New Building Work
With every project you undertake to extend or improve your home, there will be different criteria to consider and problems to solve. And no doubt architects and builders will take different views about how best to design an extension or conversion to make them energy efficient as well as pleasant to live in. It can be a delicate balance to strike-often requiring practical solutions and compromises that you may not have considered in order to achieve your goals.
Food For Thought
Cost is always a consideration, but the cheapest route may not necessarily be the most cost effective regarding long-term energy efficiency. These aspects you need to discuss in detail with your professional advisers. The following suggestions are intended as pointers to the way you approach the design and build for the future.
Siting a New Extension
If possible, locate a new extension on the side of the house where it can gain most from the effect of sunlight – often referred to as passive solar energy or solar gain. Try to incorporate ground-floor south facing windows; and think about their height and proportion to maximise the winter sun’s deeper penetration into your home, thereby absorbing free energy from the sun to help you keep your home and reducing the need for electric illumination during the hours of daylight. You might want to consider a design that incorporates some form of shading above the windows that will prevent too much solar gain in the hot summer months but admit maximum daylight in winter when the sun is lower in the sky.
Where possible, it pays to install relatively small windows facing north, in order to reduce heat loss. Similarly, grouping wall storage on the north, east and west walls provide additional insulation.
Consider the overall shape, size and layout of your extension or conversion. This can have a significant effect on thermal performance and building costs. For example, a simple cube may be cheaper to construct than a long, thin rectangular shape. However, the latter could, in the right circumstances, provide a longer south facing surface, which offers more scope for passive solar energy in the form of free sunlight and heat.
Within the design, think about having an open plan layout, with the minimum number of door openings. One room or living space is easier to heat than several individual rooms. Lightweight stud partitions are the norm for dividing up internal spaces, especially upstairs; but talk to your designer or architect about incorporating at least some internal walls built from dense masonry, which will absorb heat during the day and then radiate warmth back into the living spaces as the house cools down.
Consider introducing buffer zones into the overall design. A porch, for example, serves as an air lock, reducing heat loss and providing extra insulation against drafts and cold. A glazed conservatory on the west wall of the house can harvest solar energy in the late afternoon, and provide useful space for drying clothes. A similar conservatory helps to delay night-time cooling of the interior.
Build Tight, Ventilate Right
Take measures to reduce losses from draughts and air movement throughout the external fabric of your home. The aim is to make the building envelope as airtight as possible and then provide a controllable ventilation. Good ventilation helps provide a comfortable and healthy environment by diluting or extracting moisture and pollutants – such as nitrogen oxides, carbon dioxide, tobacco smoke and house dust mites – from within your home. The worst pollutant, moisture vapour, should be extracted from bathrooms and kitchens, which is a prime source.
Householders usually think of fitting extractor fans to provide adequate ventilation, but ordinary fans extract heat along with the pollutants. Think about whether a heat recovery ventilator might be a better solution. These units remove heat from the air flowing out of the building and then use it to warm the fresh air moving in the opposite direction. It is possible to have a centrally placed heat-recovery unit that extracts stale air from the more heavily polluted areas of the home – which is also where most heat is generated – and reintroduce fresh warmed air into areas of the home that would benefit most.
Mechanical extraction systems have to be powered by electricity, but you could have your new house built around passive stack ventilation – which works on the principle that natural convection will extract the relatively warm moist air inside the building while at the same time drawing in fresh air through trickle vents mounted in the windows or outside walls. Once installed, this type of whole-house ventilation won’t cost a penny to run.
Installing adequate insulation is perhaps the most important measure you can take to minimise your energy requirements. There are a number of materials you can use, including glass fibre, mineral wool, polystyrene and cellulose (recycled paper insulation). In the near future, there will be other natural materials to choose from, such as straw, hemp and wool. One advantage of using these materials is that they are produced locally and do not have to be imported. Plan ahead and build for the future by incorporating high levels of insulation.
