By Dr Bilsay Pastakkaya

14 September 2015 - 14:54

Floor-heating systems that send hot air into a hollow space under the floor to heat a room or bath exist since Roman times. Watercolour by General Eduard von Kallee, 1884 (c) public domain, adapted from the original:
Floor-heating systems exist since Roman times. Watercolour by General Eduard von Kallee, 1884 ©

public domain, adapted from the original.

What makes a house eco-friendly and how has the technology changed over time? Dr Bilsay Pastakkaya, who worked with fellow researchers in the UK, explains.

Eco-houses and energy efficiency

I would define an eco-house as a residence that has minimal impact on the environment, consumes minimal energy from design to demolition, and is built with eco-friendly materials and technologies – all without sacrificing the residents' quality of life.

Energy efficiency is crucial to the idea of eco-housing. If we use more of something (e.g. lighting and heating) but with the same energy input, or we use the same with less input, then we are being energy-efficient.

An eco-house derives much of its energy needs from renewable energy sources such as solar power, which can be converted into both thermal and electrical energy. Wind power can also be used to generate electricity, although it has some disadvantages related to wind availability and noise.

If we can reduce the energy requirement of our house substantially, then we can be said to live in a ‘low-energy' house. If the net energy consumption is equal to zero, we call this a ‘zero' house. If we can produce more energy from renewable energy sources than we need, then our home becomes a ‘plus' house.

Reducing energy consumption with solar power

One of the best ways to minimise the energy requirement is to design structures in a way that maximises solar gains. For example, an eco-house might have an enlarged roof facing south, with solar panels tilted at an angle that maximises solar gain.

It may seem paradoxical, but we can use solar energy not only for heating but also for cooling, such as through a trombe wall, which optimises heat gain and minimises heat loss during cold times, but also prevents excess heat in hot times.

Eco-housing is not a new concept

Human beings have always aspired to better living conditions. Down the ages, many heating and cooling systems have been developed to maintain the desired temperature of living spaces. Many of these systems are still used in eco-house design today.

Ancient Greek cities, for example, were oriented towards the south and built with south-facing windows in order to obtain sunlight for heating and illumination. Wind catchers, with various designs, were used for natural ventilation and cooling of buildings in Persia and Egypt thousands of years ago.

The first examples of wall-cooling as a heat-distribution system in buildings were seen in Roman cities. Water carried to the city via aqueducts was circulated through pipes embedded in the walls of the residences to cool down the living spaces. Romans also used hypocausts, floor-heating systems that send hot air into a hollow space under the floor to heat a room or bath.

Eco-technologies have come and gone

When considering what makes a house or building comfortable to live in, occupants often put thermal comfort (i.e., a comfortable temperature) at the top of the list.

At the dawn of the 20th century, the demand for domestic heating and hot water was satisfied by laborious and inefficient techniques and devices – especially those powered by wood and coal. The use of solar energy for these purposes, on the other hand, had the advantage that they required no cost, labour or maintenance. Many solar-powered systems were patented and commercialised around this time, and the first practical applications appeared in the 1930s.

Renewable energy applications declined in popularity as oil production increased, although they made a brief comeback at the time of the energy crisis in the 1970s. At the beginning of the 21st century, eco-technologies became popular again due to the economic, ecological and social problems related to the use of fossil fuels.

Eco-housing continues to improve, but it has limitations

The last decade has seen great improvements in eco-technologies thanks to computer-aided design and manufacturing, which have helped produce more reliable technologies at lower cost. Today, there are thousands of eco-houses all over the world built in different climactic conditions with various approaches to design and technologies.

There are always limitations when designing something, however. As mentioned earlier, orienting the building to the south is necessary for maximising solar gains, but if a tall building or hill shades your roof, all efforts for maximising solar gains will be useless.

Similar limitations exist with the heating and cooling of an eco-house. A ground source heat pump that uses the earth as a heat source requires a large area, not only for digging, but also for soil-heaping. Since the soil properties affect the system’s performance directly, you may need to carry extra soil with better properties from other places if the soil in your installation area is undesirable. This may double or triple your investment cost, which is already more expensive than its alternatives.

Eco-houses can take care of themselves

Eco-houses usually come with sensitive and accurate automation systems that maximise efficiency without sacrificing comfort. Also, remote-control systems allow you to manage or programme your eco-house when you are away.

Simulation programmes can determine the best solutions for all different scenarios. If you ensure that your house is designed and built by experts (which is really essential), you won’t have to worry about reliability, or technical or economic aspects.

Eco-housing is becoming less expensive

The cost of eco-housing varies widely depending on the design and what kind of technology is used. When a new technology comes on to the market, its price will be higher than existing alternatives. This is partly because new technology is built on expensive research and development.

Take, for example, photovoltaic (PV) panels, (otherwise known as 'solar panels'). In the 1950s, we paid more than $1,700 per watt for a PV panel with 4.5 per cent efficiency to produce 230 watts of electric power. Today, we produce the same power with 23 per cent efficiency and pay less than one dollar per watt for this technology. It is estimated that the price of PV panels, and other eco-technologies, will continue to decrease in the future.

Dr Pastakkaya is a Turkish researcher who worked with fellow academics in Nottingham, UK, on research titled New Approaches to Eco House Design and Renewable Energy Applications in Sustainable Buildings. This work was funded through the Newton-Katip Çelebi Fund, supported by the UK's Department of Business, Innovation and Skills (BIS) and the Scientific and Technological Research Council of Turkey (TÜBİTAK). 

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