2 April 2014 — ESD engineer Siân Willmot says there is much debate over the best solutions for hot water systems in the multi-unit residential sector. This article presents research conducted by GIW, which is provided to clients considering the best option for their development. She would like this piece to stimulate discussion in the industry about best-practice solutions, so please feel free to share your opinions.
There has been much confusion within the development industry between architects, services engineers, ESD consultants, other design consultants and planning authorities as to which hot water systems are most suitable for a development, particularly within the multi-unit residential sector.
With a vast portfolio within this sector, GIW has conducted research on the application of several hot water systems within medium-density multi-unit residential developments in Melbourne’s inner suburbs.
During the investigation, we have considered each major technology under a triple-bottom-line framework – economic, environmental and social impacts.
Technologies reflected within the research include the following:
- Centralised gas storage
- Centralised gas – continuous flow
- Solar with gas backup
- Centralised instantaneous condensing boiler
- Commercial heat pumps
- Instantaneous electric
Based on inputs from several manufacturers and suppliers on cost, maintenance, efficiencies, warranties, hot water delivery, redundancies and billing accuracy, we have graded each system under the appropriate triple-bottom-line analysis.
Due to reasonable capital cost, high efficiencies, low maintenance and gas fuel input, the condensing boiler met the best economic outcome. Condensing boilers for residential applications are currently available and have energy efficiency ratings of 6 Stars (recovery efficiency of 94 per cent).
Again, due to high efficiencies and gas fuel input, the condensing boiler maintained the lowest greenhouse gas emissions over a 10 year period, ahead of the gas boosted solar thermal system.
A social impact analysis considered hot water quality, warranty (for both minor and major components), billing convenience and accuracy, access and redundancy. As the electric instantaneous systems are provided per unit, they can be easily accessed, maintained and billed. In addition to this, the single units allow hot water to be shut down and maintained per individual apartment, without affecting the remainder of building occupants. This makes them the highest ranked performer under a social analysis.
Of course, other items need to be taken into account such as spatial considerations, access to fuel sources, administration and incorporation of renewable energy technologies. These and other site constraints will determine the final system selection.
Siân Willmott is an ESD engineer with GIW Environmental Solutions.