Passive houses are very well insulated, virtually airtight, buildings which minimize energy loss and improve occupant comfort. Passive house design considers the entire life-cycle of the building and uses a variety of 'passive' building solutions to eliminate conventional 'active' technologies that consume wasteful fossil fuels.
Passive Solar Design
Passive solar design is specifically used to exploit free energy from the sun, to provide warmth. A passive house is orientated so that large south facing windows absorb energy from the sun. The rooms are laid out so that the solar heat is distributed from these windows through the interior of the home. The process of capturing the solar energy is considered to be 'passive', since the building does not generate the energy itself. The heat energy comes from a natural source and is not generated exclusively by artificial means.
Provide Thermal Mass
Passive house buildings can be constructed from either dense or lightweight materials. In the case of lightweight construction, like timber frame, some internal thermal mass is incorporated. Thermal mass allows dense construction materials, typically concrete, stone, brick or tile, to store the free heat. During the day, when external temperatures are highest, a large thermal mass inside the insulated envelope will absorb the sun's heat. When the external temperature cools down in the evening, the thermal mass will naturally radiate that absorbed heat throughout the rooms.
Install Super Insulation
Insulating the building envelope is one of the most important passive house measures as it has the greatest impact on energy expenditure. In the average house, well considered and expertly installed insulation can reduce the amount of heat lost through the building envelope, by at least half. In addition, a high standard of thermal insulation will considerably improve thermal comfort for the building occupants.
Make the Building Airtight
Effective airtightness is another important contributor to passive house design. Warm air leaking from the building is a major cause of heat loss, which results in wasted energy. Improving the building's airtightness reduces the uncontrolled air flow through gaps and cracks in the building fabric and must be addressed by the designer early in the planning process.
Fit Triple Glazed Windows
High performance windows are a key contributor to the overall efficiency of the building envelope, as they are manufactured to deliver high thermal values. In passive house buildings, it is usual to combine triple-pane insulated glazing, low emissivity (low-E) glass and argon or krypton filled air gaps. Expertly designed and installed triple glazed windows will significantly reduce energy usage and improve occupant comfort.
Make Use of Waste Heat
In addition to using passive solar heating, passive houses make use of the waste heat from lighting, domestic appliances like refrigerators and washing machines, and the body-heat from the occupants of the building.
Install Heat Recovery Ventilation
Heat recovery ventilation is the process of exchanging heat energy contained in the air which is extracted from a house and transferring it to the incoming replacement air. This system can comprise either a central extract system or individual room fans. Although this ventilation method is an 'active' technology, using a small amount of electricity, it is considered to be a worthwhile contributor to energy saving. It provides the building with essential fresh air, improves occupant comfort and conserves the building's heat.
Fit Renewable Energy Heating
An underlying objective of solar passive design is the desire to dispense with conventional heating systems altogether. It is usually necessary to provide some supplementary space heating to maintain comfortable conditions on particularly cold winter days. Often this can be achieved via the low volume heat recovery ventilation system that is provided to maintain air quality. As an alternative to this, a renewable energy technology like a wood burning stove, solar heating, air source heat pumps or ground source heat pumps, may be preferred.
For more information on passive house design visit www.EcoFriendlyBuilding.com
David Stoppard is the Editor of http://www.lowenergyhouse.com/ and a group of associated websites that deal with the issues surrounding eco-friendly building. The LowEnergyHouse.com websites have evolved from an architectural practice with a keen interest in energy conscious design. Its members have set out to promote energy saving measures, sustainability and renewable energy technology in building, in order to help, protect the environment, secure future energy supplies and reduce fuel poverty.
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