Introduction

Le Corbusier[1] said that a house was a machine for living in – in this chapter we attempt to describe some of the machine's components. Unfortunately, the state of the art is such that, for a given set of inputs, say environmental and material, one isn't quite certain how the machine or building will perform. The heart of our present dilemma is that we cannot precisely say even how individual building components respond in situations outside laboratories. To take but one example, infiltration losses are difficult to determine because of the effect of workmanship, condition of seals, extent of exposure to wind and so forth. And, remembering the old adage: ‘The best laid plans of mice and men …’, if we consider that, even in a well-designed low-energy house, the occupants will undoubtedly use the house in ways that would amaze the designers, the description of a building's performance is a hazardous task indeed. What is even more difficult though is to make accurate recommendations about how to design different, more-energy-efficient buildings. Of course there are the banal (but worthwhile) solutions such as increasing the insulation level and decreasing the ventilation rate but, as we will see, the latter can only be done to a certain point which is well short of the one where occupants and designer breathe uneasily. For more-complex questions such as choosing between lightweight and heavyweight buildings our information is imperfect. And as for other areas which may become the technology of tomorrow, evacuated walls, say, we know almost nothing.

Introduction

Storage has been discussed in a number of the preceding chapters and, notably, in conjunction with passive solar heating. Here we shall cover the topic more systematically but in some cases in less detail. Storage is often the key to the successful and economical use of solar or wind energy for space and hot-water heating. While it is possible, as we have seen in Chapter 3, to drastically reduce the space heating demand of buildings, the residual demand must either be met from a conventional source of fuel or from energy stored during a period of greater availability. Most buildings using solar or wind energy have been forced to limit storage capacity because of cost and employ a fossil-fuel back-up. Research projects, such as that of the Cambridge Autarkic House Project, are responsible for most of the (rare) designs which rely only on ambient sources of energy. It is nevertheless encouraging to know that even in the UK it is possible to provide in an average year 100% of the space and domestic hot-water heating requirements with solar energy alone.

The size of the store required for any application will depend on the energy demand, the source of energy and the selection of the storage medium. Because the cost per unit of storage falls as the size increases, more and more attention is being given to projects which involve large buildings or groups of dwellings. This in turn permits new equipment to be used more economically and novel means of storage to be examined.

Introduction

Forecasting is an art in which all are likely to be wrong but some will be more wrong than others. We expect the next few years to be a time for reflection. A variety of opinions on the conservation and use of energy in buildings now exists and a limited amount of data is available. Economic recession has increased the pressure on public and private funds; and the lack of national, let alone global, strategies for resource development has hindered development of energy conservation projects and the exploitation of alternative sources of energy. The result is an atmosphere of caution which at its worst could result in inactivity and resignation and at its best could lead to significant, if somewhat restrained, progress in the use and conservation of energy in the built environment. This may have to be enough – building, after all, is another art of the possible.

Our approach in this book has been to provide designers with a systematic framework for considering the use of energy in buildings. We have tried to cover the more important of the wide variety of topics that must be considered and to provide sufficient references to allow the reader to pursue points of particular interest in depth. A great deal of information has been produced during the last few years but virtually no overviews exist. Different research groups work independently of each other and often work with different aims in view. The overall result is a jungle of papers, data, evaluations and opinions for which we have tried to offer a guide.

Introduction

Most buildings receive sunlight via windows, and in the design of passively heated buildings this warming effect is more fully exploited.

The five tasks to be accomplished in a successful design are as follows:

1. to increase the amount of sunlight entering the building by enlarging the glazed area;

2. to avoid causing excessive overheating or glare;

3. to reduce the large heat loss through the glazing;

4. to distribute the heat acquired;

5. to store the surplus for use when the sun stops shining.

There has been some sterile argument about terminology.' “Passive” and “natural” solar designs' are terms coined to differentiate the use of sunlight which provides warmth without the use of complicated controls, pumps and fans, from ‘active solar designs’ which employ solar collectors and fairly complex controls. The meaning of the terms will become more clear whilst reading the descriptions of the built examples later in this and the following chapters.

It is of interest to realize that active solar systems associated with very large thermal storage could be used to provide all the space heating and hot water in a building, even in the UK. On the other hand, passive designs can never be expected to do this in northern Europe, and there they must be regarded as fuel savers. In the US and other countries blessed with moreintense and regular winter sunshine, it is possible in cold but clear regions to rely entirely on passive solar space heating. Apart from the number of sunny days in a particular region, there are other constraints acting on the design team when dealing with passive solar buildings.

Introduction

In the wake of costs for wave power, which have exceeded original estimates, interest in the UK is tending to concentrate on wind power as a means of central electricity generation using renewable sources of energy. In such northern latitudes the use of concentrating solar collectors for power generation is not viable.

For this reason a consortium of companies in conjunction with the North of Scotland Hydroelectric Board is about to construct a 3 MW turbine in the Orkneys, illustrated in Fig. 8.1. There are also tentative plans to place large fields of vertical-axis turbines in shallow parts of the North Sea off the east coast of England. These turbines would be of the Musgrove type shown in Fig. 8.15. Studies show that up to 30% of electricity in use at a given time in the UK could be supplied from variable inputs such as wind turbines, without upsetting the grid network. Southern California Edison expects a 30% contribution by 1991.

