Building Lower Carbon Footprint Homes In NZ

Building Lower Carbon Footprint Homes In NZ

2019-11-25T10:15:58+13:00November 25th, 2019|

When we think about green house gas emissions in New Zealand vehicles and cows immediately spring to mind, but buildings produce significant green house gas emissions over the course of their relatively lengthy lifetime too.

This includes accounting for energy needs for the obvious things like heating, cooling, waste disposal and lighting, but emissions also occur during the initial construction phase or when carrying out renovations when extracting the raw materials and in the manufacture of products needed for the entire build project.

How Much Of New Zealand’s Emissions Are From New Buildings?

According to recent study ‘The Carbon Footprint Of New Zealand’s Built Environment’ from the team at Thinkstep Australasia, buildings, roads and infrastructure are responsible for approximately 13% of New Zealand’s greenhouse gas emissions.

This percentage is somewhat higher than previously speculated (2-5%) and represents a much larger piece of the country’s ‘pollution pie’. Why the difference? It comes down to two main factors; Embodied Emissions versus Operating Emissions.

  • Operating Emissions. These are those associated with the daily running of the building such as heating, cooling, lighting, appliances, waste disposal, water usage and air-conditioning.
  • Embodied Emissions. These are calculated taking into consideration the environmental costs associated with manufacturing, transporting, and assembling the materials a building is made of.

Currently the New Zealand building industry tends to focus on the Operating Emissions when looking at building greener homes – this report highlights the important need to adopt a broader view, taking into account the complete life cycle of the building.

What Is A Carbon Footprint?

The term ‘carbon footprint’ refers to the overall amount of greenhouse gas emissions associated with the production, use and disposal of an item.

Some examples of factors considered in the calculations are electricity production, transportation, raw material extraction and industrial processes involved in manufacture.

5 Ways To Reduce The Carbon Footprint Of New Builds?

In New Zealand our existing housing stock has notoriously low levels of living conditions involving water tightness, air flow and insulation to name a few. Newly built ‘greener’ homes meeting or exceeding modern housing regulations and requirements require far less energy to maintain a comfortable living environment than these older properties – thus reducing their Operating Emissions over their lifetime.

However there are obvious environmental costs (Embodied Emissions) associated with creating these new buildings – what can you do to reduce the carbon footprint associated with new builds?

  1. Choose Your Materials Carefully. This means considering both the embodied and operating emission costs and if possible choosing to build with materials that store carbon, and/or require less carbon to produce. In New Zealand building with timber is a good example – sourced locally, timber is a ‘carbon absorber’, and also an excellent insulator.  Building new timber houses results in only a fraction of the greenhouse gas emissions generated by building brick, concrete or steel houses.
  2. Comprehensive Planning. The best time to address your carbon footprint is from the very early stages of the build process. Evaluating, planning and investigating the environmental cost of everything from cladding, framing and linings right down to which paint your use is going to identify emission reduction opportunities.
  3. Think Full Life Cycle. Sometimes called a Lifecycle Assessment, this is the process of considering all of the energy, water, materials and waste in and out of the building over its lifetime in order to calculate its full environmental impact. How does it dispose of waste water? Sewerage? What energy is required for heating? Cooling etc. Can the building materials be recycled upon demolition?
  4. Location. Your choice of section and/or orientation of the building can have a huge impact on the buildings overall carbon footprint. Maximising the free energy from the sun and minimising the exposure to the cold southerly direction is vital in any build whether it be your family home or large scale apartment building. This includes considering local weather conditions and climates particularly where extreme temperatures are experienced.
  5. Keep In Mind. Sometimes efforts to reduce Operating Emissions can have the unpleasant effect of increasing Embodied Emissions. Adding solar power units for example although conducive to less daily energy usage – the environmental cost of producing, storing, transporting, installing, maintaining and replacing these units multiple times over the life span of the building may effectively cancel out any longer term benefit to the carbon footprint of the building over its lifetime (see below for more on the concept of ‘carbon debt’).

What Is Carbon Debt?

Working out how long a new building will take to “pay back” or make up for its carbon emissions produced during its initial construction phase is sometimes referred to as calculating its ‘carbon debt’.

This term essentially looks at the total Embodied Emissions created during construction versus the time it takes the newer more efficient technology associated with new build that reduce ongoing Operating Emissions to ‘make up for’ the extra emissions created during the build. Here are 4 factors that may have affect carbon debt calculations in New Zealand;

  1. Renewable Energy Production. New Zealand generates a great deal of its electricity from renewable sources such as hydropower and wind. These methods generate much less carbon emissions than other sources of electricity generation such as coal powered methods. This means lower Operating Emissions, increasing the time it takes a building to payback its carbon debt.
  2. Older Housing Stock. Much of NZ’s housing is made up of homes over 50 years old. These homes are neither energy efficient nor overly hospitable and are sometimes down right unhealthy for their occupants. Replacing these homes results in a much shorter payback period as the homes are no longer fit for purpose and require extensive upgrades particularly with regard to insulation.
  3. Harsh Weather Conditions. Parts of NZ particularly many rural areas are subject to harsh weather conditions, replacing these homes with more energy efficient alternatives is usually the best option here too – reducing the resulting operational cost to the environment by such a degree that it outweighs Embodied Emissions associated with new build consumption.
  4. Locally Sourced Building Products. As a relatively small country any products that are made locally, produced or grown here are likely to incur less emissions attributed to their production due to the reduced transportation costs. Pay back periods will be greatly reduced as the Embodied Emissions are lower overall.

What Does This Mean For NZ Moving Forward?

Applying a life-cycle perspective provides a more complete and accurate representation of the green house gas impacts of not only building a new house but for any production activity.

The significance of this approach to looking at carbon emissions allows us to shift some of the focus from just energy efficient builds (considering only Operating Emissions) to a more complete perspective over the lifespan of the building (including both Embodied and Operational emissions).

The concept of lifecycle emission assessment is particularly important for New Zealand where compared to some countries the Operational Emissions are fairly low, given the low-carbon electricity mix. It is expected that New Zealand will eventually follow a full life-cycle approach to the built environment enabling us to thoroughly evaluate the impacts of housing developments in the future. For manufacturers this will mean a shift towards a life-cycle approach for each and every product.

We can already see the emergence of this approach with the ‘Green Star Credits’ initiative developed by the NZ Green Building Council which provides an environmental assessment of the whole building over its whole life cycle is undertaken with credits awarded based on predefined criteria. Hopefully these types of accreditation will eventually become more mainstream leading to industry wide collaboration and ultimately the inevitable transition to a low emissions based economy. 

Reducing carbon emissions is a primary concern for New Zealand, and it’s one that the construction industry can play an important part in. Building greener is an important step in tackling climate change, there is always more we can do to reduce emissions of our buildings – see here for more information on sustainable building in New Zealand  or building energy efficient homes.