Main image: PolyKey Cavity Wall & Floor insulation
Winter rainfall areas are particularly susceptible to condensation on the inside surface of building shells during cold weather. The condensation is due to the differential temperatures between the heated interior air and the icy cold exterior.
This dampness not only causes damage, but can also result in mould growth and health issues. Condensation will always be a problem if there is only a single walling layer, regardless of how thick it is.
Cavity walls and their purpose
The cavity wall method of construction is to naturally insulate buildings in a cold, wet climate. It is composed of two masonry walls separated by an airspace (cavity). According to the new SANS 10400-XA, Thermal Performance Requirement, the cavity must be a minimum width of 50mm all over.
Correctly built cavity walls are marginally more energy efficient than regular double brick walls but should easily be upgraded by adding thermal insulation in the cavity. Insulating a cavity wall reduces the energy used for heating and cooling, thus reducing electricity costs and CO₂ emissions (see diagram).
Filling that gap
PolyKey is a cavity filler made by Technopol SA to address problems associated with cavity wall insulation. With the now compulsory open cavity walls, mortar droppings will become an issue during construction.
Filling the cavity will cause issues such as:
Higher moisture penetration.
Corrosion of wall ties could lead to instability of cavity walls.
Regular insulation boards used in cavity walls may shrink, causing uninsulated gaps that will result in surface condensation in areas.
PolyKey addresses all these issues. It will not shrink to form cold gaps, so, condensation is reduced and better localised to areas where it can be drained through weep holes