AIMC4 – Creating a template for tomorrow’s new home construction

By Dr Elizabeth Ness, group sustainability director at Crest Nicholson PLC, a leading UK developer of sustainable communities. Reporting directly to the CEO, Elizabeth leads the Sustainability team, which forms an integral part of the business. Much of the role of the Team is focused on seeking innovative practical solutions to drive the group’s response to the UK government’s goal of zero-carbon housing

Conventional wisdom
Conventional wisdom once suggested that housebuilders who invest in sustainable forms of construction might not be as commercially viable as their more conventional competition. Crest Nicholson’s position as one of the country’s most sustainable and innovative housebuilders, linked to its excellent 2014 trading year end results, should finally bury that myth.

During the economic downturn of 2009 it was a brave and far-sighted decision by our Chief Executive Officer, Stephen Stone, to nail the Group’s environmental colours to the mast and become part of the AIMC4 Consortium and to maintain our sustainability commitments through what has been the most difficult trading period in recent times. However, Crest Nicholson remains committed to an integrated sustainability strategy that we know will yield environmental, economic and reputational success.

We know that it is essential that we maintain our drive and continue to deliver a legacy of enduring value to the communities we create and the wider built environment while ensuring our commercial success. This is easily said but requires considerable focus and persistence to achieve. That is why we have adopted a sustainable approach to our business that strives to ensure that our everyday decision making achieves:

  • Profitable growth – through customer-led design and sustainability
  • Respect for our environment – by protecting and, where possible, enhancing biodiversity and creating sustainable lifestyle choices for our customers
  • Customers and community – by designing quality and sustainability into our homes and their surroundings.

It is pleasing to see from our successful re-entry to the London Stock Market and recent results that these key themes continue to underpin the long-term value of both the Crest Nicholson Group as well as the homes we build and the communities we create.

AIMC4
It was the need to put our commitment to customer-led design and sustainability into action that encouraged Crest Nicholson, in 2009, to join the Stewart Milne Group, Barratt Developments PLC, H+H UK Ltd and the Building Research Establishment (BRE) to form the AIMC4 Consortium.

The AIMC4 (Advanced Innovative Materials, products and process to meet the governments Code for Sustainable Homes, Level 4) project was established to help us understand how to create quality homes that were attractive, energy efficient, easy to run and cost-effective to deliver in volume using fabric-first solutions.

The project also anticipated changes to Approved Document L1A of the English Building Regulations expected in 2013, by:

  • Building a minimum of 12 low-energy homes to the anticipated Part L 2013 Regulations for private or public sale
  • Testing the market for this kind of home
  • Energising the UK supply chain and developing new and existing products
  • Developing two (possibly three) build systems and processes
  • Understanding the performance of the homes and customer attitudes toward energy efficient homes
  • Taking a significant step towards producing low-energy homes cost-effectively and in volume
  • Achieving significant progress towards the government’s goal of zero-carbon homes by 2016.

As one of the consortium partners Crest Nicholson was committed to developing robust technical and commercial solutions to meet the energy requirements of the then Code for Sustainable Homes, Level 4, using fabric-first solutions. The consortium members had all become increasingly concerned that the technical changes to home design resulting from government’s regulatory pressure did not take into account the reality of consumers’ views and the way occupiers actually operate their homes.

We have long believed that unless the low-carbon homes of the future are occupier friendly the risk is that, in the real world of resident run homes, emission reductions will not be delivered in practice.

The AIMC4 project was, therefore, developed in three key stages.

Design development
Stage one involved development of the supply chain and design/technical specification. These had to be interactive and iterative processes which involved working with both committed supply chain partners and on-site construction teams.

We knew that key to the success of the project was to engage with both known and new suppliers at all levels. With the help of these supplier partners the consortium was able to develop design solutions and processes that could deliver homes that would meet the specified Code Level 4 energy requirements. What was special was that this was achieved through a variety of energy efficient fabric and building services solutions, with-out requiring the use of renewable technologies.

Although this was a real challenge we knew that achieving this goal would help meet the government’s 2016 target of zero-carbon homes while:

  • Reducing delivery costs
  • Introducing new product suppliers and supply chains
  • Creating new construction methods; and
  • Ensuring that homes are designed to meet consumer needs without confusing or costly technologies.

Building the homes
The second stage was the construction phase and the actual creation of our ‘exemplar homes’. To fulfil our part of the project Crest Nicholson built one detached and four townhouses at our Noble Park development in Epsom. One home was constructed using H+H UK’s thin-joint Aircrete masonry system and the other four units were constructed using Kingspan TEK’s Structural Insulated Panel (SIPs) system. Other consortium members delivered a mix of the thin-joint masonry system, and three types of timber-frame using SMG’s Sigma range.

