Performance of hempcrete in a building - The Hempcrete Topic: Designing and Building with Hemp-lime - page 129

For example, the quality and particle size of the hemp shiv can affect the structural in-
tegrity of the cast hempcrete and also its mechanical behaviour (how it reacts when it is
subjected to a force which tries to stretch, dent, scratch or break it); the amount of binder
in the mix ratio can affect the acoustic properties; and variation in the degree to which the
material is compacted during placing can affect the thermal performance. In many cases,
a particular characteristic of the finished cast material will be affected by two or more of
these variables.
This concept might at first seem confusing, and indeed it is the main cause of unintended
consequences when novice builders use the material, and the reason why hempcrete has
developed an undeserved reputation in some quarters for being 'unpredictable'. In fact,
it is anything but. Those who take the time to understand these basic variables will find
that hempcrete is a versatile material with some important core characteristics, and that it
can be adapted to suit a range of situations and applications through the manipulation of
these variables. We hope that the themes that crop up again and again in the descriptions
of hempcrete's performance in this chapter will demonstrate what we mean.
It is not our intention here to provide the reader with a full account of the biological, chem-
ical and civil engineering background that underpins the use and performance of hemp-
crete. Rather, by summarizing key findings about hempcrete, with reference to relevant
standards defined by the regulations governing building materials and buildings in the UK,
we hope to aid a broad understanding of the unique way that the material performs in a
building.
Those who would like more detailed information on the science of hempcrete would do
well to start with one of two 2013 publications, which collate much of the research find-
ings to date (for full details see Bibliography ).
Sofiane Amziane and Laurent Arnaud's (2013) topic Bio-aggregate-Based Building Ma-
terials: Applications to hemp concretes deals quite comprehensively at an academic level
with a range of issues relating to the production and use of hempcrete, within the wider
general context of plant-based aggregates. The authors investigate the factors that affect
the performance of hempcrete, including binder type, variations in shiv parameters, and
mixing and placing technique, and they present findings on its vapour permeability and the
hygrothermal, mechanical and acoustic behaviours of hempcrete.
Covering much the same ground in a more accessible, although necessarily less detailed,
way, a thorough review of the literature concerning the performance of hempcrete was