GLEADLESS - SHEFFIELD - UK - architect Cedric Green

Report by Jane Linfoot and Cedric Green, November 1984




  • introduction
  • design
  • house designs
  • "moya"
  • construction
  • thermal design
  • low energy
  • solar system
  • cad (SCRIBE)
  • organisation
  • co-op work
  • costing



    This is a project involving the construction of thirteen low cost, low energy, passive solar houses and a demonstration building in Sheffield UK . Sheffield City Council have supported the project since its inception in 1982 and the Coop acquired the site in Gleadless in 1983. Having obtained planning permission for the site the Coop purchased it from the Council, paying the market price, but negotiating an arrangement by which the payment was in instalments. The majority of the construction work has been carried out on a self build basis by the Coop members, each of whom will purchase a house as they are completed. This form of labour was decided on to keep building costs low and in the hope of greater satisfaction of the occupiers with their own houses.

    Work on site began in June 1983. Initially it was expected to take 18 months to complete the project, but at the present stage it appears the final time will be closer to 3 years!

    After completion a Residents' Association composed of the householders will supervise and develop the shared aspects of the site, such as the demonstration building and the common garden area at the north of the site.

    Three basic house types were developed, namely, a three bedroomed semi detached, a semi detached starter home and a single storey court house, all offering scope for variation and extension. All materials and labour skills are traditional to the building industry. The houses have a timber frame internal construction, with brick and blockwork insulated cavity outer walls, tiled roofs and timber and glass conservatory. Construction was designed carefully to make things straightforward for self builders.

    This project has a number of unusual and interesting aspects; its solar and low energy designs, its self build approach, the cooperative organisation and the low-cost building implications. The following report aims to describe the project generally and give information on each of these aspects in more detail and in relation to the project.







    The site, at an altitude of 600 metres, is located in the suburb of Gleadless and is approximately 3 miles from the centre of Sheffield.The area is easily accessible by road and is well served by public transport. The site slopes towards the south west, and presents a pleasing aspect overlooking Meersbrook and across the valley. It is well drained; and water, gas, sewer, mains drainage and electricity services are in close proximity. The site arrangement is effectively a cul-de-sac, with no future possibility of through traffic. Access to the site has been made by constructing a short spur road off Spring Close Mount. The site, and land adjoining, is owned by the Sheffield Corporation.

    In layout the houses are arranged around a short combined pedestrian and vehicle access which is classed as a 'mews court'. Every house has a garage space and car parking space, and the intention is to try to create a feeling of community in the grouping and landscaping treatment of the space by avoiding the appearance of an estate road. Future development planned by the Corporation is for the wooded land adjoining the east side to become a recreational park. Pasture land adjoining the southern side is scheduled for further private housing development. The north side is bounded by Gleadless Road and the western side by a Corporation housing estate. But between Gleadless Road and the highest houses, there will be a communal open area, to be developed as allotments or orchard by the Residents' association.



    The Coop houses are low energy houses, and the designs incorporate features for passive solar energy collection and thermal storage. The thermal system is described in detail in its own chapter. Here we will discuss the background to the Coop designs before considering each in detail.

    The original house design was developed by Cedric Green for "Moya", a house on a small site in Suffolk, and the way in which this house type could be used at a higher density was developed and entered for the 1st European Passive Solar Housing Competition in 1980 "A House for All Seasons" where it won joint 2nd Prize.

    The aim was to provide a house which would respond to the seasons and to its users. The winter living space was designed to be small, snug and warm. In spring the walls were designed to fold outwards, allowing the house to expand and to become spacious and open plan. The project was designed to be low cost, providing the minimum of accommodation in traditional, more expensive, construction, for winter use. The conservatory provided a large area of extra space which could be used as living space constantly throughout the summer and on most spring and autumn days, yet at a cost which was relatively low. The open plan arrangement of the winter accommodation aimed to maximise use of a small space. The conservatory acted as a solar collector, and the passive solar gains from this linked to an appropriate storage system and a well insulated house structure were aimed at making a house which was nearly self-sufficient in heating, except in the coldest part of the year.

    The L-shaped conservatory was a response to the site orientation, and the plan which evolved placed the bathroom and utility space as a services core in the angle of the house not benefiting directly from solar gain, and provided a courtyard outside on to which the conservatory opened.

    Initially, the Coop project was envisaged as consisting of a cluster of these L-shaped or courtyard houses. Various factors led to the development of additional designs.

    The accommodation in the courtyard house was large enough for a family, and this was reflected in its cost. It seemed appropriate to develop a cheaper starter-home alternative, with possibilities for later expansion. This idea was increasingly attractive, as it offered scope for a higher density of site development and therefore lower individual costs for shared services. In addition to these factors, the site considered by the Coop was fairly steeply sloping in places and not suitable in these places for the L-shaped design.

