Energy conservation

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This article is about decreasing energy consumption. For the law of conservation of energy in physics, see Conservation of energy.

Energy conservation is the practice of decreasing the quantity of energy used. It may be achieved through efficient energy use, in which case energy use is decreased while achieving a similar outcome, or by reduced consumption of energy services. Energy conservation may result in increase of financial capital, environmental value, national security, personal security, and human comfort. Individuals and organizations that are direct consumers of energy may want to conserve energy in order to reduce energy costs and promote economic security. Industrial and commercial users may want to increase efficiency and thus maximize profit.

Introduction

Electrical energy conservation is an important element of energy policy. Energy conservation reduces the energy consumption and energy demand per capita, and thus offsets the growth in energy supply needed to keep up with population growth. This reduces the rise in energy costs, and can reduce the need for new power plants, and energy imports. The reduced energy demand can provide more flexibility in choosing the most preferred methods of energy production.

By reducing emissions, energy conservation is an important part of lessening climate change. Energy conservation facilitates the replacement of non-renewable resources with renewable energy. Energy conservation is often the most economical solution to energy shortages, and is a more environmentally benign alternative to increased energy production.

[edit] By country

[edit] United States

The examples and perspective in this article may not represent a worldwide view of the subject. Please improve this article or discuss the issue on the talk page. (August 2008)

The United States is currently the largest single consumer of energy. The U.S. Department of Energy categorizes national energy use in four broad sectors: transportation, residential, commercial, and industrial.^[1]

U.S. Energy Flow Trends - 2002. Note that the breakdown of useful and waste energy in each sector (yellow vs. grey) is estimated arbitrarily and is not based on data.

Energy usage in transportation and residential sectors (about half of U.S. energy consumption) is largely controlled by individual domestic consumers. Commercial and industrial energy expenditures are determined by businesses entities and other facility managers. National energy policy has a significant effect on energy usage across all four sectors.

[edit] Transportation

The transportation includes all vehicles used for personal or freight transportation. Of the energy used in this sector, approximately 65% is consumed by gasoline-powered vehicles, primarily personally owned. Diesel-powered transport (trains, merchant ships, heavy trucks, etc.) consumes about 20%, and air traffic consumes most of the remaining 15%.^[2]

The two oil supply crisis of the 1970s spurred the creation, in 1975, of the federal Corporate Average Fuel Economy (CAFE) program, which required auto manufacturers to meet progressively higher fleet fuel economy targets. The next decade saw dramatic improvements in fuel economy, mostly the result of reductions in vehicle size and weight which originated in the late 1970s, along with the transition to front wheel drive. These gains eroded somewhat after 1990 due to the growing popularity of sport utility vehicles, pickup trucks and minivans, which fall under the more lenient "light truck" CAFE standard.

In addition to the CAFE program, the U.S. government has tried to encourage better vehicle efficiency through tax policy. Since 2002, taxpayers have been eligible for income tax credits for gas/electric hybrid vehicles. A "gas-guzzler" tax has been assessed on manufacturers since 1978 for cars with exceptionally poor fuel economy. While this tax remains in effect, it currently generates very little revenue as overall fuel economy has improved. The gas-guzzler tax ended the reign of large cubic-inched engines from the musclecar era.

Another focus in gasoline conservation is reducing the number of miles driven. An estimated 40% of American automobile use is associated with daily commuting. Many urban areas offer subsidized public transportation to reduce commuting traffic, and encourage carpooling by providing designated high-occupancy vehicle lanes and lower tolls for cars with multiple riders. In recent years telecommuting has also become a viable alternative to commuting for some jobs, but in 2003 only 3.5% of workers were telecommuters. Ironically, hundreds of thousands of American and European workers have been replaced by workers in Asia who telecommute from thousands of miles away.

Fuel economy-maximizing behaviors also help reduce fuel consumption. Among the most effective are moderate (as opposed to aggressive) driving, driving at lower speeds, using cruise control, and turning off a vehicle's engine at stops rather than idling. A vehicle's gas mileage decreases rapidly highway speeds, normally above 55 miles per hour (though the exact number varies by vehicle). This is because aerodynamic forces are proportionally related to the square of an object's speed (when the speed is doubled, drag quadruples). According to the U.S. Department of Energy (DOE), as a rule of thumb, each 5 mph (8.0 km/h) you drive over 60 mph (97 km/h) is similar to paying an additional $0.30 per gallon for gas ^[3] The exact speed at which a vehicle achieves it's highest efficiency varies based on the vehicle's drag coefficient, frontal area, surrounding air speed, and the efficiency and gearing of a vehicle's drive train and transmission.

[edit] Residential sector

The residential sector refers to all private residences, including single-family homes, apartments, manufactured homes and dormitories. Energy use in this sector varies significantly across the country, due to regional climate differences and different regulation. On average, about half of the energy used in U.S. homes is expended on space conditioning (i.e. heating and cooling).

The efficiency of furnaces and air conditioners has increased steadily since the energy crises of the 1970s. The 1987 National Appliance Energy Conservation Act authorized the Department of Energy to set minimum efficiency standards for space conditioning equipment and other appliances each year, based on what is "technologically feasible and economically justified". Beyond these minimum standards, the Environmental Protection Agency awards the Energy Star designation to appliances that exceed industry efficiency averages by an EPA-specified percentage.

Despite technological improvements, many American lifestyle changes have put higher demands on heating and cooling resources. The average size of homes built in the United States has increased significantly, from 1,500 sq ft (140 m²) in 1970 to 2,300 sq ft (210 m²) in 2005. The single-person household has become more common, as has central air conditioning: 23% of households had central air conditioning in 1978, that figure rose to 55% by 2001.

As furnace efficiency gets higher, there is limited room for improvement--efficiencies above 85% are now common. However, improving the building envelope through better or more insulation, advanced windows, etc., can allow larger improvements. The passive house approach produces superinsulated buildings that approach zero net energy consumption. Improving the building envelope can also be cheaper than replacing a furnace or air conditioner.

Even lower cost improvements include weatherization, which is frequently subsidized by utilities or state/federal tax credits, as are programmable thermostats. Consumers have also been urged to adopt a wider indoor temperature range (e.g. 65 °F (18 °C) in the winter, 80 °F (27 °C) in the summer).

One underutilized, but potentially very powerful means to reduce household energy consumption is to provide real-time feedback to homeowners so they can effectively alter their energy using behavior. Recently, low cost energy feedback displays, such as The Energy Detective or wattson [1], have become available. A study of a similar device deployed in 500 Ontario homes by Hydro One [2] showed an average 6.5% drop in total electricity use when compared with a similarly sized control group.

