The ENERGY EFFICIENT HOME E-Book

Patrick Waterfield

• Herausgeber: Crowood
• Kategorie: Lebensstil
• Sprache: Englisch

Seitenzahl: 416

Veröffentlichungsjahr: 2012

Beschreibung

Reducing energy consumption and costs is an issue of ever-increasing importance, and European and national legislation aimed at reducing carbon emissions is tightening up minimum energy standards for new buildings as well as those being extended or renovated. Energy-saving measures in the home will, therefore, become ever more cost-effective throughout our lifetimes. This book covers every aspect of the efficient consumption of energy in the home including the following and much more: the position of the dwelling, its method of construction and the materials used; energy rating and the legal framework; insulation and U-values; windows and doors; conservatories, sunrooms and loft conversions; heating and hot-water systems; lighting and making the best use of daylight; ventilation; renewable energy technologies; appliances, gadgets and housekeeping; the wider environmental issues including water economy and recycling. This non-technical book is fully revised and updated to take account of recent legislation and developments in energy efficient products and techniques.

Leseprobe

The Energy Efficient Home

A COMPLETE GUIDE

PATRICK WATERFIELD

Copyright

First published in 2006 by The Crowood Press Ltd, Ramsbury, Marlborough, Wiltshire, SN8 2HR

www.crowood.com

Revised edition 2011

This e-book edition first published in 2012

© Patrick Waterfield 2006 and 2011

All rights reserved. This e-book is copyright material and must not be copied, reproduced, transferred, distributed, leased, licensed or publicly performed or used in any way except as specifically permitted in writing by the publishers, as allowed under the terms and conditions under which it was purchased or as strictly permitted by applicable copyright law. Any unauthorised distribution or use of this text may be a direct infringement of the author’s and publisher’s rights, and those responsible may be liable in law accordingly.

ISBN 978 1 84797 437 2

The author and the publisher do not accept responsibility, or liability, in any manner whatsoever for any error or omission, nor any loss, damage, injury, or adverse outcome of any kind incurred as a result of the use of the information contained in this book, or reliance upon it. Readers are advised to seek professional advice relating to their particular property, project and circumstances before embarking on any energy-efficiency/building or related work.

Cover images

Front cover, clockwise from top left: ‘passive’ house in Donegal, Ireland; Interpane glazing units in Eco-plus timber frames (courtesy of Green Building Store); PV shingles (courtesy of Solarcentury); examples of different kinds of low-energy lamp (courtesy of EST); schematic of Kingspan evacuated tube solar water heater. Back cover, from top: ‘Thermafleece’ sheep’s wool insulation from Second Nature UK Ltd; Solartwin flat-plate solar water heaters; Consol evacuated tube solar water heater; house built using Kingspan TEK structural insulated panel system.

Contents

Title Page

Copyright

Dedication and Acknowledgements

Preface to Paperback Edition

Introduction

1 Site and Built Form

2 Insulation and U-Values

3 Methods of Construction

4 Windows and Doors

5 Conservatories, Sunrooms and Loft Conversions

6 Heating and Hot Water

7 Lighting

8 Ventilation

9 Renewable Energy Technologies

10 Appliances and Housekeeping

11 Energy/Environment Rating and Legal Framework

12 Wider Environmental Issues

Glossary

Useful Contacts, Publications and Additional Information

Index

Dedication and Acknowledgements

Dedication

To self-builders and DIY-ers everywhere – especially those who really want to grasp the nettle of energy efficiency – you will need more dedication than just this one!

To Gillian Corry, of Corry Homebuilding Ltd, Saintfield, Northern Ireland, who gave me the initial inspiration to write this book.

In memory of my mother Frances, who gave me my first lessons in sustainability and helped me to realize my own dream of a ‘passive’ house.

Acknowledgements

Thanks are due to the organizations that provided images used here. The captions to the images give the name/type of the product/system/service and the name of the company that supplies/manufactures/operates it. Full contact details for each organization are given in the ‘Useful Contacts’ section at the back.

The depiction of and reference to specific products/systems/services should not be taken as endorsement of them and no responsibility can be accepted for the subsequent use of such.

Acknowledgements are also made where relevant to other sources from which images have been adapted. The details of such publications are given at the back.

Preface to Paperback Edition

When I was writing the first edition of this book, one of the constant challenges, especially in the final stages, was keeping pace with changes to the Building Regulations. At that time, the energy-related part of the regulations was going through its most significant change to date, with consultations, draft amendments, proposed and predicted elemental U-values, and so on. Trying to ensure that the content was correct at time of going to print, but still flexible enough to anticipate developments, was a real problem.

Added to this, in recent years there has been an ever-increasing array of products, techniques and technologies aimed at the expanding energy efficiency in housing market. This continues to be the case and it is practically impossible to represent every option available.

Five years on, updating the book for the paperback edition, I find myself in exactly the same position. Again, the building regulations in UK and Ireland are in the process of changing, with further upgrades signalled in the run-up to ‘carbon-neutral’ new dwellings, while the number of new low-energy and low-carbon products coming on to the market is still increasing.

