Use of roof space ventilation to address summertime overheating in New Zealand houses

Abstract

Previous research in New Zealand houses has indicated that recent increases in insulation and double glazing requirements may have led to increased problems with summertime overheating. Monitoring of a typical New Zealand house (standard three-bedroom, lightweight timber frame construction) in the Auckland region has shown that the roof space achieves extremely high temperatures in summertime and even mid-season. The roof space therefore is a heat source that has the potential to impact significantly on overall internal temperatures.

Although the principle of ventilating the roof space to outside is well established in the northern hemisphere, traditional best practice in house design in the New Zealand climate does not recommend it. However, this advice is based on older construction standards, which included single glazing and lower levels of insulation than are currently required. This paper reports on the results of a project to test the impact of passive ventilation of the roof space in a New Zealand house built to current standards, with the intention of improving comfort levels within the living spaces. The ventilation system tested consists of air vents inset into the soffits on both the north and south sides of the house, with a ridge vent along the length of the house.

The house has been monitored across summer, autumn and winter conditions, recording internal air temperature and relative humidity throughout the living spaces and roof space of the house. Results indicate that the passive ventilation is an effective measure to reduce summertime temperatures in the roof space, with subsequent impact on the temperatures experienced in the living spaces of the house. Wintertime temperatures appear to be relatively unchanged. The project demonstrates that there is a case to be made for the adoption of passive ventilation of roof spaces to improve the thermal performance of homes in New Zealand.

Previous research in New Zealand houses has indicated that recent increases in insulation and double glazing requirements may have led to increased problems with summertime overheating. Monitoring of a typical New Zealand house (standard three-bedroom,lightweight timber frame construction) in the Auckland region has shown that the roof space achieves extremely high temperatures in summertime and even mid-season. The roof space therefore is a heat source that has the potential to impact significantly on overall internal temperatures. Although the principle of ventilating the roof space to outside is well established in the northern hemisphere, traditional best practice in house design in the New Zealand climate does not recommend it. However, this advice is based on older construction standards,which included single glazing and lower levels of insulation than are currently required.

This paper reports on the results of a project to test the impact of passive ventilation of the roof space in a New Zealand house built to current standards, with the intention of improving comfort levels within the living spaces. The ventilation system tested consists of air vents inset into the soffits on both the north and south sides of the house, with a ridge vent along the length of the house\

.The house has been monitored across summer, autumn and winter conditions, recording internal air temperature and relative humidity throughout the living spaces and roof space of the house. Results indicate that the passive ventilation is an effective measure to reduce summertime temperatures in the roof space, with subsequent impact on the temperatures experienced in the living spaces of the house. Wintertime temperatures appear to be relatively unchanged. The project demonstrates that there is a case to be made for the adoption of passive ventilation of roof spaces to improve the thermal performance of homes in New Zealand.