Energy Efficient Homes

A sustainable home achieves its goals in tow ways:

1. Using eco-friendly resources and technology to harness energy in the home
2. Reduces the use of energy [electricity] in the home.

The major impact of electricity usage is not in the home, but in the production of electricity at power stations. Many burn fossil fuels which damage the environment and increase the carbon footprint of a nation.

Using energy efficient appliances in the home is one way of reducing electricity usage and, therefore, carbon emissions.

Low-Energy House

The definition of a 'low-energy house' continually changes. At present, a low energy house is considered to be one that uses around half of the German & Swiss low-energy standards for space heating. This is typically 30 kWh/m²a to 20 kWh/m²a (8,000 Btu/ft²/yr to 6,000 Btu/ft²/yr).

Energy usage below this level is referred to as an 'ultra-low energy building'.

At the extreme we have zero energy buildings, that on average over a year, use no imported energy, and may even generate a surplus [energy plus houses]. These are also referred to as autonomous buildings.

Whatever degree of low energy rating a home achieves, it is generally done though a combination of energy conservation technologies and the use of renewable energy sources. In the absence of recognized standards, the energy-use profile and environmental impact of a building can vary significantly.

Low-energy buildings typically use:

• High levels of insulation
• Energy efficient windows
• Low levels of air infiltration and heat recovery ventilation.
• Passive solar building design techniques or active solar technologies.
• Hot water heat recycling technologies to recover heat from showers and dishwashers.

Home Energy Rating

Energy assessments for each country, and region within that country account for different climatic conditions and are benchmarked according to average household energy consumption for that region.

Australia

In Australia, A 5-Star rating indicates that the house has achieved a high level of thermal energy performance, and will require minimum levels of heating and cooling to be comfortable in winter and summer. Such homes are generally more comfortable to live in, have lower energy bills, and lower costs to install heating and cooling equipment.

The house energy rating does not currently include the efficiency of any appliances fitted or used within the house.

Passive solar building design has proven energy consumption reductions of 70% to 90% in many locations, without employing any active power generation systems.

With expert design, this is achieved with little additional new construction cost over a conventional building. The limiting factor is widespread usage is the lack of industry skill and experience to both design and install such systems. Passive solar designs are much more cost effective than adding expensive PV panels on the roof of a conventional inefficient building.

• A few kWh of PV panels (costing tens of thousands of U.S. dollar equivalent) may only reduce external energy requirements by 20% to 30%.
• A 100,000 BTU high seasonal energy efficiency ratio 14 conventional air conditioner requires over 7 kW of PV electricity while it is operating, and that does not include enough for off-the-grid night time operation.
• Using passive cooling, and superior system engineering techniques, can reduce the air conditioning requirement by 70% to 90%, where PV electricity then becomes cost-effective. (Energy conservation PLUS energy generation)

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