Decarbonizing Existing Buildings: Sustainable Air-Conditioning Solutions for Thailand’s Hot and Humid Climate

Chakrapan Pawangkarat

Member ASHRAE, Past-President ASHRAE Thailand Chapter

Head of Property and Asset Management, JLL Thailand

22 March 2025

Introduction

Decarbonizing existing buildings is a crucial step toward achieving Thailand’s net-zero carbon targets. In a tropical climate where air-conditioning accounts for over 50% of a building’s energy use, improving HVAC efficiency is key to reducing carbon emissions and operational costs.

The ASHRAE Decarbonization Guide (2023) provides a structured approach for reducing emissions in existing buildings. This article applies ASHRAE’s key strategies—energy efficiency, smart controls, refrigerant management, and renewable energy integration—to the unique challenges of air-conditioning in Thailand’s hot and humid climate.

Challenges of Cooling in a Hot and Humid Climate

Thailand’s climate—high temperatures (30–35°C) and humidity exceeding 70%—creates significant cooling demands. The key challenges include:

1. High Energy Consumption: Outdated air-conditioning systems lead to excessive energy use and high carbon emissions.

2. Humidity Control Issues: Standard cooling systems struggle to handle latent heat, causing comfort issues, mold growth, and indoor air quality problems.

3. Refrigerant Management: Many existing systems still rely on high-GWP refrigerants like R-22 and R-410A, contributing to climate change.

4. Aging Infrastructure: Poorly maintained HVAC systems result in higher energy use and frequent breakdowns.

ASHRAE-Based Strategies for Decarbonizing Air-Conditioning

The ASHRAE Decarbonization Guide outlines practical steps to reduce emissions from HVAC systems in existing buildings.

1. Energy Efficiency Upgrades (ASHRAE Standard 90.1 & Guideline 36)

ASHRAE emphasizes energy conservation first before considering renewable energy sources. Key efficiency upgrades include:

• HVAC Equipment Retrofitting (ASHRAE Standard 90.1):

  • Replace outdated fixed-speed chillers with variable-speed, high COP systems.

  • Upgrade old split systems to VRF (Variable Refrigerant Flow) technology, which improves part-load efficiency.

• Building Envelope Improvements:

  • Reduce cooling loads by improving insulation, upgrading windows, and adding shading.

• Enhanced Preventive Maintenance:

  • Regular coil cleaning, air filter replacements, and refrigerant charge monitoring can improve system efficiency by 10-20%.

2. Smart Control & Demand Management (ASHRAE Guideline 36 & Standard 211)

ASHRAE highlights smart controls as a cost-effective strategy for energy savings. Implementing these solutions can significantly reduce cooling energy consumption:

• Building Energy Management Systems (BEMS) (ASHRAE Guideline 36):

  • AI-driven chiller plant optimization adjusts cooling loads dynamically.

• Occupancy-Based Cooling Control:

  • Smart thermostats and occupancy sensors adjust temperature settings based on real-time usage.

3. Refrigerant Management & Reclamation (ASHRAE Standard 15 & 147)

ASHRAE stresses proper refrigerant management to minimize direct emissions from HVAC systems.

• Transitioning to Low-GWP Refrigerants (ASHRAE Standard 34 & 15):

  • Replace R-22 and R-410A with lower-GWP alternatives like R-32 and HFO blends.

• Refrigerant Reclamation & Recycling (ASHRAE Standard 147):

  • Recover and reclaim refrigerants from decommissioned systems to reduce environmental impact.

  • Implement leak detection and regular servicing to prevent refrigerant loss.

4. Transition to Low-Carbon Cooling Technologies (ASHRAE Standard 189.1 & 100)

ASHRAE encourages the adoption of next-generation cooling systems to achieve significant carbon reductions.

• Hybrid Cooling Solutions:

  • Combine conventional air-conditioning with desiccant dehumidification to improve humidity control and efficiency.

• District Cooling Systems (DCS) (ASHRAE Standard 100):

  • Large-scale commercial and residential developments can transition to district cooling, which is 30-50% more energy-efficient than standalone systems.

5. Integrating Renewable Energy for Cooling (ASHRAE Standard 189.1 & 90.1)

ASHRAE prioritizes on-site renewable energy to complement energy-efficient HVAC systems.

• Solar PV for HVAC Power (ASHRAE Standard 189.1):

  • On-site solar panels can offset cooling energy demand.

• Solar-Assisted Absorption Cooling:

  • Absorption chillers powered by solar thermal energy reduce reliance on grid electricity.

Conclusion

Decarbonizing air-conditioning in Thailand’s existing buildings requires a multi-pronged approach based on ASHRAE’s Decarbonization Guide. By prioritizing energy efficiency, smart controls, refrigerant management, low-carbon cooling technologies, and renewable energy integration, existing buildings can significantly reduce their carbon footprint and operational costs.

With government incentives, stricter building codes, and the right engineering strategies, Thailand’s built environment can transition toward net-zero carbon cooling while ensuring indoor comfort in a tropical climate.

Acknowledgement:

"This article was generated with the assistance of ChatGPT, an AI language model by OpenAI, and subsequently reviewed and edited by the author."