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    How to deliver true low carbon housing for the planet

    In its 2019 Spring Statement the government
    said it will aim to end the use of fossil fuel-based heating systems in all new
    homes from 2025. It’s a bold move, and one that certainly brings even more
    focus on improving the sustainability credentials of the UK’s new-build housing
    stock. But what else should be done to make our homes truly low carbon and
    sustainable?

    Going beyond operational efficiency

    In the quest to reduce CO2
    emissions and produce ‘nearly zero-carbon buildings’, most designers and
    builders focus on lowering operational emissions – even if it means emitting
    more CO2 in the construction process. There’s still very little
    thought put into reducing the CO2 emitted during the build stage and
    from the materials used in the building fabric itself.

    There are, however, pockets of developments
    appearing across the UK – built by innovative SME builders harbouring a social
    conscience – that take a more holistic approach to sustainable housebuilding.

    One such development currently under
    construction is Kings Farm Close. A collection of 15 new homes on the outskirts
    of the Oxfordshire village of Longcot, the development promises affordable,
    sensitively designed dwellings fit for 21st century living.

    More significant, however, is that Kings Farm
    Close also claims to be the most sustainable housing development in
    Oxfordshire.

    Modern methods of construction

    Ian Pritchett, managing director of
    Oxfordshire-based Greencore Construction, has been championing a fabric-first
    approach to new home building, using eco-friendly, modern methods of
    construction for some time. His approach is to build to the highest standards while
    also delivering comfort and quality at a great price.

    Every Greencore home is built offsite in a
    factory using a timber frame panel system, which is insulated with a mix of
    hemp, lime and wood fibre. The hemp-lime mix provides exceptional levels of
    thermal performance – tests carried out by Bath University showed that this
    system stores nearly four times the amount of heat when compared with
    traditional insulation materials like mineral wool.

    Meeting the double carbon target

    This insulated panel system – branded as the
    Biond Building System – is manufactured almost entirely from natural materials.
    It means that Greencore’s homes, which are always built to Passivhaus thermal
    performance standards, can achieve the double carbon target of a low carbon
    footprint and low operational energy usage.

    Ultimately, it means the homes’ occupants won’t
    need to use their heating as often. This is because the hemp-lime and wood
    fibre insulation in the superstructure – and a mechanical ventilation and heat
    recovery unit – help to maintain a comfortable indoor temperature all year
    round. The heating is provided entirely by underfloor heating, leaving wall
    spaces clear for furniture and decoration.

    So, how is this possible? How does a humble
    plant-based insulation material like hemp-lime make such an impact on the
    thermal performance of a home?

    Hemp-lime ‘phase change’ properties drive thermal efficiency

    It’s all thanks to the natural ‘phase change’
    properties of hemp-lime. The moisture naturally present in the cells of the
    hemp and in the pore spaces of the composite material can change from liquid to
    vapour and back again. When this change takes place, a lot of energy is either
    absorbed or released.

    This phase change process can take place at a
    wide range of temperatures and means that energy entering or leaving one face
    of a wall is very different to the energy entering or leaving the other face.
    The reality is that the combination of good insulation and exceptional thermal
    inertia resulting from the natural phase change properties makes hemp-lime an
    extremely high performing material.

    A little hemp-lime history…

    Hemp-lime has been used as a building material
    for hundreds of years in central Europe, but was revived in the 1990s in France
    as a niche construction technique for new houses and for infilling the panels
    of historic oak-framed buildings.

    The new-build technique involves casting a wet
    mix of hemp and lime around a timber framed structure to form solid monolithic
    walls, normally finished with a lime render on the outside and lime plaster on
    the inside. This form of building has gained popularity in France and spread to
    the UK in the early 2000s.

    Avoiding the delay of drying wet hemp-lime

    Despite its rise in popularity, one major
    limitation hampers the use of wet cast hemp-lime in volume construction
    projects: it takes a long time to dry. In ideal weather conditions (warm, dry
    and breezy), drying can take as long as six to 12 months, which clearly isn’t
    practical for fast-track housebuilding in unpredictable British weather.

    To tackle this, Greencore pre-fabricates the
    superstructure of each home at its factory – ready-filled with hemp-lime and
    wood fibre insulation – before it’s shipped out to be assembled onsite. This
    means the drying process can be managed in a controlled, indoor environment.
    Once on-site, the superstructure of each building can be erected in a matter of
    days. It’s modern methods of construction with a natural, sustainable twist.

    Taking sustainability to the community

    For Greencore and its partners, however, the
    sustainability focus doesn’t stop with the homes themselves. Back at Kings Farm
    Close, developer Oxford Advanced Living (OAL) – with support from affordable
    housing provider Sovereign – has made a concerted effort to build
    sustainability into the very fabric of the community.

    “A fifth of the site’s total area will be
    shared green space,” says Martin Pike, director of OAL, “planted and managed
    with native trees to support wildlife under a biodiversity plan. This project
    has really allowed us to put into practice all our ideas and determination to
    create a genuinely sustainable community in Oxfordshire.”

    With 40% of the development given over to
    affordable housing, Greencore and OAL are keen to champion a ‘sustainability
    and quality for all’ approach to housebuilding.

    “With these homes, the same high performance
    standards are available to everyone, regardless of whether you’re renting or
    buying a home,” says Martin. “We believe that all the residents will be able to
    enjoy greener and healthier lifestyles at Kings Farm Close, and we intend to
    work closely with them to help us with future projects.”

    Alex Brooks, development manager at Sovereign,
    agrees. “These new affordable homes will not only be great places to live,
    they’ll also be good for the environment as well as keeping energy bills low
    for residents. It’s really important that we build homes and invest in
    communities that are fit for the future.”

    Support from MPs

    It’s an approach that hasn’t gone unnoticed in
    political circles, either. In March this year, Ed Vaizey, the former culture
    minister and MP for the Oxfordshire constituency of Wantage, took time out of
    his schedule to visit Kings Farm Close and see the project first hand.

    “The vast majority of new-build homes in the
    UK are of bland design, poor build quality and lack basic sustainability
    credentials,” he says. “Much of this is to do with national housebuilders
    refusing to embrace new technologies and construction methods.

    “The Kings Farm Close development, however, is
    a shining example of forward-thinking, modern housebuilding from a team of
    people who are clearly very committed to bringing sustainable living to
    everyone – whether you own, part-own or rent your home.”

    Recognition from sustainability leaders

    In October 2018, Kings Farm Close was
    recognised by sustainability charity Bioregional for its national leadership in
    implementing One Planet Living, a comprehensive framework for planning, building
    and managing greener communities.

    Nicole Lazarus, head of Bioregional
    Oxfordshire, praised the development, saying: “The Kings Farm Close team richly
    deserve recognition for their leadership in creating the kind of sustainable
    new housing we need so badly. We particularly love the natural materials used
    in the build system and the high-quality indoor environment that they make
    possible.”

    There’s a lot to be said for the power of
    plant-based materials in construction. The fact is the more of these materials
    we incorporate into buildings, the more carbon we lock up – plain and simple.

    Recent industry data shows that the
    construction of an average house produces 50 tonnes of CO2. On the
    other hand, construction of a Greencore home, using the hemp-lime timber frame
    panel system, produces very low or zero CO2 in the construction
    process.

    With construction work at Kings Farm Close
    expected to complete in the autumn of 2019, it won’t be long before the final
    residents move in and the claim of ‘Oxfordshire’s most sustainable housing
    development’ can be put to the test.