By way of a caveat, I would urge you to check for updates to Building Regulations and other statutory requirements, which may well have changed even by the time this book is published.

Energy rating certificates (EPCs in UK, BERs in the Republic of Ireland) are now in place. The economic downturn, though inevitably prompting a slow-down in the construction industry in general, including house-building, has, together with an underlying rise in energy prices, focused our attention more and more on future-proofing our dwellings against increasing running costs.

All this means that energy and the environment are finally being given a much higher profile in the construction industry than was ever the case before. Even volume commercial house-builders in the UK recognize this fact – in a recent survey, when asked what their number one concern was over the next few years, it was not the economic situation nor even the state of the industry, but how to address the forthcoming energy and environmental requirements that topped the list.

Self-builders can and should move well ahead of the volume commercial market and minimum legal requirements. I have recently put my money where my mouth is and built my own version of a ‘passive house’. Using superinsulated fabric in a compact form, it has no central heating system but just a small wood-burning stove in the main living area. A brief description is given in Chapter 11.

Solartwin flat-plate solar water heater.

Introduction

BACKGROUND ISSUES

So – you have taken the plunge and decided to build your own house or carry out renovations to your existing property. You will be aware already that there are many things that need to be taken into account – the legal requirements, technical factors, economic considerations, as well as the less tangible, aesthetic matters – all of which will determine the scope of your project. Much thought will be given, quite rightly, to how the finished design will look, how robust it will be and how much it will cost. Often, however, the energy aspects of a design are not thought through properly. This may be because the necessary information is not to hand – that is where this book comes in.

Or perhaps you are happy with your house the way it is but would like to carry out minor improvements to make it more energy efficient? Maybe you are simply looking to adopt a ‘greener’ lifestyle? Whatever your focus and proposed level of involvement, you should find something of interest in this book.

We are all aware these days of the impact of fossil fuel consumption upon the environment. The relationship between climate change and increased environmental emissions is now broadly accepted, even if we do not know exactly what changes are taking place, nor how quickly. Besides, it still makes sense to use energy efficiently to avoid the wastage of finite natural resources.

The first and most obvious way in which we think of energy is in terms of that used to heat, light, power and ventilate our homes throughout their lifetime. Lower energy consumption not only benefits the environment through reduced emissions but it also saves us money. The second less obvious issue concerns the energy taken to produce materials and products (known as ‘embodied energy’), which can be offset partly by recycling. This book focuses mainly on the energy used (or saved) by the building in use, but also makes reference to the wider environmental issues.

Let me also dispel a commonly held belief: energy efficiency need not mean ‘doing without’. The most important thing is that you end up with a house that meets your key requirements. Of course, I would like to think that energy efficiency is one of your requirements, but you do not need to change your lifestyle in order to achieve it. For those who want to make a lifestyle change, the possibilities are, of course, much greater. Personally, I do not see why we should expect to be able to walk around our houses in light clothing at all times of the year, but some people do. Also, everyone has his or her own definition of ‘comfort temperature’. There is no point in being energy efficient if you are cold and miserable any more than there is in allowing high solar gains if you cannot stand the heat in the room. Energy efficiency is not simply about saving as much energy as possible but about meeting your performance requirements for minimum energy usage and cost.

As with any building project, there will be several competing factors that need to be reconciled with each other to arrive at an optimum design. However, if you can achieve your design objectives within your desired budget and also reduce the running costs and environmental impact over the life of the building then that is surely a win-win situation.

Environmental Concerns Regarding Energy Consumption

A word or two first on the reasons for the current concern regarding the environmental impact of energy consumption.

Climate Change

The ‘greenhouse effect’ is so called because the earth’s atmosphere has the same effect upon temperatures on its surface as glass does in a greenhouse. Glass allows heat from the sun to pass through it more easily than it allows heat to be lost back the other way. This is because glass is more transparent to short-wave solar radiation than it is to the long-wave thermal radiation emitted from warmed surfaces within the greenhouse (see the illustration below). The greenhouse thus heats up and provides a warmer environment for plants. In a similar way, gases such as carbon dioxide in the earth’s atmosphere have the property of being more transparent to solar radiation than to heat emitted by the earth’s surface, thus trapping heat within the atmosphere. The greenhouse effect, it should be noted, is essential for all life on earth – we would not be here without it. What has been concerning scientists and, more lately, politicians is the ‘accelerated greenhouse effect’. Increasing levels of ‘greenhouse gases’, principally carbon dioxide (CO2), in the atmosphere are resulting in rising global temperatures. There are several sources of atmospheric CO2, but the greatest man-made one is the burning of fossil fuels.

