View all publications

Case study: Community library

Community library - South Christchurch Library and Service Centre

Photo of South Christchurch Library and Service Centre.

Summary

Client

Christchurch City Council

Site address

Cnr Colombo Street and Hunter Terrace, Beckenham, Christchurch

Total floor area

2400m2

Cost/m2

$2494 (2005, including park, landscaping and roading)

Conventional cost/m2

$2384 (4.9% below project cost)

Contract value

$4.6 m including park, landscaping and new road

Economics

The indicative economics for this case study building are set out in the table below. Note that water saving measures do not show any payback due to the method of charging water in Christchurch. However, this situation is likely to change in the future as water supplies come under increasing pressure.

Incorporating a considerable number of environmentally preferable materials and technologies in the building also has no direct payback but was accomplished for less than 1% of the total construction costs. Taking these factors into account, along with the fact that this type of building is less intensively serviced, makes this type of sustainable building a medium to long-term investment - normally acceptable to a local authority client.

Building type

Benchmark building capital cost
$/m2

ESD building capital cost
$/m2

ESD building premium (saving)
$/m2

ESD building premium (saving)
%

Annual energy cost savings
$/m2

Annual water cost savings
$/m2

Total annual cost savings
$/m2

Simple payback
(years)

20-year NPV for ESD measures
$/m2

Library

2384

2494

110

4.9

7.5

0.0

7.5

14.67

32

Environmental summary

Energy use:

  • 120 kwh/m2/annum

Water use:

  • Low-water-use plumbing fittings
  • Rain water harvesting

Stormwater design:

  • Landscape features used to retain and filter stormwater

Site:

  • Retention of mature vegetation
  • Predominant use of local indigenous species

Material:

  • Low-impact materials

Waste:

  • On-site waste management
  • Use of materials with recycled components.

Client brief

The client brief was to provide a library building that would give a much needed focus for the lower Cashmere Community in Christchurch. The building design was developed through an extensive community consultation process.

It was to be sympathetic to the residential character of the area while at the same time maintaining a civic presence. A key component of the brief was also to meet the Council's policies on environmental sustainability and energy use.

Facilities

The building houses three key functions: a community library, an education centre, and the local council service centre and advocacy team. It also provides a number of other community facilities such as formal and informal meeting rooms, a display space, a café and offices for the community constable.

Site

The site was council-owned. It had an existing building, with the rest of the site fenced off for use by the Christchurch City Council water services department.

There was a significant number of mature trees and vegetation as well as hardstand areas, several aquifier water supply wells, pump stations and other ancillary facilities. To the north, the site was bounded by Hunter Terrace and the Heathcote River.

Concept

A low-rise single-storey building in keeping with the residential nature of the site, it uses a dramatic saw-tooth form and a stepped plan sitting in a water-filled moat to create a distinctive presence.

The site was cleared of buildings, and the mature vegetation retained and tidied to create a public park for the community. In time, part of Hunter Terrace to the north of the park will be closed off and the park will spread down to the edge of the river.

The building is solid and heavily insulated to the south where back-of-house facilities are located, and gradually opens up to the park in the north. Visitors enter the building from the south and are led across to the public spaces in the north which look out onto the landscape.

The saw-tooth roof form breaks the building into four distinct blocks and allows daylight and ventilation to penetrate deep into the plan.

Figure 1: Saw-tooth roof form

figure-saw-tooth-roof.jpg

 
Text description of this figure
  • Summer sun excluded by large roof overhangs.
  • Winter sun warms thermal mass of floor slabs.
  • Artificial lights are low energy fittings linked to daylight and presence sensors.
  • Moat is used to collect and store rainwater from the roof which is used to supply toilet cisterns.
  • Low level incoming air is cooled and humidified by moat.
  • Clerestory windows allow daylight and ventilation deep into the plan.
  • Hot air rises up the inclined roof and is exhausted through high level windows.
  • Hot air above light fittings is drawn off and extracted at high level.
  • Hot air is exhausted at high level.
  • Underslab pipe work provides heating/cooling from super efficient heat pump which draws energy from the aquifiers.
  • Thermal mass of exposed concrete floor stabilises internal temperatures.
  • High than code levels of insulation reduce heat losses in winter.

Energy

The passive low-energy concept design focused on the following:

  • double glazing and higher than code insulation levels
  • north-facing glazing and large roof overhangs combined with mature vegetation to optimise solar gains
  • saw-tooth roof form to allow daylight and ventilation throughout the building
  • optimised orientation for passive solar design with north-facing glazed public areas and south-facing well insulated support spaces
  • optimised wall-to-window ratios determined through 3D energy modelling
  • strategic placement of thermal mass determined through 3D energy modelling
  • opening windows throughout the building.

These passive strategies were overlaid with the following active strategies to further minimise energy use:

  • aquifer water in Christchurch's mains supply pipes was used as energy source for a heat pump-based heating and cooling system
  • water-based under-floor heating / cooling of the slab
  • motorised window openers to optimise the use of natural ventilation and utilise free cooling
  • low-energy T5 light fittings on shared ballasts linked to daylight sensors
  • chilled-beam air conditioning in high-load rooms only, linked to presence sensors and contact switches on manual windows to ensure system switches are off when not required.

