R E - USING B UILT S PACE

THE IMPORTANCE OF EXISTING BUILDINGS During the middle part of the twentieth century the inner areas of Britain’s cities were torn apart by redevelopment. In urban centres hundreds of Victorian commercial and industrial buildings were demol- ished and replaced by modern shops and office blocks. In the areas around the urban centres hundreds of thousands of homes were cleared

away – terraced housing in the English cities run down, neglected and often multiple occupied; overcrowded tenement flats in the cities of Scotland. In their place rose estates of multi-storey social housing which promised better homes but proved unsuitable for their occupants. In their turn they, too, became neglected and run down. The process of redevel- opment too often proved negative and destructive. Established commu- nities were broken up and dispersed, their networks of social contact and interaction destroyed. Equally important, the buildings and streets which made up the familiar urban fabric also disappeared.

Fortunately it is now recognised that wholesale clearance is not the way to create successful cities. The social and economic life of urban neighbour- hoods develops slowly over time. Making prosperous and vital urban environments means building on what is there. A neighbourhood may be unpopular; its buildings may have deteriorated into disrepair. Some may need to be replaced through selective renewal. But most can be preserved, repaired and rehabilitated or converted to new uses. In the process the established social and economic life will be preserved and enhanced by new residents and new businesses. The best of the familiar buildings, streets and landmarks will be retained and restored, and can be supplemented by carefully designed new infill.

Preserving and enhancing existing urban environments is highly desirable, but it is not the only importance of existing buildings. In the context of the Kyoto protocols they are also important for the energy embodied in them. The adaptation and re-use of existing buildings saves some of the energy that would be required to construct their replacements. True, even in demolition some of the embodied energy can be retained through sal- vage and recycling of components and materials. But much more can be saved through rehabilitation and conversion. Even the most comprehen- sive refurbishment process involves stripping a building out, but keeping its basic structure. The foundations and superstructure of a building represent about 20 per cent of the total construction cost. This is an indication of the minimum embodied energy which can be saved through building re-use. In most cases it would be more because most buildings can be converted and renovated without totally gutting them. There is also the added advantage that building re-use reduces the time taken and the disruption caused by new construction.

While preserving the energy embodied in existing buildings is important, it is an even greater priority to reduce the energy consumed by the existing stock in its day-to-day use. In terms of perceived housing need, 3.8 million new homes will be required in England by 2020. If this target is

achieved these new homes will certainly be built to higher standards of energy conservation than in the past. It is unlikely, though, that they will be to such a standard as to have a neutral impact on energy consumption.

Even if they were, this would make a minimal reduction to the energy consumed by housing. In 2002 the existing housing stock was about 21.5 million homes and this was responsible for 27 per cent of the nation’s carbon dioxide emissions.¹

Reducing the environmental impact of the existing housing stock is a major priority. But it is much more difficult than achieving higher-energy conser- vation standards in new construction. The improvements that can be made in occupied homes are limited. Greater opportunities sometimes arise when houses are vacant. In the owner-occupied sector about 1.4 million homes change hands each year.² A substantial number of tenancies in rented housing also change. When homes change hands there may be an opportunity for improvements to be made. More significantly, most housing needs major refurbishment every 30 years or so. The greatest opportunities to improve the environmental performance of existing housing lies in that part of the stock which is already in need of major renovation.

Vacant and unpopular housing

In 2003 it was estimated that 3.4 per cent of the housing stock in England was vacant – about 740 000 homes. Some of this was empty dur- ing sale or transfer or while awaiting planned modernisation, conversion or redevelopment. Other stock was simply not being marketed because of poor condition, disputed ownership or abandonment.³At the same time, there was a great deal of unpopular housing. Nearly 1 million homes were estimated to be in areas of low demand. There is some overlap in these figures since some of the vacant houses are also in areas of low demand.

Nevertheless, this substantial quantity of existing housing in need of reno- vation represents both a resource – a contribution to meeting housing need – and an opportunity to carry out major improvements.

