Passive survivability refers to the building's ability to maintain critical life-support conditions in the event of extended loss of power, heating fuel, or water. This is proposing that in a disaster situation whether it be a storm that causes a power outage and is unable to keep the interior of the building cool in severe climates, a drought which limits water supply, or the gas pipes get disconnected and the building is without gas, designers should incorporate ways in which the building is then capable of continuing to shelter the inhabitants for an extended period of time.
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The term was coined by BuildingGreen President and EBN Executive editor Alex Wilson in 2005 after the wake of Hurricane Katrina. Passive Survivability is suggested to become a standard in the design criteria for houses, apartment buildings, and certain other building types. While many of the strategies considered to achieve the goals of passive survivability are not a new concept and is widely known and used throughout the decades of green building, the distinction comes from the motivation for moving towards high-performance and renewable power design buildings.
Problems
In much of the urban world with populated cities and residential areas, there is a heavy reliance on a grid for power and gas. These grids are the hub of energy for many of these societies and while they generally do not get interrupted, they are constantly prone to elements which may cause disruption. These potential hindrances can occur from a multitude of conditions ranging from natural disasters, extreme climates, and acts of man. Passive survivability aims to be prepared for when such an event may occur. One of the issues that passive survivability looks at is how to increase ventilation flow throughout a building so that a building can stay oxygenated while keeping the interior temperature regulated. Another is considering the many ways to keep thermal resistance of a building skin to prevent a room from becoming overbearing in the event of having a lack of access to standard temperature regulating systems. Key sources such as power lines, telephone lines, water pipelines, electricity boxes, or fuel pipelines, are potentially fragile components that can be and is often disrupted during such adversities as earthquakes, storms, and extreme weather. Other factors to be mindful of when applying passive survivability are:
Strategies
The over arching goal of passive survivability is to try to reduce discomfort or suffering in the event of having a key source cut off to a building. There are several different solutions to any one design problem. While many of the solutions that are presented by advocates of passive survivability are ones that have been universally accepted by passive design and other standard sustainability practices, it is important to look over these measures and apply the appropriate strategies to developing and existing buildings in order to minimize the risk of displeasure or death.
Buildings should be designed to maintain survivable thermal conditions without air conditioning or supplemental heat. Providing back-up generators and adequate fuel to maintain the critical functions of a building during outages are conventional solutions to power-supply interruptions. Indeed generators need to be part of the answer in some situations, such as hospitals. However, unless they are very large, generators support only basic needs for a short amount of time and may not power systems such as air conditioning, lighting, or even heating or ventilation during extended outages. Back-up generators are also expensive both to buy and maintain. Storing significant quantities of fuel on-site to power generators during extended outages has inherent environmental and safety risks, particularly during storms. Passive solutions, such as designing highly efficient building envelopes, providing natural ventilation and day-lighting, and incorporating passive solar design can also contribute to a facility’s passive survivability. Renewable energy systems can provide power during an extreme event . For example, photovoltaic (or solar electric) power systems, when coupled with on-site battery storage can provide electricity when the grid loses power. Emergency water supply systems such as rooftop rainwater harvest systems can provide water for toilet flushing, bathing and other building needs in the event of water supply interruptions. The list below outlines aspects of a building’s design that should be taken into consideration when planning for passive survivability.