Passive design approach to energy efficiency

The vision to achieve an energy-efficient building includes finding ways to reduce the building energy usages. Embodied energy is the energy consumed by all of the processes associated with the production of a building, from the mining and processing of natural resources to manufacturing, transport and product delivery. Embodied energy does not include the operation and disposal of the building material. This would be considered in a life cycle approach. (Milne, Geoff, 2013)

Energy consumption during manufacture can give an approximate indication of the environmental impact of the material, and for most building materials, the major environmental impacts occur during the initial processes.

Embodied energy must be considered over the lifespan of a building, and in many situations, a higher embodied energy building material or system may be justified because it reduces the operating energy requirements of the building. For example, durable material with a long lifespan such as aluminium may be the appropriate material selection despite its high embodied energy.

As the energy efficiency of building increases, reducing energy consumption, the embodied energy of the building materials will also become increasingly important.

Buildings should be designed and materials selected to balance embodied energy with factors like climate, availability of materials and transport costs.

Passive design” is an approach to building design that uses the building architecture to decrease energy consumption and improve thermal comfort. The building form and thermal performance of building elements (including architectural, structural, envelope and passive mechanical) are carefully considered and improved for interaction with the local microclimate. The ultimate vision of passive design is to eliminate requirements for active mechanical systems (and associated fossil fuel-based energy consumption) and to maintain occupant comfort at all times. (Cobalt Engineering, Hughes Condon Marler: Architects, 2009)

To successfully implement the passive design approach, one must first accomplish the following:  

  1. Understand and define acceptable thermal comfort criteria.  
  2. Understand and research the local climate, preferably with site-specific data.  
  3. Understand and establish clear, realistic and measurable energy performance targets

Passive Heating

Using building design to harness solar radiation and capture the internal heat gains is the only passive way to add free thermal energy to a building. Passive solar heating combines a well-insulated envelope with other elements that minimize energy losses and harness and store solar gains to offset the energy requirements of the supplemental mechanical heating and ventilation systems. Elements that contribute to passive solar heating include the following:

  1. Orientation
  2. Building shape
  3. Buffer spaces and double facades
  4. Space planning
  5. High-performance windows (clear, Low-E)
  6. Mixed-mode heat recovery ventilation (HRV)
  7. Low window to wall area ratio (N/E)
  8. High window to wall area ratio (S/W)
  9. Operable external shading
  10. High-performance insulation
  11. Thermal mass
  12. Minimized infiltration
Reference-Lebens, R. (1990). Passive solar heating design; Case Study Reference-

Passive cooling strategies

This prevents the building from overheating by blocking solar gains and removing internal heat gains (e.g. using cooler outdoor air for ventilation, storing excess heat in thermal mass). Elements that contribute to passive cooling include the following:

  1. Fixed/operable external shading
  2. Thermal mass
  3. Low window to wall area ratio (S/W)
  4. Passive ventilation
  5. Nocturnal cooling
  6. Stacked windows
  7. Passive evaporative cooling
  8. Earth-tempering ducts

Why is it done?

A significant advantage of Passive design strategies is that it saves money which otherwise is spent on extensive utilities towards heating and cooling. It is a clean and efficient use of energy because it is a type of energy, that is readily available and occurs naturally.

The sun is the ultimate resource for the planet earth, harnessing it, provides long term benefits for buildings. Designing the project to the orientation of predicted movements of the sun enhances the use of the daylight hours. The optimum usage of the daylight hours eases the load off of high energy usage, the prime focus of an energy-efficient building. 

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