However, this chapter seeks to deal with small, local wind turbines. It has to be pointed out that the energy derived from wind-power devices is not unending (the turbines probably should have a lifetime of 20 years or so in the absence of freak weather), is not free (the devices are quite large and thus costly) and that to some, the machines are not handsome, and to others, represent a hazard.

It may help to provide a brief checklist of advantages and problems presented by the home use of wind power, before embarking on a description of the energy and devices available.

Introduction

Definitions

The somewhat arid discussion of the semantics of active hybrid and passive systems has been alluded to in the previous chapter.

Here, an active system is really taken to mean a bolt-on arrangement, which is usually not part of the building structure (for example, a solar hot-water heating system) and which often involves pumps or fans. Of course, some solar air heaters do form the roofs of buildings (see Section 5.2) and some hot-water systems flow naturally by a thermosiphon.

Popularity of solar heating

The UK Solar Trade Association assesses how widely such systems are used, and the 1981 figures show that there are 60 firms manufacturing solar systems or components or installing them. From 1974 to 1981, 173,000 m2 of collector were produced. About 21,000 m2 of hotwater system were installed in 1981, comprising about 5000 systems. About 2400 swimming-pool systems have been installed from 1974 to 1981. The main complaints seem to involve misunderstandings either by clients or manufacturers of the likely output or benefit of a given system. There has been no ‘Gallup Poll’ of users' reactions in the UK, but in the US a study for the Solar Energy Research Institute shows these conclusions: two-thirds of houseowners strongly wish to see solar energy developed over other sources; one-third of people feel solar is technically and economically practical today for homes; two-thirds of people have not considered investing in solar technology for their homes.

Introduction

Results from the recent Better Insulated Housing Programmed are summarized in Table 11.1 which shows the fractions of energy consumed onsite for various purposes.

The experimental houses at Bebington (Fig. 4.48), which are electrically heated, indicate that only about half the electricity supplied annually is used directly for space heating.

Much of the energy provided to the lights, fridge and so on, contributes usefully during the heating season to warming the space. Capper suggests the fractions shown in Table 11.2.

One might wish to argue a little with the low figures (Leach assumes 0.8 in all cases and Siviour's conclusions are shown in Table 3.1) but the fact remains that a substantial fraction of the heating in houses arises from electricity (or gas) used in appliances. Since this energy is wholly or partly electrical (generated with an efficiency of roughly 30%), the cost to the country in terms of primary fuel, or to the consumer in terms of cost, constitutes a large part of the annual fuel bill for each house. Thus, one would expect to find regulations concerning the efficiency of appliances. There are almost none in the UK, although in the US some goods must be marked with an efficiency indicator.

In the Bo'ness study, nearly all households have a clothes washer, one-third a tumble drier, all have a fridge and 40% have a freezer. Most have a colour television. Two-thirds of the households have electric fires, one-third have calor gas and one-fifth have paraffin heaters as subsidiary heating devices.

Introduction

Traditional site planning includes evaluation of the aesthetics of a site, population densities, land-use patterns, slope, drainage, soil characteristics, incident solar radiation, daylighting, exposure to wind and numerous other considerations which are treated in standard works.[1, 2] In this chapter these subjects will be discussed only when specifically applicable to the use of ambient energy sources or the opportunity for energy conservation in buildings. In the more recent past the attitude of many designers has been one of ignoring both the natural characteristics of the site and the potential of solar and wind energy. Instead, they concentrated merely on avoiding potentially deleterious effects such as summertime overheating.

Important exceptions to this way of thinking include Olygay & Givoni who wrote classic works on climate and architecture [3,4] In an age of rapidly dwindling fossil-fuel reserves, though, it is important to use a site to best advantage. Fortunately, much can be done to conserve energy merely through good design, on both the large and small scale. In the former category especially, the possibilities depend on social conceptions of work, home and leisure but in the future we may see a closer integration of places of work and residence to reduce transportation energy. This could be encouraged by a gradual renovation of cities, resulting in their increasing attractiveness as places of residence and thus reducing the tendency towards suburban sprawl. For example, near the city home of one of the present authors, a former warehouse is being converted into flats. Among the results are a higher density and, for the occupants, less dependence on vehicular transport.

Introduction

Surprisingly enough, several years ago one of the highlights in California Governor Jerry Brown's politics was the introduction of a law forbidding the sale of any lavatory which flushes more than 141 of water. Waste disposal does not often receive such publicity although the problems it entails in both industrialized and non-industrialized countries, albeit for different reasons in the two groups, are impressive.

Here we shall deal with wastes in greater detail than we did with water systems but not because the central network is less extensive – in the UK 94% of all households are connected to mains sewers (in the US, on the other hand, the comparable figure is about 67%). Rather, it is because wastes can be a source of on-site energy if methane digesters are used. Although this tends to be less practical at the level of a single home, groupings of houses and other building types such as schools should not ignore the energy potential of the wastes they produce.

