Zero energy building (ZEB) (2)

The energy generation - energy conservation debate
One of the key areas of debate in zero energy building is over the balance between energy conservation and the use of renewable energy.
To the majority of zero energy designers, the aim of zero energy building is not only to design a building that, on balance, uses zero energy or produces zero emissions, but one that also minimises all energy use, irrespective of the fact that the energy may come from renewable resources. This approach can perhaps best be seen in the German Passivhaus standard.
However, while recognising that energy conservation has a part to play, a significant body of designers (perhaps encouraged by the HVAC sector) consider that it is of lower importance and instead rely to a greater extent on 'active' techniques (solar power, wind turbines, etc.) to make up the energy / heat shortfall.

Zero energy building (ZEB)

A zero energy building (ZEB) or net zero energy building is a general term applied to a building with a net energy consumption of zero over a typical year. This can be measured in different ways (relating to cost, energy, or carbon emissions) and, irrespective of the definition used, different views are taken on the relative importance of energy generation and energy conservation to achieve energy balance.
Although zero energy buildings remain uncommon in developed countries, they are gaining in importance and popularity. The zero-energy approach is seen to be a potential solution to a range of social and environmental issues, including reducing carbon emissions, reducing dependence on oil power, fuel imports, and the use of fossil fuels in general, and providing a measure of energy security against future energy crises.
A building approaching zero energy use may be termed a near zero energy building or ultra-low energy building. Those that produce a surplus of energy may be known as energy-plus buildings

Low-energy house

Generically, a low-energy house is any type of house that uses less energy than a regular house.
General usage
In general use, the meaning of the term 'low-energy house' has changed over time, and will certainly change in the future. Right now, it is generally considered to be one that uses around half of the German & Swiss low-energy standards mentioned below for space heating, typically in the range from 30 kWh/m²a to 20 kWh/m²a (8,000 Btu/ft²/yr to 6,000 Btu/ft²/yr). Below this the term 'ultra-low energy building' is often used.
Other uses, for example to mean any reduction in energy use below the standards demanded by current building codes, are also frequently encountered. Because national standards vary considerably, 'low energy' developments in one country may not meet 'normal practice' in another.

Beyond ultra-low energy buildings are those that use, on average over the course of a year, no imported energy (zero energy buildings), or even those that generate a surplus (energy plus houses), both of which are being built.
This can be achieved by a mixture of energy conservation technologies and the use of renewable energy sources. However, in the absence of recognized standards, the mix between these - and consequently the energy-use profile and environmental impact of the building - can vary significantly.
At one end of the spectrum are buildings with an ultra-low space heating requirement that therefore require low levels of imported energy, even in winter, approaching the concept of an autonomous building.
At the opposite end of the spectrum are buildings where few attempts are made to reduce the space heating requirement and which therefore use high levels of imported energy in winter. While this can be balanced by high levels of renewable energy generation throughout the year, it imposes greater demands on the traditional national energy infrastructure during the peak winter season
Low energy technology
Low-energy buildings typically use high levels of insulation, energy efficient windows, low levels of air infiltration and heat recovery ventilation. They may also use passive solar building design techniques or active solar technologies. To reduce energy needs for domestic hot water these homes may also use hot water heat recycling technologies to recover heat from showers and dishwashers.


