Civil Engineering Reference
In-Depth Information
This flashing system is a dramatic improvement on the use of conventional flashing
as it enables you to fill the cavity between the window and the window buck or frame.
This can be done by inserting straw, cob, bulk insulation or foam into the cavity thereby
reducing the likelihood of thermal bridges and condensation between the window and
the window buck.
Foam fill sealing of windows
Following my experience with the use of foam to seal windows in existing houses I have
no hesitation in putting up the use of foam to seal windows in straw bale houses as the
best option.
As detailed in Chapter 5, the window buck should be built with an opening 40 mm
greater in height than the overall height of the window. This will allow a 30 mm gap for
the insertion of the compression strapping and two coats of render. The two coats of
render will run from the inside to the outside of the wall beneath the window (see Figure
10.8) leaving 6-10 mm of space between the underside of the window and the surface of
the render. This in itself provides an extremely good seal of water to the bales if for some
unforeseen reason the window sealing did fail.
Figure 10.8
Expanding foam sealant in the installation of a window at its sill
Fit windows after the second coat of render
You will probably find it easier to install the window following the second coat of render,
however this is of little consequence and entirely up to you. Might I add at this point, you
will gain a better fixing of the render to the window buck if the timber is treated with the
glue and sand mix. If after applying the first coat of render you are dissatisfied with the
shape, you may wish to build up the shape of the window sill with cob prior to the
second coat. This should not be done until the first coat of render is dry (see Chapter 11
on rendering).
