Thermally efficient and bushfire resistant – could a prefab home be the answer?

There’s good reason why the Green Rebuild Toolkit features so many prefab or modular homes in regional and rural locations. Using a prefabricated construction method reduces the amount of tradespeople required to attend a possibly remote site throughout the building process, and the expense that can incur. Many elements of a prefab home arrive at the site already complete, and simply need to be assembled and hooked into utilities, meaning a faster construction time for property owners displaced by a bushfire.  

Belinda Smart, author of the Renew magazine Prefab Buyers Guide says that prefab construction can also create a more thermally efficient and bushfire resistant home. “The way that state-of-the-art prefab homes are built means that the seams and joins between elements tend to be tight, making the house airtight which reduces energy use and bills, and the risk of embers entering the home in a bushfire crisis. Many Australian prefab suppliers, particularly in the architectural home category, have developed their own insulation solutions for walls, roofing and other components, giving you greater access to modern building materials such as Structurally Insulated Panels (SIPs) for greater thermal efficiency.” 

Prefab construction methods can be divided into two broad categories: 3D or volumetric (often referred to as “modular”) and 2D (referred to as “panelised”). Both can be executed in a variety of materials, and can be combined on the same project. 

Some are like this barrel-shaped home by Designology in the fire-affected region of Kinglake (2009, Black Saturday) that can essentially be ‘shuttered down’ in the event of a bushfire. With a BAL-40 rating it’s heavy on the non-combustible materials. The heavily insulated corrugated iron curved structure allows easy water capture and storage, and the remote-operable arched awnings can be used for shade, insulation, and to capture and funnel cool breezes for cross-ventilation.  

Other methods use composite materials in the construction for fire resistance. Melbourne-based modular design and build company Habitech Systems use SIPs (Structural Insulated Panels) made from expanded polystyrene (EPS) sandwiched between plantation-grown Australian plywood and magnesium oxide (MgO) board cladding. Magnesium Oxide is fire resistant and it also makes the board incredibly strong and durable, as well as water, UV and mildew resistant. The board is made from 50 per cent recycled timber and sawdust, combined with MgO and fibreglass mesh.  

The issue of prefab home affordability is one to consider. “Generally speaking, prefab solutions do require less labour on site, but some costs may be transferred to the pre-site environment in terms of design and manufacture. Prefab houses do undoubtedly become more cost-effective once you take into consideration the speed with which you can take occupancy and the resultant savings in rent. There are also potential savings on energy bills over the life of the home,” says Belinda.