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Energy-efficient homes

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Home / Green info / Energy-efficient homes

The task of upgrading your house or building a new, low energy house can appear to be a complicated and expensive undertaking, writes John Davies, Passive House designer and owner of Plastik Architects Ltd. Whilst there are technologies that require specialist input, these are no more complicated than the more regular constructional installations. There are also simple measures that can be put in place that will not only provide environmental benefits but also substantially reduce your energy costs, such as LED lighting and shading. Increasingly, advances in alternative technologies mean that heating and cooling installations can surpass the performance of tradition energy consumptive methods.

Climatic conditions in the Balearics provide particular requirements. Whilst the winters are short, there remains a need to ensure warmth and in particular dryness to house to ensure comfortable living and reduce the need for added energy. Cooling and shading remain a key priority, over our lovely long summer months. The use of recycled, natural materials with no harmful emissions, such as cellulose insulation can even outperform equivalent harmful materials.



Passive House in Guernsey by Iain Clavadetscher

New house

Old house

Sketches courtesy of John Davies, Plastik Architects

Design: orientation

The first step to a new-build, low energy house will be careful consideration of the orientation. The designer needs to consider the best use of solar gain, heating and cooling requirements. Bedroom should be ideally to the north side and living spaces to the south, with good shading measures to prevent overheating. Existing houses can be adapted, although obviously poor orientation is not easily resolvable in an existing dwelling without radical changes.   

Design: planning

The design of a low-energy house should consider aspects of energy use at the beginning of the design concept stage. It is not an afterthought. Issues of careful planning and the selection of materials and procurement of those building materials must be considered at the outset. Planning measures such double lobbies and window locations are simple but critical issues.

Good construction detailing

When constructing a low-energy house, great care should be taken to ensure all parts are fully sealed, achieving therefore the highest energy efficiency. Airtight constructions are key and poor construction can lead to heat loss or gain. Ensure that there are no gaps around junctions, corners, doors and window frames that allow air to escape.

Also, in new builds, beware of ‘thermal bridges’, which are created when there is no insulation separating outside materials and the interior of your house. These ‘bridges’ cause heat to escape during winter, plus allow cold and damp to enter the house. It can also cause condensation around windows and doors, which can damage your house and cause discomfort, and can lead to overheating in the summertime. Energy-efficient homes should have the entire construction wrapped in insulation to prevent this from occurring.

Good quality windows and doors

Windows and doors in so-called “Passive Houses” and other kinds of low-energy homes are strategically placed, to prevent too much seasonal heat or cold. All windows should be double or even triple glazing and hermetically sealed. Secondary glazing of your existing windows can also be considered.  This enables your house to use optimal solar radiation when closed and natural ventilation when open. In winter, solar radiation passes through and heats the interior, while in summer it is blocked to prevent overheating to ensure a natural and pleasant indoor climate all year round.

Mechanical ventilation

Mechanical air renewal systems can ensure inhabitants health and energy efficiency. Mechanical ventilation secures constant air renewal, achieving the best indoor air quality reduces pollen, dust, mites and other harmful particles.


Passive House in Guernsey by Iain Clavadetscher

Energy Saving: thermal insulation

In an energy-efficient home, the insulation is continuous and covers the entire thermal envelope of the building. This warm ‘coat’ over the walls and floor ensures heat is not lost and also prevents the building from overheating. Ideally insulation should be placed on the outside – but if not possible can be placed on the inside of the walls. Thermal insulation combined with ventilation prevents condensation, damp and mould.

Energy Saving: cellulose insulation

Cellulose is mainly made from recycled newspaper. It performs to a similar level to fiberglass. It can be either blown or sprayed and has the same insulative benefits as fiberglass without the cons, such as formaldehyde and potentially harmful fire retardants.

Energy Saving: LED lighting

An average household dedicates about 5% of its energy budget to lighting. Switching to energy-efficient lighting is one of the fastest ways to cut your energy bills. LED bulbs last up to 10 times longer than compact fluorescents and 40 times longer than typical incandescent bulbs.

Energy Production: solar panels

Photovoltaics sun panels store energy for re-use in the house.

Cooling: shading

Simple shading will ensure the interior does not overheat. Heat is stored in the house structure and is released over time. External shading will ensure that the house remains cool.

Heating: heat recovery

Heat exchangers, HVACs or HRVs (Heat Recovery Ventilators) remove moisture and provide fresh air to your home that is pre-heated by the outgoing air. Energy Recovery Ventilation (ERV) is the process of exchanging the energy contained in stale or humid air from homes and using it to treat the incoming outdoor fresh air in HVAC systems. During warmer days, an ERV pre-cools and dehumidifies while in the winter season they humidify and pre-heat incoming air from outside the house. Depending on the quality of the system, you can expect to recoup anywhere from 50% of the heat in the air, to as much as 95%.

Heating: ground-sourced heating

Ground source heat pumps (GSHPs) use pipes that are buried in the garden to extract heat from the ground. This heat can then be used to heat radiators, underfloor or warm air heating systems and hot water in your home.

Heating: energy-efficient boilers

Comparison between more energy efficient boilers shows that performance can vary significantly. Poor quality boilers will only provide short-term financial gain and may require replacement in less than 5 years. In comparison, good quality boilers will not only be cheaper to run but could last beyond 10 years. Over the course of its use you will save money with a high-quality unit.

Heating: burning smoke-free fuels

Smokeless fuel such as: anthracitecokecharcoal and hexamine fuel tablets will be the near-future replacement of all other solid fuels such as coal, which cause toxic smoke emissions. They are usually supplied as briquettes. Smokeless fuels can give up to a third more heat than normal house coal and can also burn for up to 40% longer. This means that they can burn hotter for longer, meaning you need to refuel your appliance less often. These smokeless fuels can be more cost effective than your normal house coal. These can be used in a traditional open fire as an alternative to wood or coal to heat your house.

Water: harvesting

Constructing a simple water storage device that can store water for use in the house and can be used to irrigate your garden or clean your terraces is a simple method to recycle water.

Water: reusing ‘grey’ water

Water from baths, hand basins. showers, and kitchen sinks can also be used in your garden. It is important to use plant-friendly cleaning products to ensure this grey water does not pollute the soil.

Natural gas cooking

Whilst is it more complicated, a Biogas digestor tank can store methane gas from animal or human waste and other organic matter. It works together with a filtering system (to remove hydrogen sulphide and carbon dioxide) to provide ‘clean’ methane gas for cooking.


Liquid waste from septic tanks can also provide liquid fertiliser, which can be used to grow fruit and vegetables. A simple compost heap can include things such as vegetable peelings, fruit waste, teabags, plants, cardboard, paper, leaves and grass. These break down quickly and provide important nitrogen as well as moisture to the soil. Compost can then be spread on your garden to improve soil quality and to grow bigger and better fruit and vegetables.