Standby power used by consumer electronics and appliances while they are turned off accounts for an estimated 5 to 10% of household electricity consumption, adding an estimated $3 billion to annual energy costs in the USA. "In the average home, 75% of the electricity used to power home electronics is consumed while the products are turned off." [3]

[edit] Home energy consumption averages

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• Home heating systems, 30.7%
• Water heating, 13.5%
• Home cooling systems, 11.5%
• Lighting, 10.3%
• Refrigerators and freezers, 8.2%
• Home electronics, 7.2%
• Clothing and dish washers, 5.6% (includes clothes dryers, does not include hot water)
• Cooking, 4.7%
• Computers, 0.9%
• Other, 4.1% (includes small electrics, heating elements, motors, pool and hot tub heaters, outdoor grills, and natural gas outdoor lighting)
• Non end-user energy expenditure, 3.3%^[4]

Energy usage in some homes may vary widely from these averages. For example, milder regions such as the southern U.S. and Pacific coast of the USA need far less energy for space conditioning than New York City or Chicago. On the other hand, air conditioning energy use can be quite high in hot-arid regions (Southwest) and hot-humid zones (Southeast) In milder climates such as San Diego, lighting energy may easily consume up to 40% of total energy. Certain appliances such as a waterbed, hot tub, or pre-1990 refrigerator use significant amounts of electricity. However, recent trends in home entertainment equipment can make a large difference in household energy use. For instance a 50" LCD television (average on-time= 6 hours a day) may draw 300 Watts less than a similarly sized plasma system. In most residences no single appliance dominates, and any conservation efforts must be directed to numerous areas in order to achieve substantial energy savings. However, Ground, Air and Water Source Heat Pump systems are the more energy efficient, environmentally clean, and cost-effective space conditioning and domestic hot water systems available (Environmental Protection Agency), and can achieve reductions in energy consumptions of up to 69%.

[edit] Best building practices

Current best practices in building design, construction and retrofitting result in homes that are profoundly more energy conserving than average new homes. This includes insulation and energy-efficient windows and lighting ^[5]. See Passive house, Superinsulation, Self-sufficient homes, Zero energy building, Earthship, MIT Design Advisor, Energy Conservation Code for Indian Commercial Buildings.

Smart ways to construct homes such that minimal resources are used to cooling and heating the house in summer and winter respectively can significantly reduce energy costs.

[edit] Commercial sector

The commercial sector consists of retail stores, offices (business and government), restaurants, schools and other workplaces. Energy in this sector has the same basic end uses as the residential sector, in slightly different proportions. Space conditioning is again the single biggest consumption area, but it represents only about 30% of the energy use of commercial buildings. Lighting, at 25%, plays a much larger role than it does in the residential sector.^[6] Lighting is also generally the most wasteful component of commercial use. A number of case studies indicate that more efficient lighting and elimination of over-illumination can reduce lighting energy by approximately fifty percent in many commercial buildings.

Commercial buildings can greatly increase energy efficiency by thoughtful design, with today's building stock being very poor examples of the potential of systematic (not expensive) energy efficient design (Steffy, 1997). Commercial buildings often have professional management, allowing centralized control and coordination of energy conservation efforts. As a result, fluorescent lighting (about four times as efficient as incandescent) is the standard for most commercial space, although it may produce certain adverse health effects.^{[7][8][9][10]} Potential health concerns can be mitigated by using newer fixtures with electronic ballasts rather than older magenetic ballasts. As most buildings have consistent hours of operation, programmed thermostats and lighting controls are common. However, too many companies believe that merely having a computer controlled Building automation system guarantees energy efficiency. As an example one large company in Northern California boasted that it was confident its state of the art system had optimized space heating. A more careful analysis by Lumina Technologies showed the system had been given programming instructions to maintain constant 24 hour temperatures in the entire building complex. This instruction caused the injection of nighttime heat into vacant buildings when the daytime summer temperatures would often exceed 90 °F (32 °C). This mis-programming was costing the company over $130,000 per year in wasted energy (Lumina Technologies, 1997). Many corporations and governments also require the Energy Star rating for any new equipment purchased for their buildings.

Solar heat loading through standard window designs usually leads to high demand for air conditioning in summer months. An example of building design overcoming this excessive heat loading is the Dakin Building in Brisbane, California, where fenestration was designed to achieve an angle with respect to sun incidence to allow maximum reflection of solar heat; this design also assisted in reducing interior over-illumination to enhance worker efficiency and comfort.

Recent advances include use of occupancy sensors to turn off lights when spaces are unoccupied, and photosensors to dim or turn off electric lighting when natural light is available. In air conditioning systems, overall equipment efficiencies have increased as energy codes and consumer information have begun to emphasise year round performance rather than just efficiency ratings at maximum output. Controllers that automatically vary the speeds of fans, pumps, and compressors have radically improved part-load performance of those devices. For space or water heating, electric heat pumps consume roughly half the energy required by electric resistance heaters. Natural gas heating efficiencies have improved through use of condensing furnaces and boilers, in which the water vapor in the flue gas is cooled to liquid form before it is discharged, allowing the heat of condensation to be used. In buildings where high levels of outside air are required, heat exchangers can capture heat from the exhaust air to preheat incoming supply air.

[edit] Industrial sector

The industrial sector represents all production and processing of goods, including manufacturing, construction, farming, water management and mining. Increasing costs have forced energy-intensive industries to make substantial efficiency improvements in the past 30 years. For example, the energy used to produce steel and paper products has been cut 40% in that time frame, while petroleum/aluminum refining and cement production have reduced their usage by about 25%. These reductions are largely the result of recycling waste material and the use of cogeneration equipment for electricity and heating.

Another example for efficiency improvements is the use of products made of High temperature insulation wool (HTIW) which enables predominantly industrial users to operate thermal treatment plants at temperatures between 800 and 1400°C. In these high-temperature applications, the consumption of primary energy and the associated CO₂ emissions can be reduced by up to 50% compared with old fashioned industrial installations. The application of products made of High temperature insulation Wool is becoming increasingly important against the background of the currently dramatic rising cost of energy.

The energy required for delivery and treatment of fresh water often constitutes a significant percentage of a region's electricity and natural gas usage (an estimated 20% of California's total energy use is water-related.^[11]) In light of this, some local governments have worked toward a more integrated approach to energy and water conservation efforts.

To conserve energy, some industries have begun using solar panels to heat their water.^{[citation needed]}

Unlike the other sectors, total energy use in the industrial sector has declined in the last decade. While this is partly due to conservation efforts, it's also a reflection of the growing trend for U.S. companies to move manufacturing operations overseas.

