There is no doubt that we are living through a transition towards a green era of sustainability and environmental responsibility.

Increasing energy prices, concern about climate change and occupant health-consciousness are influencing people around the globe to take decisive action to make buildings and societies greener and more sustainable. ArchitectsEngineers and Designers worldwide are increasingly concerned about the current state of energy consumption and carbon emissions and are looking more and more into sustainable design to keep up with increasing demands by governments, building standards and users who are screaming  for a stark redirection of current design and construction approaches.

In the UK the focus of legislation and the construction industry seems to be about developing zero carbon homes.


Because, Some 26% of UK’s carbon emissions come from homes, making it a significant area for reducing emissions overall according to UK Green Building Council and WWF.
This target is without doubt amongst the most challenging in the world.

According to the UK’s Zero Carbon Hub an average home built in 2006 emits 3.2 tons of carbon a year and a typical 100-year-old home emits about six tons. By 2016, it is expected that all new homes will have zero carbon emissions over a year. This will be a minimum requirement for homes to even gain planning permission, which in the UK is the permit necessary to build anything. This is a very challenging target which according to many experts will be unattainable. To top it all off, the focus of these targets does not include existing homes, which will also need to be made more energy efficient. This represents an even more challenging target to achieve given that the vast majority of the housing stock required in 2020 is already built and the techniques for improving homes is also falling behind those of new build projects.

Today, despite economic meltdown worldwide, The UK government is still setting strict and very demanding targets in an effort to tackle this problem. In five years time, all new homes built in the UK will be required to be zero carbon.

What exactly does zero carbon mean?
Zero carbon homes means that the building when occupied will have zero net carbon emissions over the course of a year. Energy use will be minimised by use of thermally efficient building materials and insulation. All the energy used to heat and light the home and run its appliances will need to be off-set using zero carbon technology such as wind turbines, solar panels and ground source heat pumps. The problem is that when the target was originally set in 2006, it was envisaged that all this renewable energy would be generated on-site which would get the homes to be self sufficient and sustainable.

However, in 2008 it was decided that to be realistic, the definition needed to be relaxed to allow contributions to off-site renewable energy schemes. This would allow house-builders to make payments into new community energy schemes to off-set the carbon emissions of their homes. Today, the shift is moving back to micro-renewables and on-site energy generation as the government subsidy programme or feed-in tariffs, became the catalyst for the majority of installations of solar panels in the UK since its inception in 2009.

How is Carbon Measured in Homes?
The UK has a Code for Sustainable Homes (CFSH), where the highest level 6 is zero carbon. Regulations will require homes to move gradually up the scale before 2016. The Code for Sustainable Homes is now the new mandatory scheme for all new residences in England, and is divided into 6 different levels. Whereas a house trying to meet Level 1 requirements would need to have a 10% improvement over current regulations, a Level 6 residence has to meet a zero-carbon emission rating. Level 6 is expected to be mandatory by 2016. Again, the gap to fill is still on the existing homes as there are two things that CFSH does not address, which is refurbishment and post occupancy evaluation which in the UK currently there aren’t any formal assessments that specifically address these stages of a buildings life. There is a possibility however to certify existing homes with Passivhaus standard improvements, but again this is far from being mainstream and most experts believe building regulations in the UK are heading toward Passivhaus standards even if the government doesn’t admit it.

Code for sustainable homes diagram

RuralZED diagram showing different enhancement requirements for achieving different code levels. Image © ZEDFactory

How does the UK’s target compare with others worldwide?’
Many believe that while countries such as Germany, Sweden and China have already produced more zero carbon homes than the UK, nowhere else can rival its ambitious target for 2016. It is also worth mentioning that most countries in Europe measure the environmental impact of homes using energy efficiency and not carbon emissions. Germany and Scandinavia have historically had better building standards and some countries have decided to tackle the commercial building stock first. Either way, the goal remains the same.

How many zero carbon homes have been built so far?
Very few. In 2010 the UK government announced tax relief on zero carbon homes and so far only about 25 homes have qualified, according to the UK Green Building Council.
However, this tax relief was based on the definition that all off-set energy had to be produced on site, a definition which has since been considered unrealistic. The challenge remains as most developers still remain unconvinced that spending on average 5-10% more in construction costs towards zero carbon improvements could end up saving them triple that amount in energy savings throughout the building’s entire life.

Zero Carbon Homes Diagram

So are Zero Carbon Homes the solution?

When speaking about A solution to all the housing needs,  there are many variables which need to be taken into account beyond the new build’s ecological footprint and energy efficiency. If not planned correctly or in the right context, zero carbon  homes will become nothing more that feeders to an already disconnected suburban society and if not connected to a sustainable urban community network they could become part of the problem and not the solution. Sustainable cities and neighbourhoods are the key to making zero carbon homes a successful experiment.

Of course, reducing energy usage and looking at carbon reduction in homes is a great way forward, but again, millions of homes worldwide need a comprehensive and coordinated approach to tackling the problem. Currently, different  countries have different approaches to defining low and zero carbon buildings. This has led to a variety of terms to describe such buildings, including low energy, low-carbon, zero carbon, Passivhaus, high-performance, energy positive, eco-homes, sustainable homes and green homes.

This diversity of terminology and definition is not surprising, given the range of climatic and regulatory conditions across countries, as well as differences in housing stock, energy sources and cultural influences. One of the main factors influencing carbon emissions is the carbon intensity of the grid, which is dependent on the mix of fuels each country uses to generate energy.

The recommended standards, as well as the way they are expressed and measured, are different from country to country and the pace in which the global response is evolving does not leave much room for coordination worldwide. The truth is that no matter how many energy-efficient homes are built today, construction supply chains and methods remain the same, manufacturing processes are getting more efficient but still rely of fossil fuel for transport and implementation. All of these factors need to be addressed if a global coördinated response were to be implemented.

All of this construction issues also pale in comparison with problems of over consumption, water shortage, contamination, and over reliance on fossil fuels. Reducing carbon emissions in construction and usage in buildings is an important piece of the puzzle in this complicated game of global sustainability, but if a change in attitude and culture through a global coördinated approach to sustainability is not adopted, zero carbon homes run the risk of being left standing in the near future as really efficient suburban reflections of a culture obsessed with high tech and consumerism.

UK Green Building Council :
Zero Carbon Hub :
Zero CArbon Compendium:
RuralZED :