Make Mine a Hemp and Lime
Called the "HemPod," this one-storey building has highly insulating walls made from the chopped woody core, or shiv, of the industrial hemp plant mixed with a specially developed lime-based binder.Manyof the same features of "breathable walls" and built-in thermal mass can be found in more primitive materials such as slip-form compressed straw-clay walled buildings. But it seems more likely that more processed hemp materials combined with a lime binder would be far more durable than the clay slip walls. It will be interesting to see the data that comes out of this experiment.
The hemp shiv traps air in the walls, and the hemp itself is porous, making the walls incredibly well insulated. The lime-based binder sticks together and protects the hemp and makes the building material highly fire resistant.
..."The walls are breathable and act as a sort of passive air-conditioning system, meaning that the internal humidity is kept constant and the quality of the air within the house is very good. The walls also have a 'virtual thermal mass' because of the remarkable pore structure of hemp shiv combined with the properties of the lime binder, which means the building is much more thermally efficient and the temperature inside the house stays fairly constant."
Professor Pete Walker, Director of the BRE Centre for Innovative Construction Materials, added: "The aim of the project is to provide some robust data to persuade the mainstream building industry to use this building material more widely.
"Hemp grows really quickly; it only takes the area the size of a rugby pitch to grow enough hemp in three months to build a typical three-bedroom house.
..."Every part of the plant can be used, so there's no waste -- the shiv is used for building, the fibres can make car panels, clothing or paper, and the seeds can be used for food or oil. So it's a very efficient, renewable material.
"Lime has been used in construction for millennia, and combining it with industrial hemp is a significant development in the effort to make construction more sustainable."
Environmentally-friendly building materials are often more expensive than traditional materials, but the Renewable House project (www.renewable-house.co.uk) funded by the Department of Energy and Climate Change (DECC) and the National Non-Food Crops Centre (NNFCC) demonstrated a cost of around £75,000 (excluding foundations) to build a three-bedroom Code 4 house from hemp-lime making it competitive with conventional bricks and mortar. _SD