case studies / Environmental credentials of housing in Australia - Beachside holiday home

Environmental credentials of housing in Australia - Beachside holiday home

Scope

This case study estimates the life cycle environmental impacts of the construction, utilisation, maintenance and decommissioning of an architect (Peter Stutchbury) designed beachside holiday home, Hawks Nest, near Newcastle , Australia. The study was conducted over a sixty year period, with the home being demolished after this period. The house was assumed to be occupied by four people for the duration of the study. Appliances and fit out items were replaced every ten years.

Goal

To provide a fast and user friendly, interactive LCA case study, which allows the user to investigate the life cycle impacts of a range construction, transportation, recycling and utilisation, options.

Building details

The house is a holiday house constructed close to the ocean. Nominal construction includes

• Three bedrooms.
• A reinforced concrete ground slab and reinforced concrete suspended slab.
• External ground floor walls are a loadbearing double brick wall rendered on the outside face cement render.
• Bricks are standard clay bricks 240x110x90 mm with 25 mm cavity between courses providing insulation.
• Internal loadbearing walls are a single skin brick wall with the same bricks and bagged in the bedrooms or tiled in the wet areas.
• Walls facing onto the courtyard are a timber frame construction using 75x50 mm Oregon sections, upper floor framing uses the same 75x50 mm Oregon sections.
• External frames insulated using 75 mm wool insulation batts.
• Stud walls are lined with 10 mm plasterboard and clad externally using steel mini orb Colorbond sheets.
• The roof is supported on a recycled hardwood structure that employs 130x90 mm columns, 220x110 mm roof beams and 110x65 mm purlins, seated on top of the purlins are 50x38 mm hardwood battens which support Colorbond roof sheeting externally and 12 mm hoop pine internally.
• Walls are insulated 75 mm wool insulation batts with a medium weight foil backed sarking as a moisture barrier.
• Half round 125 mm Colorbond gutters and standard 75 mm copper downpipes direct water into stormwater pipes.
• Windows and external sliding doors are constructed using Western Red Cedar.
• 6mm laminated glass is used in all openings.
• Internal doors are either 2100mmx850 mm hollow core timber framed doors or a 2550x1700 mm cavity timber framed slider.
• The north facing external deck is constructed using 170x70 mm recycled hardwood bearers and joists, 75x25 mm recycled hardwood decking boards with a 5mm gap between boards.
• Upstairs terrace is the exposed aggregate reinforced concrete slab with a waterproofing additive in the concrete.

Utilisation of appliances can also be selected, with the default being the consumption of an average NSW household.

System boundaries

System definition

The system analysed included the manufacture of all building materials from resources in the ground, building site activities, construction equipment, repairs/maintenance, periodic refurbishment and finally, decommissioning.

Boundary limits

The entire life cycle is considered, from resources in ground through to demolition and recycling/landfill of the structure. Landfill emissions are excluded.

Transportation

Transportation mode and distance are included for each material.

Data categories

Impact assessment

Environmental impacts investigated were resource energy consumption, GGE (greenhouse gas emissions), NOx, SOx, NMVOC (non-methane volatile organic compounds), SPM (suspended particulate matter), and fresh water consumption.

Energy definition

Gross energy (GJ/t), or high heating value (HHV), is used. Feedstock energy is included for all materials except timber.

Feedstock energy

Feedstock energy is the specific energy, also termed calorific value, of a material. Traditionally, feedstock energy has not been included in the life cycle energy or embodied energy for timber. Timber is the only material treated in this way. This anomaly results in an artificially low value of embodied energy for timber of approximately 4 GJ/t. Including feedstock energy increases the embodied energy of timber by 10-20 GJ/t, depending on dryness.

This discrepancy, and the increased importance of timber products as a direct energy source (particularly in Europe), is leading to a trend to include feedstock energy for timber products. In this analysis, therefore, both values (ie timber with and without feedstock energy included) were calculated.

Greenhouse gas emissions

IPCC weighting factors (global warming potentials) are used in the calculation of greenhouse gas emissions, eg for CH4 and N2O.

Data sources and assumptions

Data

Australian LCI data. The data are maintained in EMMA (Eco-model for Material and Manufacturing Assessment), BHP's LCA data system. Construction data were based on a report entitled "The Use of Steel in Housing Construction (Sydney - Melbourne)" by W Lawson and S Craig, SOLARCH, University of New South Wales, January 1995. These data have been updated for 1999. Data for utilisation were gathered from various sources, including manufacturer data and the Australian Bureau of Statistics.

Allocation

This study did not require any allocation. Recycled materials have displacement credits allocated based on the displacement of virgin production.

The approach and allocation rules used in the LCI data conform to ISO guidelines for LCA, and attempt to simulate reality as closely as possible.