One of the challenges for a timber-framed house is that while you can insulate it well, it has very little “thermal mass”. This means that if you open a door and all the warm air rushes out (during winter), or rushes in (during summer), then the insulation is for nothing. Thermal mass helps to buffer this, keeping a more stable temperature.
One of our solutions is to build a rammed earth wall down the centre of the house. This will be 300mm thick, and about 5m long. By having it entirely in the house, it stabilises to the internal temperature. It will also be a great feature wall in what will otherwise be a quite simple extension.
Rammed earth walls are a wonderfully simple technology. You basically put in earth (in this case decomposed granite), plus 5% cement, and then pound it solid. The result is effectively a low-strength concrete, albeit much more attractive.
It turns out there are only a few people who specialise in rammed earth walls, and they’re all very friendly. We’ve picked Robert Cotterill from Rammed Earth Solutions, located on the Central Coast of NSW. He’s been spectacularly helpful from the outset, and it was good fun visiting his property to see some sample walls (above and below). Apparently it will only take a few days to construct our quite large wall, and the costs are very reasonable. It’s also a lot more environmentally friendly than concrete!
In Australia, rammed earth walls aren’t widely used outside of wineries it seems, which is a pity. If your architect or engineer is unsure, get them to obtain a copy of Building with Earth Bricks and Rammed Earth in Australia from the Earth Building Association of Australia. (Following this will also keep you in compliance with the Building Codes of Australia.)
There’s a lot more that we’ve learnt about rammed earth walls, so feel free to ask questions in the comments…