1. CONDENSATION Causes & Mitigation
Consumer, Building and Occupational Services
Department of Justice

2. Main topics: Research by UTAS on condensation in Tasmania: Causes
Tasmanian issues
Strategies
Regulatory changes
Our new Guide on minimising condensation

3. Initial research (2014) Three case study homes
One newly built home had condensation issues within 6 weeks of occupation
Key causes identified:
Lack of ventilation
Sarking touching cold roofing materials
Key problems:
Health problems
Structural issues

4. Follow up
Designer’s Guide: Condensation in Buildings (available on CBOS website)
ABCB commissioned scoping study on extent of problem. This highlighted:
Nationwide concern about condensation
Significant gaps in regulation compared to other countries

5. Most recent research (2017)
Reviewed overseas literature and regulations
Reviewed international standards for roof space ventilation
Simulated & analysed condensation risk in typical external wall systems

6. Condensation problem Vapour impermeable external wall materials
High outward water vapour flow (cold climates)
Thermal bridging
Air tight buildings (energy efficiency, bushfire protection requirements)

7. External walls: strategies
Vapour permeable building membranes
Ventilated cavity between building membrane & cladding
In cool climates: second vapour control membrane may be required

8. Roof spaces: ventilation

9. National Construction Code 2016
Currently no performance requirements to minimise condensation in NCC
Lagging behind other countries
ABCB scoping study highlighted condensation major issue
Led to proposal to change to NCC in 2019 Public Comment Draft

10. National Construction Code 2019
See: Part F6 Volume One, Part Volume Two
Class 1, 2 and 4 buildings
DtS provisions on:
Water control membranes
Roof space ventilation
Externally vented exhaust systems

11. Our new Guide (coming soon)
Practical tips & diagrams on how to reduce condensation
Aimed at wide audience
Key messages:
Vapour permeable building membranes (installed to minimise air leakage)
Externally vented rangehoods & exhausts
Vapour permeable building fabrics
Ventilation in subfloor, walls, roof space

12. Roof space best practice

13. Roof space ventilation: supply

14. Roof space ventilation: exhaust

15. Continuous gap vents

16. Wall cavity ventilation

17. Subfloor ventilation

18. More building information:
Consumer, Building and Occupational Services
New Website address:
New Online Enquiry Form (on CBOS website)
New address:
Facebook page: