The key to designing a passive building is by taking advantage of the local climate (micro-climate) and therefore, climate characteristics and classification can help with identifying approaches as early as site planning and analysis. Therefore, climate and comfort are the two fundamental measures in passive design that require attention. Passive design is a major part of environmental design, and approaches utilizing several techniques and strategies that can be employed to the buildings in all types of climates around the world such as orientation, ventilation, shading devices, thermal mass, insulation, daylighting and so on. These techniques and strategies can also be supported by various other parameters such as using technologies (passive and/or active) and customizable controls as well as enhanced by patterns of biophilic design for improving health and well-being in the built environment.
There are also passive solar technologies including direct and indirect solar gains for space heating, solar water heating systems, solar cookers, use of thermal mass and phase-change materials for slowing indoor air temperature swings, solar chimney for enhancing natural ventilation, and earth sheltering that can be considered as part of the actual design. Today, passive design strategies can be easily evaluated with the use of either simple or more sophisticated Building Performance Simulation (BPS) tools such as Ecotect, IES VE, etc. That’s why passive design is the key to sustainable building.
Here are some reasons:
- It responds to local climate and site conditions to maximize building users’ comfort and health while minimizing energy use.
- It achieves this by using free, renewable sources of energy such as sun and wind to provide household heating, cooling, ventilation, and lighting, thereby reducing or removing the need for mechanical heating or cooling. Using passive design can reduce temperature fluctuations, improve indoor air quality and make a home drier and more enjoyable to live in.
- It can also reduce energy use and environmental impacts such as greenhouse gas emissions. Well integrated passive solar home design results in comfortable internal temperatures.
- Interest in passive design has grown, particularly in the last decade or so, as part of a movement towards more comfortable and resource-efficient buildings.
The key elements of passive design are: building location and orientation on the site; building layout; window design; insulation (including window insulation); thermal mass; shading; and ventilation. Each of these elements works with others to achieve comfortable temperatures and good indoor air quality. The first step is to achieve the right amount of solar access – enough to provide warmth during cooler months but prevent overheating in summer. This is done through a combination of location and orientation, room layout, window design, and shading. Insulation and thermal mass help to maintain even temperatures, while ventilation provides passive cooling as well as improving indoor air quality. All of these elements work alongside each other and therefore should be considered holistically.
For example, large windows that admit high levels of natural light might also result in excessive heat gain, especially if they cast light on an area of thermal mass. Alongside passive design features, designers should also consider other factors such as views, covenants and local authority restrictions, and building owners’ preferences.