Thermal Performance of 6 Star Rated Houses in the Hot and Humid Tropical Climate of Darwin

Abstract

This paper evaluates the post-occupancy performance of 6 star houses in the hot and humid tropics of Darwin compared to unrated/lower rated control houses during the inactive/active phases (build-up/wet) of monsoon trough. Study is based on surveys of 61 respondents in the build-up and 44 respondents in the wet, indoor climatic measurements in 10 houses, and electricity consumption data. Actual mean vote ranged between -0.5 to 0.5 at a range of mean indoor conditions: air temperature 29.9-30.72°C, relative humidity 50.42-72.96%, and air velocity 0.23-0.35m/s. Behavioural adjustment surveys showed that the percentage of occupants in 6 star rated houses who always utilise air conditioner increased from 36% in the build-up to 50% in the wet. While percentage of fan users remained around 90% during both periods. An impact of occupants’ behavioural adjustment, house star rating, and built environment on indoor climatic conditions is discussed through analysis of monthly mean temperature and relative humidity values. Mean monthly air temperature in living rooms of 6 star houses reached highest point of 30.8°C in February 2016; while in control houses it reached 31.59°C in January 2016. Highest mean relative humidity in 6 star rated houses was 74% compared to 81% in control houses. Analysis of electricity consumption of 36 households showed that the average half-hourly consumption of households in 6 star rated houses increased from 0.58 kWh in December 2015 to 0.72 kWh in February 2016, while consumption in control houses increased from 0.72kWh in December 2015 to 0.76kWh in January 2016, and reduced to 0.75kWh in February 2016. This paper presents findings for the build-up and wet seasons only. The results of this study provide insight into the impacts of the built environment, thermal preferences, and occupant behavioural adjustment on the thermal performance and electricity consumption of households in hot and humid tropical conditions.