Carbon Zero Buildings and Passive Design
The term carbon zero refers to buildings that rely on 100% renewable energy sources generated on site to meet their operational energy needs. Over the course of a year, the total energy produced on site equals the total energy consumed by the building and its occupants, resulting in a net-zero carbon outcome.
At its most fundamental level, a building is a shelter that protects us from the environment, providing thermal comfort with minimal reliance on artificial heating or cooling. However, as the climate continues to change, many buildings are struggling to adapt. Rising temperatures, sea-level increases, and more frequent extreme weather events are placing greater demands on the built environment, particularly in climate-sensitive locations.
Passive design addresses these challenges by responding directly to local climate conditions. It involves designing buildings so that occupants remain thermally comfortable with minimal or no mechanical heating or cooling. Rather than working against the climate, passive design works with it—using orientation, shading, ventilation, insulation, and thermal mass to moderate internal temperatures naturally.
When passive design principles are combined with the smart selection of materials, it is possible to reduce construction and running costs while significantly improving thermal comfort. Thermal comfort itself is a subjective experience, defined by an individual’s sense of satisfaction with their environment and their ability to adjust it to their needs. In colder conditions, the human body releases heat, requiring buildings to be well insulated and airtight to retain warmth. In hotter conditions, the body cools itself through sweating, making airflow essential to promote evaporation and maintain comfort.
By embracing passive design, buildings can become more resilient, efficient, and comfortable, now and into a future shaped by a changing climate.
Passive Design principles:
Solar Gain: The sun’s energy is used to create internal comfort in winter but will need solar protection in summer to shade the exposed facades.
Benefits: reduces energy costs, improves thermal comfort and performance of the building, and is a good source on site to generate renewable energy.
Passive Cooling: passive elements are designed to contribute to natural ventilation including cooling strategies to prevent the building from overheating by blocking solar gains in summer with external shades and louvers.
Thermal Mass: use of materials with high thermal mass to absorb, store, and later release heat during winter nights, but should be located where the sun has little impact during summer and facing wind flow to cool down the internal areas.
Benefits: reduces energy costs, improves thermal comfort and performance of the building and moderates temperature fluctuations.
Insulation: is a crucial principle of passive design, thermal bridging and air leakage throughout external and internal spaces are to be avoided. This can happen through the structure when it is exposed internally and other building elements.
Benefits: reduces energy costs, insulation costs (it pays itself in six years), reduces greenhouse gas emissions, acoustic properties and eliminates condensation.
Airtightness: is the control of airflow within a building without any unexpected leakage of hot air in winter and vice versa in summer.
Benefits: reduced energy costs, improves thermal comfort and performance of the building.
Conclusion:
Passive Design is an approach to design buildings minimizing energy consumption and reducing use of active mechanical systems, maintaining occupants thermal comfort at all times. Some of the benefits are construction costs savings and running costs of the building during its lifetime, as a result the passive designed building will be Carbon Zero.
Passive design elements to consider when designing a building:
Orientation
Building shape and type
Buffer areas
Planning
Daylighting
Windows design
Wind orientation
Natural ventilation
External shading elements
Optimizing the use of recycling materials where it is possible.
