Lawson Public Toilet - Sustainable Design

New Lawson Public Toilet - Innovative and Sustainable Design

New public amenities have been developed as part of the Lawson Town Centre Redevelopment. The project involved a Location Study including community survey (as to preferred location) with stakeholder discussions, public 'Open House' and workshops regarding the proposed facility design, with further liaison including access committee.

The toilet has an innovative and sustainable design by Nigel Bell, ECOdesign Architects.  In recent decades, public toilet blocks within our culture have become excessively enclosed, in attempting to deal with public safety and vandalism. For the new Lawson Town Centre Amenities block, a different approach has been taken that is well accepted in Europe.  The cubicles are very private, but once you step out, are very public, resulting in the creation of public safety through openness to public gaze.  The facilities are light, airy, colourful and pleasant.  This is in accord with international and Australian trends, arising from an understanding of social-psychology.  The latest sustainable initiatives have been incorporated in the building design.

The design intent was for a colourful, somewhat sculptural, imaginative toilet block that provides more than just basic facilities.  It is a design that provides security by being open, sunny, visibly sustainable (energy, water) without a front and back (because it will be viewed from many angles).  It utilises the fall of land whilst minimising concrete (high embodied energy) and features a range of appropriate and durable materials.  It is fully accessible to all. 

This development includes full consideration of how best to make these toilets as sustainable as practicable:

• Energy use and generation (photo-voltaic solar cells) to become a net exporter of energy;
• Incorporation of skylights to maximise the sun light coming in;
• Water harvesting and reuse, with sufficient stored water to require no mains for around 50 users per day;
• Low-impact materials (consistent with requirements for durability), considering embodied energy in manufacture; and
• Social sustainability through community arts, building local capacity and 'ownership'.

Energy use

The toilet facility is designed to maximize solar / thermal benefit consistent with location on a road frontage approximately 450 off north.  It is designed so that sunlight will play across the inside of the building from early morning until late afternoon.  Furthermore, the central portion of the roof is clear polycarbonate (skylights) for further spread of natural illumination. This project will generate its own electricity from solar cells – photo-voltaics – on the rooftop as well as being grid (mains) connected.  Initial assessment by the architect shows the following:

• Total power usage (lights, water pump) = 4.32 kWhr/day
• Total power generation anticipated (6 panels) = 6 kWh/day (averaged over a year)

On these initial calculations, the building is self sufficient in electricity usage and will export about 1.5 kWhr/day back into the grid. This equals about 550 kWhr/year, or about half a tonne of CO2 saved per year.

Water use

Water efficiency is addressed by collecting and reusing water for toilet flushing.   The main limitation on water collection is tank diameter and restricted tank height.  Initial assessment by the architect shows the following:

• Roof area of building = 60 m2 (approx).
• Lawson's assumed average annual rainfall = 1200 mm/year
• Theoretical yield = 1200 x 60 L of water from the roof = 72,000 L / year
• Actual yield = theoretical yield x 0.8 (allows for evaporation, overspill) = 57,600L / year.

If demand and rainfall are both constant throughout the year and no water is lost from overflowing of the tanks during thunderstorms, the actual supply is about 57,600 /365 days = 158L / day. Assume 6 /3L flush toilets, with 4x3 L flush uses per 1x6 L flush use. Then the average water use per 'visit' = (12+6) / 5 = 3.6 L / visit. This means that  the building is 'self sufficient' for toilet flushing water for about 158 / 3.6 visits = approximately 44 visits.

Allowing for both storage and usage variations, the toilets will be self-sufficient for 40 – 50 users per day before calling upon mains water back-up. 

Therefore these public toilets are largely (but not completely) self-sufficient in everyday water use.

The water from the hand basin is being reused on-site with a soakage trench and appropriate planting (rain garden). It is a small scale example of Water Sensitive Urban Design.

This item was posted in December 2010.