INHIBITING CONDENSATION

Condensation is an increasing problem due to the trend towards more variable and extreme weather conditions producing more frequent cycles of warmth and humidity followed by cold, - ideal conditions for condensation.

In addition increasing standards of insulation create greater temperature differences between the warm and cold side of structures whilst barriers to the passage of water vapour are not as effective or non existent, again creating the perfect conditions for condensation.

Condensation occurs when warm air, containing a large amount of water vapour cools. As the air and water vapour cools, it is progressively able to hold less water vapour, the excess water being deposited in the form of droplets on cold surfaces.

The air may cool due to normal variations in outside temperature, this gives rise to condensation on single skin surfaces such as metal roof sheeting or steel boat hulls overnight.

Alternatively, the warm moisture vapour may cool as it migrates from a warm area to a cold area. This is the process that causes condensation in rooms adjacent to areas of high heat & humidity such as kitchens & bathrooms, in lofts and on roofing above suspended ceilings or underlinings, especially where the linings are insulated. The ability of moisture vapour to travel between rooms and through the joints and materials of many forms of building construction is often not appreciated.

Sprayed polyurethane insulation is effective in curing condensation problems because it is applied directly without joints onto the cold surfaces on which condensation takes place. It is the best insulation material available and transforms the previously cold surface into a relatively warm one on which condensation will not take place. In addition, because the material is continuous and has low water vapour permeability, it does not allow water vapour to travel through it to reach the cold surfaces as happens with most other insulation and building materials.

25mm thickness of sprayed polyurethane foam is sufficient to prevent condensation occuring on single skin surfaces under normal ambient conditions in the British Isles. Greater thicknesses may be required under adverse conditions of high humidity and low temperature.

25mm thickness of sprayed polyurethane foam will reduce the U-Value (potential for heat loss or gain) of a corrugated single sheet from 7.8W per sq mDegC to 0.82W per sq mDegC, a 90% reduction. Apart from solving condensation problems, the treatment will save 90% of your heat from escaping in winter and will have the opposite effect in summer, preventing solar heat gain and keeping your premises cool.