In all cases, low-energy design solutions were rigorously tested through 3D energy modelling to ensure they met the client's payback criteria, which was five years for equipment, but longer for fabric changes such as double glazing and insulation.

Project image

Photo of library.

Water

Water conservation was not a high priority, however a number of innovative techniques were employed to reduce water use and minimise the volume of sewage leaving the site. Low-water-use plumbing fittings were specified throughout, including:

  • dual-flush 3/6 litre toilet cisterns
  • waterless urinals
  • low-flow shower heads
  • taps with flow restrictors, aerators and automatic shut off.

The water-filled moat around the building is also used as a collection and holding tank for rainwater supply for the toilet cisterns.

Waste

Waste minimisation was an issue of key importance to the client:

  • The building was used as a pilot for Christchurch City Council Target Zero waste in construction study and a site-specific waste management plan was adopted and monitored during the construction.
  • The demolition contract encouraged recycling and salvage of demolition components. Volume of material salvaged and recycled was recorded and monitored.
  • The hardfill beneath the new building is partly composed of demolition material from the buildings that previously occupied the site.
  • Products with a high recycled waste component (such as ceiling tiles, cement, insulation, carpet and furniture) were specifically selected for use.
  • Space was allocated for the collection and separation of recyclable waste.

Materials

Within budget constraints, the designers sought to select environmentally preferable materials, including:

  • sustainably sourced timber and timber veneers
  • alternatives to CCA and LOSP timber treatments
  • water-based paint systems endorsed by the Environmental Choice labelling scheme
  • woollen acoustic insulation
  • rubber flexible sheet flooring
  • ceramic tiles in high-traffic areas for thermal mass and durability
  • carpet systems produced by a Natural Step company manufactured from recycled materials
  • durable external surfaces requiring no applied surface finishes (stone, glass and aluminium)
  • materials with a high recycled content
  • CFC and HCFC free polystyrene sheet insulation and pipe lagging
  • low toxicity, low-emission materials, water-based paints, low formaldehyde mdf, phenollformaldehyde plywood, low emission ceiling tiles and avoidance of flexible PVC floor coverings.

Site

The site design is an integral part of the ecological design.

  • The building footprint was designed to keep as much of the existing mature vegetation as possible.
  • With the exception of the specimen trees in the car park, the new landscape consists of native indigenous plants
  • The landscape has been designed to need no irrigation after the initial establishment.
  • Rooftop rainwater from the front three blocks is collected and harvested in the moat surrounding the building, minimising stormwater run off.
  • Rooftop rainwater from the back block is run 'gutter free' into a riverstone and gravel filter trough and then slowly finds its way into the rain garden.
  • Polluted car park stormwater is channelled into a landscaped drainage swale to filter and delay the water before discharging into the landscaped rain garden.

Transport

The building has a large 70-space car park that is often full. However, the client tries to reduce vehicle use by:

  • locating the facility in a suburban centre
  • relocating a bus stops to the entrance of the library
  • providing cycle stands for public and staff
  • providing staff shower and locker facilities to encourage cycle use
  • a council policy of not allocating parking spaces to staff.

Process

Key changes to the normal procurement process were pivotal to the environmental success of the project:

  • a design brief that clearly demanded that ecologically sustainable development (ESD) be a priority of the design
  • a realistic but taxing energy brief and a separate energy budget to pay for low-energy strategies with approved payback periods
  • the use of 3D energy modelling
  • an interview process which stressed the importance of ESD
  • a design team and project management committed to making the effort to try new techniques
  • a knowledgeable client and specific input at key dates from the Natural Step and the Christchurch City Council Target Zero team
  • a contractor who bought into the ideals of the project
  • a shopping list of energy saving and ESD options, which allowed the client to approve the adoption of specific ESD strategies based on importance, cost and payback.

Lessons learnt

Since its opening, the facility has been hugely successful, with the informal character and café attracting more visitors than anticipated. The building is also well liked by the staff and - because of this - some of the more unusual features seem to be well understood and managed.

However, it remains to be seen whether or not the building will continue to be managed as well when the novelty wears off.

Engineers took significant time and effort during commissioning and monitoring energy uses. This commissioning continues and the engineers are confident that further energy savings will be achieved.

The water-filled moat caused particular problems during commissioning. Algae build-up was not controlled sufficiently by the proposed enzyme treatment and filtration system. The actual effect of the moat on overall water use is not known because water must be topped to cope with evaporation losses.

The moat has been designed with a river boulder base to look like a dry riverbed in droughts. This facility has yet to be used and does create some additional cleaning requirements. However, the moat is a successful architectural feature and the security it provides means the building can have opening windows and doors.

Photo of library.

Credits

Client Christchurch City Council

Project manager City Solutions

Architects Warren and Mahoney

Quantity surveyors Shipston Davies

Contractor Mainzeal

Landscape architect City Solutions

Structural and civil engineers City Solutions

Electrical engineer Beca Carter Hollings & Ferner Ltd

Mechanical and fire engineers Beca Carter Hollings & Ferner Ltd