Electricity bills of 3.80 pounds a month for low carbon social housing
When it comes to paying the monthly electricity bill, Honingham residents, Gary and Keron Lawson, getting change from a fiver is commonplace. They're fortunate enough to live in the UK's first earth-sheltered social housing scheme and one of this country's most energy efficient homes.
Known as HES, (Honingham Earth Sheltered Social Housing Scheme), these single storey, multi award-winning bungalow-style homes, are part of a development of four identical properties in Norfolk that were designed for Flagship Housing Association by Dr Jerry Harrall of SEArch, (Sustainable Ecological Architecture Limited).
Having lived in the Honingham property - whose shell is constructed using Topcrete aggregate blocks from Tarmac Topblock - for just over 36 months, Gary and his wife Keron have fully embraced their new low carbon eco-friendly lifestyle. In addition to benefiting from the energy efficient design of the property, they also compost, use water butts and have a greenhouse where they grow their own vegetables. They even reuse their bath water on the garden, but it is the design and construction of the home that helps it to achieve one of the lowest carbon footprints in the UK.
Developed by architect and low carbon living specialist, Dr Jerry Harrall, the Honingham Earth Sheltered Social Housing Scheme benefits from the knowledge that Jerry gained from the construction and occupation of his award winning Long Sutton Work Life Project, which also used Topcrete blocks from Tarmac. Working with a design that would maximise the thermal mass potential, and therefore the thermal efficiency of the earth-sheltered buildings, concrete blocks were specified to achieve the lowest U-Values possible for the development. However, the starting point for the overall design was the sun. Before groundwork began, the location and construction of the buildings were orientated around the sun's path, to maximise solar gains and elevate daylight levels in the home.
By constructing each building a single room deep with extensive floo-to-ceiling glazed screens, every room in the dwelling is able to take full advantage of the sun's energy. Each Earth-Shelter boasts two bedrooms, a combined living and kitchen space and a bathroom, making them ideal for up to four residents. The design for the Earth-Shelters was simplified, which reduced the need for the use of features like skirting boards, lintels and embedded services. This, in-turn, meant that fewer tradesmen were required to complete and finish the dwellings, reducing the overall project cost further still.
Construction itself began with the formation of a concrete slab, which was used as the supporting foundation for the main exterior Topcrete block wall construction, which was constructed using 100mm thick 415mm wide Topcrete blocks. Relaying the purpose of these materials Dr Harrall explained: "By combining the high thermal mass products of Tarmac Topblock's blocks with super insulation, building designs that are orientated around the suns path can become the key solution to providing zero heated and net zero CO2 buildings."
The durability and strength of the external concrete block walls were essential to the success of the Honingham properties, as they drew their Earth-Shelter title from the design of their heat-retaining roof, which consists of a layer of earth, covering all four properties. As an essential part of the design, this posed the most significant challenge to the buildings structure because of its variable weight and the fact that it spanned the whole of the development.
In order to support this Earth-Shelter roof construction, once the exterior Topcrete walls were completed, an aluminium and steel shuttering soffit support system was erected within the confines of the structure. This was used to support the formation of a single reinforced in-situ concrete roof slab, covering the entire development. After this was struck, the external walls provided the support for the slab, whilst the internal walls were also constructed using the Tarmac's Topcrete blocks, providing the additional support needed for the earth to be moved onto the roof slab and planted with evergreen herbaceous shrubs.
To maximise the thermal efficiency gained from using Topcrete blocks combined with the concrete and earth roof, 140mm of extruded polystyrene insulation envelopes the external building fabric, helping to deliver excellent thermal efficiency with the buildings average U-Value of 0.32W/m²k. The building envelope was then completed with the inclusion of solar glazing screens with roof-mounted solar panels, providing all the energy needed to heat the domestic hot water. Internally, the dwellings were also adapted for the use of renewable energy sources, with each equipped with energy efficient task lighting and under floor heating, which can be adjusted to suit individual requirements but is not needed in the Lawson's home.
Referring to the Norfolk scheme as offering the industry an insight into the future of housing in the UK Dr Harrall said: "Honingham has provided credible evidence that high thermal mass buildings constructed using concrete blocks are probably the most appropriate construction method for use in the UK, if we are to reduce the construction industries unhealthy reliance on fossil fuels."
Commenting on the construction, Colin Marshall, technical manager for Tarmac Topblock said: "At the Honingham project, Dr Jerry Harrall has used his understanding of the thermal mass benefits offered by concrete building products to harness the natural energy of the sun. By using locally sourced Topcrete blocks at the heart of the design, he has been able to develop a low carbon, cost effective solution to the development of modern social housing, which the industry can learn from."
Continuing his campaign for low carbon housing, Dr Harrall has recently acquired a Brownfield site from South Holland District Council on which Europ'e largest earth sheltered development is now under construction.
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