At the Natural Home, we have advocated the specification and use of natural materials as best practice in building design and construction. Firstly, these materials have no adverse health effects on the occupants. Secondly, these materials typically require very little processing from their raw state to become construction materials (when compared to oil or concrete based products) and have a very low environmental impact and embodied energy as a result. Increased embodied energy goes hand in hand with increased CO2 emissions.
So where does the balance lie between the energy used in the manufacture and construction of a building versus the energy saved in is usage due to the efficiency of the building fabric?
As buildings become more energy efficient (thereby using less energy in their operation), the energy used in the manufacture and transportation of the materials becomes increasingly significant as a proportion of the energy used over the lifetime of the building.
Natural materials can also lock up or ‘sequester’ carbon from the atmosphere as they absorb it during e.g. the growing of trees, hemp and wool. Through this process they can reduce the carbon in the atmosphere. The issue with oil and concrete based materials is that they require large amounts of energy and thus CO2 emissions in their manufacture and transportation, and do not sequester carbon. Once this carbon is released into the atmosphere it stays there and continues to have an adverse effect on the climate ad infinitum unless it is reabsorbed.
If, for example, 30 tonnes of CO2 are emitted in the construction phase of a building, this CO2 will be doing 30 tonnes worth of damage every year. This energy efficient building may only emit 2.6 tonnes per year in its operation. The result is that the payback point for the energy invested in the construction versus the energy in operation is around 25 years. This makes the case for minimising the embodied energy in the materials we use to make our homes, and also designing buildings that are durable and have long lifetimes.
 ‘Embodied energy – a ticking time bomb?’ Selincourt, K., Green Building Press (2012)