Article by Julian Owen.

Most self builders want their new home to be energy efficient and environment friendly, but a true eco home takes these ideas to a higher level. Apart from being super energy efficient, it also involves the use of sustainable, recyclable building materials, management of the construction process and the planning and management of the lifestyle of the family for the rest of the time that they live in the house. A more poetic description is to “live lightly on the land”. In principle, building an eco house does not have to be complicated.  Here are some rules to follow.

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Consider Payback

Building an eco home is a worthy aspiration, but there are implications for your budget. Sometimes it means spending extra on the build to save money on running costs. There are many energy-saving and other eco features available, but it is helpful to know from the start which are the most cost effective. Some, such as using demolition rubble for hardcore cost nothing. Others involve an initial cost that is recouped over many years in reduced energy bills. A few will never pay for themselves. The time taken to pay back will be important if you do not intend to stay in the house for a long time. At the moment, energy efficiency measures do not add a lot of value to a property when it is sold, so if the payback time is 15 years and you move after 5, you may lose out. This situation will probably change in the future as the government is introducing policies that are making house buyers more aware of the value of energy efficient homes.

Start with Insulation

The single most effective step to reducing the energy needed to run a house is to increase the insulation level. By limiting the amount of heat that can escape through the building fabric, demand for heating is reduced. Because it is easy to double the thickness in a cavity wall from the minimum requirements of the building regulations, this should be done as a matter of course with a normal house. If it is to be a lot thicker than this different construction details are needed but it is still very cost-effective and once built will be there for the life of the building without needing any maintenance, replacement or repairs. Because the extra insulation makes the walls thicker there can be a loss of floors area in the house, so it may be worth looking at thinner forms of construction such as timber frame, structural insulated panels (SIPS).

Airtightness

house_heatlossIf a house is just very well insulated, most of the heat loss will be due to air seeping through the building, so an eco house should be sealed to be as air tight as possible. For the health and comfort of the occupants mechanical ventilation is essential along with a heat recovery system. In the past, air tightness has not been a concern so current building skills and practices often leave gaps and voids in the construction that allow air to circulate. Whoever builds the house has to be aware of the need for air tightness and ensure that the fabric is build correctly, using special details designed for the purpose.

Sunlight and Daylight are Free

The way that the sun enters a house through its windows can be controlled so that it warms the house in winter, but is screened out in summer when there is a risk of overheating. With a little design ingenuity, there is usually little extra cost involved in taking advantage of this free resource. Daylight is sometimes overlooked but the need for artificial lighting can be greatly reduced by careful siting of windows, particularly rooflights. Higher daylight levels also make spaces more attractive and pleasant to occupy.

Resist Eco Bling

There is a huge range of products aimed at helping people build an eco home often involving complex technology or expensive equipment which can be proudly shown off as the latest gadget. But well-designed eco house is the result of all its different components integrating together to the best possible effect. For example ground source heat pumps work most efficiently if you also install underfloor heating but are inefficient at providing hot water which could be heated using photovoltaic panels. Solar thermal panels have limited benefits because they deliver the most heat in the summer, when it is least needed and it can only be stored for a limited time.

Don’t forget embodied energy

A lot of energy and resources are used to create house. The design of an eco house should take this into account. For example triple glazed aluminium windows may reduce the heating bills, but to truly assess their value in reducing carbon emissions, you should also account for the energy spent acquiring the materials they are made from, their manufacture and transport to your site. You may find that the fuel that they save over the life of the building can never offset the carbon spent manufacturing and installing them.

Eco is about more than Energy Saving

A true eco home takes account of a lot more than simply saving fuel bills. There are many aspects of the design and construction process that are potentially harmful to the environment, either by using up finite resources or causing pollution. A lot of energy is needed to produce mains water, much of which is used for flushing toilets or watering the garden. It is easy to collect rainwater and put it to good use throughout the house. It is also fairly straightforward to recycle water from sinks and washing machines to flush toilets.

Everything incorporated into the construction should be selected to reduce the potential harm on the environment. This means favouring materials that are renewable, recycled and also recyclable when the building reaches the end of its life.

Get the Right Contractor

The standard of construction required for an eco house is high compared to a normal house and many of the construction details are unconventional. Whoever builds it must appreciate this and either have the skills or be ready to learn quickly. A lot of the features, particularly the insulation level and the air tightness are easily compromised by poor construction.

The Passivhaus Standard was developed in the early 1990’s in Germany and sets some very simple rules for achieving an energy efficient home. The principle is to use very high levels of insulation throughout the fabric of the building to reduce the heat loss to the minimum practical. In an ordinary house a lot of heat is lost due to ventilation and draughts, but a Passivhaus is sealed to be as airtight as possible. A mechanical ventilation system is used to extract heat from the air passing out of the building and warm fresh air that is being drawn in. The objective is for the house to need little or no space heating. Although the idea is very simple, a very high standard of workmanship and many special construction details are needed to succeed.

The Code for Sustainable Homes (CSH) rating system covers many more aspects of the design and construction of a house than just energy efficiency. It also measures the level of use of mains water, the pollution and waste produced, the affect of the house on the well being of the occupants and how the occupants can manage the manage the building. The analysis associated with the CSH covers all aspects of the building and how it is used, for example whether there is space to dry washing (rather than needing a spin dryer) and whether there is a composting facility. All this information is plugged into a calculation, that produces a figure, between 1 and 6. 6 is the highest possible score, but is very difficult to achieve because it requires the house to be ‘zero carbon’ which means that it must generate all the energy needed to run it on site.

Case Study: Naomi Campbell’s Massive Island Eco-House, Turkey. 

This glass domed house is completely energy and water self-sufficient and features an amazing indoor landscaped terrace. Everything about this concept house is a dream: its comfortable microclimate, its constant flow of air, light and heat when necessary, its superior landscaping, and of course the fact that it was built on the Isla Playa de Cleopatra in Turkey

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Read more: Luis de Garrido Unveils Incredible Glass-Domed Eco House Shaped Like the Eye of Horus | Inhabitat – Sustainable Design Innovation, Eco Architecture, Green Building

Article Links

http://www.passivhaus.org.uk/standard.jsp?id=17

http://www.energysavingtrust.org.uk/Professional-resources/Housing-professionals/New-housing/The-Code-for-Sustainable-Homes

http://www.energysavingtrust.org.uk

 Copyright Julian Owen, not to be reproduced, copied or distributed except for personal or education use.