Mains servicing in the UK, as elsewhere, consists of a cistern-flush toilet connected to a network of underground sewers which transport sewage and domestic waste water to a treatment or disposal facility. While to those of us who use such systems almost nothing seems more natural, it is of interest to note that the concept of using storm sewers for human wastes is only about 140 years old and the first integrated system only came into full use about 1870 in London. The first sewers merely conveyed the wastes to bodies of water where they were discharged with often disastrous consequences – sadly this practice continues today in many areas.

Introduction

This chapter takes the reader through some of the design processes which occurred during the planning of several low-energy houses. The Peterborough Houses are complex, having large air-heating solar collectors, a sophisticated ductwork system and microprocessor control. The Newnham Houses are more conventionally heated, but highly insulated. These new dwellings are discussed in Section 12.2, and in 12.3 reference is made to the rehabilitation of existing houses, including one with a passive roof-space solar collector.

New houses – three solar abdicated houses in Peterborough

The authors won a competition at the 1979 National Energy Show, for a terraced low-energy house, designed with Lucy Krall, shown in Fig. 12.1. Peterborough Development Corporation became interested after seeing the model on television and suggested that the same sort of principles could be applied to one of their houses.

In the end, a terrace of three was built, as shown in Fig. 12.2. Because a lot of domestic hot water was likely to be produced by large collectors, we felt that six-person houses should be built. Larger units also yielded a greater roof area than would smaller terraced houses. In fact, in order to provide a reasonably large area (32 m! gross), collectors were also placed on the first-storey walls.

In retrospect, this idea of dual slope collectors was probably influenced by the Autarkic House (Fig. 12.3) in which the architectural design forced the provision of collectors on three azimuths and two tilts. The whole of the southerly facade in the Peterborough Houses is glazed, since the ground floor consists of a conservatory opening into the living room.

Introduction

This chapter briefly presents some non-domestic buildings designed with energy conservation in mind.

The swimming pool, Sheiling Schools

Given the opportunity to design a swimming pool for a school for handicapped children, it was automatically part of the brief to keep the running costs to a minimum, despite the fact that water temperatures had to be maintained at 27 C for use throughout the year. The Energy Design Group made an initial study which investigated the potential of heat pumps and heat-reclaim systems, glazed and unglazed solar collectors, variable speed ventilation control and the use of a pool cover.

Initially it was felt that a heat-pump system would be preferable, using extract air as a primary source of heat. This, however, entailed expensive duct work to return the air to the boiler room, and also added considerably to the capital costs since an auxiliary gas-fired heater could not be dispensed with. Other heat-reclaim systems were dependent on the use of ozone or other very expensive purification systems which reduced their overall cost-effectiveness. (Chlorine from the pool is corrosive over the long term.)

The entire building was built to a very low budget, competitive with quotations from design-and-build contractors who offered cheap standard solutions. The over cost of energy-saving measures had thus to be kept to a minimum.

It was therefore decided to opt for high thermal insulation (100 mm of polystyrene on the roof and 80 mm of glass fibre to the walls with double glazing to all windows), a minimum volume for the building, and a high internal thermal mass.

Just as a temperature gradient exists within a structural element, a dewpoint gradient depending on the water vapour diffusion properties of the element exists too. If at any point in the structure the actual temperature is below the dew point then condensation will occur at that point.

Table A 3.1 gives some typical values of vapour resistance and thermal and vapour resistivities (thermal resistivity is the reciprocal of thermal conductivity – see Table A 2.3).

With more and more insulation being used, the designer must remember to consider both the thermal and vapour properties he or she is specifying. This is particularly true since some very good thermal insulants, for example glass fibre, are also very permeable to water vapour.

Let us now return in Fig. A 3.1 to the wall construction of Fig. A 2.1 and using the standard BRE procedure assess whether there is a risk of interstitial condensation.

The authors have rendered a valuable service to the building industry by the preparation of this volume with its wealth of actually built, rather than projected, examples. The book is well and soundly written with its emphasis maintained from start to finish on their basic theme, the necessity for the use in buildings of energy in many forms and the increasing desirability of learning how to minimize the use of non-renewable forms of energy in meeting those essential needs. Directed primarily towards architects, builders and owners in the United Kingdom, and consequently written within the scope of SI units, the book will be helpful to all who plan to build in latitudes north of the 50th parallel, where winter heating is more important than summer cooling.

Proper ventilation and the admission of outdoor air under suitable circumstances are not neglected, however. Building design features which are recommended by the authors are liberally illustrated by photographs and drawings of residential, institutional and commercial structures which actually exist. The soundness of their recommendations has been verified in most cases by the first-hand knowledge of the authors. Many of the ‘Energy’ books which have appeared in recent years have dealt almost exclusively with non-renewable forms such as the wind and the sun. These are not neglected here but their applicability is subjected to careful and objective analysis, with the intent of giving guidance which is based upon knowledge and experience rather than upon enthusiasm alone. The reader may well divide the book into three sections.