House envelopes are becoming more airtight. While this aids thermal efficiency, it can cause problems with internal moisture. BRANZ’s 2015 House Condition Survey identified mould in 49% of houses surveyed. In 22% of houses, this was rated as Moderate to Extensive.

Water vapour is produced by activities in the house such as breathing, bathing, cooking, drying and un-flued gas heating. Water vapour is lighter than the other bulk components of air, hydrogen and oxygen, so a lot of this finds its way out of the living areas by way of the ceiling. If there is more water vapour entering the ceiling space than exiting, over time, problems are likely to ensue.

New Zealand has a major problem with respiratory disease, which costs the country $6 billion a year and accounts for 10% of overnight hospitalisations (according to The Impact of Respiratory Disease in New Zealand: 2016 Update, commissioned by the Asthma and Respiratory Foundation). A contributor to this is known to be damp living conditions.

In the 1970’s it was mandatory to ventilate ceiling spaces in New Zealand. Unfortunately, this requirement has lapsed and people are now paying the price. Ventilation was often achieved by the installation of louvres in gable ends. In fact, many modern houses sport a fake louvre vent on the gable in honour of the aesthetic rather than practical aspects of that feature.

Venting the roof space is a major step in avoiding excessive internal moisture and the build-up of mould. Proprietary products can be used for that purpose, but a new product from New Zealand Steel offers a tidy, economical, and efficient solution. COLORSTEEL Dridex has the underlay bonded to the underside of the roofing material. Removing the need to have a separate membrane of underlay speeds up the roof installation process, and allows the roof space to breathe more easily. Tests conducted on a straight gable roof showed that by using COLORSTEEL Dridex instead of a separate roofing underlay, air changes in the roof space were more than doubled.

COLORSTEEL Dridex is CodeMark approved for use in residential buildings. It has been rated as “Impervious to Mould Growth” by TNO Bouw, and is approved by the Asthma and Respiratory Foundation of NZ’s Sensitive Choice programme. It is available in all common corrugate and trapezoidal profiles from local COLORSTEEL suppliers or installers.

COLORSTEEL Dridex is faster to install, looks great from underneath in exposed conditions and contributes to providing a drier, healthier environment.