Key concepts in sustainable building - The Hempcrete Topic: Designing and Building with Hemp-lime - page 90

The thermal mass of hempcrete also plays a part in achieving a good indoor air quality,
because of its implications for ventilation practices (see box on page 311 ) . In short, the in-
door air quality in hempcrete buildings is excellent. In summary, this is achieved by:
the hempcrete, together with lime or clay plasters, acting in a hygroscopic way - ab-
sorbing and releasing moisture and keeping the humidity of the indoor environment
within levels optimal for human health
there being no toxic chemicals or VOCs present in hempcrete to off-gas into the air
the thermal mass of hempcrete enabling the storage of heat in the building's fabric,
which is only released very slowly when the temperature of the nearby air cools, thus
allowing some use of natural ventilation (i.e. opening windows) to maintain indoor air
quality, without all the heat escaping.
These factors combine to ensure that a hempcrete building provides a natural, healthy and
comfortable living environment with little or no recourse to mechanical ventilation sys-
tems.