From Wikipedia, the free encyclopedia

Green Building

Green building practices

Green building brings together a vast array of practices and techniques to reduce and ultimately eliminate the impacts of buildings on the environment. On the aesthetic side of green architecture or sustainable design is the philosophy of designing a building that in harmony with the natural features and resources surrounding the site. There are several key steps in designing sustainable buildings: specify 'green' building materials from local sources, reduce loads, optimize systems, and generate on-site renewable energy.
Building materials typically considered to be 'green' include rapidly renewable plant materials like bamboo and straw, lumber from forests certified to be sustainably managed, stone, recycled metal, and other products that are non-toxic, reusable, renewable, and/or recyclable. Building materials should be extracted and manufactured locally to the building site to minimize the energy embedded in their transportation.
Low-impact building materials are used wherever feasible: for example, insulation may be made from low VOC (volatile organic compound)-emitting materials such as recycled denim, rather than the insulation materials that may contain carcinogenic or toxic materials such as formaldehyde. To discourage insect damage, these alternate insulation materials may be treated with boric acid. Organic or milk-based paints may be used.
Architectural salvage and reclaimed materials are used when appropriate as well. When older buildings are demolished, frequently any good wood is reclaimed, renewed, and sold as flooring. Many other parts are reused as well, such as doors, windows, mantels, and hardware, thus reducing the consumption of new goods. When new materials are employed, green designers look for materials that are rapidly replenished, such as bamboo, which can be harvested for commercial use after only 6 years of growth, or cork oak, in which only the outer bark is removed for use, thus preserving the tree. When possible, building materials may be gleaned from the site itself; for example, if a new structure is being constructed in a wooded area, wood from the trees which were cut to make room for the building would be re-used as part of the building itself.
To minimize the energy loads within and on the structure, it is critical to orient the building to take advantage of cooling breezes and sunlight. Daylighting with ample windows will eliminate the need to turn on electric lights during the day (and provide great views outside too). Passive Solar can warm a building in the winter - but care needs to be taken to provide shade in the summer time to prevent overheating. Prevailing breezes and convection currents can passively cool the building in the summer. Thermal mass stores heat gained during the day and releases it at night minimizing the swings in temperature. Thermal mass can both heat the building in winter and cool it during the summer. Insulation is the final step to optimizing the structure. Well-insulated windows, doors, and walls help reduce energy loss, thereby reducing energy usage. These design features don't cost much money to construct and significantly reduce the energy needed to make the building comfortable.
Optimizing the heating and cooling systems through installing energy efficient machinery, commissioning, and heat recovery is the next step. Compared to optimizing the passive heating and cooling features through design, the gains made by engineering are relatively expensive and can add significantly to the projects cost. However, thoughtful integrated design can reduce costs -- for example, once a building has been designed to be more energy-efficient, it may be possible to downsize heating, ventilation and air-conditioning (HVAC) equipment, leading to substantial savings. To further address energy loss hot water heat recycling is used to reduce energy usage for domestic water heating. Ground source heat pumps are more energy efficient then other forms of heating and cooling until you factor in the energy lost during generation and transmission if the project is on the grid.
Finally, onsite generation of renewable energy through solar power, wind power, hydro power, or biomass can significantly reduce the environmental impact of the building. Power generation is the most expensive feature to add to a building.
Good green architecture also reduces waste, of energy, water and materials. During the construction phase, one goal should be to reduce the amount of material going to landfills. Well-designed buildings also help reduce the amount of waste generated by the occupants as well, by providing onsite solutions such as compost bins to reduce matter going to landfills.

Green building often emphasizes taking advantage of renewable resources, e.g., using sunlight through passive solar, active solar, and photovoltaic techniques and using plants and trees through green roofs, rain gardens, and for reduction of rainwater run-off. Many other techniques, such as using packed gravel for parking lots instead of concrete or asphalt to enhance replenishment of ground water, are used as well.

Alternative energy
wikipedia

Biomass

Biomass, in the energy production industry, refers to living and recently dead biological material which can be used as fuel or for industrial production. Most commonly, biomass refers to plant matter grown for use as biofuel, but it also includes plant or animal matter used for production of fibres, chemicals or heat. Biomass may also include biodegradable wastes that can be burnt as fuel. It excludes organic material which has been transformed by geological processes into substances such as coal or petroleum. It is usually measured by dry weight.
The term biomass is useful for plants, where some internal structures may not always be considered living tissue, such as the wood (secondary xylem) of a tree. This biomass became produced from plants that convert sunlight into plant material through photosynthesis.
Sources of biomass energy lead to agricultural crop residues, energy plantations, and municipal and industrial wastes.
Biomass is grown from several plants, including miscanthus, switchgrass, hemp, corn, poplar, willow and sugarcane[1]. The particular plant used is usually not very important to the end products, but it does affect the processing of the raw material. Production of biomass is a growing industry as interest in sustainable fuel sources is growing.[citation needed]
Though biomass is a renewable fuel, and is sometimes called a 'carbon neutral' fuel, its use can still contribute to global warming. This happens when the natural carbon equilibrium is disturbed; for example by deforestation or urbanization of green sites. These activities are termed 'carbon leakage'.
Biomass is part of the carbon cycle. Carbon from the atmosphere is converted into biological matter by photosynthesis. On decay or combustion the carbon goes back into the atmosphere or soil. This happens over a relatively short timescale and plant matter used as a fuel can be constantly replaced by planting for new growth. Therefore a reasonably stable level of atmospheric carbon results from its use as a fuel. It is commonly accepted that the amount of carbon stored in biomass is approximately 50% of the biomass by weight.[2]
Although fossil fuels have their origin in ancient biomass, they are not considered biomass by the generally accepted definition because they contain carbon that has been 'out' of the carbon cycle for a very long time. Their combustion therefore disturbs the carbon dioxide content in the atmosphere.

Alternative energy
Wikipedia