Many New Zealand homes suffer from poor indoor air quality (IAQ). Cold, damp and mould-ridden homes can cause serious respiratory health problems. Poor IAQ can arise due to poor insulation and ventilation, and compounded when residents cannot afford heating. The main aim of this paper is to describe the process and results of modifying an existing dehumidifier to include ultraviolet germicidal UV lights. The modified device was designed to improve thermal comfort by removing moisture and perform UV filtration of the air to address mould and bacteria growth. To achieve these we combined the properties of a dehumidifier with germicidal lights (UV). The device was designed with the purpose of reducing humidity, increasing room temperature and purifying the air. Testing has shown that the modified dehumidifier with UV lights works as planned, with petri dishes showing a reduction in mould growth in most samples taken. Humidity was reduced where the device was used, and approximately 2L of water was removed in a 24-hour period. The temperature was increased where the device was used. The results show that the device reduced mould growth and increased room temperature.