|naturalspace magazine : Sustainable architecture and the natural world: Natural Space Ltd|
The Bedzed Images section demonstrates the general character of the development both inside and out and shows how the sun penetrates the interior despite the scale and density of the area. It is often the case with south facing solar architecture that the winter sun is blocked just when we need it most. The skilful section and the location of the work units in relation to the houses help in allowing the warmth of the winter sun to stream through the sunspaces and land on the floor deep into the living spaces.
"Bedzed is a truly wonderful development. The following photographs attempt to give an accurate portrayal of the character of the buildings but what is very difficult to show via the media must be experienced by visiting the site. The buildings have an authority that can't be captured by a photograph. They have a mood that says this is architecture and a weight that stirs feelings of optimism inside. There is a feeling of sincerity and honesty which is similar in a lot of ways to one's feelings when visiting a great space, as I personally have felt in visiting Jorn Utzon's church at Bagsvaerd near Copenhagen. Much of today's architecture is driven by commercialism and stylistic trends only pushing small boundaries and indeed depends upon the media to show it to good effect. Not so at Bedzed. The timeless qualities here are rooted in the purity of the materials, their simplicity and texture and the way they draw on their context while creating something new. Great architecture has always had a starting point that triggered it's direction. Here it was the building physics which demanded a certain form, an orientation and a palette of materials. To craft these together and produce a piece of architecture that feels like it will always be around is a remarkable achievement. The shear heavy mass of the buildings can almost make one feel waves on the ground while the lightness and playfulness of the cowls lifts the spirit as they move about in the wind." Tom Meikle.
We visited Bedzed in winter when the shadows were just past their greatest lengths and were pleasantly surprised to see the extent of sun penetration throughout the development. The section is organised to minimise shading and with the densities obtained has succeeded in creating a balance between sun penetration and scale. This is often very difficult to achieve in more northerly cities like Glasgow or Edinburgh or indeed Stockholm or Oslo because of the dramatic increase in shadow length as one moves north.
One of the most delightful characteristics is the playoff between the heavy mass of the traditional materials and the elegance of the cowls. The cowls have given the development a sense of place and create a positive landmark in the area. To stand momentarily and watch them sway in the breeze with their scale and colour dominating the skyline is a timely reminder of how pleasant an alternative future could be. Natural ventilation is driven into the heart of the houses by wind power alone with the stale outgoing air gives off its heat to warm the incoming air.
To the most northern part of the site lie a "healthy living centre" and a nursery (to the right of the photograph). On the left is one and two bedroom flats. The gables face west directly onto London Road. The choice of oak cladding interrupting the brickwork helps to break up their scale and increases the palette of traditional materials towards the public space. Cladding is a traditional feature on older buildings in the surrounding area. Interior views showing sun penetration early afternoon, mid January.
The sunspace is double glazed. Double has been chosen over triple so that the space may benefit greater from solar gains. Effectively the rooms beyond are protected by quadruple glazing as the sunspace is glazed on both sides. This is beneficial as a sunspace is no longer an asset during long overcast winter periods. When we visited in mid January the sunspace was warm. The photograph shows the door open so that this heat could be transmitted to the room.
This section shows the location of the Bedzed development and summarises the mix of accommodation. It demonstrates how the carefully designed section allows the sun to penetrate deep into the heart of the development.
Bedzed draws on the tradition of high density, very simple, repetitive terraces that have dominated London and indeed all the large English cities for the past 100 years. Such high density terraces whether back to back or through are usually directed in a particular way. East west locations generally work very well for both types as some degree of sunlight can be given to as many houses as possible. The house types at Bedzed however, could only benefit from the sun from a southerly aspect, as the length of shadows from an east west sun position would cause severe shading in winter, precisely when heat input from the sun is required.
The accommodation consists of 36 one bedroom flats, 16 two bedroom flats, 2 three bedroom flats, 24 maisonettes and 4 townhouses giving 82 units in total. Each of these units face south and all the non-domestic accommodation lies to the north. The site was formerly used for sewage sludge spreading and therefore the soil was contaminated with heavy metal. Rather than export this problem to another location it was decided to deal with the contamination on site. The houses were raised 1200 mm above street level and 75% of the soil was buried and capped beneath.
The section has been organised to face the domestic accommodation south to benefit from winter warming from the sun. The relationships between the living accommodation and the work spaces ensure that shading is minimised and the winter sun can penetrate deep into all of the living areas. This is often very difficult to achieve in more northerly cities like Glasgow or Edinburgh or indeed Stockholm or Oslo because of the dramatic increase in shadow length as one moves north.