    The Coop members were anxious to have semi-detached houses rather than terraced houses, and so the design developed was for pairs of semis with a continuous roof. Taking account of the slope of the site, each pair would consist of a three bedroomed, two storey house, with the possibility of future extension into the roof space and staggered in relation to this, a single storey house further up the slope, which was a true 'starter home' but could be extended upwards to provide bedrooms in the roof space later.

    The eventual site arrangement includes five L-shaped houses and four pairs of semis. In fact, only the first pair of semis was built, with one side as a starter home, as thereafter the Coop members who were having starter homes found they could afford the extra money and opted for the extra space in the larger side of the semi, and so the final three pairs of houses have staggered roofs and handed plans.

    The L-shaped House Design

    The L-shaped house plan is set out on a 640mm grid, which is determined by the 610mm square horticultural glass panes used in the vertical glazing of the conservatory. The structural centres are at 2560 mm with four grid units to each structural bay.

    The roof trusses are supported at 2560mm centres on posts at the division between house and conservatory and on the external walls of the house.

    The double row of posts between the house and conservatory support deep double beams which provide lateral stability and a services duct. The four posts at the centre of the house provide the corners of the central air duct through which air is drawn from the high level ducts along the top of the conservatory down into the hypocaust.

    The post and beam construction between the living area is closed with glazed doors on winter days with the addition of insulated shutters on winter nights. This 'wall' between the heated space of the house and the conservatory can be opened up completely to provide a continuous living space in the summer - the glazed doors are hinged and fold back against the posts and the shutters can be re-positioned to form a ceiling in the conservatory which gives summer shading to prevent overheating. In certain cases patio doors have been put in instead of folding glazed doors, but these do not allow full opening of the space between living area and conservatory.

    In order that the habitable rooms open on to the conservatory, it is preferable to locate the kitchen and bathroom in the services 'core' in the square of the house not opening on to the conservatory. The entrance of the house is also integrated on to this side of the house, leaving the conservatory aspect of the house with privacy.

    The basic house type plan consisted of three structural bays in each direction. The internal layout is very flexible, and the differing requirements and preferences of the five Coop members having these houses have given rise to five very different houses within the same basic structure. In some cases, full or half bays have been added or omitted from one wing of the house, to increase or reduce the size.

    The rooms which open on to the conservatory have high sloping ceilings, as can be seen from the section, whilst the ceilings in the services core are horizontal at 2.3m high. In some bedrooms galleries have been extended into the room, with their floors supported on the truss ties, to take advantage of the high ceiling space. Usually use has been made of the area above a flat ceiling for storage areas.

    The accompanying plans show the variations which have developed. The last of these houses to be built was varied in that the central rows of posts were placed slightly further apart, in order to accommodate a door between them. This is typical of the continual modifications and evolution of design in response of individual needs which has been part of the project. In certain cases this has produced results which are a long way from the original intentions, but the low-energy aspects of the design have remained intact.

    The Semi-detached Houses

    The semi-detached houses have certain principles and design features in common with the L-shaped houses. The ratio of conservatory area to house floor area is much smaller however. The associated reduction of potential solar collection is counteracted by the compact nature of the accommodation which leads to lower heat losses.

    In the three-bedroomed houses the kitchen, bathroom and staircase are located on the northerly side of the house, which cuts into the hillside. The living room can be opened to the conservatory to provide a continuous space in summer, using the same system of folding doors and shutters as is found in the L-shaped houses.

    In the starter home, the initial accommodation is provided on the ground floor, with the kitchen and bathroom on the north side at the 'back' of the house. The utility room or study is also located on this side of the house; this latter being the space into which the stair will be fitted at a later date. The living room and bedroom areas open on to the conservatory. The accommodation provided here is minimal, but ideal for a single person or couple, who wish to take advantage of lower rates whilst having the option of expanding their accommodation later without the expense and inconvenience of moving house.

    The starter home can be 'expanded' by making use of the roof space to provide up to three bedrooms, and inserting the dogleg stair in the downstairs utility or study area.

    The section of the starter home differs from that of the three bedroom semi. The starter home is essentially a single storey house with room for expansion in the roof space whereas the three bedroom semi is a two storey house with room for expansion in the attic. The attic space in the starter home, however, has much more headroom. The structural section and trusses used for each of these house types are different, although they are designed to have a common roof ridge. The two house types interlock beneath the common ridge, the starter home being staggered backwards and having a higher ground floor level, making this pair of houses ideally fitted to the slope of the site.

