This part of the WAVE programme tried to understand the complex airflow patterns that can occur in roof spaces and how these can be controlled in such a way that they manage moisture effectively.
Projects in the interstitial moisture stream
Roof experiments
We built an outdoor test facility to continuously monitor full-scale commercial and residential roof specimens to investigate the complex issues related to the formation and removal of interstitial moisture in roof spaces.
A main focus was the role of ventilation on the dynamics of interstitial moisture in roof spaces:
- How much roof ventilation is required to prevent moisture problems?
- If extra ventilation is required, what are the best ways to provide it?
This experimental work was supplemented by field ventilation surveys in residential and commercial environments. These gave a snapshot of the level of ventilation currently present and provided essential information for the test facility and the subsequent modelling effort.
Numerical modelling
In roof spaces - air cavities and the building elements surrounding them - heat transfer, air movements and moisture transport are strongly linked and affect the formation and the removal of condensation.
We aimed to build a comprehensive numerical model of the transport of heat, air and mass in roof spaces to interpret the data collected in the test building and to generalise this to a variety of roof designs and climatic zones. Such a model would allow us to study the performance of different roof designs and ventilation strategies and would be a fundamental tool for generating Verification Methods and design guidelines.
More information
Explore the range of web and print resources related to this stream of the WAVE programme.
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SR289 Remediating condensation problems in institutional roofs
These roofs have a common similar design entailing large roof cavities, profiled metal roofs with underlay, metal framing, batt insulation on the ceiling and acoustic tile suspended ceilings.
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Initial guidance on the moisture design of large-span roofs for schools
This report summarises the current knowledge available to provide guidance when designing large-span school roofs to minimise or prevent condensation damage within the roof space.
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The performance of wall drainage media in New Zealand
A 2010 CIB conference paper that described research to investigate the ability of various drainage members to manage moisture in New Zealand style walls subject to real climatic conditions.
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Ventilating wall cavities above windows
A 2009 article from the Journal of Building Physics looking at the design of cavities above head flashings to borrow ventilation from cavities flanking the window.
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Ventilation measured in the wall cavities of high moisture risk buildings
A 2009 article from the Journal of Building Physics looking at the risk matrix and cavity ventilation results measured with a continuous emission carbon dioxide tracer method.
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