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Commonly referred to as ZNE, achieving Zero Net Energy is to have a building that produces the same amount of renewable energy onsite as it consumes. This is measured in a 1-year term. A zero-energy building, also known as a zero net energy (ZNE) building, net-zero energy building (NZEB), or net zero building, is a building with zero net energy consumption, meaning the total amount of energy used by the building on an annual basis is roughly equal to the amount of renewable energy created on the site, or in other definitions by renewable energy sources elsewhere. These buildings consequently do not increase the amount of greenhouse gases in the atmosphere. They do at times consume non-renewable energy and produce greenhouse gases, but at other times reduce energy consumption and greenhouse gas production elsewhere by the same amount.
Most zero net energy buildings get half or more of their energy from the grid, and return the same amount at other times. Buildings that produce a surplus of energy over the year may be called "energy-plus buildings" and buildings that consume slightly more energy than they produce are called "near-zero energy buildings" or "ultra-low energy houses".
The following building and design strategies will provide insight into how your home can become ZNE.
Insulation -- 1.Adding insulation to the ceiling has the largest impact on the energy consumed in a home.
2.Avoiding thermal bridging through either double stud walls, rigid foam wrap or a combination is another important strategy.
3.Use surface mounted lights on the ceilings exposed to the outdoors. The nature of heat transfer reduces an otherwise well insulated R38 ceiling considerably with a small amount of can lights that do not allow for a proper amount of insulation above the light. An example of this is if you have a 1000 sq ft roof with R-38 and then have an attic door that is 10 sq ft that is not insulated so R-1 your resulting average roof R value is only 27.7.
Tight Construction -- 1.Blower door tests measure the amount of air that escapes a building at a standard 50 Pascals of pressure. In order to achieve a very tight envelope specially formulated tape is commonly used to seal the seams of the plywood during framing.
2.Another strategy is to use expanding foam sprayed in a thin layer in the wall cavity that is then blown full of fiberglass. The thin layer of foam seals the airflow and the fiberglass keeps this option at a reasonable price point, this is commonly referred to as ‘flash and fill’.
Fresh air -- 1.Recommended at a rate of .35 air changes per hour, meaning that all of the air in your house is replaced approximately every 3 hours. If you live in a cold or a hot climate this essentially means that you are heating or cooling the outdoors. To alleviate the lost energy we use a heat recovery ventilator, HRV or ERV depending on your climate. This mechanism has a heat exchanger that recovers the heat or cold from the exiting air and transfers it to the fresh incoming air.
2.In addition to having fresh air it is important to pay attention to the contents of the materials used, for this reason Method Homes uses plywood sheathing and only materials that have NAUF, no added urea formaldehyde as well as low and no VOC adhesives and paints.
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