New Zealand homes are warmer in winter than two decades ago, but many bedrooms remain below recommended temperatures overnight, according to BRANZ’s Household Energy End-use Project 2 (HEEP2). The study found average living-room temperatures have risen by 2.6–3.5°C across the day compared with the original HEEP research conducted from 1999–2005.
Evening living rooms now average 20.4°C, above the World Health Organization’s recommended minimum indoor temperature of 18°C. However, average bedroom temperatures fall to 16.5°C overnight and around 15.7°C by morning. Forty-one percent of overnight bedroom readings are below 16°C, while 18% fall below 14°C.
Heating patterns differ between living rooms and bedrooms. BRANZ found that 85% of households regularly heat their living rooms during winter, while only around one-third heat adult-occupied bedrooms and 41% never heat them. In homes with young children, around 40% of bedrooms are heated every day or most days in winter.
Heat pump use has increased substantially since the original HEEP study, rising from 1% of homes to more than 60%. “Heat pumps are a big part of why living rooms are warmer in winter. They heat these spaces efficiently and effectively – a real change from 20 years ago, when households relied much more on portable electric or LPG heaters,” said BRANZ Senior Scientist Vicki White.
HEEP2 includes more than 750 households across New Zealand, with a subset monitored continuously for 12 months for electricity use, temperature and humidity. “It’s encouraging to see that homes are warmer on average in winter, but temperatures still vary a lot from home to home, with many households living in colder conditions and dealing with issues like damp and mould,” White said.
The indoor temperatures report is the first of three HEEP2 reports, with studies on indoor moisture and household energy use to follow. The research was funded by the Building Research Levy, with co-funding from the Building Levy by the Ministry of Business, Innovation and Employment and the New Zealand Green Building Council, which supported the Canterbury-based study of dwellings built to Code and above Code.
