Restoration and retrofit - The Hempcrete Topic: Designing and Building with Hemp-lime - page 453

The original use of hempcrete, and still one of the most important, is in the repair or
restoration of heritage buildings. Various terminologies exist to describe old build-
ings in the UK. In this chapter we use the generic term 'heritage buildings' to en-
compass both historic buildings (those buildings considered to be of historic import-
ance: listed buildings or scheduled monuments, or those in a conservation area) and
vernacular buildings (traditional buildings constructed before around 1850 by local
craftsmen using local materials, and without recourse to formal architecture).
In fact, the vast majority of buildings constructed before the First World War were built
using natural materials including lime or earth mortars, plasters and renders, in a breath-
able solid-wall construction. As discussed in Chapters 3 and 4 , the use of vapour-perme-
able materials enabled the self-regulation of moisture levels within the structure, prevent-
ing the build-up of excessive moisture within the building's fabric. The hygroscopic nature
of many of the materials also buffered moisture levels in the indoor air, helping to keep the
internal environment healthy for the occupants.
Misguided repair during the twentieth century using hard cement renders and mortars,
gypsum plaster and non-vapour-permeable paints and finishes has left many of our heritage
buildings in a 'non-working' state. Such repairs often result in high levels of moisture be-
ing trapped in the fabric of the building, causing damage to the structure, reducing thermal
performance and leading to damp and mould within the living spaces. This has given old
buildings an undeserved reputation for being uncomfortable places to live. Thankfully, in
recent years, with increased understanding of the issues involved, there has been a resur-
gence in the use of traditional materials, and the mistakes of the past are being corrected.
This is particularly true in the case of historic buildings, and any works carried out on
them is strictly controlled by the responsible organization (for example, English Heritage
in England).