What is Passive Energy?
Mary McMahon
Mary McMahon
Passive energy, a term usually used in reference to passive solar energy, is natural energy which is directly harnessed to achieve a desired goal. By contrast, active energy is energy which is used to generate electricity. Passive energy systems require little energy or effort to maintain, and they are designed to replace traditional energy sources, reducing overall energy use rather than just switching the source of the energy.
A number of systems fall within the umbrella of passive energy. In fact, there's a high probability that the structure you are in right now takes advantage of this energy in some form or another. For example, it may have south facing windows if it is in the northern hemisphere, so that it can take advantage of sunlight for warmth. Many people use this type of energy unconsciously, as seen when people orient their furniture in a way which allows them to take advantage of natural light and warmth instead of using artificial systems for heating and lighting.
Passive energy can be used for heating and cooling in lieu of active systems. Passive heating systems can include passive solar tanks to heat water for bathing and cooking, along with windows orientated towards the sun, solariums to gather and trap heat which can be dispersed through a structure, and arrays of materials like tile which absorb heat and radiate it later, keeping temperatures stable in a building without the need for a climate control system.
Passive energy can also be used to drive air currents to improve air circulation and for cooling purposes. Other examples of passive cooling systems include curtains and shades which block sunlight during the heat of the day, or landscaping to cool a structure. Planting trees and shrubs will keep a structure cool in summer, and can help a structure stay warm in winter, by creating an insulating buffer.
People have been using passive energy in construction for hundreds of years, with many of the steps taken to harness this energy being commonsense. Structures specifically designed to be environmentally friendly often integrate passive systems as part of their design, and passive systems can also be added to the design of a conventional structure. One great advantage of this type of energy is that it usually does not require money or energy for maintenance and function, which means that once the system is installed, it will work for years. This is in contrast with active systems, which often require periodic replacement or repair, and may demand regular maintenance.
Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllTheScience researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.
Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllTheScience researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.
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Discussion Comments
I remember when it was thought to be important for a house to breathe, with so many complete exchanges of indoor air with outdoor air. It seems like energy efficiency for heating and cooling has done an about face on this idea, hasn't it?
@glasshouse- A true passive energy house follows a very strict code that can help the house reduce energy consumption by up to 90%. The homes do cost more, but in areas where the passive home sector is mature (like Germany), they only cost approximately 7% more than a normal code built home. What makes a passive home unique to American homes is the fact that most of the major energy saving investments goes into the building envelope rather than a technologically advanced HVAC system. In fact, a true passive home can be very comfortable in a temperate Mediterranean climate without a furnace or air conditioner.
Five main design elements go into a passive home:
1) Insulation- A high R-value is important in creating an airtight seal.
2) Windows and doors- Doors and Windows are often triple pane and foam sealed.
3) Elimination of thermal bridges- Framing is isolated so it does not add or draw heat into the indoor environment.
4) Optimizing Thermal Solar- Siting is very important to the design.
5) Heat Recovery Ventilation- Heat is exchanged between airflows without mixing air streams.
I hear the term passive house a lot, but I do not understand what a passive house is. What constitutes passive energy design? Is it retrofitting a home to allow it to collect more solar energy and light? Are there specific guidelines for a passive home? Are they more expensive to build than a regular code built home?
I would not be surprised to see some of the passive energy designs of the past become more commonplace. Builders are facing higher energy costs and a decline in suburbanization. Energy efficiency has become important in making new homes enticing to customers, especially those in suburban and rural areas.
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