Now, you may think that a little global warming would not go amiss in the United Kingdom and Ireland – we could save a packet on those foreign holidays. Unfortunately, as with most things to do with nature, it is not that simple. One of the main concerns with global warming is the effect upon the polar ice caps, which are already melting at an increasing rate. Large volumes of cold water flowing down from the North Pole could have the effect of pushing the Gulf Stream south. The Gulf Stream is a major contributor to our moderate climate; without it we might have a climate similar to that at the same latitude in North America – which happens to be Hudson Bay – not terribly tropical.

The greenhouse effect and why it is so-called. Glass is more transparent to short-wave, solar radiation entering the greenhouse than to long-wave, thermal radiation trying to leave it, resulting in the greenhouse warming up. Certain atmospheric gases, principally carbon dioxide (CO2), have a similar effect upon the earth’s atmosphere and surface.

The Depletion of Finite Fossil Fuels

As long ago as 1922, Frederick Soddy, who worked with Ernest Rutherford of atom-splitting fame, recognized the impending problems linked to increasing rates of fossil fuel consumption. Soddy coined the terms ‘capital energy’ and ‘revenue energy’. Capital energy, or fossil fuels, he likened to a fixed lump sum of money in the bank which, if continually used, would gradually dwindle away to nothing. Revenue energy, or renewables, on the other hand, are continually replenished and will last indefinitely.

Most people faced with the choice of, on the one hand, continually depleting a limited amount of capital and, on the other, keeping the capital while earning an income would prefer the latter, thus leaving something for their children. It seems an easy choice to make where money is concerned – why not energy and the environment?

Other Environmental Emissions

Apart from carbon dioxide, other key environmental emissions resulting from the burning of fossil fuels include particulates (tiny soot particles) and also the oxides of sulphur and nitrogen. Particulates contribute to poor air quality, especially in inner cities, while the oxides of sulphur (formed by burning coal and oil and derivatives) and those of nitrogen (a result of inefficient combustion) cause acid rain.

Cost Drivers

Another factor concerning finite resources is their effect on fuel prices. The resources (of oil and natural gas, for instance) which are the cheapest to extract are always exploited first – a basic rule of economics. Suppliers will need to raise prices to account for the increased costs of extracting ever-depleting and harder-to-reach supplies of fossil fuels. Added to this, energy cost reductions due to privatization in Britain have reached their limit. British Gas was on record in 2004 as saying that the era of cheap energy is over, the only way is up. Meanwhile, the taxation of fuels will increase to encourage energy efficiency, in line with international commitments to reduce environmental emissions.

More recently, oil prices (and thus those of other fuels) have varied considerably due to global economic swings, with a recession prompting a fall. However, following signs of economic recovery, prices have started to rise again and will continue to do so as resources are depleted and environmental taxation is increased.

Thus, however economically attractive energy efficiency measures may be today, they will become more and more so year after year and certainly during your lifetime and that of your house. This is a key reason to practise energy efficiency now. Even measures which do not appear economically attractive now may become common practice in just a few years. However, while certain measures (such as solar water heating) can be retrofitted relatively easily, others (such as building components) are more costly and/or difficult to replace. Consider this when deciding whether or not to adopt a particular energy-efficiency measure in your build.

THE SCOPE AND CONTENT OF THE BOOK

This book is very much a personal account derived from my own experience as an energy consultant, working on other people’s building projects (and occasionally on my own). A wide range of issues is covered, from site factors and methods of construction, to specific components and technologies and how they influence the energy efficiency of the design, through to the legal framework and the wider environmental issues. Reference is made also to lifestyle factors, which can be important in determining how energy efficient your home is in practice.

Consequently, the book does not go into great detail in any one area. The idea is to make you think of energy efficiency in your build and to give an insight into the options you might wish to consider. In most cases you will need to seek specialist advice, for example, from architects, engineers, product manufacturers and suppliers, and other sources of information such as books, magazines and the web (see ‘Useful Contacts’ section) in order to incorporate these options into your build.

You will notice some repetition between the sections of the book. This is intentional since it is not designed to be read sequentially from beginning to end, but to be dipped into as and when a particular issue needs to be addressed. But to avoid excessive repetition, frequent reference is made to other sections throughout. While covering a wide range of issues, the book does not set out to be all-encompassing nor to cover every energy technique and technology available on the market today. Between the writing and publication the picture will change since there are new energy-efficiency technologies and products coming on to the market all the time, in response to legislative developments and increased public environmental awareness.

The book is aimed primarily at the self-build/DIY refurbishment/extension market – which in itself covers a wide range of activities, technical knowledge and levels of involvement – although it should also be of interest to others with a concern for energy and the environment. Self-build can cover anything from actually putting brick upon brick or timber to timber yourself, to commissioning someone else to project-manage a build on your site – and anything in-between. As it covers such a wide range of issues, it is unlikely that all parts of the book will be relevant to everyone. However, I hope that you will find enough to interest you and to spur you on to greater energy efficiency.