[edit] United Kingdom

Main article: Energy use and conservation in the United Kingdom

Energy conservation in the United Kingdom has been receiving increased attention over recent years. Key factors behind this are the Government's commitment to reducing carbon emissions, the projected 'energy gap' in UK electricity generation, and the increasing reliance on imports to meet national energy needs. Domestic housing and road transport are currently the two biggest problem areas.

The UK Government has jointly funded the Energy Saving Trust to promote energy conservation at a consumer, business and community level since 1993.

[edit] Jevons paradox

Main article: Jevons paradox

Standard economic theory suggests that technological improvements that increase energy efficiency will tend to increase, rather than reduce energy use. This was first observed by William Stanley Jevons in 1865 and is called the Jevons Paradox. In The Coal Question, Jevons argued that, "It is a confusion of ideas to suppose that economical use of fuel is equivalent to diminished consumption. The very contrary is the truth."

The Jevons paradox was later revisited by the economists Daniel Khazzoom and Leonard Brookes in a series of papers about energy conservation. In 1992, the US economist Harry Saunders dubbed this hypothesis the Khazzoom-Brookes Postulate, and showed that it was true under a wide range of assumptions.^[12] Increased energy efficiency tends to increase energy consumption by two means. Firstly, increased energy efficiency makes the use of energy relatively cheaper, thus encouraging increased use. Secondly, increased energy efficiency leads to increased economic growth, which pulls up energy use in the whole economy.

This does not imply that increased fuel efficiency is worthless. Increased fuel efficiency enables greater production and a higher quality of life. For example, a more efficient steam engine allowed the cheaper transport of goods and people that contributed to the Industrial Revolution. However, energy conservation cannot be achieved through increased efficiency alone. In order for efficiency gains to improve energy conservation, the ecological economists Mathias Wackernagel and William Rees suggest that cost savings from efficiency gains be "taxed away or otherwise removed from further economic circulation. Preferably they should be captured for reinvestment in natural capital rehabilitation."^[13]

[edit] Issues with energy conservation

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Critics and advocates of some forms of energy conservation make the following arguments:

• It may be difficult for home owners or small business to justify investment in some energy saving measures. Often the available money has higher priorities, and in many cases the time and cost investment is not worthwhile.

• Condensing boilers are much more efficient than older types. Energy savings are achieved by extracting more heat, venting less heat externally. However the increased complexity results in more frequent breakdowns and much higher total servicing costs, and whether the end result is a gain is debated.

• Refrigeration is also a major factor of energy consumption, electronic Energy saving modules (ESM) can be added to some existing HVAC and refrigeration systems at little cost to conserve electricity.

• Some retailers argue that bright lighting stimulates purchasing. Health studies have demonstrated that headache, stress, blood pressure, fatigue and worker error all generally increase with the common over-illumination present in many workplace and retail settings (Davis, 2001), (Bain, 1997). It has been shown that natural daylighting increases productivity levels of workers, while reducing energy consumption.^[14] Consumers are also motivated by a number of factors, and corporate stewardship may provide an incentive for shoppers to visit stores who conserve energy. Some believe lower overhead costs may allow retailers to lower prices, stimulating consumption, however few business managers seem to agree with this view.

• The use of telecommuting by major corporations is a significant opportunity to conserve energy, as many Americans now work in service jobs that enable them to work from home instead of commuting to work each day. ^[15]

• Electric motors consume more than 60% of all electrical energy generated and are responsible for the loss of 10 to 20% of all electricity converted into mechanical energy. ^[16] No doubt, electricity consumption and associated loss by electric motors will continually grow; particularly, as the transportation sector moves to vehicles with electric drivetrains. Migrating or retrofitting any applied base of electric motors (and electric generators) with energy efficient electric motor and generator technology and systems, such as the brushless wound rotor doubly fed electric motor or generator, can dramatically reduce energy consumption and resulting emissions of carbon dioxide (CO2) and sulphur dioxide (SO2) to the atmosphere. As a bonus, the technology can have a payback period of less than a year depending on use factors.

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Zero Carbon Homes

With green issues high on the agenda this year there’s a lot being talked about and introduced to tackle one of the biggest contributors of climate change – our homes. With 27% of the UK’s overall CO2 emissions coming from our homes, reducing energy in this area of our lives is essential. Going ‘zero carbon’ in the home is one of the new terms that have been debated, in parliament and throughout the housing industry. It sounds impressive, if a little too good to be true – so what is zero carbon all about?

What Does Zero Carbon Mean?

Put simply, a zero carbon home uses less energy than it generates over a set period of time. A carbon footprint is calculated for the full life of the home, including the CO2 emissions created during the build of a house and its day-to-day energy needs. This figure is then offset by the property’s ability to produce the energy it needs itself – through wind turbines, solar panels and other renewable sources of energy – all important elements that have been purpose-built into the home in the design.

If a property is able to become fully sustainable, and even have excess renewable energy supplies that can benefit others, then it’s become a fully zero carbon home. Part of the key to going zero carbon in the home is an awareness of how to make the property itself more energy efficient and finding ways to reduce our everyday energy needs.

How Is The UK Going Zero Carbon?

Making our homes zero carbon has hit the headlines recently, with plans unveiled by the government in December 2006 that would help to make all new homes in the UK zero carbon by an ambitious 2016. It has set out plans to encourage property developers and builders to include carbon efficient measures into building design, including sources of renewable energy generation, energy efficient walls and roofs, as well as devising new ways to encourage minimal energy consumption.

Gordon Brown also announced in his pre-budget report last December that eventually it would be compulsory for new buildings to be zero carbon, and that the UK was leading the way towards becoming a nation of green homeowners. Crucially, Brown also announced that environmentally-friendly homes would be exempt from stamp duty, making them cheaper for people to buy.

What About Existing Homes?

For existing homes, the new Energy Performance Certificates or EPCs, which rate a property between A-G on its energy efficiency, look likely to have a high impact in putting green issues high on homebuyer’s and seller’s wish lists – when they are eventually introduced.

As part of the controversial new Home Information Packs in England and Wales, it was announced that EPCs would be delayed until August 2007, when only property sales of four or more bedrooms would need to be graded on their energy efficiency. These will then be rolled out to smaller property types when more energy assessors, the trained inspectors who grade homes on energy efficiency, are available.

Welcoming Changes

The measures being taken to help make the UK’s homes zero carbon have been welcomed by environmental groups. According to Friends of the Earth campaigner Liz Murray: 'The key to low- and zero-carbon housing is maximising energy efficiency of these homes in the first instance and embedding within the design a means by which energy can be generated using micropower technologies as part of the structure. 'The sooner all developers do this the better.'