Unpopular housing does not have a distinctive character. Low demand affects all types of housing and all forms of tenure. Over half is houses and bungalows with the remainder multi-storey flats of various types. About half of it is private sector stock. The remainder is social housing, though the majority (about 380 000 homes) is owned by local authorities, with a smaller amount (about 90 000) in the hands of housing associations.

Unpopular housing is characterised in the public sector by lack of wait- ing lists and high transfer requests, and by high levels of vacancy and tenancy turnover. Unpopular private housing is typified by low and falling

values, high levels of empty and abandoned homes and by high population turnover. The causes of unpopular housing and its nature varies consider- ably between the north and south of the country.

In the north of England unpopular and abandoned housing is widespread in many cities. One of the main causes is economic decline. This results in high unemployment, low wages and reduced spending power which is reflected in the neglect of housing and the environment. It is also a cause of population decline. This creates a housing surplus in which people have more choice. Once unpopular areas go into decline houses become boarded up and vandalised, forcing long-term residents out and causing more abandonment. Nevertheless, unpopular areas are often very localised with only a few streets vacant and boarded up. Such areas will not regen- erate spontaneously. Even in places with high levels of owner occupation the action of individuals cannot arrest decline. Public intervention and finance is needed, aimed both at improving housing conditions and creating a better social mix. This was the approach of the government’s Housing Market Renewal initiative of 2003. This established nine ‘pathfinder’

projects in areas of low demand in cities of the North and Midlands.

Early results of such regeneration schemes suggest selective demolition has been necessary when there is a clear surplus of homes. Sometimes hous- ing needs to be replaced with more attractive stock. Renovation has also been effective with conversion or major rehabilitation of the hous- ing and enhancement of the quality and security of the environment.

In the south of England there is generally high demand for housing. In the past poor quality housing was associated with large houses rented in mul- tiple occupation and some of these remain today. Most unpopular hous- ing is now in inner-city social housing estates and is, again, concentrated in small pockets. Many estates are associated with crime, antisocial behaviour, deprivation and low attainment which stigmatises them and makes them hard to let. Many are also of bad design and in poor condition. Addressing these problems is partly a question of management changes to introduce a more mixed population and more suitable housing. But investment and physical improvements are also vital. A range of approaches has been carried out to improve and regenerate unpopular estates.⁴

IMPROVING THE EFFICIENCY OF EXISTING HOUSING

There may be many changes that are needed to adapt existing buildings to new uses and to bring the older housing stock up to modern standards.

But to meet the public policy objective of reducing greenhouse gas emis- sions it is a high priority to make existing housing more energy efficient.

The scale of this task is immense and, in many ways, energy efficiency is more difficult to achieve in existing buildings than in new constructions.

Even in the most thorough-going refurbishment, there may be constraints posed by the existing structure which prevent the achievement of high levels of efficiency. In most vacant housing the improvements required fall well short of comprehensive and the possibilities for raising energy stand- ards will be limited. Most limited of all is the improvement of occupied housing but, even here, a range of modest changes can be made to considerable benefit.

In principle, the key concerns are the same as in new construction. On the one hand, there is the need to minimise waste by reducing the amount of energy lost in heat escaping from buildings. On the other hand, it is import- ant that the consumption of fossil fuels is reduced by ensuring that the installations and appliances in buildings are using energy in the most effi- cient way. In reducing waste the most significant change is to install much improved insulation to existing buildings. But it is almost equally important to improve ventilation since a great deal of energy is lost in warm air leak- ing out of buildings. All these changes come at a cost but they also bring benefits to householders through reduced energy bills. Some improve- ments bring very rapid financial benefits though more complex changes may have a much longer ‘pay back’ period. In overall terms it was estimated in 2004 that improving the least energy-efficient homes would cost about £5 billion but would result in savings of running costs of £1.2 billion annually.⁵ Improving insulation

