Net Zero Energy Homes
From Swikipedia
Introduction
Net Zero Energy Homes or Zero Energy Buildings (ZEBs) are buildings that have zero net energy consumption and zero net carbon emissions annually. In such buildings, the energy is produced on-site and is autonomous of the energy-grid supply. In other words, a net-zero energy home is capable of producing, at minimum, an annual output of renewable energy that is equal to the total amount of its annual consumed/purchased energy from energy utilities.
The zero-energy approach is promoted as a potential solution to a range of issues, including reducing carbon emissions, and reducing dependence on fossil fuels.
Brief Description
Energy Generation
Energy consumption in a building is reduced to very low levels through the use of highly insulated walls, ceilings and floors along with very efficient windows. With space and water heating consumption at very low levels, it is possible to generate enough energy through on-site, renewable energy systems to balance the energy consumed with the energy produced. Currently, solar water heaters and photovoltaic systems are the most common methods of energy generation.
Advantages
• Increase in energy prices does not effect the owner
• There is increased comfort due to more-uniform interior temperatures
• The total net monthly cost of living reduces to a great extent
• The reliability on energy demands improves considerably, for example, photovoltaic systems have 25-year warrantees – they seldom fail during weather problems
• The extra cost is minimized for new construction as compared to an afterthought retrofit
• The resale value increases as potential owners demand more ZEBs than available supply
• The future legislative restrictions, and carbon emission taxes/penalties may force expensive retrofits to inefficient buildings
Disadvantages
• Initial costs can be higher - effort required to understand, apply, and qualify for ZEB subsidies
• There are very few designers or builders who have the necessary skills or experience to build ZEBs
• The new photovoltaic solar cells equipment technology price has been falling at roughly 17% per year - It will lessen the value of capital invested in a solar electric generating system - Current subsidies will be phased out as photovoltaic mass production lowers future price
• Climate-specific design may limit future ability to respond to rising-or-falling ambient temperatures (global warming)
• Without an optimised thermal envelope the embodied energy, heating and cooling energy and resource usage is higher than needed. ZEB by definition do not mandate a minimum heating and cooling performance level thus allowing oversized renewable energy systems to fill the energy gap.
• Solar energy capture using the house envelope only works in locations unobstructed from the South. The concept cannot be optimized in South facing shade or wooded surroundings.
References:
http://www.oikos.com/library/green_building_glossary.html
