Shettleston Housing Association
House construction and the subsequent occupation of homes are recognised as major contributors to pressing environmental problems. Recent studies have shown that environmentally sustainable housing can bring large scale reductions in the environmental burden of housing and economic savings for landlords and tenants with only a relatively small increase in capital costs.
Of the total amount of energy used in a typical house (excepting embodied energy costs), 61 per cent goes on space heating, 22 per cent on water heating, 7 per cent on cooking and 10 percent on lights and appliances.
Our main aim in the Shettleston proposal has been to reduce tenants running costs whilst ensuring that the construction of the houses and selection of materials takes into account the full implications of their energy lifecycle. Our approach to sustainability was developed along four main approaches:
First of all in the production of the houses: by providing a high level of thermal insulation, reducing air infiltration and careful selection of the materials.
Secondly by making use of geothermal energy combined with supplementary solar panels to provide inexpensive heating.
Thirdly by the house designs themselves: by allowing greater internal flexibility, barrier free standards to the layout, allowing for secondary uses of loft spaces, creating a varied mix of house types, from family, to young person and to elderly, along with wheelchair use.
Fourthly by creating an environment which is sustainable, a car free scheme which increases safety for children, selection of plants which bring life and colour to the surroundings.
Each of these approaches is discussed in greater detail below. Clearly there were problems in achieving our aims within the budget constraints imposed by mainstream social housing. Some compromises have had to be made to meet the budgets, but the main elements of the project were all retained and the project is now on site. Completion is due in April 1999.
We have also been successful in obtaining an additional grant from Forward Scotland to cover some of the Solar panel installation and the grey water recycling system.
We have chosen to construct the houses from timber as far as possible. The use of a webbed timber beam allowed us to provide thick wall insulation and reach U values which are under 0.2Wm2Cº. The panels are filled with warmcell insulation which is made from recycled newspaper. The wall panels will be largely prefabricated apart from the external and internal skins. Prefabrication will speed the on site construction time and allow greater control over critical elements of the structure.
The floors are also in webbed timber beams and where possible span between crosswalls. The roof also uses webbed beams to form a 300mm thick fully insulated roof, spanning between ridge and eaves. Originally we planned to use Masonite beams which because of their construction, were deemed the most environmentally friendly. However the contractor chose to use Truss Joist Macmillan to supply the webbed beams. The change did affect the overall insulation slightly and we acknowledge that the TJM beam uses a small amount of glue in its construction, although it does make use of recycled timber chippings.
The floor construction is a concrete slab. We originally planned to have a timber finished floor, but altered to have a screed finish due to cost constraints. This provides a certain level of heat capacitance and allows us to provide floors which are level with the external paths.
The wall construction uses the breathing wall technique pioneered by Warmcell.
The components of the wall are selected with the correct vapour resistance to allow vapour to diffuse through the structure without the risk of interstitial condensation. We have still included a vapour barrier (BSK410) to compensate for the vapour resistance of the panelvent. Because the warmcell is applied in sprayed form between the structural studs, all voids are fully filled. This provides much better air tightness of the structure reducing air leakage resulting in further energy savings.
We have also allowed for a "services" zone in the internal face of all external walls and in kitchen walls.
The external skin is either brick, larch weatherboarding or a render system applied to a calcium silicate board panel.
Materials have been selected by considering the impact throughout their whole life cycle: during the extraction phase, the production phase, building phase, occupational phase and decomposition phase. The main issues considered in the assessment were:
the shortage of raw materials (there is a finite resource for many of them, hence our emphasis on using recycled materials)
the ecological damage caused by extraction of the raw material
the energy consumption at all stages (including transport- we have tried to select materials which can be as locally sourced as possible)
noise and odour pollution
harmful emissions, such as those leading to ozone depletion
global warming and acid rain
Some compromises have had to be made on cost grounds, for example, we have specified some small areas of zinc roof sheeting, ideally we would have preferred copper sheet because of its much longer life and greater ability to be recycled. We did investigate the use of aluminium sheet made from recycled aluminium cans, but this did not seem to be possible for very small quantities.
A number of "recycled" materials will be used:
Insulation material from recycled newspaper.
Recycled brick from the actual site has been used for the boundary wall butt and environmental work.
Recycled stone sets and paviours for the front garden areas. Recycled concrete paviours for the rear backcourts- (these are from adjacent sites and presently in storage).
Some recycled floor timbers, these boards had been kept in store by the Association, they did not have to be de-nailed or cleaned.
Some bathroom fittings from houses being demolished by another Housing Association are being used in two houses and some steel baths are being re- used.
Some of the front railings are being recycled from backcourts in Maryhill.
