDGE Buildings by IFC, https://edgebuildings.com/

• International WELL Building Institute, Prem Tinsulanonda International School Case Study, https://www.wellcertified.com/en/case-studies/prem-tinsulanonda-international-school

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