Masons products maximise airflow to prevent condensation

The improved airtightness of modern New Zealand homes has made them warmer, healthier and more energy-efficient. While this helps reduce condensation, it also limits natural airflow. Passiv Haus principles take this even further, with air changes per hour (ACH) dropping as low as three, compared to around 20 in older homes.

While airtightness brings significant benefits, it can also introduce challenges—especially in roof spaces. Without adequate ventilation, moisture builds up, creating the perfect conditions for mould growth. In fact, BRANZ scientists have found mould on structural timber and roofing underlay in several newly built homes.

Good roof space ventilation is crucial in preventing this. Masons Insul-Baffle and Ventilated Roof Battens work together to maximise passive airflow, reduce condensation and improve thermal efficiency–keeping roof spaces drier.

Ventilated battens for superior airflow

Most New Zealand homes use a ‘cold roof’ design, where insulation is placed over the ceiling lining, leaving the roof space above uninsulated and exposed to external temperatures. Without proper ventilation, moisture from inside the home can permeate through the ceiling lining and become trapped in the roof cavity, leading to condensation on cold surfaces as temperatures fluctuate.

Masons Ventilated Roof Battens are designed to solve this issue. Installed between the purlins and roofing, their open structure–featuring ventilation openings–allows air and moisture to move more freely, reducing moisture buildup and helping to keep the space dry.

Key features:

• Available in 11mm and 18mm thicknesses

• Cellular structure prevents capillary action and thermal bridging

• High compressive strength makes them effective packers

• Open design significantly increases airflow

  • 11mm batten: 6,800mm² net free open area per Lm

  • 18mm batten: 12,300mm² net free open area per Lm

Maintaining the essential roof cavity gap

For even better airflow, Masons Insul-Baffle ensures the vital 25mm gap between insulation and roof underlay is maintained.

Made from durable, clear plastic, Insul-Baffle is fitted under the eaves, preventing bulk insulation from pressing up against the roof underlay. Installed along the full length of the eaves, its unique ‘Dragon Channels’ add rigidity while promoting cross-ventilation.

Performance highlights:

• Creates an open ventilation area of approx. 32,000mm² per Lm—30% more than the required 25mm gap

• Prevents insulation from blocking airflow

• Enhances passive ventilation

A smarter approach to roof ventilation

Roof pitch, wind loads, ceiling penetrations and indoor moisture levels all impact ventilation needs. But ensuring continuous airflow is the best defence against condensation, mould and material degradation.

When used together, Masons Ventilated Roof Battens and Insul-Baffle provide a robust ventilation solution, helping to maintain dry framing, improve insulation performance and reduce the risk of corrosion in metal claddings or components.

Talk to our helpful team

For more information about roofing ventilation products, including installation and compliance documents, visit the roofing section of our website or call 0800 522 533 to speak to one of our team.