    In fact, only the first pair of semis was built with one of each type of house in the pair. The remaining three pairs were built with both halves as three bedroomed houses. The roof trusses, which are situated in the centre of each house are designed to give maximum free space across the centre of the attic where the headroom is highest, and this gives potential for future expansion. The only starter home to have been built took advantage of this potential immediately and was built with three bedrooms in the attic space. As yet none of the two storey semis have been extended into the attic space, although gable windows to the attic have been included. In these houses the dogleg stair can be continued in above the existing staircase to give accessto the attic.

    Again these houses are built relating to a one directional grid of 640mm which relates to the glass size of the horticultural panes used. The roof lights in the sloping ceilings of the bedrooms relate to this grid; the roof truss and double posts are also positioned on this grid.

    The scope for individual plan variation is less in these houses than in the L-shaped houses, but again individual requirements have resulted in differences and innovation. The most marked of these is the planned extension forward of one conservatory which will result in a double height and double depth conservatory.





















    "MOYA" - House for Mr and Mrs C Oldham - Charsfield, Suffolk

    "Moya", the house for which the original design concept was developed, was in fact built by a local Suffolk builder in the summer of 1984, whilst the Coop project was on site and provided further opportunity for design variation and development. Because of the close links with the Coop project it seemed appropriate to include details of "Moya".




























    The construction of the Coop houses is a hybrid of load bearing brickwork and timber framing. The main variation in construction is between the semi detached, two storey houses and the L-shaped single storey houses. Further variations arise from the different gradients encountered on various parts of the site, and from the desire of the Coop members to experiment with different techniques and solutions to problems as work progressed.

    The reason for the hybrid construction was to take advantage of the speed of construction associated with the erection of a timber frame which had been pre-fabricated on site. The masonry walls provide much of the thermal mass which provides a large amount of the heat storage in the building and these also provide support for the timber frame once they are constructed.

    The following paragraphs will outline the construction of the various building elements and highlight variations in these. The general annotated cross-section of the type 2 building will illustrate their relationship and the specification clauses will give further detail.


    The footings are concrete strip foundations below walls, stepped where necessary. The posts of the timber frame have pad foundations. Where there is a concrete sub-slab to the floor this has been thickened for blockwork partitions.

    Retaining Walls

    The slope of the site, which is very steep in places, meant that many of the external walls of the houses are retaining walls. The construction of retaining walls is obviously less straight-forward and more expensive than simple external walls and they did provide the self builders with problems, especially at first.

    Various methods of construction of retaining walls were tried, in order to try to overcome the practical difficulties of continuity of the damp proof membrane. What looks fairly simple on section often becomes very complex when it becomes three-dimensional.

    The height of earth retained was limited to a metre wherever possible and the variation of construction were:-

    The floor construction

    With the exception of the 6 houses at the top of the site the ground floor construction of the houses is a hypocaust construction, through which warm air from the conservatory is blown by a fan, and the hypocaust acts as a heat store. The mechanics and theory of this is explained more fully in the section on the thermal system.

    Every hypocaust has a 100mm concrete sub-slab on hardcore, sand blinding and damp proof membrane. This sub slab was laid before the external walls were built above ground level and edge insulation of styrofoam was included below it.

    The hypocaust construction was usually completed once the shell of the house was completed. In the first two houses this was constructed of bricks on edge which were arranged in spaced rows to support sheets of corrugated tin or plastic on to which concrete was poured to give a 100mm thick slab. A screed finish was put on top of the slab later.

    As the Coop members did not like this method in practice later hypocausts were constructed of bricks on edge supporting 50mm concrete paving slabs with a 50mm screed laid on top of the slabs. A further refinement was to lay two bricks flat instead of one brick on edge, as these provided a more stable base for the paving slabs than the bricks on edge.

    In certain L-shaped houses the slope of the site meant that the fill below the sub slab in the floor bays at the extreme south western end of the house was going to be excessive, so in such cases end bays had precast concrete beam suspended floors, with insulation below.

    As these parts of the floor were a long way from the central air duct where air was to be pumped into the hypocaust it was felt that sacrificing the hypocaust in these bays was not going to detract from the thermal system of the houses concerned.

    Generally, the floors in the conservatories are simply tiled concrete slabs, but in one house the hypocaust construction has been taken right through into the conservatory, with under slab insulation.

    An important element in the hypocaust construction for the functioning of the thermal system is the provision of gaps and grills to return the air from the hypocaust extremities to the onservatory.

    Also important is the arrangement of the bricks in order to direct the air moving through the hypocaust so that air will go to all parts of the hypocaust and will not short circuit and return to the conservatory before it has given up its heat to the hypocaust structure.

    Whereas in the houses on the lower part of the site the bays with suspended concrete floors are isolated from the main hypocaust construction, in the six houses at the top of the site the whole upper hypocaust floor is actually formed from precast concrete beams.

    The slope of the site in this area meant that the original hypocaust construction was not feasible. Here the cavity between the site concrete placed on the ground and the suspended concrete floor form the hypocaust cavity into which warm air from the conservatory is blown.