Most heat is lost from buildings by conduction through the external envel- ope. The aim of better insulation is to improve the thermal performance – the u-value – of the outer skin. Each of the elements of this skin – roof, walls, windows and floor – require a variety of approaches depending on the nature of the existing construction:

● Roofs.In much existing housing the roof is responsible for the greatest proportion of heat loss. At the same time, most roofs present opportu- nities for improving insulation simply and effectively. Simplest are pitched roofs where the loft space is unused. Insulating quilt can be eas- ily laid between or over the ceiling joists. Most pitched roofs already have some insulation but contemporary standards suggest this should be increased to 150–200 millimetres. Habitable loft spaces are a little more complex, but insulation board can be fixed between or over the inside of the rafters. Flat roofs present, perhaps, the greatest challenge.

Internal insulation is disruptive and often impractical. If the roof cover- ing needs replacing, an insulation decking can be laid as a base for the new roof finish. If the existing asphalt or felt is good, new insulation can be laid over the top. This comprises preformed expanded poly- styrene boards with an integral mortar topping. These need to be weighted down at the edges and at abutments. The roof needs to have an adequate kerb surround and care needs to be taken in providing appropriate drainage.

● Walls.Existing walls can be insulated externally, internally or within.

In most housing of traditional construction built in the last 50 years, the external walls will be of cavity construction. Mostly this will be a small cavity of 50 millimetre rather than the wider cavities needed for con- temporary insulation. Nevertheless, insulating cavity walls is simple and provides significant thermal improvement. New insulation can be injected from the exterior with no disruption to the residents. Internal thermal lining using insulation board or a similar new insulating layer can also be effective. It is highly disruptive, however, and care needs to be taken to avoid ‘cold bridges’ at beams and partitions. Internal insu- lation reduces room sizes to a degree and this may be significant. In older housing it may obliterate original features such as mouldings and create difficult junctions where it meets window and door openings. Exter- nally, a basic form of insulation can be provided by fixing insulating slabs which are then rendered over. This obliterates the original materials and details and is usually of bland appearance. It is inappro- priate for frontages which have significant architectural quality. A range of proprietary systems of external ‘over-cladding’ have now been developed which provide both insulation and rain protection.

These are of good appearance but need to be used on a large scale with a high degree of standardisation. They have been successfully used on large multi-storey blocks.

● Windows.A great deal of heat can be lost through windows particu- larly through the glass. Frames can transmit heat and materials, other than timber, need to be insulated. Double glazing is desirable and, on exposed façades, triple glazing. Existing casement or fixed windows can usually be re-glazed with sealed double-glazed units. Sash windows are more difficult unless purpose made for double glazing. Replacement windows may be the most effective way of reducing heat loss though this is disruptive and costly. If replacement is impractical, some bene- fit can be gained from insulated and well-fitting shutters or by hanging curtains with thermal lining. The addition of conservatories, or glazing in of balconies, has become increasingly common. Very often, though, this is done to increase living space. There may be little benefit if the

glazed extensions are poorly orientated and a net disbenefit if they are heated in winter.

● Floors. Generally the ground floors of houses are the least exposed in terms of heat loss. Insulating them is invariably highly disruptive.

Suspended timber floor can be effectively improved by fixing insulation slabs between the joists though since it involves removing most of the boards it is not often done. Solid floors can be insulated with propri- etary boards and then resurfaced with a new finish. This usually involves raising the floor level which creates difficulties around thresholds and involves removing all fittings.

Insulating existing buildings can usually be done effectively where major refurbishment is carried out. Where work required is less comprehensive, and particularly in occupied buildings, there are much greater difficulties. A pragmatic approach is required which involves implementing the simplest improvements and identifying and remedying the greatest areas of heat loss.

Controlling ventilation

Good ventilation has long been seen as critical to good health, removing stale air, and providing an input of oxygen. Flues and chimneys provided valuable ventilation in older buildings. More recently, regulations have required the installation of permanent vents to guard against condensation and the installation of mechanical extracts to remove moisture from kitchens and bathrooms. Effective ventilation is still needed but, in a more energy-conscious era, there is concern about uncontrolled air move- ment. Warm air leaks out of uncontrolled vents and flues. Cold draughts leak in through gaps around doors and windows, and service entries.

