Specifying efficient use of materials and considering their impact from manufacture to disposal.
Building materials account for a significant proportion of all material use worldwide, and construction and demolition waste accounts for over a third of all solid waste generated.
Building materials have an environmental impact at every step of the building process – from extraction of raw materials to processing and manufacturing, transportation, construction and eventual disposal at the end of a building’s useful life.
The impact can be significant – some materials require large amounts of energy in their production, others may be polluting or hazardous to building occupants. Appropriate selection can ensure efficient use, low environmental impact and minimising waste generated, which will result in improvements in the cost-effectiveness, energy efficiency and, ultimately, the comfort of a building.
This section focuses specifically on the sustainability and environmental impact of materials.
Some building and construction products carry ecolabels that allow assessment to be made of their environmental performance. These labels/assessments include Environmental Product Declarations and those from Environmental Choice New Zealand.
New Zealand statutory requirements
A key purpose of the Building Act 2004 is that buildings are designed, constructed and used in ways that promote sustainable development. Under the Act, designers, builders, local authorities and building owners must consider:
- minimising waste during construction
- using sustainable materials
- using safe and healthy materials
- energy conservation and efficiency of materials and systems
- the durability of materials.
Climate change and greenhouse gas emissions
Building design and material selection both have a role to play in our efforts to reduce greenhouse gas emissions.
Economic growth around the world has resulted in increasing levels of gas emissions such as carbon dioxide being added to the atmosphere from burning fossil fuels. These emissions are acting like a greenhouse, lifting temperatures. The result over time is rising sea levels, stronger storms and more extreme rainfall.
With other countries around the world, New Zealand has committed to reduce greenhouse gas emissions.
Buildings contribute to emissions from the energy used when they are occupied and when construction materials are extracted/processed, transported and installed. The construction industry can contribute to reducing greenhouse gas emissions by:
- improving solar design and thermal performance of new and existing buildings (including through careful materials selection and use)
- making greater use of environmental impact tools, such Green Star and Homestar for houses and NABERSNZ and BRANZ’s LCAQuick
- specifying low-carbon fuel options for space and water heating
- reducing, recovering, reusing or recycling construction waste
- helping to educate consumers on the implications of design and materials choices from a carbon perspective over the building’s lifetime.
The building industry will also be affected by the push to reduce New Zealand’s greenhouse gas emissions that is now set in law. Amendments to the Climate Change Response Act 2002 made in November 2019 set a target for New Zealand to reduce net emissions of all greenhouse gases (except methane from plants and animals) to zero by 2050.
A research study that included input from BRANZ scientists calculated how much carbon dioxide new houses can emit to help meet 2050 climate targets. New Zealand houses currently produce five times too much carbon dioxide.
A 2019 report Rethinking plastics in Aotearoa New Zealand published by the Office of the Prime Minister’s Chief Science Advisor, says that construction globally is the second biggest user of plastics, and in this country the industry uses 15% of the plastic products manufactured here. It says that use of plastics has increased in the sector as a result of more being used in new products (such as shrink wrap) and established building materials (such as pipes) changing to plastic from other materials.
The large and increasing use of plastics in building has some advantages for the environment and some disadvantages. The issues that the construction sector needs to address include:
- site practices that can lead to plastic waste entering the environment
- inefficient use of resources
- new uses being developed that do not have recycling options
- leakage of plastics into the environment through the weathering of plastic products.
Options for reducing plastic leaking into the environment include prefabricated buildings and designing buildings for deconstruction.
Updated: 04 March 2020