Appropedia needs your support - Please Donate Today

Ultra-low energy house

From Appropedia
Jump to: navigation, search

A ultra-low energy house is a house built using low energy methods, and allows a very low and very efficient use of energy. Several types of ultra-low energy houses exist. A energy-neutral or energy-positive house is even more energy efficient, the latter even producing more energy than it consumes.

Building a new ultra-low energy house[edit]

Placement[edit]

Ultra-low energy houses are generally sited so as to create as little of a negative impact on the surrounding ecosystemW as possible, oriented to the sun so that it creates the best possible microclimate (typically, the long axis of the house or building should be oriented east-west), and provide natural shading or wind barriers where and when needed, among many other considerations. The design of a sustainable shelter affords the options it has later (ie: using passive solar lighting and heating, creating temperature buffer zones by adding porches, deep overhangs to help create favorable microclimates, etc).[1][2] Sustainably constructed houses involve environmentally-friendly management of waste building materials such as recycling and composting, use non-toxic and renewable, recycled, reclaimed, or low-impact production materials that have been created and treated in a sustainable fashion (such as using organic or water-based finishes), use as much locally available materials and tools as possible so as to reduce the need for transportation, and use low-impact production methods (methods that minimize effects on the environment).[3][4]

Aerodynamics[edit]

Rounded, aerodynamic buildings lose less heat.

Insulation[edit]

Insulation of a sustainable home is important because of the energy it conserves throughout the life of the home. Well insulated walls and lofts using green materials are a must as it reduces or, in combination with a house that is well designed, eliminates the need for heating and cooling altogether. Installation of insulation varies according to the type of insulation being used. Typically, lofts are insulated by strips of insulating material laid between rafters. Walls with cavities are done in much the same manner. For walls that do not have cavities behind them, solid-wall insulation may be necessary which can decrease internal space and can be expensive to install.[2] Energy-efficient windows are another important factor in insulation. Simply assuring that windows (and doors) are well sealed greatly reduces energy loss in a home.[5] Double or Triple glazed windows are the typical method to insulating windows, trapping gas or creating a vacuum between two or three panes of glass allowing heat to be trapped inside or out.[1][4] Low-emissivityW or Low-E glass is another option for window insulation. It is a coating on windowpanes of a thin, transparent layer of metal oxide and works by reflecting heat back to its source, keeping the interior warm during the winter and cool during the summer. Simply hanging heavy-backed curtains in front of windows may also help their insulation.[2] “Superwindows,” mentioned in Natural Capitalism: Creating the Next Industrial RevolutionW, became available in the 1980s and use a combination of many available technologies, including two to three transparent low-e coatings, multiple panes of glass, and a heavy gas filling. Although more expensive, they are said to be able to insulate four and a half times better than a typical double-glazed windows.[6]

Green roofs or “living roofs” are a popular choice for thermally insulating a building. They are also popular for their ability to catch storm-water runoff and, when in the broader picture of a community, reduce the heat island effect (see urban heat island) thereby reducing energy costs of the entire area. It is arguable that they are able to replace the physical “footprint” that the building creates, helping reduce the adverse environmental impacts of the building‘s presence.[7][8]

Paint[edit]

Equipping roofs with highly reflective material (such as aluminum) increases a roof's albedo and will help reduce the amount of heat it absorbs, hence, the amount of energy needed to cool the building it is on. This is important for buildings in hot climates.

Energy efficiency of domestic appliances[edit]

Energy efficiency and water conservation are also major considerations in sustainable housing. If using appliances, computers, HVACW systems, electronics, or lighting the sustainable-minded often look for an Energy StarW label, which is government-backed and holds stricter regulations in energy and water efficiency than is required by law.[9][10] Ideally, a sustainable shelter should be able to completely run the appliances it uses using renewable energy and should strive to have a neutral impact on the Earth’s water sources[11]

Modifying traditional houses to the ULE standard[edit]

Existing houses can be adapted to reduce the energy needs. For this, an energy audit can be performed. This often results in list of specific measures that can be implemented for your house. These include plugging holes, implementing heat recovery ventilation, increasing the insulation, ...

Plugging holes[edit]

It may seem trivial, but most houses (even those build today) are often very leaky. Trough leaks everywhere around the house, much of the heat generated is wasted. Heated air may escape e.g.:

  • trough hollow walls into the roof
  • trough gaps around ceiling light fittings
  • trough vents and chimneys
  • trough gaps left during construction (e.g. between floors and walls)
  • via gaps around windows
  • via gaps around the cables/pipework
  • via floors and ceiling voids
  • via gaps where ceiling and wall join the eaves
  • via garage doors and regular doors[12]

Other techniques to increase thermal efficiency[edit]

  • Draught-excluding strips (also known as "excluders") can be screwed on doors and garage doors (most effective on outer doors/garage doors).
  • Curtains can be used at night. Perhaps surprisingly, they are very effective in reducing heat escape trough the windows.

Special types of ULE houses[edit]

Passive solar house[edit]

A passive solar house is a ultra-low energy house that achieves this low energy use (or even energy-neutrality) by means of large, well-insulated windows (that let in large amounts of sunlight, heating the building at cold days; windows can be covered at hot days), very rigourous insulation, airtightness and efficient ventilation[13].

