All buildings should be affordable, safe, healthy, sustainable, comfortable and desirable, and unfired earth as a building material achieves these basic benchmarks.
Earth building is appropriate, renewable and sustainable technology that allows developers to aim for – and achieve – carbon zero impacts. The practice is ancient and yet still most relevant as the ultimate green building material. But how is it a fit with the modern world in a practical sense from design, through construction and operation?
Are earth materials and products available for sale? Are there consultants who understand it, who are confident and competent designing and specifying the use of it? Are subcontractors available to tender on work and get it done? Can it be built quickly and efficiently? Can other trades be integrated into the construction process smoothly? Can it achieve the look and quality of finish clients and architects are looking for?
The answer is yes to all of the above. It is worth noting, however, that with any unfamiliar material or process you need to do some research and learning, and with earth building experience is more important.
A good place to start is the Earth Building Association of Australia (EBAA.) The EBAA is a not-for-profit association with the aim to foster and promote the use of unfired earth in Australia and worldwide. It exists to help and provide information, and it has a useful website and practitioners page that lists a number of suppliers, consultants, contractors and subcontractors. It sells a book on the subject of earth building, and it hosts a national earth building conference each year to share practical skills and knowledge on earth building. In November 2017, it will host its first international conference.
The most common techniques of earth building used in Australia are earth brick (puddled mud brick and pressed earth bricks) and stabilised rammed earth. Cob is having a renaissance and medium density and light earth is emerging in colder climates as a response to legislation around R-values.
Mud brick and cob are often chosen by self-builders and for use in community buildings programs due to better utilisation of labour and reduced set up costs. There are locations in Australia where professional builders are engaged in these techniques and products like bricks, mortar and earth renders and coatings are readily available locally.
Rammed earth subcontractors specialise in building just walls utilising machinery and equipment, so they rely on high volumes of work and necessarily are often more used to travelling for work. It is more possible to employ a rammed earth contractor anywhere in Australia, though with travel comes additional costs associated with living away from home, travelling, transport of equipment and machinery and cost of living away from home. Rammed earth is more portable, though higher costs are naturally reflected in wall rates. In remote locations, these costs affect all building systems, though it is more likely earth will win out due to wide spread availability of suitable local material.
In parts of Australia such as WA, where heavy mass buildings like cavity brick and rammed earth dominate the market, rammed earth subcontractors are more widely spread and therefore locally available. In addition to this suitable materials are easily available and well understood. This has led to a more competitive industry in WA.
The speed of construction with earth brick and rammed earth can match or exceed that of standard lightweight construction when you consider an earth wall is completed in one process. There are no following trades insulating, cladding, lining rendering, plastering or painting. The rammed earth walls of a home may be totally completed in two to five weeks. For very large projects, rammed earth projects sub contractors sometimes team up. The time frame for building earth walls meets standard industry contractual obligations and expectations. Rammed earth and other unfired earth wall construction techniques meet modern OHS requirements in full.
Conduits for electrical and communication services are generally built into rammed earth walls during construction, as are hold down bolts, so this needs planning and consideration. An electrical/communications/TV plan not just a great idea, it is essential.
There are a growing number of architects, engineers, builders and tradesmen with earth building experience. There are also a number of suppliers of admixtures, sealers, earth renders, earth bricks, earth mortars and paints available.
So how much maintenance is required and how efficiently do earth walls operate? What are their sustainability credentials? What is it like for occupants of earth buildings? Is it possible to enjoy fresh air without blowing energy efficiency out the window?
Earth walls are durable, non-toxic, non-allergenic, fire proof and sound proof. Rammed earth with an off form finish requires a dust down and seal, and after that, it’s done. And most people love the look of earth walls, especially rammed earth walls, which have a slick modern natural aesthetic.
The limitation with renewable energy like PVs is storage. Earth offers thermal mass with the lowest embodied energy. It is the battery through fabric energy storage (FES).
Earth walls work well both externally and internally, though it is important to design for climate for best results. The earth walls absorb, store, and radiate not just the warmth of the day but also the coolness of the night. Not only does earth balance temperature, but its hygrothermal properties allows earth walls to also balance humidity.
Furthermore, the permeable nature of earth and the characteristics of clay endow earth walls with phase change like properties through the latent heat of vaporisation. As climate change predictions manifest themselves and we are subjected to heat waves and rapid fluctuations in temperature, the value of FES will come to the fore.
A number of architects are winning international and national prestigious awards for homes and public buildings built with unfired earth. This high exposure of earth walled buildings plus a desire for more natural healthy building alternatives augurs well for earth building, as does any focus on life cycle design. Unstabilised earth walls have extremely low embodied energy, and the sustainability credentials of earth are second to none.
Hopefully, the international movement away from conditioned sealed and insulated buildings and toward climate responsive naturally conditioned buildings will catch on here. The benefits of mass-linked ventilated naturally conditioned buildings include better energy efficiency, improved stability of internal conditions through fabric energy storage, better indoor air quality, higher productivity and appropriate levels of adaptive comfort based upon a direct feedback link with external conditions.
And yes, your building can communicate with the outdoors and you can enjoy fresh air guilt-free, because ventilation doesn’t ruin energy efficiency in mass-linked ventilated buildings as it does in light weight insulated buildings and well sealed conditioned buildings. In actual fact, ventilation is necessary for energy efficiency in mass buildings.
Surely earth buildings are more than dreams; they should be the aspiration of modern sustainable architecture in an advanced economy.