Roof insulation is comparatively simple to install in an existing building, installing wall insulation can be difficult if not possible in some older houses. However, when building a new home or extension be sure to take full advantage of effective insulation, which is easy to incorporate into the walls during construction. Minimise the potential for ‘thermal bridges’ – vulnerable areas in the external fabric where heat can travel easily to the outside. Make sure that insulation is continuous, eliminating cold spots where condensation can occur.
Floor insulation is essential in new building work and can be installed with comparative ease when compared with a similar exercise in an older property.
When designing the roof covering for a new extension or loft conversion, try to construct what is known as warm roof system, whereby the insulation is contained within the sloping roof. This allows spaces within the roof void to be kept warm and used as habitable space. It also avoids having to ventilate the roof void above the insulated ceiling, thus reducing drafts and heat loss.
Where practicable, use timber as your prime building material. This is, without doubt, the ‘greenest’ structural material available, provided you can ensure the wood comes from certifiable sustained managed sources. It also has the advantage of being a beautiful material that is relatively easy to work.
In addition, consider using second-hand materials, such as used bricks and recycled steel. And look for building blocks made from a high content of granulated blast furnace slag. Rammed-earth construction is now a recognised means of building walls, you would need a professional to check that the soil is suitable in the area where the building is to be constructed.
Take Advantage Of Natural Light
Every modern building or extension must be wired for light and power, but when given the opportunity, it makes sense to take maximum advantage of natural light to eliminate dark corridors and landings. Conventional roof lights – windows built into the roof structure – is one solution, but many architects are recommending ‘light pipes’ to introduce daylight into the more inaccessible parts of a building. Essentially, the light is gathered from outside (usually at roof level) and transferred down a highly reflective tube to a diffuser mounted on the ceiling. Some fittings include a ventilator and an electric light so the same source is used to illuminate the interior at night.
For your new bathrooms and cloakrooms, choose slimline dual flush sanitary ware that uses relatively little water to flush the WC. And why use drinking water to flush the toilet or wash your clothes, when there are viable options for collecting rainwater for such purposes? Large storage tanks buried below ground are used to collect rainwater that’s shed from your roof. This harvested water is pumped directly to the toilet systems and, if you wish, to your washing machine. Being soft water, it is ideal for washing clothes. The costs of installing and running a system that recycles rainwater is considered by some environmentalists to be counter-productive; however, a number of local authorities are already insisting that building contractors include such systems in their plans for new housing developments. If you can afford it, you could install a similar system that collects greywater-water discharge from wash hand basins, baths and showers. Unlike rainwater, which is relatively pure, grey water requires a settlement tank and filtration. Water from your kitchen sink, which contains grease and other contaminants, is not suitable for reuse.
You have more options to choose from when deciding on a heating system for a new house. You can install concealed ducting that will distribute heated air to every room in the building. Electronically heated elements built into the structure will radiate heat gently across the entire floor surface. This type of installation is often used to heat extensions. Most people still opt for a conventional wet central heating system, driven by gas fired or oil-burning boiler. If you have the option, choose a condensing boiler, which is more economical to run.
This is a much-disputed issue, but one which is definitely gaining popularity. You can hope to do little more than contributing to heating your water if you install solar panels on the roof of an existing house. However, by using photovoltaic cells in the form of roof tiles, you can safely cover a large area of the south facing roof and thereby collect enough solar energy to recover a significant proportion of your electricity bill.
With a small outlay, you can install dedicated solar panels that are designed to power a single lamp in order to illuminate a shed, garage or porch. This seems an ideal way to provide illumination without having to run an electric cable the length of your garden.
It may seem little an attractive proposition to harness the wind to provide electrical power in your home. However, unless you live in a rural area of the country, where power is unlikely to make a measurable difference to your electricity bill. It might be worth erecting a turbine high up on a well-supported wall, but, even then, you would need to live on a fairly exposed site where wind speeds are favourable constant. You will need consent from your local authority before you install a wind turbine.