There is an ever-increasing number of publications and organizations aimed at self-builders these days, reflecting the growing interest in self-building. Lists of many of these are contained in the ‘Useful Contacts’ section. There may be a self-build organization or cooperative in your area – such groups can be a useful source of information and an opportunity to share experiences with like-minded people. But if no such organization exists, why not start one? The Hocker ton Housing Group in Nottingham and the Ashley Vale Action Group in Bristol (see the ‘Useful Contacts’, section 16–18) are examples of community self-build projects with an energy and environmental focus. Even if you are not intending to be involved in the build, except in the concept (and, of course, in the financing), at least you should be aware of the energy-related issues that will influence the internal environment and running costs of the finished product – after all, you are going to have to live in it.

The focus is on the United Kingdom and Ireland, with reference to the regulations and vernacular building styles in these islands. Did you know that there are more self-builders in Ireland (north and south) than in the whole of Great Britain? So come on England, Scotland and Wales – it is time to play catch-up!

THE LAYOUT OF THE BOOK

The book is divided into chapters addressing issues as they occur along the process of a build. Thus we start with the site itself and plan form (how the house is to be laid out) and move on to the methods of construction, building fabric and components, glazing, insulation and so on. Conservatories and loft conversions, two of the most common areas of DIY/self-build are addressed separately. We then look at the services, that is, heating, hot water, lighting and ventilation, including renewable energy technologies, an area of increasing interest, and then move on to appliances and lifestyle factors – or what happens when the build is finished and you are actually living in it – which apply equally well to existing homes. We finish with the wider environmental issues, such as water economy and embodied energy, as well as the regulatory requirements. Finally, at the end of the book are a glossary and a list of useful contacts and further information.

PLANNING YOUR BUILD

This book focuses on the energy-related aspects of housing design and refurbishment, for the self-builder or the DIY-er. It does not, therefore, attempt to cover all the issues that you might encounter in the design and construction of your project. There are other books, periodicals, magazines and websites (see the ‘Useful Contacts’, section 16–19) which do this, covering important issues such as project planning and management, budget setting and control and planning applications. However, good forward planning is the key to achieving a good energy-efficient building, as it is to achieving success in all aspects of the design.

The Design Process

It is almost always worth engaging an architect, even for the smallest loft conversion or conservatory/sun room. A qualified architect (a member of the RIBA, the RIAS, the RSUA or the RIAI) will not only have the experience to put your thoughts into practice, he or she will also be able to visualize your ideas and express them in drawings in a way that will satisfy planners and Building Control.

We have all heard of cases where the architect-client relationship has become strained or has broken down. That is not a reason not to engage an architect; there are doubtless many more cases where the relationship has worked well and the client’s visions have been successfully translated into a building, but that does not make interesting gossip, television or magazine articles. What is most important, especially in a self-build project, is that you select an architect who has had experience of working with self-builders. You will not be embarking on a self-build project without some clear ideas of what you want and an intention to be involved in the design process if not the actual construction. A starting point might be a local self-build organization or architectural body. Alternatively, you might hear of someone by word of mouth. But whatever means you use to locate potential architects, always ask to see examples of their work. Everyone has his or her own particular sense of aesthetics, and designers often adopt a trademark style. Thus you should satisfy yourself that the architect’s style is in keeping with your own concept.

Budget-Setting and Control

This is one of the areas where projects can most easily come unstuck. All too often, unless realistic budgets are set and adhered to, there comes a time in the design or the construction process when cuts are looked for, and the energy-efficiency elements are usually the first casualties. A good architect should be able to work within an approximate pounds per square foot (or metre) figure which gives you the space you want within your budget. Specific technologies such as renewables can then be factored in as additional costs within the whole project.

It is not likely that the building you end up with will be exactly that represented by the architect’s final drawings. There will probably be some changes – it is one of the advantages of self-build that you can more easily accommodate modifications along the way. However, and especially if you are working with outside contractors, be aware that such changes may become disproportionately expensive, the more so the further you go down the design and construction processes. It is much better to put the time into the early design and project-planning stages to avoid having to make such changes later.

Blobs on a page: the earliest stage of the design process showing the preferred location of zones from a solar viewpoint. The same exercise can be repeated for other factors such as functionality, views, privacy and noise.

If you are carrying out extensive refurbishment measures to an existing property, say insulation and boiler/heating system replacement, make sure the latter is sized on the basis of the thermally improved fabric. Also, include all energy-efficiency measures in the standard specification rather than as ‘extras’ since otherwise you may find that contractors try to charge more for them.

The Earliest Design Stage

At the very earliest stage of the design, even before you have engaged an architect, you can carry out a simple exercise of placing ‘blobs’ on a page (see the illustration on page 11). Mark down where you want the various ‘zones’ of the house from a solar/energy point of view (see the section ‘Passive Solar Design’ in Chapter 1). Then carry out the same exercise from a functional viewpoint in terms of the interrelationship between areas. Then perhaps do the same thing again with access in mind. Do it as many times as you like from all the different viewpoints you can think of: views, privacy, noise, for instance, and see where issues conflict and where they complement each other. In this way you can address each issue, avoiding time-consuming and possibly costly changes further down the line. The order in which you carry out the exercise and the priority you assign to each issue will be up to you. However, if you adopt this kind of approach, at least you will be able to say that you took on board all the aspects at an early stage and arrived at an optimum balance.

