Managing Condensation and Indoor Air Quality

About this course.

Because the same improvements that make homes efficient also remove the accidental ventilation that older homes relied on to carry moisture away. Older Australian homes were typically draughty and poorly insulated, so they constantly exchanged indoor and outdoor air; water vapour from cooking, showering, drying clothes and simply breathing dispersed before it could cause trouble. As homes are sealed and insulated for comfort and energy performance, that moisture can accumulate indoors unless ventilation is deliberately designed in. Combined with cold surfaces, trapped moisture condenses, and persistent damp feeds mould — so condensation is, in part, a side-effect of higher-performing homes that must be actively managed.

For much of the past, the typical Australian house effectively ventilated itself by accident. Gaps around windows and doors, unsealed floors, vents and a generally loose building envelope meant air leaked in and out continuously. This wasted energy and made homes hard to heat and cool, but it had one incidental benefit: it kept indoor humidity roughly in step with outdoors, so the moisture generated by everyday living was diluted and carried away before it could condense or support mould. The house was, in a sense, "breathing" — not by design, but by leakage.