The Reality of Zero Carbon

But how easy is it to build a zero carbon home? It’s certainly not a cheaper way for developers to create homes, but it is possible by using innovative design and materials, and will be more and more common once measures are put in place that make green building compulsory. Currently however only a very small number of the 150,000 homes built each year are sufficiently green enough to be classified with zero carbon status.

But zero carbon homes do exist, most famously the BedZED housing estate in Sutton. There, a BedZED home needs only 10% of the energy needed to heat a standard home to the same temperature, and has a range of renewable energy sources that make it completely zero carbon.

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Warning from the International Energy Agency

Energy consumption is tied closely in to climate change issues, with the burning of fossil fuels impacting on global CO2 levels in particular. This makes the prospect of an ever increasing demand for more and more energy a bleak picture for the environment in the future indeed.

So when the International Energy Agency warned that an anticipated 50% increase in energy needs by 2030 would be served largely by coal reserves, there was an outcry from scientists and climate change advisers.

Who Are The International Energy Agency?

The International Energy Agency, or IEA, is a worldwide advisory body providing information to governments across world about all things energy related. This includes long-term analysis of the world's energy requirements, and projections on how this need will be served - in other words, the level of non-renewable and renewable energy sources needed for the world's commerce, industry and individuals.

Anticipated Growth In Energy Needs

According to the IEA's chief executive, Nobuo Tanaka, energy needs - if left unchecked by governments across the world - would rise by 50% by 2030 alone, and this need could only be realistically provided by coal reserves. This could have devastating effects on global CO2 levels and undo the global efforts to help fight climate change. If levels of energy creation from coal raised by this amount, the amount of CO2 emitted into the atmosphere as a result of this would rise by a staggering 57% - from 27 giga tonnes to 42 giga tonnes a year.

The Rise Of Industrialising Nations

Much of the increase in anticipated energy growth can be attributed to the industrialisation and economic development of several large countries - most notably India and China, whose joint populations total two billion. Levels of energy would need to complement a changing fortune for these two nations.

According to Mr Tanaka: " The emergence of new major players in global energy markets means that all countries must take vigorous, immediate and collective action to curb runaway energy demand… rapid economic development will undoubtedly continue to drive up energy demand in China and India… this is a legitimate aspiration that needs to be accommodated and supported by the rest of the world."

The Alternative Policy Scenario

The outlook for energy was somewhat less negative after the IEA took into consideration the various different long-term policies and commitments different nations had taken in order to curb their carbon footprint and reduce overall energy needs - including binding protocols such as the Kyoto treaty. Projections using these figures then suggest that CO2 emissions from energy would rise by 25% by 2030. This is still a worrying increase but halves the worst case scenario picture, which was based on nothing being done to check energy consumption.

A Global Solution To The IEA's Warning

There is, according to the IEA, the possibility to stabilise energy consumption at 2005 levels by 2030 - but that solution needs to be implemented globally and quickly. This includes an increased reliance of nuclear energy and more investment into CO2 storage technology.

It's a stark warning from the IEA, and is yet another reason why governments need to act on climate change now. Here in the UK, the climate change bill was announced in parliament, a binding commitment to reduce overall CO2 emissions, to the backdrop of this news. Elsewhere, other parts of the world are also beginning to act accordingly.

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Winter Energy Savers

When the nights draw in and the chill of winter hits our homes it’s the time to wrap up warm and enjoy the indoors. Unfortunately, it’s also the season that we tend to rack up high energy bills – especially after all the major energy companies raised their prices throughout 2006.

However there are ways to minimize the blow to your wallet this winter and still keep your home snug. If you’re smarter with the energy you use and prepare your property in advance of cold weather, you can keep winter energy costs as low as possible.

Insulate your Home

A lot of the energy we use to heat our homes is wasted due to properties being ill-prepared and under-insulated. Up to a third of heat produced in the home is lost through the walls, but some forward planning before the cold snap starts will help to retain as much heat in your home as possible.

Consider installing cavity wall insulation. This helps to keep heat inside the home and evenly distributes it around each room. Cavity wall insulation works by being injected into the cavity between the inner and outer layers of brickwork in your external wall and acting as a barrier to heat loss. Insulating your walls will cost around £260 for an average sized home, but with an annual energy bill reduction of £130-160, the investment will pay for itself after two years.

Invest in Draught Excluders

There are also some energy saving tricks you can put into action straightaway. Firstly, install draught excluders underneath all your doors. This is a quick and simple way to retain energy in each room by stopping cold draughts from circulating. Draught excluders can be inexpensively purchased from hardware and DIY shops, or you can make your own ‘door snake’ with leftover carpet cuttings and materials.

Similarly, you should also draught proof all windows in the home, particularly single glazed panes. Applying a sealant or self-adhesive strip will achieve this at a reasonable cost. Alternatively, investing in double glazing throughout your home will also reduce escaping heat significantly. If you’re unable to double glaze your entire property, think about double glazing for the rooms you tend to use and heat the most.

Keep Your Boiler in Good Shape

Your boiler going on the blink in the middle of winter can be both a cold and expensive inconvenience. Give your boiler an MOT before the winter months, and consider the benefits of taking out heating cover for your boiler. This will protect you from an unexpected repair bill if the worst does happen.

The average boiler lasts between 10-15 years, so next time you’re replacing yours, invest in a high efficiency condensing boiler that can cut your energy bills by £190-240 a year and significantly cut CO2 emissions. Or an extra money saver for your existing boiler is to fit an insulating jacket.

Take a Closer Look at your Energy Bills

Make sure you’re with the best value energy supplier before winter draws in and your bills start increasing. You should check if your current provider has any offers that you’re not currently taking advantage of. It’s also worth carrying out a check of tariffs offered by other energy suppliers. Try using an impartial comparison and switching website to see if you could save money by switching to another energy supplier.

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Water Saving Tips

Despite being an island surrounded by water it doesn’t take long for some areas in the UK to run dry come summer. During 2006, several water companies issued hosepipe and sprinkler bans, and almost declared further restrictions on the remaining supply.

Being efficient all year round with water will help ensure our reservoirs remain at a healthy level. It also pays to reduce the amount you use, as more and more of us are switching or move to water metered supplies. Here are some water saving tips to help you on your way to reducing, preserving and using water wisely.

Fix Leaky Taps

Not only are they irritating to hear day in, day out, they also waste an excessive amount of water. A tap losing one drop a second wastes 15 litres of water a day. Usually tightening the tap will solve the problem, otherwise enlist the help of someone who knows what they’re doing.