The Bedzed Ecological section examines the design strategy and looks at how physics led architecture can arrive at a zero carbon lifestyle. We look at how the combination of the energy solutions and material use both in their sourcing and in their physical properties contributed to the success of the development.
The main objective of the development of Bedzed was to realise a carbon free living and working environment by means of renewable energy sources. For this to be achievable it was important to reduce the heating loads as much as possible so that the building structure could benefit from passive solar gain. It is important to remember that in achieving a low heating strategy only very little amounts of energy would trigger a rise in temperature or likewise a fall will trigger slight temperature reductions. Therefore to avoid discomfort from temperature swings as the sun comes and goes the structure would need to have sufficient thermal mass to store and return excess heat and so stabilise the climatic environment.
Building physics then dictated the site arrangement, the design and material choice. It was also a prime strategical objective to source as many materials from within a 35-mile radius of the site and so reduce the transport pollution and therefore the embodied energy of the materials. Use of water would be minimised, the design would encourage a more positive lifestyle where work could be local, transport pollution minimised and even food could be produced in the green areas.
The result was a south facing rows of terraces with super-insulated envelopes, airtight construction, passive ventilation and sun space buffer areas to the front of the houses. The finished product has produced conditions that have resulted in a carbon neutral lifestyle for the inhabitants.
The passive solar design together with the super insulated, airtight and heavy massed structure has removed the dependency on conventional central heating systems. A 130kW combined heat and power unit fuelled by tree surgery waste generates electricity for both the houses and offices. A by-product of this returns hot water to the spaces via a small district heating system. Heating is supplemented with the solar gains and from general gains from living and cooking which are measurable in super-insulated environments. The system is linked up to the national grid so that excess energy could be sold to the grid and bought back when demand is high.
The large playful ventilation cowls provide wind powered natural ventilation and help prevent the houses from overheating.
The houses have been fitted with 777 sq m of photovoltaic solar panels that are used to generate power for 40 electric cars which allows each vehicle to travel approximately 40 miles per day. This was financed through European and UK government funding. The choice of materials was governed by the building physics requirement to produce super-insulated heavy weight structures and the decision to source as much as possible from a 35 mile radius of the site. This was a realistic choice in the sense that Beddington has a large product catchment area that includes Greater London, Brighton and the Weald.
Below the soil lay gravel beds and consideration was given to exploit this for use as concrete aggregate. It proved however uneconomical on a project of this relative small size to sieve and batch the gravel for this purpose. Instead it was decided to extract gravel to use as subgrade under the roads.
External walls are constructed of an inner leaf of concrete block to provide thermal mass, 300mm rockwool insulation, brick or timber stud and oak weather boarding externally. Roofs and ground floors that have high compressive loads used 300mm polystyrene.
Floors are pre-stressed concrete providing thermal mass. Local FSC certified oak from Croydon and South East England was chosen for the external weatherboarding. Bricks were sourced 20 miles away and were laid on fully filled mortar beds to help achieve the air tightness specification while blocks were sourced further afield at Ipswich.
Timber windows were sourced from a Danish company because of quality demand and the fact that small local companies had problems supplying such a large order to the required specification. They also lacked the experience to supply the level of air tightness required for the glazing. The windows to the sunspaces have double glazing on both sides with one low-E pane and argon filling giving a mid pane U-value of 1.0 w/m2K. North, east, west and aluminium rooflights have triple glazing with two low-E panes and krypton filling giving a mid pane U-vale of 0.6 w/m2K.
A high density polythene was used for the damp proofing and cavity trays were bituminised polyethylene that can be adjusted on site.
A steel frame construction system was used for the workspace areas and uses 95% reclaimed steel (not recycled) from within the 35 mile radius. The newly formed steel was only used where curved sections were required.
Timber stud framing and plasterboard was used for internal partitions where 90% of the timber was reclaimed.
Floors are local ash to the sunspaces, reclaimed floorboards to the workspace mezzanine level, linoleum to kitchens and bathrooms and floor tiles were UK clay.
Paving slabs were bedded in recycled crushed glass instead of sand, 30% of the slabs are porous to allow the surface water to find it's own way back to the watercourse.
Green roofs were planted with low maintenance sedum mats. Rainwater is stored in large tanks below each house and is used for toilet flushing. This water is topped up using a small on site biological sewage treatment plant.
Kitchens are fitted with well located meters for residents to monitor their water consumption. Washing machines are water efficient and toilets are low flush.
The porous areas of paving and the areas of sedum roofs allow the surface water to find it's own way back to the watercourse.
|naturalspace magazine : Sustainable architecture and the natural world : copyright Natural Space Ltd 2004|