The Hidden Danger in Every Old House

“If you can’t hit 0.6 ACH on a brand-new build, you probably shouldn’t be building.”Let’s stop tip-toeing around the reality of the Australian housing market. We are throwing up volume-built boxes and high-density apartments that are practically end-of-life before they’ve even seen their first winter. We sat down with Linden Thorley, architect, Passive House designer, and chair of the Australian Passive House Association Retrofit Committee.We take a look into why retrofitting the existing 9.5 million homes in Australia is the single biggest business opportunity for trades over the next decade. Linden walks us through the differences between a cosmetic renovation and a high-performance retrofit, detailing how his team utilises the PHPP (Passive House Planning Package) to model data and manage moisture, insulation, and ventilation risks case-by-case.We don't hold back on the real pain points of the industry either. We talk about the skyrocketing costs of business insurance, why Australian labour rates are fundamentally shifting project costs, and how to structure building contracts using provisional sums for airtightness so builders aren't crushed by unexpected site variations.Linden also breaks down his frustrations with legacy bank valuations that prioritise bloated 300-square-meter floor plans over highly efficient, smaller family homes.Finally, we hit the political wall: how heritage advisors and council planners are actively preventing energy efficiency upgrades, and the clever, practical drawing tricks CHAPTER MARKERS00:00 – Introduction02:08 – The Passive House Association Retrofit Committee & Playbook04:12 – Finding the Ideal Market: How Long Does the Shift Take?05:45 – Passive House as a Design-Agnostic Calculation Tool07:11 – Can a House Be Great If It Doesn’t Reach Certified EnerPHit?09:00 – Retrofitting Multi-Story Blocks vs. Standard Residential10:38 – Managing Airtightness Expectations with the Builder13:36 – How to Contract for Airtightness: The Provisional Sum Solution15:21 – Dealing with Double Brick and Suspended Timber Floors16:23 – The Spray Foam Debate in Subfloors vs. Walls18:41 – The New Build Advantage vs. Retrofit Blind Spots19:16 – A Case Study: Turning a 25 ACH House into an 8 ACH Home22:27 – Threading Centralized MVHR Systems Through Bulkheads23:28 – The Necessity of the ECI Process for Architects26:16 – Why Don’t We Just Knock Them All Down?27:43 – Renovation vs. Extension vs. Retrofit29:47 – Do We Overcomplicate the Carbon Conversation?31:14 – Lessons from Toronto: The 100 Macnab High-Rise Retrofit32:38 – Drawing the Line: When to Demolish an Existing Fabric37:28 – Forcing Council’s Hand with Legal NCC Clauses39:34 – Is Passive House Actually a Premium-Priced Product?41:11 – Breaking Down the True Cost of Australian Site Labour44:46 – Linden’s Fire Loss & Installing His Own INTELLO Membrane48:26 – Thermal Envelope vs. High-End Cabinetry53:03 – The Intensity Slump on Modern Australian Building Sites55:26 – Overheads, Insurance Hikes, and Free Market Economics57:41 – The 3-Story Walk-Up: How Codes Limit Small Footprint Living58:21 – Why Banks Hate Small Homes and Force Massive Floorplates01:01:45 – Macroeconomics, Inflation, and Building for the Top 10%01:08:37 – MEGT Mindful Moment: Harnessing the Un-Jaded Apprentice Mindset01:11:16 – Connect with Linden ThorleyLINKS:Our Sponsors:Pro Clima - https://mindful-builder.captivate.fm/proclimaMEGT - https://mindful-builder.captivate.fm/megtConnect with us on Instagram: @themindfulbuilderpodConnect with Hamish:Instagram: @sanctumhomesWebsite: www.yoursanctum.com.au/Connect with Matt: Instagram: @carlandconstructionsWebsite: www.carlandconstructions.com/Mentioned in this episode:Proclima Sponsor