Take a Shower instead of a Bath

A long soak in the bath is a great relaxant, but did you know that having just one can use up to 100 litres of water? An average shower cuts your water consumption by a third and leaves you just as clean, so have a bath as a treat instead of part of your daily routine. However, beware – some modern power showers used are also water guzzlers, so turn down from the maximum setting to use in moderation.

Save Water in the Kitchen

There are lots of things you can do in the kitchen to help save water. Instead of running the tap till it gets cold to drink, keep a handy jug of chilled water to drink. When boiling the kettle to cook or make a cup of tea, only boil as much as you need. And rather than wash potatoes and other vegetables under the tap, wash all of them in a single bowl of water. Even making small changes like these will help reduce daily water consumption.

Water Efficient Appliances

You can make high water consumption products more efficient in the way they run by taking advantage of some of the free or cheap products that the main water companies offer. For example, a hippo or save-a-flush is an unnoticeable addition to your toilet but can save up to 2,000 gallons of water a year.

In the long term, you may wish to consider a dual flush toilet that flushes with less water. And when you next come to replace washing machines or dishwashers, try and purchase an energy efficient model as these are also designed to use less water.

Install a Water Butt

Gathering rain water outside using a water butt is an efficient and cheap way to water flowers and plants. It can keep your garden in top condition without using a sprinkler or hosepipe. Water butts, which are lightweight and barrel sized, are usually available at a discounted price from your council.

Turn Off the Tap

It’s an old cliché, but turning the tap off when brushing your teeth saves more water than you may realise - over six litres every minute. If the entire adult population of England and Wales remembered to do this, we could save 180 mega litres a day, enough to supply nearly 500,000 homes. Also try and make a conscious attempt to turn off the tap when shaving and washing your face in the basin.

Only Wash a Full Load

Whether it’s a load of washing in the washing machine or dishes in the dishwasher, only switch on if you’ve got a full load to wash. That way, you’ll be making optimum use of the water that’s used in a cycle, and avoid using these appliances needlessly. It’s also possible on most modern machines to select a half load option which will reduce the amount of water used accordingly.

Sprinklers and Hosepipes

Hosepipes use around 1,000 litres of water an hour; sprinklers even more. Leave them in the shed in favour of more water efficient alternatives. Use leftover water and rainwater from your water butt for the garden. Washing the car the old fashioned way – with bucket and sponge – is equally as effective but miles more efficient.

Pipe Lagging

Ensure your water pipes and external taps are lagged in time for the cold winter months. If pipes are more heat efficient, it will help avoid them freezing, leaking or even bursting, which wastes high quantities of water. Insulating pipes will also save you on your winter heating bills.

Flush with Care

Currently the average person in the UK flushes the toilet 35 times a week, but not always for the right reasons. Try and avoid flushing away tissues, cotton balls, make-up facial wipes. Put them in the bin to avoid a needless flush.

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Passive Solar Energy use

By Emil Bedi, CANCEE and Hakan Falk, "Energy Saving Now".

Comments by Energy Saving Now.
The following sample house, in article about Passive Solar design, do not comply with our understanding of sustainability or efficiency. It represents popular opinions within the Architectural community and from this point of view it is very interesting. It also promotes an understanding of thermal mass and wider temperature bandwidth, that are essential issues for energy saving and as such very positive. About the sample (not the principles), we have the following to clarify,

• The displayed building is very nice to look at and we find it attractive from a design perspective.
  
  
• Many of the principles mentioned are important and complaint with what we are promoting on Energy Saving Now.
  
  
• The sample building with large glass areas and the functionality is only valid for very limited geographical areas.
  
  
• The savings are expected to be 15% and we assume that this is in comparison to normal buildings in USA and the area where it is built. If it is compared to a building according to the Swedish Building Codes, the energy consumption will be 2 to 3 times higher than the Swedish house. If it is located in a cold or warm climate, the surface temperature on the glassed areas will be very uncomfortable.
  
  
• A 15% energy saving can be achieved in many easier ways and even in existing buildings. If you use paint for the building, that are Aluminium based instead of normally Titan, the saving will be around 15% and work in all geographical areas. It would also provide better comfort.
  
  
• With the extended allowed temperature variation and operation policies, nearly all buildings will give 15% or better performance.
  
  
• Sustainable buildings, based on long experience, was standard until a couple of hundred years ago. They used the location, thermal mass and/or insulation. A very common feature was the small window openings and covering of the windows to regulate the indoor temperatures depending on time of day and seasonal changes.

The values of the sample are the emphasises on thermal mass and natural regulation of the environment. This is opposing the current energy wasting design principles in the building and HVAC industry and as such very refreshing. The sample can be discussed and there are much more efficient ways to design for energy efficiency. We suggest that you carefully assimilate the information on "Energy Saving Now", before you go ahead and build. But if you absolutely want to build a glass house, read this article carefully.

Article about passive solar design.
Passive solar design, or climate responsive buildings use existing technologies and materials to heat, cool and light buildings. They integrate traditional building elements like insulation, south-facing glass, and massive floors with the climate to achieve sustainable results. These living spaces can be built for no extra cost while increasing affordability through lower energy payments. In many countries they also keep investment in the local building industry rather than transferring them to short term energy imports. Passive solar buildings are better for the environment while contributing to an energy independent, sustainable energy future.
Passive solar system uses the building structure as a collector, storage and transfer mechanical equipment. This definition fits most of the more simple systems where heat is stored in the basic structure: walls, ceiling or floor. There are also systems that have heat storage as a permanent element within the building structure, such as bins of rocks, or water-filled drums or bottles. These are also classified as passive solar energy systems. Passive solar homes are ideal places in which to live. They provide beautiful connections to the outdoors, give plenty of natural light, and save energy throughout the year.

HISTORY
Building design has historically borrowed its inspiration from the local environment and available building materials. More recently, humankind has designed itself out of nature, taking a path of dominance and control which led to one style of building for nearly any situation. In 100 A.D., Pliny the Younger, a historical writer, built a summer home in Northern Italy featuring thin sheets of mica windows on one room. The room got hotter than the others and saved on short supplies of wood. The famous Roman bath houses in the first to fourth centuries A.D. had large south facing windows to let in the sun’s warmth. By the sixth century, sunrooms on houses and public buildings were so common that the Justinian Code initiated “sun rights” to ensure individual access to the sun. Conservatories were very popular in the 1800’s creating spaces for guests to walk through warm greenhouses with lush foliage.

