Passive homes are a new design concept that relies on natural elements (such as weather and lighting) that influence a building and manipulate them in a way that is useful to the occupants, as opposed to creating the same conditions using energy. They use design elements that reduce the need for artificial lighting by allowing more sunlight into the space with reflective materials and paints and reduce the need for artificial ventilation by making design decisions that allow more open naturally ventilated areas. They are also able to reduce the overall energy usage of the house for cooling and heating with careful manipulation of insulation and ventilation within the confines of the house. Due to the increased reliance on natural elements, the design should incorporate the climate, environment, and weather of the location. Passive homes built according to the relevant international standards use 40% to 80% less energy than equivalent traditional homes. It also requires the design team to be well versed in the specific architecture involving passive homes to apply the principles which are relevant to the location and make required adjustments as required.
Passive homes can be thought of as an innovative solution to the energy crisis, where the residential use of energy is reduced by utilising natural phenomena. This is especially evident if a passive home is able to reduce or eliminate the need for air conditioning or heating as they consume most of the energy in a building. In addition to the reduced energy use, passive house building also aims to eliminate the use of natural resources such as water and timber. Water-use is reduced through harvesting rainwater and recycling water where possible, and timber is substituted for other materials for building elements and furniture, or ethically sourced timber is used, which are generally more sustainable than even timber substitutes.
The primary advantage of passive houses is the reduced energy usage, which, in addition to being environmentally friendly, is also likely to save costs and be more cost effective in the long term. Maintenance is also minimised as there are fewer building services to maintain. This is also applicable to the repair of building services as the very minimal services present in the home is not likely to require repair for many years. Certain proponents argue that passive building environments are healthier than traditional environments sue to the cleaner air and natural temperatures possible, although this is debatable, as natural air is not always cleaner than conditioned air. Passive homes also maintain their internal temperature and comfort for longer in the event of power failures and rely less on external supplies of power and water.
Passive houses have several requirements for operation, as specified in their certifications such as PHI and PHIUS+, which are distinct from other green building certifications such as LEED. They generally consider the principles of passive building design – superinsulation, airtightness, thermal performance, lighting, shading, and orientation, and mechanical ventilation. The former principles deal with the indoor air quality and comfort whereas the latter reduce the need for energy-suing artificial services.