    The Timber Frame

    As can be seen from the sections, the timber frame is much more extensive in the one storey house design than in the semi detached houses, although in both cases the timber elements are all cut and drilled according to detailed timber schedules, and lists of elements leads to great speed in frame construction.

    Considering the single storey house first, the timber frame is prefabricated initially. Once frame construction begins the frame can usually be erected in a weekend on top of the sub slab of the floor. The frame is supported by a series of temporary posts which support the frame until the external walls are built. The frame is squared, levelled and anchored and then provides the setting out for the external walls which are built up to the frame. In later houses the backs of the trusses were supported on a wall plate and the temporary posts removed and used on the next house.

    The advantage of this method is that the roofing felt can be put on immediately the frame is secured, the external walls can be built up and the temporary supporting posts can be removed once the walls have been built to support the frame. The roof can be tiled immediately, the conservatory glazed and the whole building envelope can be completed in a smooth, fast operation.

    With the semi detached houses, the timber elements are pre-fabricated and integrated and fixed as the external walls are built.

    Here there are variations on the number of trusses used. This particular self-build group is short of people confident in carpentry skills, and so in some cases, instead of having a truss and boarding on the gable walls, brickwork load bearing gable walls have been taken to roof level.

    Axonometric views show the timber frame construction.

    Internal Partitions

    Initially, all the internal partitions were designed to be stud partitions, for ease of construction and later flexibility. Coop members, again due to a lack of carpenters, found blockwork construction preferable, although this entailed thickening of the floor slab below partitions and obstruction of the hypocaust in places. Blockwork partitions were also preferred due to their increased sound insulating properties.

    Where precast concrete beam floors were used, blockwork partitions were limited to one storey in height, so upper floor partitions were constructed in studding.


    The external walls were constructed of an outer skin of brickwork, a 75mm cavity, 100mm inner skin of insulating 'Thermalite' blockwork with foam cavity fill insulation injected after construction.

    The floor was insulated with 1m wide 50mm thick styrofoam edge insulation. In the semis the first floor ceiling joists were 125mm deep and insulation was put in here in addition to between the 125mm roof rafters. Where the attic space was not going to be used immediately, extra insulation was included above the first floor ceilings. Generally 200mm of fibreglass insulation was used, in between the joists.

    In the single storey houses, where the ceilings sloped, separate ceiling joists were positioned below the roof joists to allow for at least 200mm of insulation and to give space for ventilation, over the insulation.

    Where the ceilings are flat 200mm insulation is included between the ceiling joists.

    The shutters provide winter insulation between the houses and their conservatories.

    The Shutters

    The shutters are constructed from plywood glued to a simple timber framing with a 25mm polystyrene insulating core. They were made on site initially, but later were subcontracted.

    They are situated on the outside of the doors between the living and the conservatory areas. They are designed to be closed on winter evenings, and are intended to be moved to make a horizontal ceiling in the conservatory to provide summer shading. Various methods of fixing and shutter operation have been devised, depending on the preferences of individual house owners. The original concept was to have four shutters to each bay, hinged in pairs from the structural posts for winter use, and hinged to swing upwards from the beams for summer shading. This system utilises hinges with removable pins.

    Different methods of shutter fixing adopted include simple sliding shutters, which are more easy to operate with patio doors.

    The Conservatories

    The detailing of the conservatories is in keeping with the original design philosophy of the houses; they are designed to be simple to build, and to be glazed with horticultural glass to keep costs low. In fact, regulation changes meant that the roofs of the conservatories are glazed with 4mm float glass or toughened glass rather than with horticultural glass. For safety, where toughened glass was not used, an inner pane of polycarbonate or acrylic was specified, fixed with beads under the sloping glazing.

    The grid of the whole house is a 640mm grid, with larger bays of four grid units. This grid size originates from the horticultural glass which comes in 610mm panes.

    The conservatory frame is built of simple planed timbers, and the glazing is carried out as indicated in the details, with a putty-free method which makes glass installation much quicker and easier.

    Instead of using rebated timbers, stops are planted on each vertical glazing bar. The glass is bedded on a pvc covered foam strip and held in place by parting beads pinned to the stops. On the roof glazing beruing strips are screwed to the glazing bar, holding the glass down on the pvc covered foam strip.

    Variations on these details have been used in practice, depending on personal taste.

    At the base of each vertical glass window a kick panel of pvc is fixed for safety.

    Louvred panels are included for ventilation.

    The Spandrell Panel Collector

    The spandrell panel solar collector is constructed with a black painted ply panel, with insulation between the panel and the inside of the house. The glazing of the panel is fixed with beads using horticultural glass to the same detail as in the conservatory.

    In certain cases where rooms have a high ceiling in the single storey houses, the spandrell collector begins higher up, the area below it being glazed to let light into the room above the shelf over the double beams.



