Passive solar buildings in the United States were in such demand by 1947, as a result of scarce energy during the prolonged World War 2, that Libbey-Owens-Ford Glass Company published a book entitled Your Solar House, which profiled forty-nine of the nations greatest solar architects.

In the mid-1950’s, architect Frank Bridgers designed the world’s first commercial office building using solar water heating and passive design. This solar system has been continuously operating since that time and the Bridgers-Paxton Building is now in the National Historic Register as the world’s first solar heated office building.
Low oil prices following World War 2 helped keep attention away from solar designs and efficiency. Beginning in the mid-1990’s, market pressures are driving a movement to redesign our building systems to more in line with nature.

Passive Solar Space Heating

There are few basic architectural modes for the utilisation of passive solar utilisation in architecture. But these modes, as presented below, can be developed into many different scheme, and enrich the design. The essential elements of a passive solar home are: good siting of the house, many south-facing windows (in Northern Hemisphere) to admit solar energy in winter (and, conversely, few east or west facing windows, to limit the collection of unwanted summer sunshine), sufficient interior mass (thermal mass) to smooth out undesirable temperature swings and to store heat for night time and a well-insulated building envelope. Siting, insulation, windows orientation and mass must be used together. For least variation of indoor temperature the insulation should be placed on the outside of the mass. However where rapid indoor heating is required some insulation or low heat capacity material should be placed at the inside surface. There will be an optimum design for each micro-climate and indications are that a careful balance between mass and insulation in a structure will result not only in energy savings but in initial material cost saving as well.

Site
Landscaping and Trees
According to the U.S. Department of Energy report, “Landscaping for Energy Efficiency” (DOE/GO-10095-046), careful landscaping can save up to 25% of a household’s energy consumption for heating and cooling. Trees are very effective means of shading in the summer months as well as providing breaks for the cool winter winds. In addition to contributing shade, landscape features combined with a lawn or other ground cover can reduce air temperatures as much as 5 degrees Celsius in the surrounding area when water evaporates from vegetation and cools the surrounding air. Trees are wonderful for natural shading and cooling, but they must be located appropriately so as to provide shade in summer and not block the winter sun. Even deciduous trees that lose their leaves during cold weather block some winter sunlight - a few bare trees can block over 50 percent of the available solar energy.

Windows

All effective passive systems depend on windows. Glass or other translucent materials allow short-wave, solar radiation to enter a building and prohibit the long-wave, heat radiation, from escaping. Windows control the energy flow in two principle ways: they admit solar energy in winter, so warming the house above the otherwise cool to cold internal conditions; and by excluding sun from the windows (by orientation and shading) there exist the opportunity to use ventilation to cool the otherwise warm hot house in summer. If use is to be made of the sun’s heat, then it has to reach buildings when it is useful. Generally, the sun should be able to reach the collection area between 9 a.m. and 3 p.m. in winter with as little obstruction and interference as possible.Trees on the site or the neighbours’ site might shade the vital areas of the building. This need to be checked and the building located to minimise any such interference. It is possible to plan a house to have its main outlook in any direction and still be an efficient low energy building. The building envelope, i.e. the walls, floor and roof are the important elements in design, rather than the location of internal spaces. If a window needs to face west it requires correct shading and its size restricted.

Glass permits sun radiation of wavelengths 0.4 to 2.5 microns to pass through it. As this radiant energy collides with opaque objects on the other side of the glass, it’s wavelength increases to 11 microns. Glass acts as an opaque barrier to light of this wavelength thereby trapping the sun’s energy. The amount of light penetrating a glass is dependent on the angle of incidence. The optimum angle of incidence is 90o. When sunlight strikes the glass at 30o or less, the most radiation is reflected.

Understanding the Solar Spectrum and Heat Transfer
To make good choices on glazing, it is needed to understand a bit about light and heat. The sunlight that strikes the Earth is comprised of a variety of wavelengths and different glazing will selectively transmit, absorb, and reflect the various components of the solar spectrum. Likewise, reducing glare (via reflection or tinting) is helpful in the workplace by allowing the transmission of visible, or natural, light it is possible to save energy for artificial light. But perhaps the greatest effect on human comfort levels is determined by infrared heat transfer. By specifying the right type of glass, it is possible to trap the infrared heat for warmth, or reflect the infrared heat to prevent warming.

There are three ways that heat moves through a glazing material. The first is conduction. Conductive heat is transferred through the glazing by direct contact. Heat can be felt by touching the glazing material. The second form of heat transfer is radiation; electromagnetic waves carry heat through a glazing. This produces the feeling of heat radiating from the surface of the glazing. The third method of heat transfer is convection. Convection transfers heat by motion, in this case, air flow. The natural flow of warm air toward colder air allows heat to be lost or gained.
The R-value of a glazing - its insulating capabilities or resistance to the flow of heat - is determined by the degree of conduction, radiation, and convection through the glazing material. However, air infiltration will also determine the overall R-value of a glazing system. The amount of heat that travels around a glazing is as important as the heat transfer through a glazing. Air can leak in or out of a building around the glazing via the framing. The quality, workmanship, and the installation of the entire glazing system, including the framing, affects air infiltration.
Advances in glass technology have perhaps been the single largest contributor to building efficiency since the 1970s and they play an important roll in solar design. Some window advances include:

• Double and triple pane windows with much higher insulating values.
• Low emissivity or Low-E glass employing a coating which lets heat in but not out.
• Argon (and other) gas filled windows that increase insulating values above windows with just air.
• Phase-change technologies that can switch from opaque to translucent when a voltage is applied to them.

Basic Glass Types
Glazing materials include glass, acrylics, fibreglass, and other materials. Although different glazing materials have very specific applications, the use of glass has proven the most diverse. The various types of glass allow the passive solar designer to fine-tune a structure to meet client needs. The single pane is the simplest of glass types, and the building block for higher performance glass. Single panes have a high solar transmission, but have poor insulation - the R-value is about 1,0. Single pane glass can be effective when used as storm windows, in warm climate construction (unless air conditioning is being used), for certain solar collectors, and in seasonal greenhouses. Structures using single pane glass will typically experience large temperature swings, drafts, increased condensation, and provide a minimal buffer from the outdoors.