CHAPTER 1

Site and Built Form

MICROCLIMATE

The term ‘microclimate’, as it sounds, refers to such climatic factors as solar gains, and wind speed and direction immediately around a building. With an existing building, as well as with a new one, several measures may be taken to reduce the negative aspects of our climate and to enhance the positive ones. The orientation of your house is a key one in creating a microclimate around the building. Think of your house responding to the climate in much the same way as a plant, opening up to the sun while avoiding excessive heat, seeking shelter from cold winds and being open to favourable winds, being able to ‘close up’ at night (in practice, this might mean shutters or even simply good, thick, well-lined curtains). This practice is embodied in vernacular styles of architecture all around the world and which vary according to climate. Many of such simple principles are also embodied in the ancient Chinese practice of feng shui. The recommendation may be phrased something like ‘place your house in the belly of a sleeping dragon’, but the actual meaning is ‘seek a sheltered spot’.

Optimum size and position of a shelter belt (for instance, coniferous trees) relative to a proposed or existing dwelling.

Shelter

This is one of the primary functions of a house – to provide that basic need for shelter from the elements. Fortunately, in a European maritime location such as Britain and Ireland have, the summer prevailing wind is from the south-west, with harsher, winter winds coming from the north and the east. This means that a south-facing house can not only embrace solar gains but also turn its back on the unwanted cold winds. Reducing the impact of wind, particularly cold winds, can reduce the heat loss from your house, especially in exposed sites. The movement of air along the outside walls of a building reduces the surface temperature of the walls and increases heat flow from the inside. This is even more true if the wall is wet. In an exposed site, planting or earthworks can significantly improve the heat retention of the dwelling, as well as protecting it from the possibility of water ingress from driving rain. Look for land forms and vegetation that provide shelter and shade where needed. If none such exist, consider how they might be introduced.

Coniferous species should be used for shelter since these will retain their foliage in the winter when the cold winds are at their fiercest. You might think that the best form of planting would be that with the densest foliage. In fact, experience has shown that foliage of medium density, or trees planted not too close together, is actually more effective, absorbing the wind rather than deflecting it, which can cause eddies and vortices. The correct sizing of the shelter belt or planting (when fully mature) will also provide a sheltered area on the leeward side, which can again be beneficial in exposed sites (see the illustration on page 13). A shelter belt of H (height) positioned with at least 5 × H of open space on the windward side, can provide up to 10–15 × H of sheltered space on the leeward side.

Evergreen hedges, rows of coniferous trees or even high fencing can be used to good effect to attract, deflect or accelerate winds in the vicinity of the building (see the illustration below). Generally, you should be wary of channelling winds towards your building. However, for a very sheltered site you might wish to enhance favourable south-westerly winds for summer ventilative cooling. This aspect is also addressed in the section on natural ventilation in Chapter 8.

Even if it is not possible to shelter the house from cold winds, you can use the form of the building itself to provide a sheltered outside area. The longer the leading edge of the roof on the windward side, the greater the extent of the sheltered area on the leeward side (see the illustration on top of page 15).

This plan view shows how evergreen hedges, rows of coniferous trees or high fencing can be used to good effect to attract, deflect or even accelerate winds in the vicinity of the building.

The longer the leading edge of a roof on the windward side, the greater the extent of the sheltered area on the leeward side.

Shading

There may be times when shading is an advantage, for example, in more southerly latitudes in the summertime or perhaps to prevent a conservatory from overheating in midsummer. Deciduous trees to the south (not too close to the house) can provide some shade to the house and/or garden areas in summer while allowing the sun’s rays to pass through in winter (see the illustration on bottom of page 15), when solar gains are most useful. Unless such planting already exists, however, it will take many years to become effective. Other means of shading, by the building itself (for instance, roof overhangs) or specific shading devices, are addressed in the section on passive solar design.

Deciduous trees to the south can provide shading in summer while allowing useful solar gains in winter.

The Sun-Trap

We have all experienced the phenomenon of the ‘sun-trap’, whether in our own home, that of friends or on visits to the gardens of stately homes, for example. A sun-trap is a south-facing area which traps the heat of the sun and protects from the wind. The shelter may come from natural features such as surrounding higher ground or planting (hedges, rows of trees) or from man-made structures such as walls. The effect can be heightened by the provision of masonry elements in the form of walls and paving which soak up the sun’s heat and reradiate it back later in the day. With the appropriate orientation and sheltering, the house, or indeed the whole site, can become a sun-trap.