We did have problems in trying to get the Contractor to think seriously about recycling materials. Because they could not clearly identify the costs or sources, it became difficult for them to cost the work. They were also worried about liability, particularly when we located a source for concrete roof tiles. In this case we had sourced a number of tenements in Drumchapel which were about to be demolished, but demolition contractors said that it would cost too much to remove the tiles carefully because of the additional edge protection and safety measures that would be required. We finally opted for a new concrete roof tile produced in Scotland.
We also tried to source recycled brick in Scotland, but had no luck in doing so. We did locate such brick in the South of England but it did not make practical sense to transport it up to Scotland.
Untreated materials which use less, or preferably no, glue or chemicals, and exclude PVC, have been preferred, in summary:
Orientated strand board for some wall sheathing and webbed beams.
Larch battens and counterbattens avoid the need for chemical preservation treatment.
Larch weather boarding applied externally will be untreated, available from Perthshire.
Timber windows and other water sensitive timbers to be treated with Boron preservative, not CCA.
Untreated softwoods in preference to MDF cill boards, skirtings.
High Density Polyethylene HDPE pipe for drainage within houses and for downpipes, instead of uPVC.
Low odour paints and stains which are resin oil based with no toxic emissions from biocides
Finding an alternative to PVC was difficult and in the end we have had to resort to PVC gutters. We had quite some discussion over the merits of HDPE pipe. Whilst it does not use PVC, it needs to be installed using a special jointing system which makes it more difficult to dismantle in the future. However we still plan to use it for rain water pipes but eventually had to resort to PVC pipes for internal soil pipes.
We did investigate larch windows which were very environmentally friendly, unfortunately costs were too high for this project.
Getting timber to be Boron treated proved to be very difficult. There is only one sawmill in Scotland which does this and timber would have had to have been transported to Inverness for treatment. In the end we resorted to a water based aqua vacvac treatment for those timbers which required treatment, but kept the treatment down to a minimum.
Materials which have a relatively low embodied energy:
concrete roof tiles instead of clay tiles, use slightly less energy. We have decided not to use recycled Scottish Slate, since the material is not being replenished and such demand only results in buildings in remote country areas being stripped to meet the demand. If there was a Scottish slate quarry in operation we would have considered it.
Brass ironmongery was considered instead of aluminium, but in the end we chose aluminium ironmongery made in the UK rather than opt for imported brass.
Larch weather boarding in preference to western red cedar which is largely imported
windows and doors made from softwoods derived from sustainable sources
(most of the materials noted above)
Heating and Ventilation system
After initial investigations of the site history it was discovered that a disused coalmine exists deep underground. We have devised a scheme in association with "enconsult" which uses the preheated water in the flooded coalmine to heat the houses.
The calculation for the SAP rating resulted in a figure of 125 (to round down to 100) which is exceptionally high.
It is worked out for a ground floor flat and would result in an estimated annual heating bill of £19.33p with water heating at £55.48, although this figure could be reduced further if a commercial fuel tariff was used. The figure for heating does not take into account any solar pre-heated of incoming ventilated air, which could reduce costs still further.
The heating system is illustrated in the attached diagram.
The system works as follows:
The water in the coalmine, which is 100 metres below ground level, will be at a temperature of about 12ºC throughout the year. This water is heated by geothermal action from the planets molten core and will last the life of the planet. A well hole has been drilled down to the mine and an in-line pump will then pump the warmed water through a heat pump, boosting the temperature to 55ºC. There are two heat pumps which function at off peak periods to make use of economy 2000 tariff. The water will be stored in a large, well insulated, thermal storage tank and the warm water will then be distributed to each house to provide heating to radiators. Each flat will have its own thermostat and timer switch. Low temperature heating is entirely appropriate for well insulated properties, as there is no need for large heat inputs and the risks of scalding by touch are eliminated.
The water in the thermal store is pumped through indirect coils in each hot water cylinder in order to heat the water to 45ºC. Although warm water can be taken from the cylinder, we are providing electric immersers so that tenants who require higher temperatures for washing dishes etc., can boost the temperature of water in the cylinder. The energy required to raise water from 45ºC to 60ºC is much less than a system which heats water from a cold start.
Heating and hot water would be charged as a service charge as part of the rent, although the actual running costs are expected to be very low. The advantage in having tenant control over heating the hot water is that expensive metering controls are avoided.
In addition, a solar roof has been designed immediately above the thermal store.
The roof is South facing, pitched at a designed 35ºC and will provide a solar panel with a total area of 36m2. The solar panels will provide additional heating to the thermal storage tank, mostly during the afternoon when a large part of the tanks heat will have been dissipated.
Domestic cold water will come from the mains supply. However cooled water from the heat pumps is a by product of the geothermal arrangement and we will take this cold water into a large storage tank and then feed the WC cisterns in all the houses. Such water can also be pumped to the small water feature in the front garden. Residual water from the geothermal supply needs to be discharged back into the ground at a point below the water table.
