Sonia Holzheimer
Engineer
Sonia Holzheimer is a mechanical engineer and co-founder of SEQUAL, a Cairns-based consultancy specialising in HVAC design for hot-humid tropical climates.
Her work sits at the intersection of energy efficiency, ventilation, and health, where good intentions don't always lead to good outcomes. She has a particular interest in how ventilation standards, humidity, and real-world building operation interact, especially in climates where moisture is the dominant design challenge.
She is frequently engaged to investigate buildings experiencing mould, condensation, or poor indoor air quality, spaces that comply on paper but fail in practice. This has shaped her perspective on the limitations of common design assumptions, including the way humidity is measured and managed in buildings.
Sonia is a Fellow of Engineers Australia and a Registered Professional Engineer of Queensland. She contributes to Standards Australia ventilation sub-committees and is an active member of industry groups including the AIRAH IAQ26 technical committee, the organising body behind Australia's national indoor air quality conference, coming to Cairns in September 2026.
She also founded Cool Engineers, a platform aimed at making engineering more visible and inspiring the next generation to better understand the systems that shape how we live and breathe.
