Restoration and retrofit - The Hempcrete Topic: Designing and Building with Hemp-lime - page 459

edges' to get maximum thermal performance out of the system. This might include, for
example, installing a wood-burning stove instead of the open fire, adding hempcrete solid-
wall insulation (if possible to the outside of the wall), fitting natural-fibre loft insulation in
the loft, reducing air leaks (but crucially not all of them), possibly introducing controlled
ventilation, and installing natural insulation between suspended timber floors.
Hempcrete, sometimes alongside other natural-fibre insulations such as hemp-fibre or
sheep's-wool quilt insulation, has proved itself capable of bringing solid-walled heritage
properties up to a modern standard of insulation if used as part of a sensitive and thoughtful
restoration or retrofit of the building. In the case of listed buildings, this is sometimes
a little more difficult, because it is necessary to work within the sometimes exacting re-
quirements of the responsible body with regard to maintaining the original appearance of
the building inside and out. This can limit, for example, the available thickness within
walls or roofs into which hempcrete can be cast. However, under the Building Regulations
2010, listed buildings, buildings in conservation areas and scheduled monuments are ex-
empt from Part L of the Building Regulations (Conservation of fuel and power), so there
is no longer a specific standard to be met. It is also worth noting that, according to English
Heritage, special consideration under Part L should be given to “buildings of traditional
construction with permeable fabric that both absorbs and readily allows the evaporation of
moisture (which can conflict with modern materials and methods)”. 3
The aim for such buildings should be to improve energy efficiency as far as is reasonably
practicable without affecting the character of the building or increasing the risk of long-
term deterioration of the existing fabric. For a thorough discussion of how to retrofit insu-
lation and renewable energy solutions to improve the sustainability, energy efficiency and
comfort of heritage buildings without detriment to their character or to the vapour-perme-
able building fabric, a good resource is The Old House Eco Handbook by Marianne Suhr
and Roger Hunt (see Bibliography ) .
Benefits of hempcrete for heritage buildings
Not only is hempcrete a suitable insulation material for use in a range of situations in older
buildings, but in fact there are many situations, especially in listed buildings, where hemp-
crete is the only suitable insulation material. It is worth reiterating that, as with any struc-
tural intervention in an old building, hempcrete should be applied only within the con-
text of a holistic review of the thermal performance of the entire building, undertaken by
someone with specialist knowledge about the way in which old buildings work. That said,