Episode 13: The Hidden Risk of Better-Insulated Homes: Leaky Building Syndrome.

Better insulation should mean a healthier, more comfortable home—but if it’s not paired with the right moisture management, it can quietly create the conditions for mould, rot, and “leaky home” failures. In this episode, builder Simon Clark unpacks Leaky Building Syndrome (catastrophe's in New Zealand and Canada) and explains why Australia’s push toward energy-efficient homes can backfire when builders don’t understand drainage planes, ventilated cavities, vapour diffusion, and humidity control. Simon breaks it down simply: modern wall systems are no longer “hollow and forgiving.” Once insulation fills the cavity, moisture can get trapped—so you need a wall that can shed water, drain it, and dry it. He shares SHM’s practical five-part approach: keep water out, don’t rely on cladding to be waterproof, use vapour-permeable membranes, build ventilated cavities for drying, and actively manage indoor humidity (increasingly with heat recovery ventilation / HRV). You’ll also hear the homeowner questions that reveal whether your builder truly understands building science: What happens when water gets behind the cladding? How does it dry? How are you controlling humidity inside the home? You’ll learn:Why insulation changes the moisture game (and how walls can become “moisture traps”) The difference between cladding as a rainscreen vs a real waterproofing strategy What vapour-permeable membranes do (the “Gore-Tex jacket” concept) and why older sarkings are being phased out How ventilated cavities create drying pathways behind cladding—and why they’re non-negotiable How much water vapour households generate daily—and why HRV can be the difference between comfort and condensation The 3 questions to ask your builder to avoid hidden long-term risk Who it’s for: Homeowners planning a new build or renovation (especially higher-insulation, higher-airtightness projects), architects/designers, and anyone wanting a healthy, durable, moisture-safe home—not just a pretty one. If you'd like to know more, please reach out to Sustainable Homes Melbourne or call us on 1800 683 697.