Ecotecture, West Sussex / Uncategorized  / Sustainable retrofit and extension of Cottage in Sussex

Sustainable retrofit and extension of Cottage in Sussex

This lovely site situated in West Sussex, was a great project and brief, to transform and uplift an existing house into a new eco house with green retrofit features and ecological design. Our clients were experienced self builders and developers, however their previous projects had not centred around energy efficiency so they needed expert advice on green sustainable design. We were recommended by a planning consultant Chris Barker director at ECE planning ( for our design expertise in retrofit and low energy building. We cover most areas in the South east within 100 miles of our office, covering Kent and Surrey as well as West Sussex


The existing house in Sussex

Early architects sketch for makeover









Planning consent in rural situations

Firstly we had the difficult task of gaining planning for a considerable uplift in floor area. The site, nestling on the edge of a Sussex village is cradled into the hill with the front drive curling up to the house. The demographics meant that we had to be careful to design the house so it didn’t appear overly extended whilst at the same time upping the floor are considerably. Initial designs were submitted to council for pre application advice which was positive before submitting for planning consent. This stressed the ecological and low carbon nature of the project. The design featured many of the factors of good solar design to ensure a building that delivers a high level of performance. Usual consideration larger windows to south and western elevation for solar gain, smaller on lesser sides in conjunction with shading devise to prevent overheating.

Gitted inside



Extensions under construction











Matching the architect you get on with well is an important part of a project and often overlooked. Building your own home should be as stress free as possible. People often find us through the RIBA as we are a Registered Chartered Architects Practice. This means we have committed and demonstrated high standards of professionalism and business effectiveness on order to gain entry on the register. In fact I can feel a whole other blog coming on the way we approach service in this office. I don’t suppose the kettle being on and having an office dog would earn us brownie points, but it does add a human touch to this whole creation of beautiful light and open spaces!

Green eco design

Whether you are looking for a modern, contemporary or traditional approach to your design and specification of a project is what makes it leading edge in our book. For example traditional detailing in old style buildings often contain thermal bridges which act as conductors to heat having a detrimental effect on the performance of your house if not detailed properly.  Put simply if you imagine heat as a liquid in a fish bowl, holes in the glass means the water will flow out. Create a building with gaps in the thermal envelope and it does the same. Puts a whole new perspective on the avoidance of air leakage as well. We follow the principal of passivhaus in our designs and so use the PHPP (Passivhaus planning pack) where appropriate. This centers on the fabric first approach as a way of reducing energy demand.


External wall insulation being fitted


Finished new Sussex Cottage









Fabric Design for the Cottage

The Passivhaus design methodology was founded after experts examined a low energy home with lots of bolts-ons like photovoltaics, solar thermal, and found the energy consumption was not reduced. It was only by then examining the fabric as a focus that tangible results were seen.

The clients wanted a low carbon home. So the junctions between the new eco extensions to increase the footprint and the retrofit options required for the existing house structure were pivotal.  Two different constructions types create differential thermal movement with associated air leakage issues. These were married successfully by the use of a carefully specified external wrap around thermal envelope with corresponding high levels of air tightness targets.

The existing building in traditional cavity wall, leaky and uninsulated was upgraded by using external wall insulation wrapping around the whole building, with a combination of cladding and render finish. The new build parts were more simply built in solid insulating blockwork with external wall insulation.  We also hacked up the old floor and re-laid it incorporating 200mm closed cell insulation below new screed incorporating underfloor heating, which together with thick layers of attic insulation meant the whole house envelope was a continuous insulated layer, a tea cosy approach.


Internal of living/kitchen area


Final kitchen design








Green services

Having reduced the energy demand at source with the retrofit/new build we then turned to the services. Our clients wanted to reduce their reliance on fossil fuels. In the construction the old floor joists were removed and replaced with easi joists, joists constructed using a steel web to allow for the installation of the MVHR system (mechanical ventilation and Heat recovery) where ducting can pass through the joists in the floor zone. They are also perfect for service wiring though its important to remember to install any horizontal soil pipes before fixing the joists in position! A wood burning stove was also installed together with traditional boiler for very cold months.

Front elevation

New front approach


Living room with wood burning stove


Jo Saady

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