Perhaps the most common glass product used today is the double pane unit. Double pane glass is just that: two panes manufactured into one unit. Isolated glass (thermopane) incorporate a spacer bar (filled with a moisture absorbing material called a desiccant) between the panes and are typically sealed with silicone. The spacer creates a dead air space between the panes. This air space increases the resistance to heat transfer; the R-value for double pane is about 1,8-2,1. Huge air spaces will not drastically increase R-value. In fact, a large air space can actually encourage convective heat transfer within the unit and produce a heat loss. A rule of thumb for air space is between 1 and 2 centimetres. It is also possible to go as large as 10-12 centimetres without creating convective flow, but at that point you are dealing with a very large and awkward unit. The demand for greater energy efficiency in building and retrofitting homes has made insulated glass units the standard. With good solar transmission and fair insulation, such unit is a large improvement over the single pane. Windows, doors, skylights, sunrooms, and many other areas utilize double pane glass.

HIGH PERFORMANCE GLASS
High performance or enhanced glass offers even better R-value and solar energy control. By further improving the insulating capability of glass, it is possible dramatically increase also design options. What were once insulated walls may become sunrooms. Solid roofs and ceilings become windows to the sky. Dark rooms can “wake up” to natural light, solar heat gain, and wonderful views. For a relatively small increase in cost it is possible to improve efficiency, provide better moisture and UV protection, and gain design flexibility. A variety of high performance glass is now available.

What are the advantages of this glass? Low emissivity (Low-E) glass is succeeding double pane glass in energy efficient buildings. Emissivity is the measure of infrared (heat) transfer through a material. The higher the emissivity, the more heat is radiated through the material. Conversely, the lower the emissivity, the more heat is reflected by the material. Low-E coatings will reflect, or re-radiate, the infrared heat back into a room, making the space warmer. This translates into R-values from 2.6 to 3.2. In warmer climates it is possible to reverse the unit and re-radiate infrared heat back to the outside, keeping the space cooler. Low-E glass improves the R-value, UV protection, and moisture control.Gas-filled windows increase R-value. Properly done, gas-filling will increase the overall R-value of a glass unit by about 1,0. The air within an insulated glass unit is displaced with an inert, harmless gas with better insulation properties. Typical gases used are Krypton and Argon.

Window curtains
In addition to decorative functions, curtains can be used to reduce the heat losses that occur during the cold months as well as the heat gains during the warmer months. The plywood box over the curtain top prevents warm ceiling air from moving between the glass and curtain. The curtain should drop at least 30 cm below the window for it to be effective. The optimum condition would be for it to drop to the floor.

Thermal mass
Solar radiation hitting walls, windows, roofs and other surfaces is adsorbed by the building and is stored in thermal mass. This stored heat is then radiated to the interior of the building. Thermal mass in a solar heating system performs the same function as batteries in a solar electric system (see chapter on photovoltaics). Both store solar energy, when available, for later use.

Thermal mass can be incorporated into a passive solar room in many ways, from tile-covered floors to water-filled drums. Thermal mass materials, which include slab floors, masonry walls, and other heavy building materials, absorb and store heat. They are a key element in passive solar homes. Homes with substantial south-facing glass areas and no thermal storage mass do not perform well.

It is important to know that dark surfaces reflect less, therefore, absorb more heat. In case of a dark tiled floor, the floor will be able to absorb heat all day and radiate heat into the room at night. The rate of heat flow is based on the temperature difference between heat source and the object to which the heat flows. As described above heat flows in three ways - conduction (heat transfer through solid materials), convection (heat transfer through the movement of liquids or gasses), and radiation. All surfaces of a building lose heat via these three modes. Good solar design works to minimize heat loss and maximize efficient heat distribution. The need for thermal mass (heat-storage materials) inside a building is very climate-dependent. Heavy buildings of high thermal mass are consistently more comfortable during hot weather in hot-arid and cool-temperate climates, while in hot-humid climates there is little benefit. In cool-temperature climates the thermal mass acts as a cold-weather heat store thus improving overall comfort and reducing the need for auxiliary heating, except on overcast or very cold days. In intermittently heated buildings, however, it tends to increase the heat needed to maintain the chosen conditions.

Providing adequate thermal mass is usually the greatest challenge to the passive solar designer. The amount of mass needed is determined by the area of south-facing glazing and the location of the mass. In order to ensure an effective design it is important to follow these guidelines:

Locate the thermal mass in direct sunlight. Thermal mass installed where the sun can reach it directly is more effective than indirect mass placed where the sun’s rays do not penetrate. Houses that rely on indirect storage need three to four times more thermal mass than those using direct storage.

Distribute the thermal mass. Passive solar homes work better if the thermal mass is relatively thin and spread over a wide area. The surface area of the thermal mass should be at least 3 times, and preferably 6 times, greater than the area of the south windows. Slab floors that are 8 to 10 centimetres thick are more cost effective and work better than floors 16 to 20 inches thick.

Do not cover the thermal mass. Carpeting virtually eliminates savings from the passive solar elements. Masonry walls can have drywall finishes, but should not be covered by large wall hangings or lightweight panelling. The drywall should be attached directly to the mass wall, not to covers fastened to the wall that create an undesirable insulating airspace between the drywall and the mass.

Select an appropriate mass colour. For best performance, finish mass floors with a dark colour. A medium colour can store 70 percent as much solar heat as a dark colour, and may be appropriate in some designs. A matte finish for the floor reduces reflected sunlight, thus increasing the amount of heat captured by the mass and having the additional advantage of reducing glare. The colour of interior mass walls does not significantly affect passive solar performance.

Insulate the thermal mass surfaces. There are several techniques for insulating slab floors and masonry exterior walls. These measures should introduced to achieve the energy savings. Unfortunately, problems in some case can arise like with termite infestations in foam insulation for perimeter slabs. This can complicate the issue of whether and how to insulate slab-on-grade floors.

Make thermal mass multipurpose. For maximum cost effectiveness, thermal mass elements should serve other purposes as well. Masonry thermal storage walls are one example of a passive solar design that is often cost prohibitive because the mass wall is only needed as thermal mass. On the other hand, tile-covered slab floors store heat, serve as structural elements, and provide a finished floor surface. Masonry interior walls provide structural support, divide rooms, and store heat.

When developing a thermal storage system or simply comparing materials it is useful to look at the storage capacity of the proposed building materials which is referred to as the volumetric heat capacity (J/m3. Deg. Celsius) or more commonly the specific heat and the rate at which the material can take up and store heat. Some examples of common storage materials are given in the following table:

Material	Density (kg/m3)	Volumetric heat capacity (J/m3. Deg. C)
Water	1000	4186
Concrete	2100	1764
Brick	1700	1360
Stone: marble	2500	2250
	Materials not suitable for thermal storage
Plasterboard	950	798
Timber	610	866
Glass fibre matt	25	25

Early solar designers used water (stored in large containers) as the heat storage medium. Although water is cheap, the containers and the space they take are not. Some solar designers turned to rock storage bins as reservoirs for thermal mass. It took three times as much rock to store the same amount of heat as an equivalent volume of water and the moist warm environment of the bins became breeding grounds for odor producing fungi and bacteria. The high cost and the foul odors started to give solar design a bad name. Both water and rock heat storage require complicated control systems, pumps, and blowers. Heat storage is not common in today‘s solar energy utilisation. Main reason for this is that all of these systems rely on electricity, require maintenance, and are subject to periodic breakdown.