It does differentiates from regular energy-neutral/energy-positive houses in that it doesn't simply add sufficient power sources (ie PV-panels, wind turbines, ...) to level out the energy use, but focuses primarily on energy conservation instead.

The basic requirement for passive solar heating is that the solar collectors must face the prevailing sunlight (south in the northern hemisphere, north in the southern hemisphere), and the building must incorporate thermal mass to keep it warm in the night.

However, there are some remarks to be made. First off, for windows intended for passive solar heating, and placed in houses in temperated climates, we must target the windows on the south at an inclination that is optimal for letting in most heat in winter (and not in summer). If it were to be inlinated for letting in most heat in summer, additional cooling would be needed, and the efficiency of the system would be reduced.

Also, we must differentiate between windows intented for passive solar heating and windows for daylighting. For the latter, we probably also need to change the inclination so that less UV light (which is the light that warms the house) can enter, or alternatively, inclinate the windows for letting in most heat in winter (in the latter situation you would then also use it for passive solar heating).

A recent, somewhat experimental solar heating system is called "Annualized geo solar heating". It is practical even in regions that get little or no sunlight in winter.[14] It uses the ground beneath a building for thermal mass. Precipitation can carry away the heat, so the ground is shielded with 6m-long skirts of plastic insulation. The thermal mass of this system is sufficiently inexpensive and large that it can store enough summer heat to warm a building for the whole winter, and enough winter cold to cool the building in summer. The sloped water-tight skirts of insulation extend upto 6m from the foundations for the purpose of preventing heat leakage between the earth used as thermal mass, and the surface.

In annualized geo solar systems, the solar collector is often separate from (and hotter or colder than) the living space. The building may actually be constructed from insulation, for example, straw-bale construction. Some buildings have been aerodynamically designed so that convection via ducts and interior spaces eliminates any need for electric fans.

A more modest "daily solar" design is very practical. For example, for about a 15% premium in building costs, the Passivhaus building codes in Europe use high performance insulating windows, R-30 insulation, HRV ventilation, and a small thermal mass. With modest changes in the building's position, modern krypton- or argon-insulated windows permit normal-looking windows to provide passive solar heat without compromising insulation or structural strength. If a small heater is available for the coldest nights, a slab or basement cistern can inexpensively provide the required thermal mass. Passivhaus building codes in particular bring unusually good interior air quality, because the buildings change the air several times per hour, passing it though a heat exchanger to keep heat inside.

In all systems, a small supplementary heater increases personal security and reduces lifestyle impacts for a small reduction of autonomy. The two most popular heaters for ultra-high-efficiency houses are a small heat pump, which also provides air-conditioning, or a central hydronic (radiator) air heater with water recirculating from the water heater. Passivhaus designs usually integrate the heater with the ventilation system.

References[edit]

  1. Cite error: Invalid <ref> tag; no text was provided for refs named ReferenceA
  2. 2.0 2.1 2.2 Hamilton, Andy, and Dave Hamilton. The Self-sufficient-ish Bible: an Eco-living Guide for the 21st Century. London: Hodder & Stoughton, 2009. Print.
  3. Snell, Clarke, and Tim Callahan. Building Green: a Complete How-to Guide to Alternative Building Methods : Earth Plaster, Straw Bale, Cordwood, Cob, Living Roofs. New York: Lark, 2005. Print.
  4. 4.0 4.1 Hamilton, Andy, and Dave Hamilton. The Self-sufficient-ish Bible: an Eco-living Guide for the 21st Century. London: Hodder & Stoughton, 2009. Print.
  5. Cite error: Invalid <ref> tag; no text was provided for refs named McDilda.2C_Diane_Gow_2007
  6. Hawken, Paul, Amory B. Lovins, and L. Hunter Lovins. Natural Capitalism: Creating the next Industrial Revolution. Boston: Little, Brown and, 1999. Print.
  7. Cutlip, Jamie. Green Roofs: A Sustainable Technology. UC Davis Extension, Oct. 2006. Web. 26 Oct. 2010.
  8. GREEN ROOF RESEARCH PROGRAM. Michigan State University - Department of Horticulture. Web. 27 Oct. 2010.
  9. How a Product Earns the ENERGY STAR Label : ENERGY STAR." ENERGY STAR. Web. 27 Oct. 2010.
  10. Brown, Lester Russell. Plan B 4.0: Mobilizing to save Civilization. New York: W.W. Norton, 2009. Print.
  11. Water Conservation. Mono Lake Committee. Web. 27 Oct. 2010.
  12. Practical Self-Suffiency by Dick and James Strawbridge]
  13. http://en.wikipedia.org/wiki/Passive_house
  14. Stephens, Don. September 2005. "'Annualized Geo-Solar Heating' as a Sustainable Residential-scale Solution for Temperate Climates iwht Less than Ideal Daily Heating Season Solar Availability." ("Requested Paper for the Global Sustainable Building Conference 2005, Tokyo, Japan"). Greenershelter.org website. Retrieved on 2007-09-16.

External links[edit]