Because of the air tightness of the dwellings, we have incorporated a simple ventilation system in the four terraced houses which will take pre-heated air from the void between roof tiles and sarking and pressurise the houses slightly. This has the effect of reducing draughts as well as making use of solar pre-heat to the incoming air. Air quality is greatly enhanced.
The majority of the houses also rely on passive stack ventilation systems for kitchens and bathrooms.
House design and layout
The houses are laid out to make maximum use of this tight site. They are largely orientated East West giving good daylight to both front and back gardens. In total there are 16 dwellings, providing a variety of types and sizes, but designed to cater for families, young couples and the elderly.
In all cases buffer draught lobbies have been created to reduce energy losses and create additional storage and utility rooms. Living rooms open into the kitchen and dining area, allowing ease of movement between the spaces. A ground floor toilet is also provided to the terraced houses, capable of taking a wheelchair for any visitors, or indeed future use by an occupant. The straight stair could have a stair lift fixed to it. Different layouts are possible on the ground floor and two options are shown. Upstairs there are three bedrooms with built in storage.
The roof structure is trussless and allows the loft space to be floored and used as storage. It would be accessed by a Ramsay ladder. A fixed stair could be installed but more onerous regulations then come to play. The attic room is high enough to stand in and has a skylight.
The single entrance flats use a similar device on the top floor, except that we have shown the loft space as a gallery deck which opens into the living room area.
There is a shared external stair at the rear which provides the upstairs flats with access to the back garden.
The corner flats are accessed from a glazed atrium, designed to bring light and space into the main circulation area. The principle being that elderly people can meet in this space, and even sit and pass the time with their neighbours. Flats at street edge all achieve some Southern light, and privacy is obtained by raising the floor level above the street level.
There is a single wheelchair flat which has its own entrance and car bay. It is designed for wheelchair circulation and connects through into the close so that communication with neighbours is maintained. The access into the close is not to ideal disabled standards due to the tightness of space.
The site is close to shops and public transport. A decision was taken after discussion with local planners that a car free scheme would be most appropriate for the site.
We have therefore designed a scheme as "car free", providing only 4 on street car bays, made on the existing road line, as well as an individual bay for use in the wheelchair standard house. Making the scheme car free allows the creation of a semi private front garden space which gives the houses added privacy, better security, increased safety for children and a much more pleasant environment. Discussions are continuing with the Roads Department and Planning so that a workable legal agreement can be drawn up to ensure tenants within the scheme do not own, or have access to a car. The four visitor bays will be marked as residential parking for visitors only, with the aim of deterring parking by drivers unconnected with the scheme.
The front area is screened from the street by a low hedge, deep in character, with trees showing their trunks above and a canopy which allows clear views under tree and over hedge. One entrance is provided through a pergola. A semi public gravel path leads to each of the individual houses, with the route passing a small water feature.
Each house and flat has its own private space as well, screened by wicker fencing. Binstores are provided in screened areas to the house fronts. In the corner flats bins are located to the rear of the properties.
Wall surfaces are provided with cable stays for wire trellis work which will take a selection of creepers and wall friendly plants. Such growth will provide additional protection to the walls as well as reducing noise levels and creating a more pleasant climate.
Downpipes at the rear have water barrels to provide water for gardening and space has been provided for composting of plant debris.
Deep plant beds have been provided in the atrium space so that climbers and vines can grow up to the second floor, both at the glazed front and around the stairwell. They will be fed by water from the cold water storage tank.
We are presently developing a scheme which will encourage waste separation and waste recycling within the scheme.
Client Group Involvement
The house designs have been developed after meetings with the Housing Associations Development Committee. A Tenants sub group was set up to develop some of the sustainable themes, with the aim of encouraging an understanding of the issues involved.
In addition to regular design meetings attended by the Association and its consultants, a special technical seminar was held and a number of other Housing Associations invited to attend, including representatives from Planning and Building Control. Issues discussed included the breathing wall system, under floor heating, material selection for sustainability and geothermal energy. The seminar produced a lot of useful feedback from those that attended.
There were also in-house meetings to explain to all Housing Association staff what the aims of the housing proposal were. Maintenance staff contributed to the specification of materials and set about collecting materials from other sites which could be used in the project.
Comments on Structure
Reasonable soil conditions are to be found over the site at shallow depth below the existing ground surface. This has permitted the use of a concrete beam foundation cast integrally with the ground slab, thus dispensing with the need for underbuilding walls.
The choice of timber frame for the flats and terraced houses reflects the architectural requirements for high insulation values and allows much of the structure to be prefabricated. This will lead to improved quality control and speed of construction.
Architects on the project were John Gilbert Architects.
Sustainable Housing for everyone?
We do not presume that the Shettleston scheme is the answer to sustainable housing. It will however demonstrate some of the techniques which sustainable developments must take on board. We have learnt a lot in developing the ideas for this unique project and hope to be able to incorporate many of the ideas in other new build and rehabilitation projects.