    The design of the single storey court houses is based on one that received a second prize in the 1980 First European Passive Solar Housing Competition and consists of an L-shaped plan with a continuous greenhouse/conservatory inside the angle enclosing a small court. The concept which dominates the design is of the greenhouse as a seasonal extension of the living spaces, which are small, but with the addition of the conservatory extension, are effectively quite spacious. The semi detached houses are similar to the L-shaped houses in the principles of design, conservatory, shutters and thermal storage.

    The wall which separates the rooms from the conservatory consists of an inner plane of glazed doors and occasional opaque panels where appropriate, and an outer plane of insulated hinged shutters. The shutters hinge back in winter to open half the area over the glazed doors, but in summer the whole of the shutter plane is raised to form a complete ceiling in the conservatory and the doors and panels fold right back, to open the room to the conservatory. Even when the glazed doors between room and conservatory are closed the small rooms retain a spacious feel due to the lack of visual barrier between the rooms, the conservatory and the outside. This is obtained without the disadvantages of draughts and heat loss which usually accompany large glazed windows, due to the conservatory which acts as a buffer zone. Summer overheating of the conservatory is prevented by the shutter ceiling, which provides shading and isolates the solar gain through the conservatory roof glazing, where it can be dissipated through ventilators or, if required, drawn into the heat store.

    Thus, the role of the conservatory in the house design can be seen to be many fold. Not only does it provide extra living space for much of the year, but it also acts as a buffer zone, reducing heat and ventilation losses from the side of the house it covers, in addition to its function as a passive solar collector of both direct and diffuse solar radiation.

    Before going on to discuss further the various parts of the house concerned with collection and use of solar energy, it is worth considering the other features and measures incorporated in the design, which aim to minimise the energy consumption of the house. The lower the energy consumption of the house the more significant the contribution of solar energy becomes when considered as a proportion of energy consumed. High levels of insulation are used in the roof and walls of the house. 200mm minimum of insulation is incorporated above ceiling level, using a structure of separate roof and ceiling joists to give space for this in cases where ceilings are sloping. The external walls have 75mm cavities, with insulated thermalite blockwork inner skins, and cavity wall insulation. The houses are dug into the hillside on the northern sides to reduce exposure and here are insulated on the earth side of the retaining walls.

    Windows on the northerly sides of the house are kept to a minimum and where they do occur they are small. All windows are double glazed and all door and window openings are draught stripped to reduce infiltration heat losses which can be significant. Lobbies and porches also reduce ventilation heat losses from the houses, as do the conservatories.

    Night shutters are incorporated on the large glazed areas facing on to the conservatory. These south facing 'windows' get considerable direct solar gain on sunny days and the use of night shutters ensures that the overall effect of the large south facing glazed areas is energy gain, not energy loss.

    The choice and sizing of the backup heating system is important. Gas was the fuel chosen here, for a number of reasons. It is relatively cheap per unit of energy when compared to electricity and oil; it is clean and convenient and the cost of gas boilers and appliances is low when compared to solid fuel appliances. Predictions of energy usage for each house were made using SCRIBE and this enabled radiators to be sized fairly accurately (rather than over sizing 'to make sure' as often happens) and appliances were selected to ensure maximum efficiency at the required output.

    In energy terms then the houses were 'well insulated, well sealed boxes' but the internal planning of the houses can also have an effect on their energy consumption. Bathrooms and kitchens were located on the coolest side of the houses, whereas living rooms were placed on the sunny, warmer side of houses.

    On the site, the houses were arranged so as not to overshadow each other and each was orientated to maximise the solar gain.

    These summarise the design considerations and features which are important for the low energy aspects of the house. Features of the design specifications involved with the solar energy collection and storage aspects come into three main categories, which are energy collection, transfer and storage.


    The main solar collector is the conservatory, which acting like a greenhouse, collects energy from direct radiation and also diffuse radiation, which results in a temperature rise of the air in the conservatory. The warmest air is at the top of the conservatory, where the spandrell panel collector acts to heat the air further. The spandrell panel collector is an insulated matt black surface with glass panels in front, and an air space between the two. The black panels behind the glass absorb the solar radiation and air passing between the glass of the panels is warmed. The spandrell panel collector is situated above the glazed doors between the conservatory and the living area and warm air from the conservatory is drawn through the spandrell collector and warmed further before being transferred to the heat store, via ducts and a fan.

    The air ducts are arranged slightly differently, depending on the house type, the basic principle being that they are air tight and sealed and allow air to be sucked from along the top of the spandrell collector, down via a vertical duct and into the heat store which is under the floor. Air transfer is by a single fan situated at the base of the vertical duct. This fan is switched on automatically by remote sensor when the air in the spandrell collector reaches a certain temperature, and switches off again if the air falls below a certain temperature. The fan prevents reverse siphoning of air out of the heatstore.

