I just attended a one day class regarding zero net energy. Turns out there are at least four ways to define this. It can be as simple as getting your power bill to zero by feeding in enough on-site-produced energy to zero out what you use from the grid. OR you can be zero net energy if your produce enough on-site energy to cover the amount of fuel it actually takes to produce the off-site energy you use. (Nationally, it takes an average of 3.4 units of raw energy at a power plant to deliver 1 unit of energy to the consumer.) The third way to define this is to have your one-site energy production truly produce the total amount of energy your site uses (can still feed into the grid and pull from the grid as long as you take the same or less amount from the grid that you feed back). The fourth definition is to address the emissions coming from production of all the energy used on-site. The ability to do this can vary widely depending on the fuel mix and how the grid electricity is produced.
The main message really came down to "be efficient in the use of energy BEFORE deciding how to produce energy on-site". Trying to achieve net-zero energy usage provides quite a strong incentive to become a more efficient energy user. When a home is designed and built to be efficient and zero net energy, it can actually make ownership cost less than current conventional construction. This can be true for both new construction as well as remodeling/retrofitting.
To achieve this, there are some changes that need to be made in the design and construction process. The major change is to have an integrated team that produces an integrated building. This means everyone involved in the process comes on board at or near the beginning: architect, contractor/builder, mechanical engineer, energy engineer, tradesmen. Having everyone at the table (with the owner if doing a custom build) by the time the schematic design starts means there will be a high level of common understanding among the players which is much more likely to produce the desired results. Too often in the conventional approach, these various people are brought into the process only close to the time to implement their specific task. They have no overall view of what the project is trying to accomplish and so have little incentive to strive for anything beyond the current norm.
And, boy, did we find out what a sad state the current norm is in! Picture after picture showed such poor design as well as horribly sloppy installation in project after project. No wonder buildings are not performing anywhere close to the modeled data for a newly constructed project. And remodeled and retrofitted buildings are just as shameful.
So to have the best outcome, make sure to have all players at the table from the start and keep revisiting plans before any actual construction starts. Make sure that as one part gets tweaked, the other parts are reviewed to keep all properly integrated. And once construction begins, inspect and test all along the way to verify that what was specified in the plans is done in reality.
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