Building performance

Building performance in use

The environmental performance of Buxton Public School has been monitored by NSWPWS. Twelve months of electricity, gas and water consumption data has been used to assess the school's environmental performance as part of the international Green Building Challenge (GBC) program. The GBC method rates buildings according to many criteria ranging from urban context, site issues, detailed design criteria, indoor air quality, life cycle impacts, costs, resource and energy use. The end result is a comparison of a building to (a) general benchmarks and (b) benchmarks for buildings of equivalent function, size, operating schedule and other factors.

To create a benchmark for the GBC exercise, NSWPWS modelled data to simulate a typical new school built from the Component Design Range. As seen below there is not a great deal of variance between this benchmark and the performance of Buxton. To give a better sense of the improved energy performance of recent schools designed with the Component Design Range, a comparison with an earlier benchmark is included. This is the 'target for low energy design and operation' for schools taken from the Building Owners and Managers Association, Energy Guidelines (1994).

What follows has been derived from the PWS GBC study, with cross verification from Buxton School's energy, water and gas bills, from information gathered on a site visit and from inspection of plans and specifications.

Annual consumption of energy by end use (MJ/m3/yr)

What this comparison shows is that the most dramatic reductions in energy consumption are achieved by avoiding mechanical cooling and ventilation altogether. This is the major reason that the NSWPWS benchmark's total energy consumption is so much lower (46%) than the BOMA benchmark.

Looking at individual uses of energy, the NSW benchmark school uses nearly 30% less energy for water heating and 38% less for lighting than the BOMA benchmark.

The comparisons between the NSWPWS benchmark school and Buxton school are not as dramatic, which is not surprising given the benchmark school's energy consumption is already very low. The figures show that Buxton school uses the same amount of energy for lighting and equipment as the benchmark school. However Buxton does show a significant saving (20%) on energy used for space heating. This can be attributed to the more rigorous use of insulation - an improvement that will no doubt be taken up in the design of future NSW schools.

Overall, Buxton uses 15% less energy than the benchmark school. Besides space heating efficiencies, this saving is explained by Buxton's on site pv generation and its purchase of green power from the electricity supplier.

Water consumption (m3/yr)

This shows clearly the success of Buxton's water management strategy - capturing rainwater and using it on site for irrigation and toilet flushing have achieved savings of 60%. The on site sewage treatment plant also plays an important role, with the treated water being used for subsurface irrigation of a large area of the grounds. This efficiency also translates into significant cost savings for the school - as it only has to draw half its requirements from the mains supply.

Other performance indicators

This table shows that Buxton School has reduced greenhouse emissions compared to the benchmark school by 15%, and it has achieved this with only a slight increase in capital costs, which is eventually cancelled out by slightly lower annual life cycle costs.