Finishes for hempcrete - The Hempcrete Topic: Designing and Building with Hemp-lime - page 423

should be given time to dry out fully before any non-porous surface finishes are applied,
however limited in area (see Chapter 19, page 264 ).
The second reason why internal surface breathability is desirable is to do with indoor air
quality and human health. As discussed in earlier chapters, a breathable wall buffers mois-
ture, absorbing and desorbing it from the air in response to changes in internal humidity,
thereby maintaining a healthy indoor air quality. If non-porous surface finishes are applied,
this function is reduced, and it is in the kitchen and bathroom where it is especially needed,
since it is here that excessive moisture is created by human activity, leading to significant
changes in the relative humidity of the internal air.
For this reason, we recommend that tiled surfaces should be kept to an absolute minimum,
for example for splashbacks behind sinks, and waterproof paints should never be used. In-
stead of trying to make the surface of the wall water-resistant, the answer is to increase
surface breathability through the use of finishes that are especially good at regulating hu-
midity, such as clay plasters and certain paints. Where large areas of tiling is necessary,
for example in showers and wet rooms, think about this at the design stage and try to site
these against internal walls (that are not constructed from hempcrete) so that the external
hempcrete wall remains breathable.