Evaluation
The third and final stage was an as-built performance evaluation followed by a 12-month post occupancy study.

These are areas of new home construction which need much more study to understand how low carbon homes perform and how they meet the lifestyle needs of the modern home occupier. Crest Nicholson has always believed that in order to understand how its homes perform we must conduct studies and then work with the findings from post-construction evaluation. Also, as important as technical data is to discover how the owners of our homes actually operate them, to get the best from their home, residents have to know how to use the systems that now form part of today’s energy efficient property.

These areas of build and occupant evaluation therefore formed an essential part of the AIMC4 project.

The first stage of the evaluation exercise was an as-built energy efficiency evaluation of the AIMC4 fabric performance. In order to understand the actual thermal performance of the fabric, we conducted comprehensive thermal imaging and a limited number of co-heating and heat flux tests prior to occupation. A series of air-tightness tests were carried out at differing stages during the build (weathertight, first-fix, second-fix and at completion).

How residents operate their homes
Crest Nicholson has always known that the overall success of the AIMC4 project in terms of mitigating carbon emissions depends not only on build specification but, significantly, on how residents operate their homes and how their behaviour affects expected reductions in energy and water usage (and therefore cost).

Therefore, the second stage of the evaluation, which started in 2012, and is still running, was the post-occupancy evaluation.

For the post-occupancy evaluation, all homes were subject to a comprehensive environmental audit to establish what equipment is being used and the potential energy use of that equipment. Electricity, gas and water sub-circuits are also monitored. Sensors establish indoor air quality, temperature levels and the opening and closing of windows to contribute to understanding of the overall energy analysis. A weather station was fixed on-site to correlate energy and ventilation use with real-time external conditions.

The consortium created clear user guides for the residents of each of the homes. This included quick-start guides for heating controls and the ventilation systems which themselves had been modernised and simplified by working with the suppliers.

Everyone has a personal and very subjective approach to comfort, heating levels and ventilation requirements within their home and part of the AIMC4 study is how occupants react to energy display meters and whether they use these meters to adjust the way they operate their homes.

Measuring in-use energy performance and customer behaviour is a long-term exercise and information is still being gathered. However, we are already beginning to better understand our customer’s lifestyles, living habits, motivations and how their behaviour affects a modern home’s energy and water usage.

Applying the lesson learnt
In total, 17 AIMC4 homes have now been built by the consortium developer partners at five sites across the UK. To ensure the lessons learnt throughout the project are captured and com-municated findings have been provided as a continuous process via technical papers, conferences, exhibitions, seminar presentations, press releases and visits to the AIMC4 sites.

The findings from the AIMC4 project will provide evidence to help us achieve the government targets, as well as determine which new home build products work best to meet the demanding energy efficiency standards that confront the whole industry.

There is still a way to go before we can introduce all the lessons we are still learning from our involvement with AIMC4 but we are proud to be a part of this market leading and pioneering industry consortium. The joint learning will be a huge benefit for our customers as we deliver the low carbon homes of the future.

Although not yet complete, key lessons learned from AIMC4 include:

  • Early engagement between project partners is essential to build an effective and open collaboration with a clear project structure and clear roles, work tasks, communication and reporting channels.
  • A phased approach with interactive assessment is essential to find the best suppliers, develop trust and to facilitate partnering.
  • The commercial challenge of achieving cost-effective delivery of homes to the energy requirements of Code Level 4 outweighs the technical challenge of the project.
  • Engagement with sector stakeholders including government, trade bodies and policy influencers is essential to ensure the results of the project will be relevant not only to the project partners but also to the wider industry.
  • Where projects are subject to external regulations and standards, some contingency allowance has to be made in order to allow for possible changes to them, e.g. the exact requirements of the Building Regulations some years ahead could not be known at the start of this project. This featured on the project’s risk register, which was continuously updated.
  • Research projects like AIMC4 and innovation throughout the sector would be considerably assisted if there were more consistency and certainty in government policy and regulations.About AIMC4AIMC4 is a £6.4 million project, with £3.2 million investment from the consortium partners, matched with £3.2 million from the government-backed Technology Strategy Board. The consortium comprises five members: developers, Stewart Milne Group, Crest Nicholson Plc and Barratt Developments Plc; plus H+H UK Ltd; and the Building Research Establishment.