The aim of controlling ventilation is to prevent the unwanted passage of air in and out of the building while, at the same time, being able to pro- vide all the ventilation necessary for health and comfort. It is possible to install a ducted system of ventilation which passes through a heat exchanger at roof level. For most existing housing this is a far too com- plex approach. Good control can be achieved by a number of small-scale improvements which involve minimal disruption and modest cost:

● Draught stripping. A good deal of air leaks around door and win- dow openings. This can usually be stopped by a range of proprietary draught-stripping products, though there are some problems fitting effective seals to sash windows. Openings to unheated spaces such as loft hatches should also be sealed. Draught stripping may be supple- mented by fitting of additional lobby doors which are particularly effective at front entrances.

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ALTHAMSTOW Priory Court estate was built in the early 1950s and comprised mostly six-storey slab blocks. The flats were of generous standards but were poorly insulated and constructed. By the 1980s technical shortcomings had led to condensation problems and extensive water penetration – both through leaking roofs and cracking walls. A regeneration scheme started in the 1990s involved the redevelopment of some blocks but fourteen of the slab blocks

were comprehensively refurbished. This involved new lifts, internal improvements and the development of unused ground floor space to provide flats for disabled tenants.

The technical problems were addressed by giving the buildings an entirely new external envelope. A proprietary over-cladding system was installed to provide a rainscreen and insu- lation to the outside of the existing walls.

New double-glazed windows were built into the new external skin. On top of each block innovative barrel-vault lightweight roof shells were constructed. These prevented rain from reaching the existing roof covering which was topped with new insulation panels. The scheme ensured that the blocks were given a high level of thermal protection entirely by adding insulation externally. This meant the improvement work could be done with little disruption to the internal space.

6.1 Typical block before improvement

6.2 An identical block after addition of new external skin

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● Controllable vents. Permanently open vents should be closed and fitted with grilles which can be opened and closed. Chimneys should be sealed and fitted with dampers or vent grilles. Trickle vents can be installed in window frames to help combat condensation. These adjustable vents can provide close control of air movement, though the ability to open windows and doors provides control of large-scale ventilation.

● Air extract. In areas of high humidity it may be necessary to use extractor fans. To reduce energy use these should be closely controlled by a timer or a humidistat. Linking the fan to the lighting circuit is an effective way of controlling bathroom fans. There are proprietary

‘trickle vent’ systems which use little energy. A range of passive vents is now available which could be effective in replacing powered extrac- tors altogether.

● Venting appliances.Gas burning appliances, particularly boilers, require a supply of oxygen to operate. Providing oxygen is essential to prevent an unhealthy build-up of carbon dioxide. To prevent combustion air being drawn in without control it is helpful to provide fresh air ducted directly to boilers and, perhaps, to cookers. Boilers are also available with ‘balanced flues’ which drawn in and expel gases simultaneously direct to the outside.⁶

In most existing buildings it is impractical to install complex air handling sys- tems. It is important, though, to devise a ventilation strategy which can be implemented through a range of simple measures. This will identify what level of air change is needed in each room and provide the necessary inlets and outlets to achieve it without causing excessive air movement throughout the house.

Using energy more efficiently

It is important to reduce the waste of energy in existing housing by better insulation and ventilation. It is also important to ensure that the systems and appliances that use energy in the home do so in the most efficient way. Partly this efficiency lies in using each source of energy for its most appropriate purpose. For example, electricity is not efficient when being used to produce heat. Its use for heating and generally for cooking should be avoided. At the same time, it is the only practical method of providing lighting and powering household appliances. Greater efficiency should be a key consideration when adapting or installing energy-using equipment:

● Heating.One of the consequences of reducing the waste of energy is that more heat is retained within the home and heating systems can be