    The heatstore into which the warm air is blown is an underfloor cavity, with a heavy floor slab above, and often bricks for extra storage spaced within the cavity. This is referred to as a hypocaust and although each operates similarly, it can be constructed in various ways.

    Regardless of its method of construction, the principle of operation is similar, in that warm air from the conservatory is blown into the underfloor cavity, where it gives up 75% of its heat to the floor slab above and remaining heat to obstacles it passes and the slab below. Having travelled the length of the hypocaust (the air flow direction being determined by the arrangement of 'obstacles' within the hypocaust) the air is released back into the conservatory through ventilation grilles, now cooled.

    The floor slab stores the heat and releases it slowly to the rooms above. The release of heat does not appear to be impaired by carpet on the floors of the rooms, but seems to be more affected by the floor finish beneath the carpet.

    The actual hypocaust construction is done in one of two ways; the cavity is formed between a 50mm concrete cover of the earth below the floor and a floor formed of precast concrete beams with block infill and covering screed, or a 100mm concrete sub slab is laid and bricks are spaced out over this to support concrete paving slabs with a screed on top. The choice of method used depends largely on the cost of labour, as the first method is more expensive for materials, and the second method, whilst being cheaper in terms of materials, is more labour intensive.

    The construction of the house with thick, heavy bases of retaining walls, and blockwork inner skins to external walls and in certain cases, blockwork inner partitions, also provides a fairly heavy construction envelope with associated heat storage properties.

    The houses also have 'bread box water heaters', which effectively act as solar pre heaters for the conventional hot water tank. Water, on its way to the hot water cylinder, passes first through a black painted cylinder behind glass placed in a position where it will receive a lot of direct solar gain. On a sunny day the water reaches the main water tank at a warm temperature and so cools the existing hot water in the tank much less than would a normal cold water feed and also requires much less energy to bring it up to an acceptable hot water temperature. The bread box water heater can be drained and by-passed in winter to prevent freezing, although in a normal winter this should not be required as the thermal mass of the water in the tank and the double glazing will prevent freezing.

    These are the more practical descriptions of the solar features of the designs, which are also summarised in diagrammatic form.
















    1. The buildings are orientated to maximise solar gain and arranged to avoid overshadowing each other.

    2. High insulation levels in roof and walls to conserve energy.

    3. Small windows on the 'dark' northern side of the house; windows are double glazed.

    4. Economical planning of the heated area of the house.

    5. Large amount of thermal mass in the building structure.

    6. Control of ventilation and condensation using conservatory and lobby as buffer zones.

    7. Weather stripping to all door and window openings.

    8. Conservatory as passive solar collector of direct and diffuse radiation.

    9. Spandrell panel solar collector inside conservatory.

    10. South facing double glazed doors opening on to conservatory to maximise direct solar gain in 'heated area' of house.

    11. Fan assisted transfer of solar heated air from collector to heat store.

    12. Hypocaust floor heat store.

    13. Bread box water heater.

    14. Insulating night shutters.

    15. Use of planting and hinged shutters to give summer shading to conservatory.

    16. North side of house dug into slope, with additional earth berming for shelter and insulation.






    In June 1983, when the Coop Project started on site, SCRIBE was at the stage of being primarily a three dimensional and thermal modelling program. Although development work had been taking place on SCRIBE for three years previously, the version of the program at that time was limited when compared to its present capabilities.

    In the summer of 1983 a range of plotters came on to the market at a price which for the first time was compatible with the rest of the hardware equipment used with SCRIBE. This meant that further development of the SCRIBE system for draughting purposes was now worthwhile.

    Work on enhancements for SCRIBE was fairly intensive for the next year, using work and drawings for the Coop scheme to test, give feedback and often instigate the various improvements to the program. The way SCRIBE was used throughout the Coop scheme reflects this developmental role. The techniques which we used towards the end of the project were the result not only of experimentation with and integration of microcomputers into the architects' office, but also of the increased capabilities of the program.

    Bearing this in mind, the description below outlines how SCRIBE was actually used on the Coop project, and describes the final methods which were adopted, after both program enhancements and experience.

    At the site planning stage of the Coop scheme, SCRIBE was used intensively as a design tool, giving instant projects and perspectives of various site arrangements from all angles. This was useful, not only from the design aspect, but it also helped the Coop members and prospective members to know what to expect. It made them much more familiar with the site and the project at a stage when most laymen would find it difficult to visualise more than the site as a field!

    SCRIBE was also used at this early stage to determine the layout of the houses in such a way as to maximise the solar gains and to reduce shading on the solar collectors (here the conservatories). A quick run through of the SOLPRO module with the three dimensional model of the site showed where the sun would reach at every hour through the day for any chosen day in the year. This provided a quick, but essential, check that shading had been minimised in such a solar scheme.