Miscellaneous Factors Concerning Planting

Much has been said in recent years on the subject of fast-growing conifers, planted in order to provide shelter quickly (or, more often, privacy). These can then become a nuisance for owners and neighbours alike, by either blocking the sun and views or requiring frequent maintenance. Feuds and even lawsuits have resulted. Consider instead slow-growing, lower-lying shrubs – and live at peace with your neighbours. As far as possible, indigenous species should be used as these will be better suited to the climate, soil conditions and exposure levels. Indigenous species will also provide a habitat for insect and animal life, which will enhance your garden. If possible, leave at least one corner of your garden semi-wild – the natural habitats of many delightful creatures such as butterflies and birds are being lost through the development and over-cultivation of gardens.

On another planting subject, use slow-growing grass when sowing new lawns. While it will take longer for the lawn to become established, you will save energy – your own as well as that of your lawn-mowerin not having to cut the grass as often.

PASSIVE SOLAR DESIGN

There are two basic approaches to energy efficient design, as characterized by interaction with the outside environment. These are the ‘selective’ approach and the ‘exclusive’ approach. The first makes use of natural solar heating, natural ventilation and day-lighting to offset the energy otherwise used in providing a comfortable internal environment – in other words, ‘passive solar design’. The term indicates that use is made of the sun ‘passively’, by virtue of the design of the building, without ‘active’ systems such as solar collectors. Passive solar design may involve increasing the area of your south façade and of the external surfaces of the building as a whole, since single-storey structures are more easily accessed by natural means.

With the exclusive approach the emphasis is on reducing the external surface area for a given volume (that is, achieving a compact form) and using high levels of insulation and advanced glazing systems, for instance – in other words ‘super-insulation’. Passive solar design is the subject of this section, while super-insulation is addressed in Chapter 3.

The two approaches are not entirely mutually exclusive and can be combined in a single building. Elements of passive solar design can be incorporated in the south façade of a super-insulated building, while the super-insulated approach would be a feature of the north side of a passive solar house. However, it may be easier to regard them as separate methods in order to examine the pros and cons of each.

Orientation and Solar Gain

A word here in case this book should ever get as far as the Southern Hemisphere – for ‘south’ read ‘north’ and vice versa. I remember a visiting academic from Australia who kept referring to passive solar houses being ‘north-facing’ – which was right where he came from, but very confusing for us.

Orientation, the direction your house faces, is something you will be able to influence only if you are building from scratch. Even then you will be limited by constraints such as planning permission, access and the position of adjacent dwellings. There may also be other considerations such as privacy and views which you wish to take into account. Such competing factors need to be reconciled to arrive at an optimum design.

Ideally, to make best use of heat and light from the sun your house should face south; this does not mean that the front entrance must be to the south, rather, the house should address available solar gains in terms of its layout and the area and position of glazing. So you would have higher levels of glazing on the south façade and your main daytime-occupied areas on the south side of the house. Nor does the house have to face south direct – 25 degrees or so on either side will not make that much difference.

The early Navaho native Americans sited their dwellings in large, south-facing caves, to provide shade in summer and solar gains in winter.

Dwellings too close together can overshadow one another (RHS). Locate your house to the north of your plot to maximize potential solar gains (LHS) while taking care not to deny solar gains to your neighbour to the north.

The early Navaho native Americans knew the value of passive solar design. They sited their settlements in large caves at the foot of south-facing cliffs, beside a river. The river gave them water, sustenance and a route for transportation. In addition to shelter and security, the cave gave them shade from the hot high summer sun while allowing the lower winter sun angles to penetrate to the rear of the caves (see top illustration above).

The ideal site is one gently sloping to the south, where there are less likely to be obstructions to solar gains in the form of other buildings, trees and the ground itself. In a smallish plot you should try to maximize the amount of south-facing garden by placing your house to the north end of the site (while taking care not to deny solar access to your neighbours to the north). This will reduce the likelihood of your being overshadowed by other buildings to the south and will also give you plenty of south-facing garden for the cultivation of plants and general amenity value (see the bottom illustration above). This works especially well if access is from the south since you will then have greater separation from the road, which will be better for acoustic and privacy reasons.

I remember once, just after completing my master’s course on energy in buildings, hitch-hiking in Cornwall and getting a lift from a local farmer. When I explained to him what I had been doing (passive solar design, mostly) he immediately understood and told me the story of how he had approached the design of his own house. It was situated on his own land and he had had ample opportunity to observe, over the seasons, the orientation and the height of the sun, exactly where it rose and set at different times of the year, the position of any obstructions, and also the wind direction through the seasons and especially where the coldest winds came from. He used this information, which he never wrote down but kept in his head, to position and lay out his house for optimum solar gains and protection from harsh winds. Fortunately, you do not need to spend years observing your own site, nor enrol on a master’s course, as the following section shows.

A sun path diagram for latitude 52 degrees North, showing solar altitude angle and orientation at different times of the day and year.

Sun-Path Diagrams

With the use of a sun-path diagram you can see where the sun will rise and set at different times of the year and its altitude angle (height in the sky) at any time of day. The sun-path diagram differs according to latitude and it is important to get the right one in order to be accurate in your calculations. Times shown are equivalent to GMT, that is, not taking into account daylight-saving adjustments.

