Key concepts in sustainable building - The Hempcrete Topic: Designing and Building with Hemp-lime - page 74

[carbon offsetting] to compensate for carbon emissions reductions that are diffi-
cult to achieve on site. 2
Lamentably, not only does this definition appear to focus entirely on energy in use, with
no reference to lifecycle analysis (LCA) or embodied carbon, but it even then offers con-
tractors a 'buy-out' alternative to putting effective measures in place. In light of this, the
chance that we will have anything resembling zero-carbon homes by 2036, let alone the
government's target of 2016, seems increasingly unlikely.
Synthetic insulation
The insulation value of materials that can be introduced into our homes, both new and ex-
isting, to reduce energy loss through the building's fabric is of course a necessary focus.
But unfortunately there has been no thought given in the regulatory framework to the em-
bodied energy of any particular product.
Most highly efficient insulation materials are responsible for very high carbon emissions in
their manufacturing process, and in many cases are made from the very carbon-based pet-
rochemicals the use of which we are trying to limit. In addition, these materials are often
made many thousands of miles away from the location in which they are used, and are
therefore responsible for significant fuel use in their transport.
To properly assess a material's embodied energy means conducting a thorough LCA of the
carbon emissions associated with it at every stage during its life. This includes the carbon
cost of obtaining the raw material, the manufacturing processes, transport, how it is used,
the implications of its use compared with an equivalent material, and removal and disposal
or recycling at the end of its life. The failure to gather this information and use it for mean-
ingful comparison between different materials has led to a rush towards the use of high-
embodied-energy, synthetic insulation products and a blind assumption that 'any extra en-
ergy consumed now will be worthwhile for the energy savings further down the line'. Un-
fortunately, the more that we examine the true figures involved, this simply doesn't stack
up, with synthetic solutions often consuming more energy in their production than they
will save in the next 20-30 years. 3
Furthermore, there is concern that the indiscriminate use of synthetic insulation products
is contributing to hazardous indoor air quality conditions in many buildings. Lightweight
insulation materials rely for their effectiveness on stopping the loss of heated air from the
building. This obviously requires the elimination of any open channels or gaps in the fab-