# What is drier? Understanding humidity in green-certified dwellings: a winter case study from Auckland, New Zealand

## TL;DR

This study examines indoor humidity in green-certified apartments in New Zealand and questions current humidity guidelines.

## Contribution

The study compares relative and absolute humidity metrics in green-certified buildings and suggests a reevaluation of current guidelines.

## Key findings

- Relative humidity frequently exceeded the recommended 40-60% range in winter.
- Absolute humidity remained within acceptable epidemiological limits.
- Residents reported satisfaction with indoor humidity despite high relative humidity.

## Abstract

Despite the growing emphasis on green-certified buildings, there remains a notable gap in understanding their humidity performance, particularly in residential settings. This study addresses this gap by evaluating the wintertime humidity performance of 40 subsidised, 7-Homestar certified apartments for older residents in Auckland, New Zealand. While current building science guidelines recommend an optimal relative humidity (RH) range of 40% to 60%, our results show frequent exceedances of this range. However, when assessed using absolute humidity (AH), the apartments consistently fell within the epidemiologically acceptable range of 8–14 g/kg. This discrepancy highlights the need to reconsider which humidity metric—RH or AH—better reflects acceptable indoor environmental quality for health and comfort. Resident feedback indicated satisfaction with indoor humidity levels, despite elevated RH. This study calls for a reassessment of humidity guidelines in green-certified buildings to better balance occupant health, comfort, and energy efficiency.