Building Performance

Building plan

Air Quality

Embodied Energy

Operational Energy

Water and Waste water

Building plan

Over the first year of occupation both external and internal temperatures have been monitored. Results show that the house warms up quickly in the morning, without meeting the peak midday and evening temperatures. The measured temperatures also show that the insulation works to prevent heat losses at night, allowing the house to maintain a relatively steady temperature throughout the diurnal cycle. The chart below shows temperatures measured at head height on the ground floor.

Summer 1999-2000 Indoor-Outdoor Temperature Differences

From the table it can be seen that the house effectively buffers the occupants from the extremes of summer temperatures. Winter temperature monitoring is yet to be completed. The occupants have access to ceiling mounted fans for cooling and electric heating, but report that the temperature in the house is usually very comfortable. Consequently supplementary heating and cooling was used on very few occasions during the test year.

Ventilation levels have also been monitored. After a year of occupation wind speeds and direction were measured at roof level, and in each room of the house in SE and NE wind conditions, with all the windows and louvres open.

The results show that high levels of airflow are achieved in the house, effectively cooling and adding to the comfort of occupants. The high air change rate was found to continue even when the louvres and windows were closed (a full air change ocurred in under two hours), indicating that the louvres cannot be fully closed off. This has implications for active heating and cooling mechanisms, as heating in particular will be quickly lost through the louvres. Because the house is in a temperate climate, where little heating energy is required, this was felt to be an acceptable compromise, outweighed by the cooling benefits of the high airflow. However, the detail design could be refined by developing a louvre system which could be sealed more effectively. This would allow the occupants to exclude hot air in the summer, and minimise heat loss in the winter.

Air Quality

Indoor air quality testing was carried out by Envirotest and the University of Queensland, immediately prior to occupation and after a full year of occupation. The table below summarises the findings of the tests after a full year of occupation, and compares them with standard acceptable levels. The tests have demonstrated the Healthy House has levels of volatile organic compounds, polar compounds and formaldehyde below detectable limits, and that carbon dioxide and respirable particles are well within acceptable guidelines in the entire house. The only contaminant to exceed acceptable levels is the level of airborne micro-organisms, which reach a high level in the master bedroom and children's bedrooms. This could be due to the half height walls which separate the bathrooms from the other upstairs rooms. These permit damp air to circulate in the upstairs rooms, and possibly facilitate the growth of airborne micro-organisms. With respect to all other contaminants the house has performed well within acceptable limits.

Embodied energy

An audit of the embodied energy of the house is being carried out by staff at the University of Queensland. While the house makes use of low embodied energy materials and construction strategies, it is still a relatively large house, with a large surface to volume ratio. While the house may achieve a low level of embodied energy per metre squared, the large amoount of materials required to construct this house may lead to a relatively high level of embodied energy per occupant. Further analysis will determine how this house compares with other houses on the Gold Coast.

Operational energy

Electrical systems have been metred over the first year of occupation, to breakdown the proportions of energy used in each area of the house and evaluate the solar hot water and electrical systems. The following pie chart summarises energy end use characteristics of the house.

The household uses an average of 15kWh/day, and this compares with a Queensland average of 19kWh/day.* Given the high level of occupancy in the house (five people, compared with a Queensland average of 2.7 people per household), this represents an impressive reduction in energy consumption. The savings can mainly be attributed to the passive cooling strategy, but also to the solar-electric hot water system. The solar-electric hot water system typically uses 2.5kWh/day, compared to (approximately) 10 kWh/day for an all electric system.

The pumps which pressurise the household water supply and recirculate the greywater through the sand filtration system consume 2.2kWh/day, on average. The research team suggest that the municipal system would use approximately 0.6kWh/day to perform the equivalent functions. Thus there is a potential energy penalty of 1.6kWh/day for the decentralised water services used in the house.

* This 1998-1999 average is for electricity use only, and is taken from the Electricity Supply Association of Australia website: www.esaa.com.au/head/portal/informationservices/data

The monthly end use breakdown for household electricity shows that there is a seasonal trend, peaking in winter. The increase can be attributed to cooler temperatures and reduced sunshine hours, as the rise is mainly due to increases in hot water energy and electricity use in bedrooms. Winter energy use could be decreased by sealing the house more effectively, reducing heat loss through the louvres, for example. Increasing the level of insulation in the house would also reduce heat losses. The energy consumed by the solar-electric hot water system could also be reduced, by installing low-flow devices at showers and hot water taps in the house (this would have the added benefit of reducing water use).

When supply from the photovoltaic system is taken into account, the amount of energy imported from the grid will be further reduced. As the system was commissioned in September 2000, supply information is not yet available, but it is anticipated that the PV array will supply approximately 10kWh/day, more than half of the household requirements.

Water and waste water

Both rainwater and grey water were monitored for quality and quantity used over the test year, and the systems have been refined in response to the testing.

Rainwater testing established that levels of nitrogen, phosphorus and heavy metals were well within the levels specified by the National Health and Medical Research Council Australian Drinking Water Standards. However, drinking water often didn't pass tests for faecal and total coliform counts. As the acceptable level for these contaminants is zero, the design team consider the standards to be very strict. After heavy rainfall (ie more than 50mm), the faecal and total coliform levels have exceeded 300cfu/100ml, and it is suggested that the main source of contamination is bird and possum faeces. Because the source is non-human, it is not considered likely that the water contains pathogenic organisms. However, a domestic UV disinfection unit is to be installed.

Quality of Rainwater

Over the test year it was found that the greywater could not meet the guidelines set by the Department for Natural Resources for reuse on site. As a result, an additional UV disinfection unit was installed in the system. After UV treatment, the greywater has a measured total coliform count of less than 10, which is well within guidelines for use in above ground irrigation and for toilet flushing. However, current regulations prohibit the use of greywater by individual households. The Healthy House research team hope that by proving that onsite greywater treatment can meet health standards, they will help to pave the way to modification of the statewide guidelines.

Quality of grey water, before and after filtration
(nb these tests were carried out before the UV disinfection unit was installed)

Because the greywater has not been available for reuse over the test year, the total water imported has been higher than anticipated. This was exacerbated by the drought in the area over the test period, which reduced the amount of rainwater available to the house. Rainfall was gauged at the site for the test year, and was measured at 1030mm, only 70% of the average annual rainfall in the area.

The Department of Natural Resources estimate that when greywater is utilised, 60% of the current household water needs could be met by rainwater and reused greywater. While the payback period for these systems is long (if ever) for the householder, independent systems like this reduce the burden on local infrastructure and reduce the requirement for new reservoirs in growing residential areas.