The illustration below shows a sun-path diagram for latitude 52 degrees North. Imagine your house positioned in the centre – on an actual chart you could draw a thumbnail plan sketch of it there. Ideally, for a planned new build, face south or as near as possible. If constrained to be off-south, or in the case of an existing house, position the house on the diagram according to the actual orientation.

Cylindrical sun path diagram allowing examination of the shading effect of adjacent buildings, nearby trees and high ground. (Adapted from Achard and Gicquel, see ‘Useful Contacts’, section 2)

Then take a time of year, say 21 June, the summer solstice. At latitude 52 degrees N and reference longitude of the Greenwich meridian, the sun will rise in the north-east at approximately 3.30am GMT (or 4.30am BST). At solar noon it will be due south and reach a maximum altitude angle of just over 60 degrees, before setting at around 8.30am in the north-west. At the spring and the autumn equinox, 21 March and 21 September, the sun-path is the same, rising due east at 6am, reaching a maxi mum altitude angle at solar noon of around 38 degrees and setting due west at 6pm. At the winter solstice, 21–22 December, the sun does not rise until about 8.30am, tracking across from the south-east to the south-west and setting at around 3.30pm, reaching a maximum altitude angle at solar noon of only around 15 degrees. There are free programs which can be downloaded from the web for plotting sun-path diagrams – just type ‘sun-path diagram’ into your search engine. I found one at www.usc.edu/dept/architecture/mbs/tools/ecsdnld.html but there are sure to be others.

Note that you will need to adjust the times to represent longitude either side of the reference longitude. Add 4 mins for every 1° East and subtract 4 mins for every 1° West. Knowing where the sun will be and when, you can then plot the sun angles at different times of the day and year on to sketch plans and elevations to observe the actual solar access in different parts of the house. Rooms can be located on the plan and windows sized and positioned according to the desired solar access at a given time of the day and year. Roof overhangs can be sized accurately to keep out higher summer sun angles if desired. An alternative type of sun-path diagram is shown in the illustration on page 19. This is known as a cylindrical projection and allows you to examine more easily the effect of existing buildings, large trees and steep rises in contours, for example, such as might present obstructions to solar gains. The time of day and the duration of any obstruction at a given time of the year can be assessed, as shown. Again, you should be able to find down-loadable programs to provide this type of sun-path diagram.

This does not need to be a detailed or lengthy process, but it can be worthwhile to make sure that you select the optimum position on site, orientation and plan form layout for your house with respect to solar gains, while taking into account other constraints mentioned already.

Solar Resource

Just in case you should question the point of designing for solar access in this part of the world, especially in the more northerly parts of the British Isles, you may be surprised to know that southern parts of Scotland have similar average daily solar radiation levels to the midlands of England, while Northern Ireland has similar levels to the south-east of England (see the illustration on page 21).

The Midlands and the southerly regions of Ireland, meanwhile, are on a par with the south-west of England. Of course, higher latitudes tend to have lower average external temperatures – Tiree, on the west coast of Scotland, is one of the sunniest parts of the United Kingdom, but is also prone to being windy and therefore cold. However, if anything, that improves the viability of passive solar design – a more favourable balance of supply and demand.

Plan Form

Generally speaking, you should try to put your main daytime occupied areas on the south façade. Ideally, the kitchen is best located on the south-east side; there it will get the morning sun but be less prone to overheating (an obvious risk in kitchens) in the afternoon, when temperatures both inside and outside are more likely to have risen. The living room, on the other hand, may benefit from solar gains later in the day and could be located to the south-west side.

To the north you can place ‘buffer zones’ such as corridors, storage areas and garages – in fact, any area that does not need significant daylight or does not need to be heated to the same comfort temperatures as occupied areas. In a two-storey house a typical ground-floor layout might look something like this (see the illustration on page 22).

Bedrooms do not tend to be occupied during the daytime and therefore do not need to be south-facing, although they may benefit from morning sun and, generally, a bright, sunny aspect. Bathrooms can also be located to the south-east, to receive morning sun and help to combat the dampness that can be associated with them (although ventilation, dealt with in Chapter 8, is an equally if not more important issue). In a two-storey house, the first floor layout might look something like the illustration on top of page 23.

Map of the United Kingdom and Ireland showing approximate annual average levels of solar radiation. (Adapted from McNicholl and Lewis, see ‘Useful Contacts’, section 2)

For a single-storey dwelling, you will have more competition for the south façade. However, since bedrooms are not primarily occupied in the daytime, a layout such as this might be adopted (see illustration at bottom of page 23).

These plans are intended to represent the location of zones from a solar/thermal viewpoint only and should not be taken as blueprints for a house design. There will be other factors to be taken into account, including the functional interrelationship between rooms, space-allocation, visual amenity and the impact on the external appearance of façades.

