By Eamonn Ryan
The following article is derived from an ASHRAE UK presentation on ASHRAE UK chapter’s upcoming Hot Climate Design Guide, by Frank Mills, FASHRAE and professional consulting engineer. This is Part 4 of an eight-part series.

ASHRAE’s approach to achieving net-zero buildings can be summarised through the ‘Lean, Clean, Green’ strategy. Freepik
To achieve true net-zero buildings, it is crucial to consider all energy consumption within the building. ASHRAE’s standards aim to cover the full spectrum of energy use, including both operational and embodied energy, ensuring that every aspect of a building’s energy profile is accounted for. This comprehensive approach ensures that energy consumption is minimised, that systems are highly efficient, and that renewable or low-carbon energy sources are incorporated wherever possible.
ASHRAE’s approach to achieving net-zero buildings can be summarised through the ‘Lean, Clean, Green’ strategy:
- Lean: Ensure buildings are as energy-efficient as possible by optimising design, insulation and energy systems
- Clean: Use energy-efficient systems, such as high-performance HVAC and lighting systems, to meet the building’s operational needs
- Green: Incorporate renewable energy sources, such as solar panels or wind power, and consider energy recovery technologies to reduce the building’s carbon footprint
While renewable energy systems such as solar panels can be a critical component of net-zero buildings, the focus should first be on making the building as efficient as possible. In many cases, building owners and operators may attempt to meet net-zero targets by purchasing green energy or offsetting emissions through external projects, but this approach does not address the root of the problem—inefficient building design and systems. The more sustainable and cost-effective approach is to first reduce energy consumption through design and engineering and then integrate renewable energy sources.
Global case studies
Across the globe, there are numerous examples of buildings that have achieved net-zero status through innovative design and engineering. These case studies not only showcase what is possible but also offer valuable insights into how similar strategies can be applied in diverse climates.
- The Bullitt Center, Seattle: Often referred to as the “greenest commercial building in the world”, the Bullitt Center features a large roof that overhangs the building by several metres to capture solar energy. This design allows the building to generate all of its energy needs from solar power, achieving net-zero energy use.
- Hawaii Research Center: In Hawaii, a research facility has used two massive arrays of solar panels to generate the energy needed for the building. Though the upfront cost was significant, the building now operates at net-zero energy consumption.
- Blackpool Visitor Centre, UK: This building features integrated solar panels in the atrium roof, which not only generate electricity but also provide shading to keep the space cool. This example demonstrates how small-scale, integrated solutions can be used to achieve net-zero goals without massive infrastructure investments.
- La Jolla Office Building, California: An example of how traditional buildings can be made energy-efficient, this office building in La Jolla uses methane waste gas to generate power, providing both electricity and cooling for the building via heat pumps and absorption chillers.
These case studies highlight the diversity of solutions available for achieving net-zero buildings. Whether through large solar arrays or innovative use of waste energy, each project demonstrates that net-zero goals are achievable across different climates and building types.