    SCRIBE was also used to do thermal analysis of the house designs. The more simple steady-state heat loss calculation module was used to give an early estimate of radiator sizes and boiler output requirement. The dynamic thermal modelling calculations (SPIEL) were more important, as they provided forecasts of the total environmental performance of each house design, and the heating costs. This program allowed cost benefit comparisons to be made for increased insulation and the use of different construction materials. The results also gave the opportunity of checking for problems, such as cold areas, interstitial condensation, and gave information on the predicted way the hypocaust would work, such predictions being based on figures rather than intuition.

    The three dimensional models of each house type generated for these thermal calculations were also used to give interior and exterior views of the houses.

    At the stage when the house plans were being drawn, early in the project, SCRIBE had not been developed fully enough to be used for such finished drawings, and dimensioning was also a later enhancement. This was regrettable as the Coop scheme represents a housing scheme to which SCRIBE is well suited. A number of similar houses with variations is ideal for gaining maximum benefit from such a system. Once the basic plan has been put in amendments can easily be made to the model and a lot of repetitive drawing time can be saved.

    SCRIBE was used for most of the Co-op details, where a library of details was built up over the period of the project, and amended and developed as necessary. Such a method involves similar time to drawing by hand when the details and element libraries are first being created, and also a good system of organisation so that information stored is easy to find again. Thereafter, it will save a lot of time.

    As we used SCRIBE in the office, we were determined to use the system to save drawing time where we could and to enable us to do analysis which, if done by hand would not be feasible. We found that by using SCRIBE the initial design ideas and possibilities could be explored more thoroughly, especially the three dimensional implications at an early stage. The whole aim was to use the computer system to best advantage, rather than being pedantic and trying to use the computer for everything. There are certain things that people do much better than computers, and where this was the case we admitted it.

    Thus, the drawing techniques we developed were hybrid techniques. Finished perspective drawings and sketches are done using the SCRIBE output as a skeleton to trace over. The most successful view to take for a perspective can be explored exhaustively just using the computer model.

    Hatching and shading are usually done by hand on drawings. Notes are often added using the word processor, and printing on to transtext, as this is quicker for larger blocks than using the text module in SCRIBE.

    The drawings are done using an A3 plotter because as yet (1981) the larger plotters are still disproportionately more expensive. If larger drawings are needed, we put all the necessary information to a smaller scale on an A3 sheet and enlarge to A1 by photocopying, a process which is now accurate whilst giving good results.
















    The way in which Sheffield Solar Building Coop was to be run was determined at a very early stage in the project, by the small group of people initially involved. Monthly Cooperative meetings were held from a very early stage.

    Whereas in some self build projects each group member builds their own house and the only work done jointly is on the shared parts, such as the road and service provision, this solution to group organisation was rejected here. One reason for rejecting this method was the difficulty of financing the building of all the houses at one time. In addition to this, the lack of building experience of most members of the group meant that no-one felt confident about, or indeed wanted to be involved in, such solo efforts. There was also a fairly strong ideological desire on the part of many group members to run the project on cooperative principles. The outcome of this was that the Cooperative was formed under the umbrella of ICOM - the Industrial Co-ownership Movement. The Coop was registered as a Friendly Society, non-profit making limited liability company, with its 'employees' the self-builders, as it 'owners'. The capital was #250 from each member.

    Initially, the group involved numbered about seven; however the site finally chosen and its relatively high price meant that to make the price of each building plot economically viable, it would be necessary to fit thirteen houses on the site. The group size was correspondingly increased.
    The original members had come together following an article in the local newspaper on Cedric Green's solar house designs. Other people had joined in after hearing about the project and inevitably some people had withdrawn at various stages. An advertisement was put in the local paper to find people to join in the project to increase the numbers to thirteen.

    Of the thirteen people who eventually became the building members of the Coop, fewer had building skills than had originally been intended. The only person with carpentry skills dropped out at a very late stage and it was not possible to replace him with a person with similar knowledge. This lack of previous building experience led to very slow progress of the project initially and extended the expected duration of the project. The later profile of Coop members will outline the skills of the group.







    The organisation of the project was based on the Coop members working together, initially on two houses. As each house was completed it was to be sold to its owner, and work on the next house could begin. In this way the Coop could limit the amount of money it needed to borrow at any one time. In practice, work was often in progress on more than two houses at a time, because it was more practical and economical to excavate and put in foundations of a number of houses together in the dry weather. The main object was project planning to ensure that it was always possible to complete and sell the next house in progression, whilst remaining within the loan limit. At the same time, it was important to ensure that there was always indoor work to be done during the bad weather. How this worked can be seen in the chapter outlining the site diary.