Design for Future Changes

There will be a cost and energy advantage in taking into account possible future changes in use. For example, a bedroom could be made into a study. If there were a bathroom en suite that would not work so well unless access could be made from another bedroom instead. If you think you might want an additional bathroom in the future, this could be located in a suitably sized multi-purpose room. Ideally, this would be located adjacent (horizontally or vertically) to the existing bathroom, to facilitate the supply of hot and cold water and minimize disruption. At times these factors may conflict with passive solar and other functional requirements, but should be taken into account nevertheless, as part of a total life-time low-energy approach.

Notional ground-floor layout for a two-storey house from a passive solar viewpoint.

Notional first-floor layout for a two-storey house from a passive solar viewpoint.

Notional floor layout for a single-storey house from a passive solar viewpoint.

The Upside-Down House

If your site slopes to the north or is very tight and you cannot avoid overshadowing by existing buildings, all is not lost – but you will need to be more inventive in accessing those solar gains. You should still locate your building as far to the north of the site as possible, to reduce overshadowing, while at the same time taking care not to deny solar access to your neighbours to the north (see left-hand side of illustration in centre of page 17).

Convention has it that daytime-occupied areas are on the ground floor and bedrooms on the upper floor(s). However, this may not be ideal from a solar gain viewpoint, especially in a tight urban site (see right-hand side of illustration in centre of page 17). A solution may be to turn the house upside-down, so that the main daytime-occupied areas are raised up and more able to receive solar gains. This can be particularly effective on a tight site sloping steeply to the south, so that the ground floor at the north façade becomes the first floor at the south façade (see the illustration at top of page 24). If the main access is also from the north, people’s expectations on entering the building about the kinds of room you should have, can be met, while you are still getting the sun when and where you want it most.

The ‘upside-down’ house – a solution to a tight site, allowing solar gains to daytime-occupied spaces.

South-Facing Glazing

South-facing, vertical glazing has the property of being, to an extent, self-regulating with regard to solar gains. The illustration at the bottom of this page, shows that, in the summer, when the sun angle is higher, much of the solar radiation is reflected off the glazing, whereas in winter, with lower sun angles, more of the radiation is transmitted through the glazing. The higher sun angle also means that the area of window ‘seen’ by direct radiation (called the ‘solar aperture’) is lower in real terms in summer than in winter. Furthermore, south-facing glazing, even single glazing (which I do not recommend, by the way) is neutral over the year in terms of the balance of energy gained (from the sun) and lost (from the house). South-facing double glazing (or better) can be a significant net contributor to heating in the building over the year. However, care must be taken not to allow excessive solar gains, leading to overheating.

South-facing glazing is self-regulating to a degree, reflecting away more solar radiation from the high summertime sun and allowing more of the lower wintertime sun to pass through. (Adapted from Achard and Gicquel, see ‘Useful Contacts’, section 2)

Shading can be incorporated into the design of roof overhangs and window reveals, sized according to sun angles from the sun path diagram.

Solar Shading – Fixed or Movable?

There may be times when you want to screen out solar gains from your house. This can be done by deciduous trees, as mentioned previously; however, if none such exist where you want them, you will be waiting many years for the shading to become effective. There will be times, therefore, when you need the shading to be positioned in or on the building. This is best done in theory with external, movable shading, which allows you to screen out solar gains before they penetrate the glazing and which also can be adjusted depending on the weather conditions, time of day, time of year and so on.

However, external shading is exposed to the elements and movable systems are more prone to breakdown, especially if automated (in which energy is required for motors). Further, they may not fit in with your architectural aesthetic, in which case fixed shading may be more suitable. This can be incorporated into roof overhangs and depths of window reveals (see the illustration above) using angles from the sun-path diagram to determine the optimum dimensions. The disadvantage of fixed shading is, of course, that it is fixed – it cannot be repositioned at different times of the day or year. The next illustration on page 26 shows how this can be a disadvantage, especially in the spring time, when there may be modest solar gains available while the outside temperature is still low. Fixed shading, sized to screen out the higher summer sun angles, may block too much of the useful springtime solar gains.

Shutters, Blinds and Solar Control Films

A good set of shutters (something the Victorians knew) can serve well as shading devices, as well as providing security and night-time insulation (if well-fitting). Blinds can be used, of course, although they tend to be something of an afterthought. Careful consideration of the geometry of the building, as mentioned above, may reduce the need for blinds. While horizontal blinds work well on south façades, vertical louvres are more effective on east and west façades, when the sun is at a lower angle (see the illustration on page 27).

If blinds complement your desired look, glazing systems are available which incorporate the blinds between glazing layers. While more commonly seen in offices, for example, to provide privacy with glazed internal walls, these might be worth considering. Their advantages include space-saving and protection from dust build-up, although if the mechanism were to fail it could prove costly.

Fixed shading can work well at most times of the year except spring, when there is still a heating demand, but the sun, at a mid-height in the sky, may be screened out, thus denying solar gains. (Adapted from Achard and Gicquel, see ‘Useful Contacts’, section 2)

Other variations on the blind theme are prismatic blinds and parabolic blinds (see the illustration at the bottom of page 27