Civil Engineering Reference
In-Depth Information
finishes as soon as possible, and the slow drying of hempcrete is therefore seen as a negat-
ive attribute of the material.
We would hope that the construction industry will adapt to using natural materials, rather
than the use of natural materials being adapted for the construction industry. There is no
reason, except perhaps extra scaffolding costs or a desire to apply the external render be-
fore the onset of winter, why the exterior of a hempcrete building could not be left un-
rendered while the internal fixings and fittings were done and the use of the building com-
menced. The external finish could be applied several months later without detriment, as
long as the hempcrete walls were not in such an orientation or elevation as to be exposed to
driving rain, in which case they would need some temporary protection from the weather.
Currently, however, the construction industry is a long way off from this kind of thinking,
and at the present time anything that requires finishes to be applied later than they would
be on a conventional build causes suspicion and uneasiness. Drying time will always be an
important issue, and is of course dependent on local conditions, but with good site organ-
ization and planning there are some obvious things you can do to minimize delays.
The effect of temperature on drying time is easy to predict, since warm air 'holds' more
moisture (really meaning that the warmer the air, the more moisture can evaporate into it).
Water droplets passing out of the open structure of the unfinished hempcrete wall do so
more quickly if the air next to the wall is warmer.
Take appropriate steps, therefore, to maximize temperatures next to the wall. Outside the
building, the effect you can have on temperature is limited, though don't underestimate the
importance of clearing away anything that is stopping sunlight from falling on the wall's
surface; in particular, make sure that nothing is left leaning up against, or stacked very
close to, the wall. Inside, maximizing the temperature might mean sealing up and heating
the interior space, if you are really worried that drying is happening too slowly. Avoid us-
ing gas-powered space heaters, as these emit a certain amount of water vapour into the air
as the gas is burnt. If you have to resort to heating, however, think about what happens as
soon as the temperature falls again. As the temperature of the air next to the wall drops,
the wall is likely to reabsorb some of the moisture that was released into the air, if it is still
present as moisture in the interior space.
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