Civil Engineering Reference
In-Depth Information
we want is not a damp-proof course but one
with a capillary break, which will let water
pass down through it but won't let it travel
upwards.
the construction industry actually provides
us with houses that do this. The cavity-wall
system will never provide a thermally
efficient, cost-effective solution to house
building, and no amount of tinkering with it
will alter this. However, if we did continue to
use the cavity-wall system, the cavity would
have to become very wide just to allow
enough space to fit in the amount of insula-
tion it would need to match the thermal
efficiency of a strawbale wall.
For thermal efficiency, use insulating
materials
To meet the challenges of the twenty-first
century - to build houses that are energy-
efficient and require very little fuel to heat
them - we have to make sure that the
foundations do not allow cold into the
house via what's known as a 'cold bridge'.
The space we live in needs to be wrapped
in a complete thermal envelope, with no
gaps. So, while taking into account all of
the above points, we also need to choose
materials that will act as a heat/cold barrier,
and use enough of them to actually work!
Ideally these materials need to be non-
porous, loadbearing and environmentally
sustainable as well. The only real option at
the moment for the internal skin of a plinth
foundation is recycled foamglas block. The
infill between the outer and inner skin could
be either a different type of recycled foam-
glass (recycled foamglass [rfg], available in
small chunks), or leca.*
Low-impact foundations
Clearly the most low-impact foundation you
can possibly design is one that requires no
intervention at all but simply uses the Earth
itself. For all foundations the topsoil must be
removed because this will always compress
and compact, and if you have very deep
topsoil this might mean that your foundation
needs to be quite tall, to bring your building
clear above ground level. But wherever you
have good bearing soil, there is never any
need to dig trenches into the subsoil. The
most you may need to do is widen the width
of your foundation as it touches it.
However, you may have some trouble
arguing this with your building inspector,
because these methods are not detailed
in the Building Regulations Guidelines
(mind you, neither are quite a few other
common building methods). It's a common
misconception that all houses need to have
cement-filled trenches as their foundations.
Insulating materials need to be sufficiently
insulating to at least meet Building Regula-
tions, but the Regulations in the UK and
Ireland do not as yet go far enough to
provide thermally efficient houses. Although
we know that we need to reduce our
dependence on fossil fuels and our energy
needs, which can be partially achieved by
building houses that require very little heat,
the government is reluctant to insist that
Another low-impact solution is to use
pillars or piers instead of a strip foundation.
* Foamglas is a rigid, lightweight and highly insulating material made from recycled bottles - see www.foamglas.co.uk. Recycled
foamglass (rfg) is available from www.lime.org.uk or www.womersleys.co.uk. Leca, also known as Optiroc, is lightweight blown
clay particles, sometimes used in agriculture for aerating soil.
