Myth Vs Fact: Overheating in some New Zealand homes is caused by “too much insulation”. 

Let’s kill the myth: insulation doesn’t create heat.

What’s driving overheating in many new homes and apartments is solar gain (from large and/or unshaded glazing), plus not enough ventilation/air movement to purge the heat - particularly at night. 

Work done around NZ Building Code H1 changes also indicates more insulation assists to reduce daytime overheating risk; the real problem is heat getting in and getting stuck.

Fix the cause, not the scapegoat:

✅ External shading first (stop sun before it hits the glazing)

✅ Smarter glazing and orientation decisions

✅ Designed crossflow / stack ventilation with good ventilation night purge

✅ Where natural airflow is limited (such as in some apartments), consider mechanical ventilation that supports summer purge

 

At IAONZ, our message is simple: keep insulation for winter comfort, health and efficiency - and pair it with good passive design and deliberate airflow, backed by guidance from NZGBC, MBIE, BRANZ and others.