    Each building member of the Coop was required to work on the project for a certain number of hours each week. The required number of hours varied from 20 to 30 hours, depending on the size of house that person was having. The working of hours was operated in a flexible way, and any person having done less hours than they should have done over a six month period was required to pay the Coop for the hours they had not worked. This amount was paid in cash, worked out on an hourly rate.

    Once a person's house was completed to a 'habitable shell' standard it was sold to them. The house price included the site cost, an amount for shared road and service installations and the cost of materials. A refundable premium of £2,000 was also added to make sure that they did not stop working until all the houses were completed! The costs involved are outlined in the chapter on finance.

    Only hours worked by the man of each house were counted - these are the people referred to as 'builder members' of the Coop. Wives & partners were members of the Coop and whilst many did spend many hours working on site, not just making tea but often doing heavy work - these hours were not counted. This was decided at the beginning of the project. The suggested site rule, from the Self Build model rules, banning women and children from the site altogether was not adopted.

    Within this basic framework there were variations, with the Coop occasionally employing skilled labour from outside the Coop for certain jobs and individual Coop members employing skilled labour from outside for certain jobs on their own houses.

    Plastering and electrical work were the main tasks for which outside labour was used. Any decision over questions of cost or hour allocation were made at the monthly Cooperative meetings of all members.

    Before the start of the project on site the Coop had agreed to employ a full-time site foreman, but this was not done, and site coordination was taken on by the most experienced builder in the Coop. The lack of an official coordinator did cause problems, especially in the early stages, due to the inexperience of many members. Towards the end of the project things ran more smoothly, as various people became more accustomed to roles and took responsibility for the various 'departments' with more confidence and with the benefit of experience.
    In the early stages, there were many cases of 'learning by mistakes' but occurrence of crises, which at first, it must be admitted were regular events, diminished with experience. The severity of most such crises was in fact exaggerated by initial panic and evidence only remains of one or two!

    Luckily many of the Coop members had jobs involving shift work, which meant that they times when they worked on the site were staggered. This meant that there were rarely times when there were too many people for the jobs or space available.

    Architectural students from the University also came to work on the site as part of their course work, supervised by Cedric Green. As well as doing general labouring jobs, small groups took responsibility for building the porches on some of the houses.

    The fact that the project was going to run a lot longer than the initially anticipated 18 months became obvious at a fairly early stage. Mostly people began to view the hours they worked at the Coop as a way of life or a hobby rather than a chore, and also as an investment. People also found that it was much easier to work their hours once they had moved into their houses on the site and did not have to spend time travelling each time they worked on the site.

    House and plot allocation

    In theory, it is difficult to imagine how thirteen building plots on a site could be allocated to thirteen families, in a way that maximised satisfaction and minimised argument. In practice, the allocation was very logical and did not present a problem.

    There were three house types, and generally people's requirements and budgets matched them to a particular house type.

    The site layout suggested a sensible sequence of plots on which building should take place and the position of house types on the site layout was also fixed.

    Thereafter, it was simply a matter of sorting out at which stage in the project people were going to be in a position to buy their Coop houses. Some people had distinct preferences to move in as soon as possible and others had reasons for wanting to put this off for as long as possible! These timescale variations acted as a deciding factor in determining who had which of the houses of each
    house type.












    The low cost of the house is achieved by a combination of:

    1. The compact planning of the heated and finished area of the houses (excluding greenhouse & conservatory)
    2. The inexepensive additional area of the conservatory extension to living space
    3. A design based on a structural grid of 40mm with minimum waste of materials and use of standardised doors, windows and components
    4. Construction to a habitable minimum standard to be finished by owner/occupier
    5. Reduced building time by rapid erection of timber frame and completion of weathertight envelope
    6. Simple design and use of off-the-peg standardised elements allow greater use of unskilled labour in the construction process
    7. Involvement of house owners in the Cooperative, contributing labour on construction of own houses and communal facilities (drainage, road, landscaping, communal rooms)


    The houses were conceived as being low cost, providing compact and minimal heated living areas, in traditional construction. The conservatories aimed to provide extra space to expand into, giving extra living space for summer and sunny autumn, spring and even winter days. This expandable living space was provided at much lower cost, whilst also doubling as a solar collector.

    The running costs of the houses was to be minimised, by providing a very well insulated building envelope to the heated area, and by using solar energy contributions for space and water heating. This was confirmed by the monitoring of no. 11 in 1987-88.

    In practice the Coop members have found that the money they had available allowed for much more than the 'basic' finishes initially intended. In the cases of the single storey court houses some have been built in an extended form, so that the resulting heated living area is very large. In many cases the basic fittings intended have been rejected in favour of luxury fittings. The self build aspect of the houses has contributed considerably to the minimising of the cost.


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