Thermal insulation

Materials generally available for building purposes can be classified into two generic groups - bulk materials and reflective foil laminates (RFL). The first of these relies on the resistance of air trapped in pockets between the fibres of the blanket type materials (mineral fibre materials) or the cells formed in the foamed structure of board or slab type materials (usually made from plastics such as polystyrene and polyurethane foams). The second reflects radiant energy away from the object or surface being protected. Thermal insulation in the outer fabric of a building is a vital component of an energy-efficient design strategy. The key to successful energy-efficient design is the control of heat flow through the external fabric. All the solar energy gained could be easily lost from an inadequately insulated building before it is able to be of benefit. It will have been noted that some materials have a very much higher thermal resistance per unit thickness than others irrespective of their density. The fact that air is a good insulator especially if it is bounded by a bright foil surface to limit radiation transfer can be very useful as well.

Cooling
In many parts of the world a passive solar building needs cooling as much as heating. One of the best, time proven methods of cooling is thermal coupling with the earth’s constant temperature. Dropping the ground floor at least one meter into the earth provides a more even exterior temperature which aids cooling as well as heating. Adequate structural engineering, drainage, and damp proofing are essential in below ground areas. Thermal isolation is the best and most economical way to temper the building’s environment. Using the earth’s thermal mass keeps the house at a reasonable temperature, and so does good insulation. Shades located outside and inside the windows, ventilation and reflective films on the windows are also very important in order to control temperature inside the building.

External Shades and Shutters
Exterior window shading treatments are effective cooling measures because they block both direct and indirect sunlight outside of the home. Solar shade screens are an excellent exterior shading product with a thick weave that blocks up to 70 percent of all incoming sunlight. The screens absorb sunlight so they should be used on the exterior of the windows. From outside, they look slightly darker than regular screening, but from the inside many people do not detect a difference. Most products also serve as insect screening. They should be removed in winter to allow full sunlight through the windows. A more expensive alternative to the fibreglass product is a thin, metal screen that blocks sunlight, but still allows a view from inside to outside. Hinged decorative exterior shutters which close over the windows are also excellent shading options. However, they obscure the view, block daylight completely, may be expensive and may be difficult for many households to operate on a daily basis.

Interior Shades and Shutters
Shutters and shades located inside the house include curtains, roll-down shades, and Venetian blinds. Interior shutters and shades are generally the least effective shading measures because they try to block sunlight that has already entered the room. However, if passive solar windows do not have exterior shading, interior measures are needed. The most effective interior treatments are solid shades with a reflective surface facing outside. In fact, simple white roller blinds keep the house cooler than more expensive louvered blinds, which do not provide a solid surface and allow trapped heat to migrate between the blinds into the house.

Reflective Films and Tints
Reflective film, which adheres to glass and is found often in commercial buildings, can block up to 85% of incoming sunlight. The film blocks sunlight all year, so it is inappropriate on south windows in passive solar homes. However, it may be practical for unshaded east and west windows. These films are not recommended for windows that experience partial shading because they absorb sunlight and heat the glass unevenly. The uneven heating of windows may break the glass or ruin the seal between double-glazed units.

Ventilation
Ventilation is the changing of air in buildings to control oxygen, heat and contaminants. Ventilation may occur in few forms. Building orientation, form, plan and user actions also alter air flow paths. Natural ventilation consumes no energy and has few if any running costs, but depends on weather conditions and can be difficult to control. Mechanical and air-conditioned ventilation are energy-driven alternatives to natural ventilation, normally dictated by building type, site and function. They can be particularly efficient as supplements to natural ventilation. Mechanical ventilation uses fans and ducts to supply and extract air in localised areas such as a kitchen. Air conditioning both treats and supplies air. It is particularly useful to cool air below ambient temperatures.

SOLAR ARCHITECTURE & ACTIVE SYSTEMS
It is important to design the house with the aim to incorporate active solar systems (see below) like collectors or photovoltaic modules as well. The building should orient these appliances due south. Tilt of the solar collectors should be in Europe and North America more than 50° (from horizontal) to maximize winter heat collection. Solar collectors should be thermally locked with the roof. Non-tracking photovoltaics receive the most yearly insolation (exposure to the sun’s rays) when tilted at an angle, from horizontal, equal to the building’s latitude. Design of the building’s roof should be done to such angles and southern orientation as integral aspects of the building. Hot water collectors and photovoltaic panels should be located as close as possible to their main areas of use. It is important to concentrate these areas of use. For example, putting the bathrooms and kitchen close together economizes on their installation and minimizes energy loss. All appliances should be selected with efficiency as the prime criterion.

SUMMARY

Passive use of sunlight contributes around 15% of space heating needs in typical building. It is important source of energy savings which can be utilised everywhere and almost at no extra cost. There are some principles which can help a designer to harness solar energy through thermally efficient buildings.

SITE
It is important to become familiar with the energy flows of house surroundings. The nature and relationship of the lay of the land, water courses, vegetation, soil types, wind directions, and exposure to the sun should be investigated. A site suitable for solar design should balance and complement these elements. It must have unobstructed exposure to the sun from 9 am to 3 pm during the heating season.

HEATING
In Northern hemisphere orientation due south of the main solar insolating spaces, i.e. greenhouse, and/or main daytime activity areas is important. Glass should be open to the sun patterns during the winter. By facing of the windows to the south, and virtually none to the north maximaze solar gain. Multiple pane glass in all windows is recommended.

THERMAL MASS
Thermal mass including masonry floors, walls and water storage is important to absorb ambient heat during the day and release it at night. Insulation of the building further minimize heat loss through windows, walls and roof.

NATURAL HEAT FLOW
It is useful to design the house with the natural heat flow in mind. Hot air rises, so placing some activity areas on a second floor to draw heat up from a lower collector area and across other areas can save a lot of energy. Buffer areas of the building (unheated rooms, or partially heated spaces such as utility rooms, vestibules and storage areas) should be oriented due to the north to lessen the impact of the winter’s cold. Using a vestibule on doors to the exterior can lead to energy savings. Vestibules cut heat loss and provide a buffer zone between the exterior and the interior.

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