After the September earthquake in Christchurch, many people were interested in which structural elements of the homes affected had fared well, and which had not. After the latest quake, with even more damage, this has again been a topic of interest. In addition, many people are starting to see the value of built in ‘self sufficiency’ features that may help you through the early days of a disaster.
Regarding structural reliability, concrete slab foundations and masonry chimneys have come under scrutiny, with the NZ Wood organization advocating timber pile foundations have more structural integrity and are more easily repaired than concrete. It is important to note, however, that most of the serious damage to both concrete slabs and masonry in the September quake was to older, unreinforced systems, as outlined in a very useful report by Andrew Buchanan and Michael Newcombe of the Department of Civil and Natural Resources Engineering at the University of Canterbury, Reinforced slabs and masonry such as the super insulated Rib Raft foundations and Timbercrete walls and chimneys in ebode homes, performed well.
Notwithstanding earthquakes, the thermal massing properties of both the concrete slab and Timbercrete walls in an ebode significantly reduces the additional energy needed for heating over the life of the house, which timber pile foundations do not provide. So it’s a case of balancing performance over the life of the house with performance in extreme and unpredictable situations.
Most of the damage to foundations in the first quake was due to ground liquefaction, which is not something that can be controlled by the structure of the building – specific engineering for the local geological conditions may help, but the forces of nature are very unpredictable and in some cases it may be better to build elsewhere. This is why ebode always obtains a geotechnical report before beginning design work on a house – and if you are buying land, you may wish to consider doing this before purchasing.
Timber wall framing was also found to perform well in the first Canterbury earthquake, although the Buchanan & Newcombe report did touch on the fact that damage to linings could potentially affect the bracing in a house. We believe that the heavier linings (13mm vs the average 10mm) and wider exterior framing (150mm vs the average 90mm) used in ebode homes should generally improve their resilience in an earthquake.
The structure of your home aside, many people affected by the Christchurch earthquake found that lack of heating, power and water were the most immediate problems to overcome. While most urban ebode homes are not specifically designed to be autonomous, they have many features which may help you cope in the immediate aftermath of a disaster, and can easily be upgraded to a fully autonomous home.
The Pyro Classic fire, in addition to providing efficient and low emission heating, can also be used for cooking and water heating when other services are cut off. All ebode homes have a large non-potable water storage system, and water from this can be boiled and used for drinking in emergencies. The system can also be upgraded to a potable system, either at the time of building or later. And every ebode home includes a grid connected photovoltaic electricity system, which is capable of producing enough power to run key appliances during power outages. As it is a legal requirement for all grid connected systems to shut down if there is a mains power outage, the standard PV system would require the addition of a battery backup facility in order to be used in an emergency.
We expect the issues of maintaining body and soul as well as structural stability in disasters to become a more frequent topic of concern with our clients, and are happy to discuss options with anyone looking at building a truly sustainable home.